Midterm 1 (Lectures 1-6)

Question 1

What is microbiology the study of?

Answer 1

The study of microorganisms that are too small to be seen by the naked eye (need microscope to view).

Question 2

Who invented the (simple, light) microscope? What did they examine? What did they call microorganisms at the time?

Answer 2

Antoni van Leeuwenhoek
- Examined water
- “Animalcules” = microorganisms (saw tiny animals, fungi, algae, unicellular protozoa)

Question 3

What are the 6 categories of Leeuwenhoek’s microorganisms? Describe if they are prokaryotic or eukaryotic.

Answer 3

1. Bacteria => prokaryotic
2. Archaea => prokaryotic
3. Fungi => eukaryotic
4. Protozoa => eukaryotic
5. Algae => eukaryotic
6. Small multicellular animals => eukaryotic

Question 4

Prokaryotes lack a…?

Answer 4

Nucleus

Question 5

Leeuwenhoek microorganisms can be seen with a _____ microscope.

Answer 5

Light microscope

Question 6

What category of microbes are NOT included in Leeuwenhoek’s microorganisms? What microscope is used to view them?

Answer 6

• Viruses
• Electron microscope

Question 7

What are acellular agents that can cause disease?

Answer 7

Viruses

Question 8

Why are viruses considered acellular/noncellular?

Answer 8

• Lack complex cellular structures
• Cannot carry out any metabolic pathway
• Can neither grow or response to the environment
• Cannot reproduce independently
• Need the chemical and structural components of the cell they infect to replicate

Question 9

What is the “Golden Age of Microbiology?”

Answer 9

• 1800’s
• Improved microscopes
• New lab techniques
  = Microbiology at forefront of scientific disciplines

Question 10

What 4 questions lead to major discoveries during the golden age of microbiology?

Answer 10

1. Is spontaneous generation of microbial life possible?
2. What causes fermentation?
3. What causes disease?
4. How can we prevent infection and disease?

Question 11

What is abiogenesis?

Answer 11

Aristotle’s theory that “living things arise from nonliving matter.”

Question 12

Describe Francesco Redi’s experiments.

Answer 12

Decaying meat:
1) Flask unsealed = maggots
- Meat exposed to flies = laid eggs = maggots

2) Flask sealed = no maggots
- Meat was kept isolated from flies, maggots
never developed

3) Flask covered with gauze = maggots

• Maggots didn’t arise from the meat itself but from fly eggs
• Scientists began to doubt Aristotle’s theory of abiogenesis

Question 13

Scientists agreed that large animals could not arise spontaneously, but believed ________ could.

Answer 13

Microbes

Question 14

How did John L. Needham’s experiments reinforce the idea of abiogenesis?

Answer 14

• Boiled (to kill the microorganisms) beef gravy and infusions of plant material in vials
• Tightly sealed vials with cork
• Some days later, microorganisms were detected in the infusions

Question 15

How did Lazzaro Spallanzani disprove Needham’s findings? What were his conclusions?

Answer 15

• Boiled infusions for 1 hour
• Sealed the vials airtight
• Infusions remained clear unless he broke the seal

Conclusions:
- Needham failed to heat vials sufficiently or had not sealed them tightly enough
- Microbes exist in air and can contaminate experiments
- Spontaneous generation of microbes does NOT occur; all living things arise from other living things

Question 16

Why did critics still not believe Spallanzani’s findings?

Answer 16

• Thought sealed vials did not allow enough air for organisms to survive, and
• Prolonged heating destroyed the “life force”

Question 17

How do “swan-necked” flasks work in creating a sterile environment?

Answer 17

• Allow air flow
• Dust particles or microbes stay in the tube part (“the bend of the neck”), not allowed into flask

Question 18

How did Louis Pasteur further prove abiogenesis is not possible?

Answer 18

• Experiments with swan-necked flasks
• Upright flasks = no microbial growth even after 18 months
• Tilted flask (“break the seal”) = dust from the bend seeped back into flask = cloudy infusion with microbes within a day

Question 19

Who discovered the cause of fermentation?

Answer 19

Louis Pasteur

Question 20

What was a problem in 19th century France?

Answer 20

Spoiled wine (was sour, acidic)
- Wine makers funded research to find cause (of fermentation and spoilage)

Question 21

What were the differing opinions of scientists for the cause of fermentation?

Answer 21

• Some believed it was air
• Some believed it was living organisms

Question 22

Describe Louis Pasteur’s experiments that showed the causes of wine spoilage and fermentation.

Answer 22

Flasks of grape juice, heated:
1) Flask sealed
- No fermentation, no microbes = abiogenesis NOT possible

2) Swan-necked flasks (open to air via curved neck)
- No fermentation, no microbes = air does NOT ferment grape juice

3) Flask inoculated with bacteria and sealed
- Bacteria reproduce; acids are produced = bacteria cause wine spoilage

4) Flask inoculated with yeast and sealed
- Yeasts reproduce; alcohol is produced = yeast causes fermentation (converts sugars to alcohol)

Question 23

What did Pasteur’s experiments lead to?

Answer 23

• Development of pasteurization
• Began the field of industrial microbiology (intentional use of microbes for manufacturing products like bread, cheese, etc.)

Question 24

What is pasteurization?

Answer 24

• Process of heating liquids just enough to kill most bacteria
• Increases shelf-life of product

Question 25

What did Eduard Buchner's experiments demonstrate?

Answer 25

- Demonstrated that fermentation does not require living cells - Showed enzymes promote chemical reactions (i.e. the microbe's enzymes cause fermentation) => This work began the field of biochemistry

Question 26

Who HYPOTHESIZED that microorganisms are responsible for causing diseases?

Answer 26

Louis Pasteur - "Germ Theory of Disease"

Question 27

What are pathogens?

Answer 27

Organisms that cause disease in a host.

Question 28

Who was the first to SHOW that bacteria can cause disease? Explain.

Answer 28

Robert Koch (studied etiology) - Animals suffering from anthrax => found rod-shaped bacteria (Bacillus anthracis) that produce endospores in blood - Injected endospore in mice => produced anthrax

Question 29

What is etiology?

Answer 29

The study of causative agents of disease.

Question 30

Describe Koch's 4 postulates.

Answer 30

1. Causative agent must be found in every case of disease and be absent from healthy hosts 2. Agent must be isolated and grown outside the host 3. When agent is introduced to healthy susceptible host, the host must get the disease 4. Same agent must be found in the diseased experimental host

Question 31

Describe some advances in laboratory microbiology that Robert Koch and his colleagues are known for.

Answer 31

- Simple staining techniques - First photomicrograph of bacteria - First photograph of bacteria in diseased tissue - Techniques for estimating bacterial number in a solution - Autoclaving (use of steam to sterilize growth media) - Use of Petri dishes - Bacterial transfer techniques - Bacteria as distinct species

Question 32

What is autoclaving?

Answer 32

Use of steam to sterilize growth media.

Question 33

Who recommended hand-washing for medical students?

Answer 33

Ignaz Semmelweis - Observed women giving birth where medical students were trained dying from puerperal fever (Streptococcus infection) - Medical students recommended to wash hands with chlorinated lime water

Question 34

Who invented antiseptic techniques?

Answer 34

Joseph Lister - Sprayed wounds, surgical incisions, and dressings with carbolic acid (phenol)

Question 35

Who founded the first school for nurses?

Answer 35

Florence Nightingale (Nightingale School for Nurses) - Introduced cleanliness and other antiseptic techniques into nursing practice

Question 36

What is epidemiology?

Answer 36

The study of the spread, frequency, and distribution of diseases. - When and where? - How are they transmitted?

Question 37

John Snow laid the foundation for epidemiology through his work with __________ cases.

Answer 37

Cholera - London epidemic in 1854 - Mapped occurrence of cholera cases => showed that they centered around a public water supply (water contaminated with sewage) - Infection control (set standard for good public hygiene to prevent spread of diseases)

Question 38

Who set the standard for good public hygiene to prevent spread of diseases?

Answer 38

John Snow

Question 39

Who coined the term "vaccination" or "vaccine?"

Answer 39

Edward Jenner (field of immunology) - Named after Vaccinia virus

Question 40

Edward Jenner found that inoculation of a boy with pus collected from a milkmaid's _______ lesion (mild disease) made the boy immune to the deadly ________ infection.

Answer 40

1) cowpox 2) smallpox - Intentionally infected the boy (introduced antigens to boost/prime immune system)

Question 41

Who discovered an arsenic-based chemical drug that was active against the causative agent of syphilis (Treponema pallidum)?

Answer 41

Paul Ehrlich (field of chemotherapy) - "Magic bullets" - Serious side effects in humans (arsenic = toxic)

Question 42

What is chemotherapy?

Answer 42

Development and use of drugs to treat infectious diseases.

Question 43

What 2 questions does the "Modern Age of Microbiology" focus on?

Answer 43

1. What are the basic chemical reactions of life? (biochemistry and microbial metabolism) - Design of herbicides and pesticides - Disease diagnosis and patients' responses to treatment - Treatment of metabolic diseases - Drug design 2. How do genes work? - Microbial genetics - Molecular biology - Recombinant DNA technology - Gene therapy

Question 44

What are the most diverse group of cellular microbes?

Answer 44

Prokaryotes - Thrive in various habitats - Exist in a variety of shapes (rods, spirals, etc.)

Question 45

What is the typical size of prokaryotic cells?

Answer 45

1.0 µm in diameter or smaller.

Question 46

Name 2 characteristics of prokaryotic cells.

Answer 46

- Lack a nucleus - Lack membrane-bound internal structures

Question 47

Which 2 domains are prokaryotic organisms divided into?

Answer 47

1. Bacteria 2. Archaea

Question 48

In prokaryotes, transcription (mRNA synthesis) and translation (protein synthesis) occur _____________.

Answer 48

Simultaneously

Question 49

What are some functions of bacterial cell walls?

Answer 49

- Provide structure, shape, and protection from osmotic forces - Assist in cell attachment - Can provide antimicrobial drug resistance

Question 50

What bacteria lack cell walls?

Answer 50

Mycoplasma

Question 51

What bacteria are considered the smallest free-living cells?

Answer 51

Mycoplasma - Often mistaken for viruses due to small size and lack of cell wall - Have most other features of prokaryotic cells

Question 52

What is the primary component of bacterial cell walls?

Answer 52

Peptidoglycan

Question 53

What is the structure of peptidoglycan?

Answer 53

- Polysaccharide made up of 2 different sugars (NAG & NAM) - Peptide chains cross-link the sugar chains (tetrapeptide crossbridge)

Question 54

How do Gram-positive and Gram-negative bacteria differ in their cell walls?

Answer 54

- Gram-positive bacteria have a thick peptidoglycan layer that contains unique chemicals (teichoic/lipoteichoic acids) - Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing phospholipids, proteins, and lipopolysaccharides (LPS)

Question 55

How do Gram-positive and Gram-negative stain? Why?

Answer 55

- Gram-positive = purple (retain colour even after washing with alcohol due to thicker layer of peptidoglycan) - Gram-negative = pink (lose purple dye after washing with alcohol, counterstain with pink dye)

Question 56

What is Lipid A in Gram-negative bacteria, and why is it significant?

Answer 56

- Lipid A is part of the LPS outer membrane - Endotoxin that can cause fever, vasodilation, inflammation, shock, and blood clotting

Question 57

What is the prokaryotic cytoplasmic (plasma) membrane referred to as? What is it composed of?

Answer 57

Phospholipid bilayer - Lipids - Integral proteins (embedded in lipid bilayer) - Peripheral proteins (outside, attached to lipid bilayer)

Question 58

What are glycocalyces, and what are the 2 types?

Answer 58

- Glyocalyces = gelatinous, sticky substance (polysaccharides, polypeptides, or both) that surrounds the outside of prokaryotic cells 1) Capsule = firmly attached to cell surface - Composed of organized repeating units of organic chemicals - Provides protection and aids in attachment 2) Slime Layer = loosely attached - Sticky, water-soluble layer - Aids in attachment

Question 59

What structure is responsible for movement of prokaryotic cells? Describe its function.

Answer 59

Flagella (structure varies depending on if Gram-positive or Gram-negative) - Rotation propels bacterium through environment - Rotation is reversible (counterclockwise or clockwise) - Bacteria moves in response to stimuli (taxis) => attracted to source of stimuli (e.g., food) or repelled from toxin

Question 60

What are the 3 main parts of bacterial flagella? Describe them.

Answer 60

1. Filament => outside the cell 2. Hook => attaches filament to basal body 3. Basal body => anchors flagella (filament + hook) to cell wall

Question 61

Name different types of flagella arrangements.

Answer 61

Arrangements are suited to bacterial environment: - Peritrichous (multiple flagella spread out all over bacterial cell) - Single polar (single flagellum found at one end of cell) - Tuft of polar (tuft of flagella extending from one end or both ends of cell)

Question 62

What family of bacteria have a unique flagellar structure and thus motion? Explain.

Answer 62

Spirochetes = Gram-negative spiral-shaped bacteria - Endoflagella form an axial filament - Corkscrew motion

Question 63

Spirochetes include bacteria that cause what diseases? Name the bacteria.

Answer 63

- Lyme disease => Borrelia burgdorferi - Syphilis => Treponema pallidum

Question 64

What are fimbriae?

Answer 64

External structure of prokaryotic cells: - Sticky, bristle-like projections (shorter than flagella) - Aid in bacterial adherence - Help form biofilms

Question 65

What are biofilms? What external structure serves an important function in biofilms?

Answer 65

- Biofilm = thin gelatinous layer (colony) of bacterial cells - Fimbriae serve important function

Question 66

What are (conjugation) pili?

Answer 66

- Special type of fimbriae (longer than fimbriae, but shorter than flagella) - Form conjugation channels (connections between bacteria) => transfer DNA from one cell to another during conjugation

Question 67

How many pili do bacteria typically have?

Answer 67

1-2 per cell

Question 68

Rank flagella, fimbriae, and pili from largest to smallest.

Answer 68

Flagella > pili > fimbriae

Question 69

What is the cytosol in prokaryotic cells? What does it contain?

Answer 69

- Liquid portion of cytoplasm - Contains cell's DNA in region called the nucleoid

Question 70

What is the nucleoid in prokaryotic cells? Where is it found?

Answer 70

- Nucleoid = region containing the prokaryotic cell's DNA - Found in the cytosol

Question 71

Name structures found in the cytoplasm of prokaryotic cells.

Answer 71

- Inclusions / Inclusion Bodies (may include reserve deposits of chemicals) - Ribosomes (polypeptides, rRNA) - Cytoskeleton (protein fibers like actins, tubulins)

Question 72

What are some roles of the cytoskeleton in the cell?

Answer 72

- Cell division - Cell shape - Segregate DNA molecules - Move through the environment

Question 73

What are endospores, and which bacteria form them?

Answer 73

Defensive structures formed (inside the cell) under unfavourable conditions by some Gram-positive bacteria, such as Bacillus and Clostridium.

Question 74

How do some bacteria form endospores?

Answer 74

1. DNA is replicated (new copy of DNA) 2. Instead of going through mitosis, invaginate to synthesize membrane around new DNA (forespore) 3. Cytoplasmic membrane grows and engulfs forespore within a second membrane 4. Vegetative cell's DNA disintegrates 5. Cortex of peptidoglycan is deposited between the 2 endospore membranes, and chemicals accumulate within endospore 6. A spore coat forms around the endospore (protects from harsh conditions) 7. Endospore matures and is released from original cell 8. Under favourable conditions, each endospore germinates to form a vegetative cell

Question 75

Why are endospores significant to healthcare and food safety?

Answer 75

- Resistant to extreme conditions like heat, radiation, and chemicals - Don't divide/grow (challenge for treating diseases)

Question 76

How many membranes does an endospore have? In addition, what other structure does it have that aids in its protection?

Answer 76

2 membranes and a spore coat.

Question 77

Name some shapes prokaryotic cells can take.

Answer 77

- Coccus - Coccobacillus - Bacillus (rod-shaped) - Vibrio ("V" shape) - Spirillum - Spirochete - Pleomorphic (many different structures) - Star

Question 78

What are the 3 main methods of asexual reproduction in prokaryotic cells? Briefly describe them.

Answer 78

1. Binary fission => cell replicating DNA and splits into 2 daughter cells 2. Snapping division => part of vegetative cell breaks off and becomes new bacterial cell 3. Budding => new genetic material forms cytoplasm + membrane, outgrows from parent cell

Question 79

What is the most common method of reproduction in prokaryotes?

Answer 79

Binary fission

Question 80

What unique reproduction method is found in Epulopiscium?

Answer 80

Viviparity – live offspring emerge from the body of the dead mother cell (first noted case of viviparous behaviour in prokaryotic world).

Question 81

What is the largest known bacteria, that is also NOT pathogenic.

Answer 81

Epulopiscium

Question 82

Arrangements of prokaryotic cells are a result of...?

Answer 82

- Planes of cell division - Separation of daughter cells

Question 83

Modern prokaryotic classification is based on genetic relatedness of _____ sequences.

Answer 83

rRNA (conserved, don't change)

Question 84

What domain of prokaryotes are NOT known to cause disease?

Answer 84

Archaea

Question 85

Describe some characteristics of archaea.

Answer 85

- Lack true peptidoglycan - Cell membrane lipids have branched hydrocarbon chains - Reproduce by binary fission, budding, or fragmentation - Are cocci, bacilli, spirals, or pleomorphic - Include extremophiles (thermophiles, acidophiles, halophiles)

Question 86

What is the largest group of archaea?

Answer 86

Methanogens => convert CO2, H2, and organic acids to methane gas (CH4)

Question 87

What are deeply branching bacteria, and where are they found?

Answer 87

- Autotrophic (synthesize their own nutrients) bacteria similar to the earliest bacteria - Live in habitats similar to those that existed on early Earth

Question 88

Give 2 examples of deeply branching bacteria.

Answer 88

- Aquifex - Deinococcus

Question 89

What bacteria is considered to represent earliest branch of bacteria?

Answer 89

Aquifex

Question 90

What bacteria has an outer membrane similar to Gram-negatives, BUT stains Gram-positive?

Answer 90

Deinococcus

Question 91

What do phototrophic bacteria contain?

Answer 91

Photosynthetic lamellae that contain different pigments.

Question 92

What are the 5 groups of phototrophic bacteria? What are the divisions based on?

Answer 92

Divided based on pigments and source of electron for photosynthesis (most are autotrophic): 1. Cyanobacteria (blue-green bacteria) 2. Green sulfur bacteria 3. Green non-sulfur bacteria 4. Purple sulfur bacteria 5. Purple non-sulfur bacteria

Question 93

What are low G+C Gram-positive bacteria?

Answer 93

Gram-positive bacteria with less than 50% G+C content in their genome.

Question 94

What phylum are low G+C Gram-positive bacteria classified in? What groups are included?

Answer 94

Firmicutes phylum - 3 groups: 1. Clostridia 2. Mycoplasmas 3. Other low G+C Gram-positive bacilli and cocci

Question 95

Name some low G+C Gram-positive bacteria.

Answer 95

- Clostridium tetani - Clostridium perfringens - Clostridium difficile - Mycoplasma - Bacillus anthracis - Bacillus thuringiensis - Bacillus polymyxa - Bacillus lichenifomis - Listeria (monocytogenes) - Lactobacillus - Streptococcus - Enterococcus - Staphylococcus (aureus)

Question 96

Describe characteristics of Clostridia low G+C Gram-positive bacteria.

Answer 96

- Rod-shaped - Obligate anaerobes - Many form endospores

Question 97

Which bacteria is associated with tetanus?

Answer 97

Clostridium tetani

Question 98

Which bacteria is associated with gas gangrene?

Answer 98

Clostridium perfringens (causes gas to form in soft tissues, leads to amputation)

Question 99

Clostridium difficile is associated with _________.

Answer 99

Diarrhea (C. difficile thrives when gut microbiome is disrupted)

Question 100

What microbes are related to Clostridium?

Answer 100

- Epulopiscium - Sulfate-reducing microbes - Selenomonas (live as part of biofilm/plaque that forms on teeth)

Question 101

What is the appearance of Mycoplasma colonies described as?

Answer 101

"Fried egg"

Question 102

What diseases do some species of Mycoplasma cause?

Answer 102

- Pneumonia - Urinary tract infections

Question 103

Describe some characteristics of Mycoplasma low G+C Gram-positive bacteria.

Answer 103

- Facultative or obligate anaerobes - Lack cell walls - Smallest free-living cells - Colonize mucous membranes of the respiratory and urinary tracts

Question 104

What do Mycoplasma colonize?

Answer 104

Mucous membranes of the respiratory and urinary tracts.

Question 105

Describe characteristics of Bacillus low G+C Gram-positive bacteria.

Answer 105

- Many are common in soil - Form endospores - Some members cause human and animal disease

Question 106

What bacteria causes anthrax (inhalation and cutaneous types)?

Answer 106

Bacillus anthracis

Question 107

What bacteria is used by farmers and gardeners as an insecticide (its toxin is)?

Answer 107

Bacillus thuringiensis

Question 108

Bacitracin antibiotic is produced by what bacteria?

Answer 108

Bacillus lichenifomis

Question 109

Bacillus polymyxa produces what antibiotic?

Answer 109

Polymyxin

Question 110

Describe some characteristics of Listeria (monocytogenes) low G+C Gram-positive bacteria.

Answer 110

- Rod-shaped - Contaminates milk and meat products - Capable of reproducing under refrigeration

Question 111

What conditions are caused by Listeria monocytogenes?

Answer 111

- Can cross placenta in pregnant women and infect the fetus - Meningitis and bacteremia in immunocompromised individuals

Question 112

Describe some characteristics of Lactobacillus low G+C Gram-positive bacteria.

Answer 112

- Grows in the body, but rarely causes disease - Used in the production of various foods (yogurt, buttermilk, pickles, etc.) - Used as a probiotic

Question 113

What diseases do Streptococcus and Enterococcus cause?

Answer 113

- Pharyngitis - Scarlet fever - Impetigo - Fetal meningitis - Pneumonia - Wound infections

Question 114

There are various strains of multi-drug-resistant _____________.

Answer 114

Streptococci

Question 115

What bacteria is one of the most common inhabitants of humans?

Answer 115

Staphylococcus - Produces toxins and enzymes that contribute to disease

Question 116

What diseases does Staphylococcus aureus cause?

Answer 116

Invades the body and causes diseases such as: - Bacteremia - Food poisoning - Toxic shock syndrome - Pneumonia - Wound infections

Question 117

_________________ is resistant to antimicrobial drugs (penicillin and cephalosporin).

Answer 117

Methicillin-resistant Staphylococcus aureus (MRSA)

Question 118

Name some high G+C Gram-positive bacteria.

Answer 118

- Corynebacterium (diphtheriae) - Mycobacterium tuberculosis - Mycobacterium leprae - Actinomycetes (Actinomyces, Nocardia, Streptomyces)

Question 119

Describe Corynebacterium high G+C Gram-positive bacteria. Name one that causes a disease.

Answer 119

- Pleomorphic aerobes and facultative anaerobes - Corynebacterium diphtheriae causes diphtheria

Question 120

Describe characteristics of Mycobacterium high G+C Gram-positive bacteria.

Answer 120

- Aerobic rods that sometimes form filaments - Slow-growing (often require months to show a visible colony on agar growth medium) - Cell wall contains mycolic acid (long carbon-chain) - Acid-fast bacilli (AFB) => stain with acid-fast stains such as the Ziehl-Neelsen stain

Question 121

What bacteria causes tuberculosis?

Answer 121

Mycobacterium tuberculosis

Question 122

What bacteria causes Hansen's disease (leprosy)?

Answer 122

Mycobacterium leprae

Question 123

Describe Actinomycetes high G+C Gram-positive bacteria, naming the important genera.

Answer 123

Form branching filaments resembling fungi: - Actinomyces => some species are opportunistic pathogens - Nocardia - Streptomyces

Question 124

What high G+C Gram-positive bacteria can degrade many pollutants?

Answer 124

- Nocardia (can degrade waxes, petroleum, hydrocarbons, detergents, etc.) - Part of Actinomycetes

Question 125

______________ species produce important antibiotics (chloramphenicol, erythromycin, tetracycline).

Answer 125

Streptomyces

Question 126

What is the largest and most diverse group of bacteria?

Answer 126

Gram-negative proteobacteria

Question 127

Name the 6 classes of Gram-negative proteobacteria.

Answer 127

1. Alphaproteobacteria 2. Betaproteobacteria 3. Gammaproteobacteria 4. Deltaproteobacteria 5. Epsilonproteobacteria 6. Zetaproteobacteria

Question 128

Name some alphaproteobacteria.

Answer 128

- Rickettsia - Brucella

Question 129

Describe characteristics of Rickettsia Gram-negative bacteria.

Answer 129

- Alphaproteobacteria - Aerobic rods that live and reproduce inside mammalian cells (intracellular pathogen) - Transmitted through bite of an arthropod (vectors of disease)

Question 130

What human diseases do Rickettsia alphaproteobacteria cause?

Answer 130

- Typhus - Rocky Mountain spotted fever

Question 131

What is an obligate intracellular pathogen? Give examples.

Answer 131

- Pathogen that has to infect a host organism’s cells in order to reproduce and survive - Examples: Viruses, Rickettsia alphaproteobacteria

Question 132

Describe Brucella alphaproteobacteria and diseases it causes.

Answer 132

- Can survive phagocytosis by WBCs - Causes brucellosis in humans (characterized by chills, sweating, fatigue, and fever) - In animals it causes spontaneous abortions and sterility

Question 133

What bacteria causes brucellosis in humans? What are the symptoms?

Answer 133

- Brucella - Symptoms: chills, sweating, fatigue, and fever

Question 134

Name some betaproteobacteria.

Answer 134

- Neisseria (gonorrhoeae) => diplococci that inhabit mucous membranes - Bordetella (pertussis) - Burkholderia

Question 135

What bacteria causes gonorrhea?

Answer 135

Neisseria gonorrhoeae

Question 136

What bacteria causes whooping cough (pertussis)?

Answer 136

Bordetella pertussis

Question 137

What bacteria colonizes moist environmental surfaces, and thus is found in respiratory passages of cystic fibrosis patients?

Answer 137

Burkholderia - Respiratory tract produces extra fluid/mucus in CF patients (genetic mutation) = creates ideal conditions for bacteria to grow/infect

Question 138

What is the largest and most diverse class of proteobacteria? Name its 5 subgroups.

Answer 138

Gammaproteobacteria: 1. Intracellular pathogens => thrive inside phagolysosomes in WBCs (acidic pH) 2. Glycolytic facultative anaerobes 3. Pseudomonads 4. Purple sulfur bacteria 5. Methane oxidizers

Question 139

Name some intracellular pathogenic gammaproteobacteria.

Answer 139

- Legionella - Coxiella

Question 140

Name the 3 families of glycolytic facultative anaerobes (gammaproteobacteria), and the bacteria they include.

Answer 140

1. Enterobacteriaceae (Escherichia, Salmonella, Proteus, Shigella, Yersinia, Klebsiella) 2. Vibrionaceae (Vibrio) 3. Pasteurellaceae (Haemophilus)

Question 141

What bacteria causes Legionnaires' disease?

Answer 141

Legionella (intracellular pathogenic gammaproteobacteria)

Question 142

What bacteria causes Q fever?

Answer 142

Coxiella (intracellular pathogenic gammaproteobacteria)

Question 143

What do Escherichia gammaproteobacteria cause?

Answer 143

Gastroenteritis

Question 144

What do Salmonella gammaproteobacteria cause?

Answer 144

Typhoid (Salmonella typhi)

Question 145

What do Proteus gammaproteobacteria cause?

Answer 145

UTI (urinary tract infection)

Question 146

What do Shigella gammaproteobacteria cause?

Answer 146

Shigellosis

Question 147

What do Yersinia gammaproteobacteria cause?

Answer 147

Plague (Yersinia pestis)

Question 148

What do Klebsiella gammaproteobacteria cause?

Answer 148

Pneumonia

Question 149

What do Vibrio gammaproteobacteria cause?

Answer 149

Cholera (Vibrio cholerae)

Question 150

What do Haemophilus gammaproteobacteria cause?

Answer 150

- Meningitis - Middle ear infections - Pneumonia

Question 151

What do Pseudomonads (gammaproteobacteria) cause?

Answer 151

Urinary tract, ear, lung, infections (important pathogens of humans and animals) - Often in burn patients

Question 152

What is the significance of Pseudomonads in healthcare?

Answer 152

They often cause infections in burn patients (because their skin is compromised).

Question 153

Name some deltaproteobacteria (wide variety of metabolic types).

Answer 153

- Desulfovibrio - Bdellovibrio - Myxobacteria

Question 154

Describe Bdellovibrio bacteria.

Answer 154

- Gram-negative deltaproteobacteria - Single flagella - Pathogen of other Gram-negative bacteria - Lives in periplasmic space (b/n cytoplasm and cell wall) => induces death

Question 155

Describe epilsonproteobacteria. Give examples of some.

Answer 155

Gram-negative rods, vibrios, or spirals: - Campylobacter jejuni - Helicobacter pylori

Question 156

What bacteria causes gastroenteritis?

Answer 156

Camplyobacter jejuni (epilsonproteobacteria)

Question 157

What bacteria causes peptic ulcer disease?

Answer 157

Helicobacter pylori (epilsonproteobacteria)

Question 158

Describe zetaproteobacteria.

Answer 158

- First discovered based on DNA sequences (DNA is common in oceans) - Only 2 organisms have been cultured - Mariprofundus ferroxydans is the only species to be formally named

Question 159

Only 2 organisms have been cultured of ___________________.

Answer 159

Zetaproteobacteria

Question 160

________________ is the only species to be formally named of zetaproteobacteria.

Answer 160

Mariprofundus ferroxydans

Question 161

Name other Gram-negative bacteria aside from the proteobacteria.

Answer 161

- Chlamydias - Spirochetes (Treponema pallidum, Borrelia burgdorferi) - Bacteroides

Question 162

What Gram-negative bacteria causes syphilis?

Answer 162

Treponema pallidum

Question 163

What Gram-negative bacteria causes Lyme disease?

Answer 163

Borrelia burgdorferi

Question 164

Describe Chlamydia bacteria.

Answer 164

- Gram-negative - Grow intracellularly in mammals, birds, and some invertebrates - Some are smaller than viruses (0.2 µm in diameter) - Most common sexually transmitted bacteria in the US

Question 165

What is the most common sexually transmitted bacteria in the US?

Answer 165

Chlamydia bacteria

Question 166

Describe Bacteroides and the diseases/symptoms they can cause.

Answer 166

- Gram-negative bacteria - Inhabit skin & digestive tracts of humans and animals - Non-pathogenic normally, but opportunistic (become pathogenic if person becomes immunocompromised) - Some species cause infections => diarrhea, fever, foul-smelling lesions, gas, and pain

Question 167

Describe characteristics of eukaryotic cells.

Answer 167

- Have nucleus - Have internal membrane-bound organelles - 10-100µm in diameter - May have cell wall (e.g., plants), cilium, or flagella (structurally different from prokaryotes)

Question 168

What eukaryotes have a cell wall?

Answer 168

- Fungi - Algae - Plants - Some protozoa

Question 169

Plant cell walls are made of...?

Answer 169

Cellulose

Question 170

Fungal cell walls are composed of...?

Answer 170

- Cellulose - Chitin (most abundant polymer in nature) - and/or Glucomannan

Question 171

Algal cell walls are composed of a variety of _______________.

Answer 171

Polysaccharides

Question 172

All eukaryotic cells have _____________________.

Answer 172

Cytoplasmic membranes

Question 173

Describe eukaryotic cytoplasmic membranes.

Answer 173

- Fluid mosaic of phospholipids + proteins - Steroid lipids help maintain fluidity - Contain membrane rafts = regions of lipids & proteins - Selectively permeable (control movement into and out of cell)

Question 174

Describe eukaryotic flagella.

Answer 174

- Shaft composed of tubulin => arranged to form MTs within cell membrane - Filaments anchored to cell by basal body - Single or multiple; generally found at one pole of cell - Undulate rhythmically to propel the cell in their environment (DON'T ROTATE)

Question 175

Describe the structure (MT arrangement) of eukaryotic flagella.

Answer 175

- Cell membrane extends over entire length - 9+2 MT arrangement (9 doublets outside, 2 central) - Basal body has 9+0 MT arrangement (9 triplets)

Question 176

Describe reproduction in eukaryotic cells.

Answer 176

- Requires division of nucleus and cytoplasm - Sexual (gametes + zygotes formed) or asexual (cell dividing into 2 daughter cells) - Algae, fungi, and some protozoa reproduce both sexually and asexually

Question 177

What are the 2 types of nuclear division in eukaryotes?

Answer 177

Nucleus contains genetic material (has to be replicated to create copy of genome): 1. Mitosis => partitions replicated DNA equally between 2 nuclei 2. Meiosis => partitions chromatids into 4 nuclei (gametes)

Question 178

Describe cytokinesis in eukaryotes.

Answer 178

Cytokinesis = cytoplasmic division: - Different types (formation of a cell plate, formation of a partition furrow, or budding) - In some algae and fungi, postponed or does not occur at all, resulting in multinucleated cells called coenocytes

Question 179

What are the different types of cytokinesis in eukaryotes?

Answer 179

1. Formation of a cell plate 2. Formation of a partition/cleavage furrow 3. Budding => yeast (fungi) - Bud grows inside, separates from parent to become daughter cell

Question 180

What does postponed or skipped cytokinesis result in? What eukaryotes does this happen in?

Answer 180

- Result in multinucleated cells called coenocytes - In some algae and fungi

Question 181

How were eukaryotic organisms classified? How are they classified now?

Answer 181

- Early: grouped organisms based on structural similarities - Modern: based on similarities in nucleotide sequences (genetic relatedness)

Question 182

What are the 5 eukaryotic microorganisms?

Answer 182

1. Protozoa 2. Fungi 3. Algae 4. Slime molds 5. Water molds => Include both human pathogens and organisms vital for human life

Question 183

Describe characteristics of protozoa.

Answer 183

- Unicellular eukaryotic cells - Lack cell wall - Motile (cilia, flagella, and/or pseudopods) - Great morphological diversity - Different stages in life cycle (trophozoite, cyst) - Require moist environments - Most are chemoheterotrophic - Very few are pathogens

Question 184

Protozoa are ______________trophic, meaning...?

Answer 184

- Chemoheterotrophic - Obtain nutrients by phagocytizing bacteria, decaying organic matter, other protozoa, or the host tissues

Question 185

What are 2 life stages of a protozoa?

Answer 185

1. Trophozoite => motile feeding stage 2. Cyst => resting stage (more resistant to harsh conditions)

Question 186

Name some pathogenic protozoa.

Answer 186

Mostly infect immunocompromised individuals (e.g., people infected with HIV): - Trichomonas => STDs - Giardia => GI infection - Trypanosoma => sleeping sickness - Leishmania => cutaneous leishmaniasis - Plasmodium => malaria - Cryptosporidium => GI infection - Toxoplasma => toxaplasmosis - Entamoeba => GI infection

Question 187

What type of microbe is Trichomonas? What diseases does it cause?

Answer 187

- Protozoa - Sexually transmitted diseases (STDs)

Question 188

What protozoa cause gastrointestinal infection?

Answer 188

- Giardia - Cryptosporidium - Entamoeba

Question 189

What microbe causes toxoplasmosis?

Answer 189

Toxoplasma (protozoa)

Question 190

What microbe causes malaria?

Answer 190

Plasmodium (protozoa)

Question 191

What microbe causes sleeping sickness?

Answer 191

Trypanosoma (protozoa)

Question 192

Leishmania, a _____________, causes ________________.

Answer 192

- Protozoa - Cutaneous leishmaniasis

Question 193

Describe characteristics of fungi.

Answer 193

- Chemoheterotrophic - Cell walls typically composed of chitin - Include yeasts (unicellular), molds, mushrooms - Some fungi are dimorphic => produce both yeast-like and mold-like shapes in response to environmental conditions

Question 194

Some fungi are dimorphic, meaning...?

Answer 194

Produce both yeast-like and mold-like shapes in response to environmental conditions.

Question 195

What are the 2 basic morphologies of fungi? Describe them.

Answer 195

1. Molds => composed of long filaments called hyphae - Septate hyphae = multiple cells separated by walls/septa - Aseptate hyphae = one large cell containing multiple nuclei 2. Yeasts => small, globular, and composed of a single cell

Question 196

Describe reproduction in fungi; are they asexual or sexual?

Answer 196

- All have some means of asexual reproduction (involve mitosis + cytokinesis) - Most also reproduce sexually (form gametes => have 1/2 the genetic material from parent and fuse to form diploid organism)

Question 197

What is the significance of fungi?

Answer 197

- Decompose dead organisms and recycle their nutrients - Help plants absorb water and minerals - Used in manufacture of foods/beverages - Produce antibiotics (e.g., penicillin) and other drugs - Serve as important research tools (e.g., yeast in genetics) - Can spoil fruit, pickles, jams, and jellies - 30% cause diseases of plants, animals, and humans

Question 198

___% of fungi cause diseases of plants, animals, and humans.

Answer 198

30%

Question 199

__________ are diseases caused by fungi.

Answer 199

Mycoses

Question 200

What is dermatophytosis?

Answer 200

Infection of the skin by fungi (e.g., Athlete's foot, ringworm).

Question 201

What fungi cause dermatophytosis?

Answer 201

- Trichophyton - Microsporum - Epidermophyton floccosum

Question 202

__________ causes infection of the mucous membranes? What disease does it cause specifically?

Answer 202

- Candida albicans (opportunistic pathogen) - Candidiasis, yeast infections

Question 203

What fungi cause respiratory tract infections? What diseases do they specifically cause?

Answer 203

- Coccidioides => coccidioidomycosis - Blastomyces dermatitidis => blastomycosis - Histoplasma capsulatum => histoplasmosis - Pneumocytis jirovecii => pneumonia

Question 204

What microbe causes histoplasmosis?

Answer 204

Histoplasma capsulatum (fungi)

Question 205

What fungi causes pneumonia?

Answer 205

Pneumocytis jirovecii

Question 206

Describe characteristics of algae.

Answer 206

- Photoautotrophs - Non-pathogenic - Differ widely in distribution, morphology, reproduction, and biochemical traits - Most are aquatic (live in the photic zone of fresh, brackish, and salt bodies of water)

Question 207

What are the different morphologies of algae?

Answer 207

- Unicellular - Colonial - Simple multicellular bodies

Question 208

Describe reproduction in unicellular and multicellular algae.

Answer 208

Unicellular: - Asexually (mitosis + cytokinesis) - Sexually (gametes form zygotes that undergo meiosis) Multicellular: - Asexually (fragmentation => part of the body/organ can break away) - Sexually with alternation of generations

Question 209

What are helminths? Why are they of microbiological interest?

Answer 209

- Helminths = parasitic worms - Have infective microscopic/diagnostic stages (e.g., eggs/larvae) that occur in samples of blood, urine, and feces

Question 210

What are vectors? What are the 2 types?

Answer 210

Vectors = animals that carry pathogens: 1. Mechanical vectors => carry pathogen without being infected (physical transport/transmission) 2. Biological vectors => infected, pathogen completes part of their life cycle

Question 211

What 2 classes of arthropods are disease vectors? Describe them and give examples.

Answer 211

1. Arachnida - Archanids have 4 pairs of legs - Ticks, some mites 2. Insecta - Adult insects have 3 pairs of legs and 3 body regions - Fleas, lice, flies, and mosquitoes

Question 212

What are the most important arthropod vectors vectors of disease?

Answer 212

Mosquitoes (carry viruses and protozoan diseases like malaria)

Question 213

Describe characteristics of viruses.

Answer 213

- Minuscule (need electron microscope to view) - Acellular - Exist in extracellular and intracellular states - Contain either DNA or RNA (never both) - Cause infections in humans, animals, plants, and bacteria - Do not carry out metabolic pathways - Do not reproduce independently - Use the host cell’s metabolic pathways for replication

Question 214

Why are viruses considered obligate intracellular pathogens/parasites?

Answer 214

To survive, need to infect host cell and use its machinery to replicate and produce new virus progeny.

Question 215

Describe the extracellular and intracellular states of viruses.

Answer 215

- Extracellular: virions (don't grow/reproduce) composed of capsid, nucleocapsid, envelope, and nucleic acid - Intracellular: viral nucleic acid (capsid falls apart)

Question 216

What are the components of a virion?

Answer 216

- Capsid - Nucleic acid (DNA or RNA) - Envelope (in some cases)

Question 217

What are viruses without an envelope called?

Answer 217

Naked viruses

Question 218

What is one of the largest viruses?

Answer 218

Smallpox virus (even larger than some bacteria, like Chlamydia)

Question 219

Describe the viral genome.

Answer 219

- DNA or RNA (never both) - Single-stranded (ss) or double-stranded (ds) - ssRNA viruses can be (+) or (-) - Can be linear and segmented, or single and circular - Genomes are much smaller than those of cells (depend on host cell for most of their metabolic processes => only need genes for capsid proteins, enzymes, etc.)

Question 220

Viruses are classified based on their...?

Answer 220

Genome (DNA viruses or RNA viruses)

Question 221

What virus infects the tobacco plant?

Answer 221

Tobacco mosaic virus

Question 222

Most viruses infect only a particular host's cells: what determines what host a virus infects?

Answer 222

- Affinity of viral surface proteins for complementary proteins on host cell surfaces - Some viruses can only infect a particular kind of cell in a host (e.g., neurotropic virus only infects neurons) - Some viruses can infect many kinds of cells or many different hosts

Question 223

What is the structure/function of a viral capsid?

Answer 223

- Houses and protects viral nucleic acid - Helps determine the shape of the virion - Composed of protein subunits called capsomeres (made of single or multiple protein types) - Facilitates attachment and entry in non-enveloped viruses

Question 224

What are the 3 basic viral shapes?

Answer 224

1. Helical => "rod structure" (e.g., tobacco mosaic virus) 2. Polyhedral 3. Complex => "bullet" (e.g., rabies virus)

Question 225

How do viruses acquire an envelope, and what is its composition?

Answer 225

- Acquired from the host cell membrane during replication or release (e.g., through budding) - Composed of phospholipid bilayer and proteins - Some proteins are virally coded glycoproteins (spikes)

Question 226

What is the role of the viral envelope?

Answer 226

Envelope proteins/glycoproteins help in host recognition, binding, and entry.

Question 227

Are enveloped or naked viruses more fragile?

Answer 227

Enveloped viruses (e.g., wash with soap detergent = become vulnerable and lose infectivity)

Question 228

What is virus classification based on?

Answer 228

1. Type of nucleic acid 2. Presence of an envelope 3. Shape and size - Viral genera have only been organized into families

Question 229

What is the difference between positive-sense and negative-sense RNA viruses?

Answer 229

- +ssRNA = similar to mRNA; can be directly translated into proteins - -ssRNA = complementary to mRNA; must be converted to +ssRNA before translation

Question 230

Why are viruses dependent on host cells for replication?

Answer 230

They lack organelles and enzymes necessary for independent reproduction.

Question 231

Viral replication usually results in ____________ of host cell.

Answer 231

Death & lysis

Question 232

What are the 5 stages of viral replication?

Answer 232

1. Attachment 2. Entry (capsid disassembles) 3. Synthesis 4. Assembly 5. Release

Question 233

How do animal viruses attach to host cells?

Answer 233

- Via chemical attraction between viral proteins (capsid/spike) and cell receptors = recognition - Use glycoprotein spikes or other molecules (co-receptors) for attachment

Question 234

After viral attachment to host cell, what allows for its entry?

Answer 234

Change in host cell's membrane structure upon attachment allows for entry.

Question 235

What are the 3 main entry mechanisms for animal viruses? Describe them.

Answer 235

1. Direct penetration - Viral proteins attach to host receptors - Viral genome is released from capsid into host cell 2. Membrane fusion - Spikes attach to host receptors - Envelope fuses with host cell membrane - Virus enters host cell and disassembles its capsid 3. Endocytosis - Spikes attach to host receptors - Host cell membrane engulfs virus - Virus enters cell in endosome - After entry, virus leaves endosome and disassembles its capsid

Question 236

How does viral genome synthesis differ for DNA and RNA viruses?

Answer 236

- DNA viruses => replicate in the nucleus - RNA viruses => replicate in the cytoplasm

Question 237

Describe synthesis of dsDNA viruses.

Answer 237

Viral genome synthesis: - Each strand of DNA acts as a template for its complementary DNA strand Viral protein synthesis: - mRNA is synthesized by the host RNA polymerase - Viral proteins are made in the cytoplasm

Question 238

What dsDNA virus is synthesized differently (an exception)?

Answer 238

Hepatitis B viruses - Replicate DNA from an RNA intermediary (DNA => RNA => DNA) - Reverse transcription

Question 239

What are viruses with ssDNA genomes called?

Answer 239

Parvoviruses

Question 240

Describe synthesis of ssDNA viruses.

Answer 240

- DNA strand folds back on itself (regions that have complementary base pairs) to form dsDNA - That dsDNA is then replicated by cellular DNA polymerase - Newly replicated strand is released as ssDNA

Question 241

What are the 4 types of RNA viruses?

Answer 241

- +ssRNA - Retroviruses (+ssRNA) - -ssRNA - dsRNA

Question 242

Retroviruses are a type of _______ virus.

Answer 242

+ssRNA

Question 243

What type of viruses convert their RNA to DNA through reverse transcription?

Answer 243

Retroviruses

Question 244

For RNA viruses, replication of RNA genome is often performed by what viral enzymes?

Answer 244

- RNA-dependent RNA polymerase (host cells don't replicate RNA) - Reverse transcriptase / RNA-dependent DNA polymerase (converts RNA => DNA)

Question 245

Describe synthesis of +ssRNA viruses.

Answer 245

Viral genome synthesis: - Transcription of complementary -ssRNA by viral RNA polymerase - Further transcription: -ssRNA acts as template to create copies of +ssRNA Viral protein synthesis: - +ssRNA acts as mRNA => directly translated

Question 246

Describe synthesis of -ssRNA viruses.

Answer 246

Viral genome synthesis: - Transcription of complementary +ssRNA by viral RNA polymerase - Further transcription: +ssRNA acts as template to create copies of -ssRNA Viral protein synthesis: - Transcribed +ssRNA also acts as mRNA => directly translated

Question 247

Describe synthesis of dsRNA viruses.

Answer 247

Viral genome synthesis: - Unwinding of dsRNA into -ssRNA and +ssRNA strands - Transcription of complementary -ssRNA/+ssRNA strands by viral RNA polymerase - Newly transcribed strands synthesized into dsRNA Viral protein synthesis: - Transcribed +ssRNA also acts as mRNA => directly translated

Question 248

What enzyme do retroviruses use for replication?

Answer 248

Reverse transcriptase (RNA-dependent DNA polymerase)

Question 249

What is an example of an retrovirus?

Answer 249

HIV

Question 250

Describe retrovirus synthesis.

Answer 250

Viral genome synthesis: - In the cytoplasm, reverse transcriptase converts the viral +ssRNA into viral DNA - Viral DNA transports into the nucleus and integrates into the host genome - Host genome is transcribed, creating new viral +ssRNA Viral protein synthesis: - The newly transcribed viral +ssRNA acts as mRNA => directly translated

Question 251

Where do DNA and RNA viruses assemble?

Answer 251

- DNA viruses = in the nucleus - RNA viruses = in the cytoplasm

Question 252

How do naked vs. enveloped viruses get released from host cells?

Answer 252

- Naked viruses => released by exocytosis or lysis (lysis kills infected cell) - Enveloped viruses => released by budding to acquire part of host membrane (does NOT kill the cell)

Question 253

Why do enveloped viruses cause persistent infections?

Answer 253

Enveloped viruses are more persistent because they do not kill the host cell upon release (budding).

Question 254

What determines the number of viruses produced in a host cell?

Answer 254

- Type of virus - Virus size - Initial health of host cell

Question 255

What is viral latency?

Answer 255

Period from the time virus infects and till symptoms show.

Question 256

Describe latency of animal viruses.

Answer 256

- When animal viruses remain dormant in host cells (proviruses) - May be prolonged for years with no viral activity (e.g., HIV develops into AIDS) - Incorporation of provirus into host DNA is permanent

Question 257

What are proviruses or latent viruses?

Answer 257

- Viruses that remain dormant in host cells - Viral genome becomes integrated into host DNA (provirus e.g., HIV)

Question 258

How do viruses contribute to cancer (neoplasia, uncontrolled cell division) development?

Answer 258

- Activation of oncogenes (promote cell division) - Inactivation of tumour suppressor genes (normally repress cell division) - Some viruses carry oncogenes or promote existing ones in hosts

Question 259

______% of human cancers are associated with virus infections.

Answer 259

20-25%

Question 260

Which human cancers are associated with viruses?

Answer 260

- Burkitt’s lymphoma: Epstein-Barr Virus (EBV) - Hodgkin’s disease: Epstein-Barr Virus (EBV) - Kaposi’s sarcoma: Kaposi sarcoma-associated herpesvirus - Cervical cancer: Human papilloma virus (HPV) - Liver cancer: Hepatitis B (causes cirrhosis of liver)

Question 261

What cancers is Epstein-Barr Virus (EBV) associated with?

Answer 261

- Burkitt's lymphoma - Hodgkin's disease

Question 262

Kaposi's sarcoma can be caused by what virus?

Answer 262

Kaposi sarcoma-associated herpesvirus

Question 263

Cervical cancer can be caused by what virus?

Answer 263

Human papilloma virus (HPV)

Question 264

Why can’t viruses be grown in standard microbiological media?

Answer 264

Viruses require a host cell to replicate and produce new virions (need cell system).

Question 265

What are the 3 types of media used for culturing animal viruses?

Answer 265

1. Mature organisms (ethical concerns, expensive to maintain) 2. Embryonated eggs (inexpensive, sterile, nutrient-rich medium) 3. Cell cultures (continuous, inexpensive and easy to maintain)

Question 266

Why are embryonated eggs (e.g., fertilized chicken eggs) used for culturing animal viruses?

Answer 266

- Embryonic tissues provide ideal site for growing vaccines - Inexpensive, sterile, nutrient-rich medium

Question 267

What are viroids? Describe their characteristics.

Answer 267

- Extremely small, circular pieces of ssRNA - Lack a capsid - Do NOT code for proteins - Infectious and pathogenic in plants (adhere to complementary plant RNA => plant enzyme degrades dsRNA, resulting in disease state)

Question 268

How are viroids pathogenic in plants?

Answer 268

1) Viroid (ssRNA) adheres to complementary plant RNA 2) Plant enzyme degrades the dsRNA 3) Results in disease state

Question 269

What are prions?

Answer 269

- Proteinaceous infectious agents - Do NOT contain nucleic acids (no genome) - Cause disease by misfolding normal cellular PrP into prion PrP

Question 270

What is the difference between cellular prions and pathogenic prions?

Answer 270

Cellular (c-PrP): - Has alpha-helices Pathogenic (p-PrP): - Has beta-pleated sheets

Question 271

What organisms make cellular prions? What is thought to be their function?

Answer 271

- c-PrP made by all mammals - Function not well-understood but thought to be involved in normal synaptic development/function

Question 272

How do pathogenic prions reproduce and cause damage to infected tissues?

Answer 272

- Multiply by conversions => p-PrP causes c-PrP to refold into p-PrP (change in conformation), thus increasing [p-PrP] - p-PrP group into multimers => get deposited as amyloid plaque (cause damage)

Question 273

What are diseases caused by prions called? How are they transmitted? Are there any treatments?

Answer 273

- Spongiform encephalopathies (large vacuoles form in brain = "spongy") - Transmitted by ingestion, transplantation, or contact of mucous membranes with infected tissues - NO standard treatment for any prion disease

Question 274

What diseases do prions cause in humans and animals?

Answer 274

Human prion diseases: - Variant Creutzfeldt-Jakob disease (vCJD) - Kuru (fatal neurodegenerative disorder) Animal prion diseases: - Mad cow disease (Bovine SE) - Scrapie (sheep & goats)

Question 275

Why are prion diseases difficult to treat?

Answer 275

No standard treatment exists.

Question 276

What are antimicrobial agents? What do they take advantage of?

Answer 276

- Drugs that can treat infectious diseases - Take advantages of differences between microbial cells and mammalian cells - Target cellular structures and pathways specific to microbial cells to reduce side effects

Question 277

What are the different ways to classify antimicrobial agents?

Answer 277

1. Type of microbe affected (anti-bacterial, anti-fungal, anti-viral, etc.) 2. Targeted pathways (cell wall inhibitor, RNA transcription inhibitor, protein synthesis inhibitor, etc.) 3. Spectrum of action (narrow vs. broad spectrum) 4. Effects (microbiocidal vs. microbiostatic)

Question 278

What is the difference between narrow-spectrum vs. broad-spectrum antimicrobial drugs?

Answer 278

- Narrow = effective against few organisms - Broad = effective against many organisms (not the best choice => can also disrupt normal microbiota and cause 2ndary infections)

Question 279

What is the difference between microbiocidal vs. microbiostatic drugs?

Answer 279

- Microbiocidal = kills microbes - Microbiostatic = inhibit microbial growth

Question 280

What is one example why an antimicrobial drug may have toxic side effects in mammalian cells?

Answer 280

Can affect mitochondria of mammalian cells, as mitochondria are related to bacteria (endosymbiotic theory).

Question 281

Who is credited with the discovery of penicillin? What microbe produces penicillin? Briefly describe its antibiotic effect.

Answer 281

- Alexander Fleming - Produced by mold (fungus) Penicillium chrysogenum - Inhibitor of cell wall synthesis (peptidoglycan) = β-lactam

Question 282

Who coined the term "chemotherapy" to describe chemicals that selectively killed pathogens?

Answer 282

Paul Ehrlich ("magic bullets" = arsenic compounds that killed bacteria that caused syphillis)

Question 283

What term describes chemicals that selectively kill pathogens?

Answer 283

Chemotherapy

Question 284

Who discovered sulfanilamide (type of sulfonamide) and why was it significant?

Answer 284

Gerhard Domagk; it was the first commercially produced antimicrobial drug for bacterial infections.

Question 285

Who coined the term "antibiotics" to describe antimicrobial agents produced naturally by organisms? Explain.

Answer 285

- Selman Waksman - Discovered that other microorganisms are sources of useful antimicrobials (e.g., streptomycin is produced by Streptomyces)

Question 286

What term describes antimicrobial agents produced naturally by organisms?

Answer 286

Antibiotics

Question 287

What are the differences between semisynthetic and synthetic antimicrobials?

Answer 287

- Semisynthetic = chemically altered antibiotics for effectiveness (e.g., longer lasting, easier to administer) - Synthetic = antimicrobials completely synthesized in a lab

Question 288

What are the 6 mechanisms of action of antimicrobial drugs?

Answer 288

1. Inhibiting cell wall synthesis 2. Inhibition of protein synthesis 3. Disruption of cytoplasmic membrane 4. Inhibition of general metabolic pathway 5. Inhibition of DNA or RNA synthesis 6. Inhibition of pathogen's attachment or entry into host cell

Question 289

Why are new bacterial cell walls synthesized? How?

Answer 289

Synthesize new cell wall to grow and divide: - New "building blocks" (sugar units = NAG + NAM) are synthesized in the cytoplasm, - Transported across the cell membrane to the cell wall, - And incorporated into existing cell wall - Peptide linkages (cross-links) are formed to hold the sugar chains together

Question 290

Describe β-lactam antibiotics and how they work. What is an example of one?

Answer 290

- Functional groups = β-lactam rings - Effective against Gram-positive bacteria - Inhibit enzymes that cross-link NAM subunits in peptidoglycan = weak cell wall = bursts from osmotic pressures - Examples: Penicillin, Methicillin, Imipenem, Cephalothin

Question 291

Why are β-lactams more effective against Gram-positive bacteria?

Answer 291

- Gram-positive bacteria have a thick peptidoglycan layer that β-lactams can easily target - Gram-negative bacteria have an outer membrane that prevents easy access to peptidoglycan

Question 292

What are the benefits of semisynthetic derivatives of β-lactams?

Answer 292

- More stable in acidic environments = can be taken orally - More readily absorbed - Less susceptible to deactivation - More active against a broader range of bacteria

Question 293

What are some non-β-lactam drugs that inhibit cell wall synthesis? Describe them.

Answer 293

- Vancomycin & cycloserine => interfere with alanine-alanine bridges that link NAM subunits in many Gram-positive bacteria - Bacitracin => blocks NAG & NAM transport from the cytoplasm - Isoniazid & ethambutol => disrupt mycolic acid formation in Mycobacterium species (e.g., tuberculosis, leprosy)

Question 294

What antibiotics interfere with alanine-alanine bridges that link NAM subunits in many Gram-positive bacteria?

Answer 294

- Vancomycin - Cycloserine

Question 295

What antibiotic blocks NAG & NAM transport from the cytoplasm?

Answer 295

Bacitracin

Question 296

What antibiotics disrupt mycolic acid formation in Mycobacterium species?

Answer 296

- Isoniazid - Ehtambutol

Question 297

What are the drawbacks of antimicrobial drugs that inhibit peptidoglycan synthesis (β-lactams)?

Answer 297

- Have no effect on existing peptidoglycan layer - Only effective for actively growing bacteria - Less effective against Gram-negative bacteria - Bacteria can develop resistance via β-lactamase enzyme (penicillinase), which breaks the β-lactam ring found in the drugs (now inactive)

Question 298

How are fungal cell walls different from mammalian cells?

Answer 298

They are made of various polysaccharides not found in mammalian cells, including β1,3-glucan.

Question 299

How do echinocandins (antifungal drug) work?

Answer 299

- Inhibit β1,3-glucan synthase (enzyme that synthesizes β1,3-glucan), disrupting fungal cell wall formation - Results in weaker cell wall, susceptible to osmotic shock

Question 300

What fungal species are echinocandins effective against?

Answer 300

- Fungicidal against Candida spp - Fungistatic against Aspergillus spp

Question 301

What antibiotic inhibits β1,3-glucan synthase in fungal cells?

Answer 301

Echinocandins

Question 302

How do polyenes disrupt fungal membranes? Give examples of these drugs.

Answer 302

- Bind to ergosterol in fungal cell membranes, forming channels/pores that disrupt membrane integrity - Examples: Nystatin, Amphotericin B

Question 303

Why are bacteria not susceptible to polyenes?

Answer 303

Lack sterols in membrane.

Question 304

Why do polyenes have some toxicity to humans?

Answer 304

Human cholesterol (found in cell membrane) is similar to fungal ergosterol, causing side effects.

Question 305

What antimicrobial drugs inhibit ergosterol synthesis? What microbes do they affect?

Answer 305

- Azoles (e.g., fluconazole) - Allylamines (e.g., terbinafine) - Are antifungals & antiprotozoans (harmless to humans because cells do not produce ergosterol)

Question 306

Polymyxin is an antibiotic produced by ____________________.

Answer 306

Bacillus polymyxa

Question 307

How do polymyxins (antibiotic) work?

Answer 307

- Disrupt cell membrane of Gram-negative bacteria - Toxic to human kidneys/liver = reserved for topical use (less toxic when applied to skin)

Question 308

_____________ disrupts transport across cell membrane of Mycobacterium tuberculosis.

Answer 308

Pyrazinamide

Question 309

Pyrazinamide (antibiotic) is effective against...?

Answer 309

Intracellular, non-replicating bacterial cells.

Question 310

Prokaryotic ribosomes are ___S.

Answer 310

70S (30S & 50S)

Question 311

Eukaryotic ribosomes are ___S.

Answer 311

80S (40S & 60S)

Question 312

Why can drugs that inhibit protein synthesis (i.e. target prokaryotic ribosomes) have some side effects in mammalian cells?

Answer 312

Mitochondria contain 70S ribosomes similar to prokaryotic ribosome.

Question 313

What are some examples of antimicrobial drugs that inhibit protein synthesis?

Answer 313

- Aminoglycosides (streptomycin, gentamicin, tetracyclines) - Chloramphenicol - Lincosamides - Streptogramins - Macrolides - Fomivirsen - Oxazolidinone - Mupirocin

Question 314

How do aminoglycosides (e.g., streptomycin, gentamicin) work?

Answer 314

Change shape of the 30S small subunit, preventing correct mRNA codon reading (induce kink).

Question 315

How do tetracyclines inhibit protein synthesis?

Answer 315

Block tRNA docking site (don't allow tRNA to bring new AA), terminating protein elongation.

Question 316

What are some side effects of tetracyclines?

Answer 316

Discolouration of teeth and nails in some patients.

Question 317

How does chloramphenicol inhibit protein synthesis?

Answer 317

Binds to the enzymatic site of 50S large subunit, preventing peptide bond formation.

Question 318

How do lincosamides, streptogramins, & macrolides (e.g., erythromycin) inhibit protein synthesis?

Answer 318

Bind to sites on the 50S large subunit; prevent ribosome movement along mRNA from one codon to next (synthesis stops).

Question 319

How does fomivirsen (synthetic anti-viral drug) inhibit protein synthesis?

Answer 319

- Antisense nucleic acid - Complementary to specific mRNA of the pathogen, creating dsRNA that blocks ribosome attachment - dsRNA eventually degraded

Question 320

____________ stops protein synthesis by blocking initiation of translation.

Answer 320

Oxazolidinone (prevents ribosome binding to mRNA)

Question 321

How does Mupirocin inhibit protein synthesis?

Answer 321

Interferes with charging of tRNA => selectively inhibits isoleucyl-tRNA synthetase (chain terminates where isoleucine is supposed to be present).

Question 322

_____________ is used as a topical drug to treat skin infection by Gram-positive bacteria.

Answer 322

Mupirocin

Question 323

What are the different types of antimetabolic agents?

Answer 323

- Drugs that interfere with the electron transport chain (in protozoa & fungi) - Heavy metals (arsenic, mercury, antimony) inactivate enzymes - Agents that disrupt tubulin polymerization & glucose uptake (many protozoa & parasitic worms) - Drugs that block viral activation (keep virus in dormant stage, prevent triggering pathway) - Metabolic antagonists (e.g., sulfa drugs block nucleotide synthesis)

Question 324

How do sulfonamides (sulfa drugs) inhibit nucleotide synthesis?

Answer 324

Inhibit nucleotide biosynthetic pathway: - Are structural paralogs of para-aminobenzoic acid (PABA) = precursor in folic acid synthesis - Compete with PABA for the enzyme that converts it to dihydrofolic acid (competitive inhibitors)

Question 325

Why do sulfa drugs not affect humans?

Answer 325

Humans obtain folic acid from diet and do not rely on the pathway the drugs target.

Question 326

___________ affects the same nucleotide synthesis pathway as sulfonamides.

Answer 326

Trimethoprim

Question 327

How do protease inhibitors work against HIV?

Answer 327

Prevent HIV proteins from being processed by proteases, stopping assembly of new virions.

Question 328

What antimicrobial drugs inhibit prokaryotic DNA gyrase?

Answer 328

- Quinolones - Fluoroquinolones - Prevent proper coiling and uncoiling of replicating bacterial DNA

Question 329

How does rifampin inhibit RNA transcription?

Answer 329

It binds to bacterial RNA polymerase, inhibiting transcription.

Question 330

____________ binds to bacterial DNA; prevents normal transcription.

Answer 330

Clofazimine

Question 331

Rifampin & clofazimine are used for treatment of _________________.

Answer 331

Mycobacterium diseases (tuberculosis & leprosy)

Question 332

How do reverse transcriptase inhibitors work?

Answer 332

- Treatment of retroviral infection (e.g., HIV) - Block viral replication by inhibiting reverse transcription of viral RNA genome into complementary DNA

Question 333

How do nucleotide or nucleoside analogs inhibit DNA/RNA synthesis? What are they effective against?

Answer 333

- Structually similar to purines/pyrimidines => get incorporated into DNA/RNA, interfering with their function - Distort shape of DNA/RNA; prevent further replication, transcription, or translation - Most often used against viruses (once virus infects cell, has to replicate = more susceptible to analogs) - Also effective against rapidly dividing cancer cells

Question 334

How do attachment antagonists work? Give examples of such drugs.

Answer 334

They block interactions between viral attachment proteins and host receptors (required for attachment & entry into cell). - Examples: pleconaril, arildone

Question 335

Pleoconaril is a synthetic drug antagonist of receptors for...

Answer 335

Picornaviruses (cold viruses, poliovirus, coxsackievirus)

Question 336

___________ is a synthetic drug that prevents uncoating of poliovirus.

Answer 336

Arildone (interrupts viral replication cycle)

Question 337

What are Pleconaril and Arildone used for?

Answer 337

Pleconaril prevents attachment of picornaviruses; Arildone prevents poliovirus uncoating.

Question 338

What are the characteristics of an ideal antimicrobial drug?

Answer 338

- Readily available - Inexpensive - Chemically stable (at room temp, long shelf-life, maintains concentration in body) - Easily administered (e.g., orally) - Non-toxic & non-allergenic - Selectively toxic against wide range of pathogens (doesn't harm beneficial microflora)

Question 339

What are clinical considerations in prescribing antimicrobial drugs?

Answer 339

- Spectrum of actions - Effectiveness - Route of administration - Safety and side effects

Question 340

Why are broad-spectrum antibiotics not always desirable?

Answer 340

Can kill normal microflora and reduce microbial antagonism, resulting in: - Secondary infections => opportunisitic pathogens become pathogenic because they lose competition from normal microflora (e.g., Candida yeast) - Superinfections => one or more of the normal microflora population overgrow if resistant to antibiotic you are taking

Question 341

How is antibiotic effectiveness tested?

Answer 341

1. Kirby-Bauer test (diffusion susceptibility test => determines effectiveness in preventing microbial growth) 2. MIC test (minimum inhibitory concentration test => determines drug potency, minimum concentration that can inhibit microbial growth) 3. MBC test (minimum bactericidal concentration test => determines drug concentration required to kill microbe)

Question 342

What test determines drug potency?

Answer 342

MIC (minimum inhibitory concentration) test

Question 343

Describe the Kirby-Bauer diffusion susceptibility test.

Answer 343

1) Small disks of paper containing standard [drug] 2) Disks placed on surface of agar growth medium inoculated with the pathogen 3) Antimicrobial drugs diffuse through the agar 4) Zone of inhibition = growth inhibition seen around the disk - The larger the zone of inhibition = the more effective the drug is - Use standardized tables with properties of drugs and compare with zone of inhibition to see effectiveness of drug

Question 344

Describe the MIC (minimum inhibitory concentration) test.

Answer 344

1) Standardized amount of pathogen is added to a serial dilution of the antimicrobial agent in tubes/wells containing liquid growth medium 2) After incubation, turbidity in the medium indicates growth - Determines drug potency = minimum [drug] that can inhibit growth - The lower the minimum [drug], the more effective the drug is

Question 345

What is an Etest?

Answer 345

Combination of aspects of MIC & Kirby-Bauer tests: 1) Test strips with different concentrations of drug are put on a bacterial lawn 2) Determine minimum [drug] that can inhibit growth of the bacteria (don't want higher [drug] because then side effects increase)

Question 346

Describe the MBC (minimum bactericidal concentration) test.

Answer 346

Determines amount of drug required to kill the microbe: 1) Samples taken from clear MIC tube or Kirby-Baeur inhibition zone 2) Transferred to plates containing drug-free growth medium - Appearance of bacterial growth indicates bacteriostatic effect - The lowest [drug] for which no growth occurs is the MBC

Question 347

What are some common routes of administration for antimicrobials?

Answer 347

- Topical for external infections (drugs with high toxicity not as readily absorbed) - Oral (no needles, self-administered) - Intramuscular (drug via needle into muscle) - Intravenous (delivers drug directly to bloodstream => more preferred when infection in extremities)

Question 348

The drug's route of administration affects...?

Answer 348

- Drug distribution and concentration at the infected tissues (once in system, metabolized by kidney/liver) - Drug toxicities

Question 349

What drug is more toxic to the fetus in pregnant women? What is its effects?

Answer 349

Tetracyclines can cause: - Malformation of skull - Weakened & stained tooth enamel (forms complex with Ca++)

Question 350

What is the therapeutic index?

Answer 350

The ratio of the highest tolerable drug dose to the effective drug dose. - Higher index = higher doses can be tolerated

Question 351

What is the therapeutic window?

Answer 351

The range of drug concentrations that are effective without being excessively toxic.

Question 352

What antibiotic are some individuals allergic to?

Answer 352

Penicillin (anaphylactic shock if taken)

Question 353

What microbes are associated with secondary infections and superinfections, as a result of antimicrobials causing a disruption of the normal microbiota?

Answer 353

- Candida albicans (candidiasis) - Clostridium difficile (colitis)

Question 354

What are potential side effects of antimicrobial drugs?

Answer 354

- Toxicity (to kidneys, liver, or nerves) - Allergic reactions - Disruption of normal microbiota

Question 355

Some pathogens are naturally resistant to drugs. Explain.

Answer 355

- Selection pressure due to antibiotic use => develop resistance - The ones that are resistant outgrow the susceptible ones

Question 356

What are 2 ways bacteria acquire resistance to antimicrobial drugs?

Answer 356

1. New mutations of chromosomal genes (may make the pathogen less susceptible) 2. Horizontal gene transfer (transformation, transduction, and conjugation): acquisition of mutated genes or R plasmids that contain resistance gene

Question 357

R plasmids contain...?

Answer 357

Resistance gene

Question 358

What are the 3 ways horizontal gene transfer can occur?

Answer 358

1. Transformation 2. Transduction 3. Conjugation

Question 359

What mechanisms do bacteria use to resist antimicrobials?

Answer 359

- Enzyme production (e.g., β-lactamase) that destroys or activates drug - Slow or prevent drug entry into cell (e.g., capsules attached to cell surface) - Alter drug targets (so it binds less effectively) - Alter their own metabolic chemistry (e.g., get folic acid from environment instead of making it) - Efflux pumps (pump drug out of cell before it can act) - Biofilms (delay diffusion of drug into cells = [drug] kept at minimum)

Question 360

What does Mycobacterium tuberculosis produce to resist antimicrobials?

Answer 360

Produces MfpA protein that binds to DNA gyrase = prevents binding of fluroquinolone drug.

Question 361

What microbe is more prone to develop drug resistance to others?

Answer 361

Staphylococcus aureus

Question 362

What is multiple resistance? Where does it usually develop?

Answer 362

- Multiple resistance = pathogen can acquire resistance to more than one drug - Common when R plasmids exchanged - Develops in hospitals and nursing homes (constant use of drugs eliminates sensitive cells)

Question 363

What are multiple-drug-resistant pathogens? What are they also called?

Answer 363

Bacteria resistant to at least 3 antimicrobial agents (superbugs).

Question 364

_______ resistance can occur when drugs are similar in structure (or have common pathway).

Answer 364

Cross resistance

Question 365

What strategies help slow antimicrobial resistance?

Answer 365

- Maintain high [drug] in patient for sufficient time (to eliminate all pathogens before they give rise to resistant strains) - Use antimicrobial agents in combination - Use antimicrobials only when necessary - Develop new variations of existing drugs (2nd/3rd generation drugs) - Search for new antibiotics, semisynthetics, and synthetics (e.g., bacteriocins)

Question 366

_____________ occurs when one drug enhances the effect of a second drug.

Answer 366

Synergism (additive)

Question 367

Give examples of drug synergism.

Answer 367

- Penicillin + Streptomycin => inhibition of cell wall by penicillin makes it easier for streptomycin to enter bacterial cells - Calvulanic acid enhances Penicillin effect by inhibiting β-lactamase

Question 368

Antibacterial proteins used by some bacteria to inhibit other bacterial strains.

Answer 368

Bacteriocins

Question 369

Normal/indigenous microbiota/flora are organisms that...?

Answer 369

Organisms that colonize the body's surface without normally causing disease.

Question 370

The microbiome begins to develop during ________ process and much of it is established during _______________ of life.

Answer 370

- Birthing process - First months of life

Question 371

Describe resident microbiota.

Answer 371

- Part of the normal microbiota throughout life (e.g., re-establish colonies after showering) - Are mostly commensal

Question 372

Describe transient microbiota.

Answer 372

- Remain in the body for short period - Found in the same regions as resident microbiota - Cannot persist in the body (competition, immune system, body chemical/physical changes)

Question 373

Why cannot transient microbiota persist in the body?

Answer 373

- Competition from other microorganisms - Elimination by the body's defense cells - Chemical or physical changes in the body (e.g., during menstrual cycle = vagina's pH changes)

Question 374

Where are resident microbiota found in the body?

Answer 374

- Respiratory tract (nose, trachea, bronchi) => NO microbiota in alveoli - Upper digestive tract (teeth, gingiva, lining of cheeks, pharynx, saliva) - Lower digestive tract (intestines) => bacteria mostly strict anaerobes - Urinary & reproductive tract - Skin (dead skin layers, hair follices, pores of glands) => not best/suitable environment because dry, gets washed constantly - Eyes => tears wash most microbiota from eyes

Question 375

What are opportunistic pathogens?

Answer 375

Normal microbiota that cause disease under certain circumstances.

Question 376

What are some conditions that trigger opportunistic pathogens?

Answer 376

- Introduction into unusual site in body - Immune suppression (diseases, malnutrition, stress, aging, radiation, chemotherapy, immunosuppressive therapy) - Changes in the normal microbiota - Stressful conditions can disrupt normal microflora (physical/emotional stress, hormonal changes, diets)

Question 377

Esherichia coli (E.coli) is a normal flora in the colon, but if enters the _______, it can cause ____________.

Answer 377

- Urethra - Urinary tract infection (UTI)

Question 378

Microbial ___________ and ___________ prevents opportunistic pathogens to cause disease.

Answer 378

- Antagonism - Competition

Question 379

AIDS patients often die of ____________________.

Answer 379

Opportunistic infections (because HIV infection suppresses the immune system)

Question 380

What are reservoirs of infection? Why?

Answer 380

Sites where pathogens are maintained as a source of infection. - Why? Most pathogens cannot survive for long outside their host

Question 381

What are the 3 types of reservoirs of infection?

Answer 381

1. Animal reservoir (zoonoses) 2. Human carriers (asymptomatic, healthy carriers) 3. Nonliving reservoir (contaminated soil, water, food => through feces/urine)

Question 382

What are zoonoses? How are they acquired?

Answer 382

- Spread of disease from animals to humans (animal reservoir) - Acquire through various routes: direct contact with animal or its waste, eating animals, etc.

Question 383

What are healthy human carriers?

Answer 383

- Asymptomatic but infective individuals - Some individuals eventually develop illness, others not

Question 384

What virus causes rabies?

Answer 384

Lyssavirus species

Question 385

What is the difference between contamination vs. infection?

Answer 385

- Contamination = the mere presence of microbes in or on the body (does not always lead to an infection) - Infection = when organism evades body's external defenses, multiplies, and becomes established in the body

Question 386

What are the 4 portals of entry through which pathogens enter the body?

Answer 386

- 3 major pathways: skin, mucous membranes, placenta - Parenteral route circumvents the usual portals (not natural)

Question 387

Describe the skin's role in infection.

Answer 387

- Outer layer of dead skin cells (epidermis) acts as a barrier to pathogens => water permeable, dry - Sweat and oils (sebum) secreted on the skin may have antimicrobial properties - Some pathogens can enter through openings or cuts - Larvae of some parasitic worms can burrow into the skin - Some fungal pathogens can digest outer layers of skin (produce certain enyzmes)

Question 388

Describe the roles of mucous membranes in infection.

Answer 388

- Line the body cavities that are open to the environment (respiratory, GI, urinary, reproductive tracts) - Provide a moist, warm environment hospitable to pathogens - Presence of layer mucus, antimicrobial peptides, acidic stomach pH, mucosal immune system, and normal microbiota provide a barrier to infectious microbes

Question 389

________________ is the most common site of entry for pathogens.

Answer 389

Respiratory tract (entry through nose, mouth, or eyes)

Question 390

What are the barriers to infection found in mucous membranes?

Answer 390

- Mucus (secreted by goblet cells) - Antimicrobial peptides - Acidic stomach pH - Mucosal immune system - Normal microbiota

Question 391

What are the components of mucous membranes?

Answer 391

- Mucus (secreted by goblet cells) - Epithelium - Basement membrane - Lamina propria (connective tissue, blood vessels, nerves, immune cells)

Question 392

Describe the placenta's role in infection.

Answer 392

- Typically forms effective barrier to pathogens (even normal microbiota) - Pathogens may cross the placenta and infect the fetus => spontaneous abortion, birth defects, or premature birth

Question 393

What are some pathogens that can cross the placenta?

Answer 393

- Toxoplasma gondii (protozoan) - Treponema pallidum, Listeria monocytogenes (bacteria) - Cytomegalovirus, Erythrovirus (DNA viruses) - HIV/Lentivirus, Rubivirus (RNA viruses)

Question 394

What is the parenteral route of entry?

Answer 394

- Puncture of skin or mucous membranes by contaminated nail, thorn, hypodermic needle - Accidental/unintentional exposure (NOT a true portal of entry)

Question 395

What is adhesion?

Answer 395

- Adhesion = process by which microorganisms attach themselves to cells/tissues - Required to establish colonies successfully within the host - Pathogens use adhesion factors for attachment to tissues

Question 396

What are some adhesion factors (adhesins) pathogens use for attachment to tissues?

Answer 396

- Specialized structures (e.g., suckers and hooks in some helminths) - Attachment molecules (e.g., glycoproteins, biofilms)

Question 397

__________ on the surface of viruses and bacteria bind to receptors on host cells. They determine _____________.

Answer 397

- Glycoproteins - Determine tissue or host specificity

Question 398

Sticky web of bacteria and polysaccharides, called a _________, such as dental plaques.

Answer 398

Biofilm

Question 399

Some pathogens may have more than one type of adhesin, while others may change adhesin over time. Provide examples of each.

Answer 399

- More than one = Bordetella (whooping cough) - Change over time = Plasmodium (malaria)

Question 400

Infectious disease results if the invading pathogen alters normal body function; also referred to as __________.

Answer 400

Morbidity

Question 401

Etiology is the study of the cause of disease. What are some categories of diseases?

Answer 401

- Hereditary (genetic) - Congenital (birth defects) - Degenerative (aging of cells) - Nutritional - Endocrine (hormonal) - Mental (emotional/psychosomatic) - Immunological (hyper/hypoactive immunity) - Neoplastic (tumour) - Infectious - Iatrogenic (medical treatment/procedure => surgical error) - Idiopathic (unknown cause) - Nosocomial (healthcare-associated)

Question 402

"Hepat-" refers to the?

Answer 402

Liver

Question 403

"Terato-" refers to?

Answer 403

Defects

Question 404

"Septi-" refers to?

Answer 404

Rotting (presence of pathogens)

Question 405

What ways can diseases be classifed?

Answer 405

- Taxonomic categories - Affected body system - Longevity (acute vs. chronic) - Severity - How they spread (local vs. systemic) - The effects they have on populations

Question 406

Disease transmitted from one host to another.

Answer 406

Communicable disease

Question 407

What is the difference between acute vs. chronic disease?

Answer 407

- Acute = symptoms develop rapidly, last shortly - Chronic = mild symptoms that develop slowly and last a long time

Question 408

What is a focal infection?

Answer 408

Infection site that serves as a source of pathogens for infections at other sites in the body.

Question 409

What is the difference between symptoms vs. signs?

Answer 409

- Symptoms = subjective characteristics of disease felt only by the patient (pain, nausea, headache, etc.) - Signs = objective manifestations of disease observed or measured by others (swelling, redness, vomiting, diarrhea, fever, etc.)

Question 410

Symptoms and signs that characterize a disease or an abnormal condition.

Answer 410

Syndrome

Question 411

___________________ infections lack symptoms but may still have signs of infections.

Answer 411

Asymptomatic or subclinical

Question 412

Germ theory of disease was developed by ____________.

Answer 412

Louis Pasteur (infections by microbes cause disease)

Question 413

Robert Koch studied etiology and showed that...?

Answer 413

- Bacillus anthracis causes anthrax - Mycobacterium tuberculosis causes tuberculosis

Question 414

Koch's postulates are a series of...?

Answer 414

A series of essential conditions that scientists must demonstrate or satisfy to prove that particular microbe causes a particular disease.

Question 415

What are exceptions to Koch's postulates?

Answer 415

- Some pathogens can't be cultured in the lab - Some diseases caused by combination of pathogens and other cofactors - Ethical considerations (e.g., pathogens that require a human host)

Question 416

What is pathogenicity?

Answer 416

Ability of a microorganism to cause disease.

Question 417

What is virulence?

Answer 417

Microorganism's degree of pathogenicity (ability to cause disease).

Question 418

What are some virulence factors?

Answer 418

- Adhesion factors - Biofilms - Extracellular enzymes - Toxins - Antiphagocytic factors

Question 419

Francisella tularensis (rabbit fever) is more/less virulent than Candida albicans (vaginitis).

Answer 419

More virulent

Question 420

Describe extracellular enzymes (virulence factors). Give examples.

Answer 420

- Secreted by pathogens to dissolve structural chemicals in the body - Help pathogen maintain infection, invade, and avoid body defenses - Examples: hyaluronidase (Clostridium perfringens), collagenase (Clostridium & Streptococcus), keratinase (ringworm fungi => Trichophyton, Microsporum, Epidermophyton), mucinase (Entamoeba histolytica), kinase (Streptococcus & Staphlyococcus), coagulase

Question 421

Secreted by pathogens to dissolve structural chemicals in the body.

Answer 421

Extracellular enzymes

Question 422

Hyaluronidase is secreted by...?

Answer 422

Clostridium perfringens (digest hyaluronic acid = polysaccharide, glue-like structure that holds cells together)

Question 423

Collagenase is secreted by...?

Answer 423

Clostridium & Streptococcus species (digest collagen = major matrix protein that gives tissues structure)

Question 424

Keratinase is secreted by...?

Answer 424

Fungi that cause ringworm => Trichophyton, Microsporum, Epidermophyton floccosum (digest keratin = protein in skin, hair, nails)

Question 425

Mucinase is secreted by...?

Answer 425

Entamoeba histolytica (digest mucus to attach to mucous membranes)

Question 426

Kinase is secreted by...?

Answer 426

Streptococcus & Staphylococcus species (digest blood clot to enter bloodstream and spread)

Question 427

Pathogens that secrete coagulase cause...?

Answer 427

Formation of blood clot: - Pathogen lives inside to protect themselves from immune cells - Digest clot when time is right

Question 428

Chemicals that harm tissues or trigger host immune responses that cause damage.

Answer 428

Toxins

Question 429

Toxemia refers to...?

Answer 429

The presence of toxins in the bloodstream.

Question 430

What are the 2 types of toxins?

Answer 430

1. Exotoxins (cytotoxin, neurotoxin, enterotoxin) 2. Endotoxin (Lipid A)

Question 431

Endotoxins are only produced by...?

Answer 431

Gram-negative bacteria

Question 432

What are some examples of exotoxins?

Answer 432

- Cytotoxin (kill host cells) - Neurotoxin (affect nerve cell function) - Enterotoxin (affect cells of the GI tract => e.g., excess release of fluids)

Question 433

Enterotoxins (type of exotoxin) affect cells of the...?

Answer 433

GI tract

Question 434

Cytotoxins (type of exotoxin) kill...?

Answer 434

Host cells

Question 435

What is an example of an endotoxin?

Answer 435

- Lipid A component of LPS from Gram-negative bacteria - Released upon cell death - Causes fever, inflammation, blood coagulation, shock, etc.

Question 436

What is something that causes fever called?

Answer 436

Pyrogenic

Question 437

What are toxoids?

Answer 437

Inactivated forms of toxins (used for vaccination).

Question 438

Describe some general characteristics of exotoxins.

Answer 438

- Metabolic product (protein or short peptide) secreted from living cell - Mainly Gram-positive and Gram-negative bacteria - High toxicity - Typically unstable > 60C - Non-pyrogenic - Strong antigenicity (stimulate antibody production) - Toxoid formation with heat or formaldehyde

Question 439

Describe some characteristics of endotoxins.

Answer 439

- Gram-negative bacteria - Lipid A of LPS - Low toxicity (can be more at higher concentrations) - Stable for up to 1 hour at autoclave temp (121C) - Pyrogenic - Weak antigenicity - Don't form toxoids

Question 440

What are some representative diseases associated with exotoxins?

Answer 440

- Botulism (Clostridium botulinum) - Tetanus (Clostridium tetani) - Gas gangrene (Clostridium perfringens) - Diphtheria (Corynebacterium diphtheriae) - Cholera (Vibrio cholerae) - Plague (Yersinia pestis) - Staphylococcal food poisoning

Question 441

What are some representative diseases associated with endotoxins?

Answer 441

- Typhoid fever (Salmonella typhi) - Tularemia (Francisella tularensis) - Endotoxic shock - UTIs - Meningococcal meningitis

Question 442

_______________ factors prevent phagocytosis by the host's phagocytic WBCs (macrophages and neutrophils).

Answer 442

Antiphagocytic factors

Question 443

What are some antiphagocytic factors?

Answer 443

- Bacterial capsules => composed of chemicals not recognized as foreign (e.g., hyaluronic acid capsule) - Antiphagocytic chemicals (Neisseria gonorrhoeae) => prevent fusion of lysosome and phagocyte - M protein (Streptococcus pyogenes) => inhibits phagocytosis - Leukocidins => directly destroy phagocytic cells

Question 444

What bacteria produces M protein to inhibit phagocytosis?

Answer 444

Streptococcus pyogenes

Question 445

__________ directly destroy phagocytic cells.

Answer 445

Leukocidins

Question 446

What allows Neisseria gonorrhoeae to survive inside phagocytes?

Answer 446

Antiphagocytic chemicals (prevent fusion of lysosome and phagocyte)

Question 447

What are the 5 stages of infectious diseases following infection?

Answer 447

Can transmit disease at any stage: 1. Incubation period (no symptoms/signs => short if highly virulent) 2. Prodromal period (vague, mild general symptoms => e.g., tired, headache) 3. Illness (most severe signs and symptoms) 4. Decline (declining signs/symptoms => if medical intervention or immune response) 5. Convalescence (no signs/symptoms)

Question 448

Pathogens leave their host through multiple portals of exit often in materials the body secretes/excretes. Give examples.

Answer 448

- Eyes (tears) - Ears (earwax) - Mouth (saliva) - Skin (blood, flakes) - Anus (feces) - Urethra (urine) - In males => seminal vesicles (semen) - In females => mammary glands (milk), vagina (blood, secretions)

Question 449

What is transmission or transmissible diseases?

Answer 449

The movement of pathogens from reservoir or a portal of exit to another host's portal of entry.

Question 450

What are the 3 modes of transmission?

Answer 450

1. Contact 2. Vehicle 3. Vector

Question 451

Describe the types of contact transmission.

Answer 451

1. Direct contact transmission => involves body contact between hosts (can occur within a single individual too) 2. Indirect contact transmission => pathogens are spread from host to host by fomites (drinking glasses, toothbrushes, etc.) 3. Droplet transmission => spread of pathogens in droplets of mucus by exhaling, coughing, sneezing

Question 452

Describe the types of vehicle transmission.

Answer 452

1. Airborne transmission => when pathogens travel more than 1m via an aerosol (via sneezing, coughing, AC systems, sweeping) 2. Waterborne transmission => water contaminated with sewage (fecal-oral infection like cholera), important in the spread of GI diseases 3. Foodborne transmission => spread of pathogens in/on foods (contaminated with feces, inadequately processed/cooked/refrigerated) 4. Bodily fluid transmission => blood, urine, saliva can carry pathogens (prevent contact with conjunctiva, breaks in the skin, mucous membranes)

Question 453

Airborne transmission is when pathogens travel more than __ meter via an aerosol.

Answer 453

1 meter

Question 454

Vector transmission can occur via...?

Answer 454

- Biological vectors (e.g., biting arthropods => serve as host for some stage of pathogen's life cycle) - Mechanical vectors (passive transport, not infected)

Question 455

Epidemiology allows us to gain important information on how to...?

Answer 455

Treat and prevent infectious diseases.

Question 456

Disease occurrence is tracked using what measures?

Answer 456

- Incidence = # of new cases of a disease in a given area during a given period of time - Prevalence = # of total cases of a disease in a given area during a given period of time - Frequency (e.g., 1 in 100,000 individuals) - Geographic distribution (e.g., how dense are the cases in certain locations?)

Question 457

Number of new cases of a disease in a given area during a given period of time.

Answer 457

Incidence

Question 458

Number of total cases of a disease in a given area during a given period of time.

Answer 458

Prevalence

Question 459

What are the 3 types of epidemiological studies?

Answer 459

1. Descriptive epidemiology => tabulation of epidemiological data, identification of index case (the first case) 2. Analytical epidemiology => retrospective: determines probable cause/mode of transmission/prevention methods 3. Experimental epidemiology => tests hypothesis regarding disease cause, applies Koch's postulates

Question 460

What is descriptive epidemiology?

Answer 460

- Careful tabulation of epidemiological data concerning a disease (location/time of cases, patient information) - Main goal = source of disease (where it started, how it spread) - Identification of index case (the first case) important

Question 461

Why is identification of the index case (the first case of a disease) difficult or impossible?

Answer 461

Person could have recovered, moved, died, etc.

Question 462

What epidemiological study is useful in situations when Koch's postulates can't be applied?

Answer 462

Analytical epidemiology

Question 463

Describe analytical epidemiology.

Answer 463

- Seeks to determine the probable cause, mode of transmission, and methods of prevent - Often retrospective (investigation occurs after an outbreak has occured) - Useful when Koch's postulates can't be applied

Question 464

Describe experimental epidemiology.

Answer 464

- Tests a hypothesis concerning the cause of a disease - Application of Koch's postulates

Question 465

The earliest known descriptive epidemiological study was by...? Describe it.

Answer 465

- John Snow => studied 1854 cholera outbreak in London - Carefully mapped location of cases => found that they were clustered around the Broad street water pump - Determined disease spread via contamination of drinking water by sewage

Question 466

Describe the various ways epidemiologists report data.

Answer 466

- Average annual incidence on a map of a geographical area - Graphs (% of cases by week of onset, # of deaths by age)

Question 467

What does "endemic" mean?

Answer 467

Disease that occurs continually and stably within in area (e.g., Sub-Saharan Africa endemic for malaria).

Question 468

Disease that occurs in low numbers in an area is called...?

Answer 468

Sporadic

Question 469

What is the difference between an epidemic and pandemic?

Answer 469

- Epidemic = disease occurrence is higher than expected in an area - Pandemic = epidemic in more than one continent

Question 470

Epidemics are not defined according to the absolute number of cases, but...?

Answer 470

How much it exceeds the expected occurrence in an area (e.g., epidemics may have fewer cases than non-epidemics).

Question 471

What is needed for epidemiological classification?

Answer 471

- Good recording of disease prevalence in area or population - E.g., healthcare providers are required to report certain infectious diseases to their local, state/provincial, and national health departments

Question 472

_________________ are required to report certain infectious diseases to their local, state/provincial, and national health departments.

Answer 472

Healthcare providers

Question 473

What are nosocomial infections? What are the different types?

Answer 473

Healthcare-associated infections (acquired by patients while they are in a healthcare setting): - Exogenous => pathogen acquired from healthcare environment - Endogenous => pathogen arises from patient's normal microbiota - Iatrogenic => results from medical procedures (surgery, catheters, intubation, hypodermic needles) - Superinfections => use of antimicrobial drugs inhibits some resident microbiota, allowing other microbes to thrive

Question 474

What are factors influencing nosocomial infections?

Answer 474

- Exposure to numerous pathogens in a healthcare setting, including drug-resistant strains - Weakened immune system of patients - Transmission among healthcare providers, patients, and visitors

Question 475

What are ways to control nosocomial infections?

Answer 475

- Medical asepsis (good housekeeping, hand washing, sanitary food handling, proper hygiene, etc.) - Personal protective equipment (PPE = masks, gloves, gown, etc.)

Question 476

What are some Canadian public health organizations?

Answer 476

- Health Canada - Public Health Agency of Canada (PHAC)

Question 477

What are some American public health organizations?

Answer 477

- National Public Health Agency - Centers for Disease Control (CDC)

Question 478

What organization coordinates public health efforts worldwide?

Answer 478

World Health Organization (WHO)

Question 479

How do public health agencies work to limit or interrupt disease transmission?

Answer 479

- Enforce cleanliness of water and food supplies - Work to reduce disease vectors and reservoirs - Establish and enforce immunization schedules - Locate and treat individuals exposed to contagious pathogens - Establish isolation and quarantine measures - Educate the public on healthy choices to limit diseases (e.g., STDs)

Question 480

Why is it necessary to maintain a high drug concentration for sufficient time in a patient when treating an infectious disease?

Answer 480

Ensures that all the bacteria, including any that may have slower growth rates, are exposed to the drug, preventing the survival and potential development of resistant strains.