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BMS2052 MICRO > WEEK 1: MICROBIAL DIVERSITY AND PATHOGENESIS > Flashcards

WEEK 1: MICROBIAL DIVERSITY AND PATHOGENESIS Flashcards

1
Q

What 4 things does Archaea have in common with bacteria?

A
  1. Anucleate cells (Cells without nucleus)
  2. Cell envelope
  3. Generally has a single chromosome (but some exceptions)
  4. Varies in shape and size
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2
Q

What 3 things does Archaea have in common with eukaryotes?

A
  1. DNA replication, transcription and translation more like eukarya
  2. HISTONES in DNA
  3. Share similar enzymes in DNA replication of eukaryotes (DNA polymerase ,primase etc)
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3
Q

What process that contributes to the greenhouse gas effect are species of archae involved in?

A
  • Methane production from Cows!
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4
Q

What are the 4 basic shapes of bacteria?

A
  • Spherical (Cocci)
  • Rod-shaped (Bacilli)
  • Spiral (Spirochaete)
  • Curved (Commas)
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5
Q

What is an example of a spiral shaped bacteria?

A
  • Helicobacter pylori
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6
Q

What is an example of a curved shaped bacteria?

A
  • Cholera
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7
Q

What are the 5 specialised structures of MOST (but not all) bacteria?

A
  • Cell wall
  • Outer membrane
  • Capsule
  • Flagella
  • Endospores
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8
Q

Which part of the bacteria can contain the pathogenic aspect?

A
  • The outer membrane
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9
Q

Which feature of bacteria determines the shape?

A
  • The cell wall
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10
Q

In general, how thick is the gram positive layer of peptidoglycan?

A
  • It is thick

- 20-80nm thickness

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11
Q

Which two secondary cell polymers are attached to the peptidoglycan in a gram positive bacteria?

A
  • TEICHOIC ACID: Joined by phosphate groups

- LIPOTEICHOIC ACID: Extends to the surface of peptidoglycan

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12
Q

What charge does a gram positive bacteria cell wall possess?

A
  • Negative charge
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13
Q

What is the peptidoglycan layer made up of?

A
  • Peptido

- Glycan

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14
Q

What does Peptido in the peptidoglycan layer consist of?

A
  • Four amino acids (tetrapeptides)

- Both D and L amino acids

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15
Q

What does the Glycan in the peptidoglycan layer consist of?

A
  • TWO alternating sugars
  • NAG (N-acetyl glucosamine)
  • NAM (N-acetylmuramic acid)
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16
Q

Which molecule NAG and NAM similar to structurally?

A
  • Glucose
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17
Q

Which type of amino acids are ONLY unique to the bacterial cell wall?

A
  • The D amino acids
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18
Q

What are 6 functions of the cell wall in gram positive bacteria?

A
  1. Maintains SHAPE of bacteria
  2. Provides STRUCTURAL SUPPORT
  3. Contributes to PATHOGENICITY
  4. Site of action of some antibiotics
  5. Attachment
  6. Peptidoglycan provides RIGIDNESS to cell
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19
Q

How thin is the peptidoglycan sheet in gram negative bacteria?

A
  • The thin sheet of peptidoglycan –> 1-3nm
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20
Q

What does the thin peptidoglycan layer in gram -ve bacteria do?

A
  • Allows bacteria to have GREATER flexibility

- Makes it SENSITIVE TO LYSIS

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21
Q

How many periplasmic spaces are there in gram negatvie bacteria?

A
  • 2!
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22
Q

What percentage of lipid makes up the OM of gram negative bacteria?

A
  • 15%
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23
Q

What are 4 things that the OM in gram negative bacteria contains?

A
  • Protein (porin peroteins)
  • Lipoprotein (Brauns Lipoprotein)
  • Phospholipid (membrane bilayer)
  • LPS in uppermost layer
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24
Q

What are the two components of the LPS layer?

A
  • Lipid A

- O specific Polysaccharide side chain –> O ANTIGEN

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25
Q

What does Lipid A function as in the LPS layer of gram negative bacteria?

A
  • An endotoxin

- Released in salmonella to cause nasty immune responses

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26
Q

Which part of the LPS is used to evade immune defenses via antigenic variation?

A
  • Glycan O antigen —> Molecular mimicary and evasion
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27
Q

What are 3 positive things that LPS does for BACTERIA?

A
  • Helps with the structural integrity of OM and allows certain chemicals in (permeability)
  • Increases the negative charge of cell membrane + stabilises the membrane structure
  • ESSENTIAL FOR BACTERIAL SURVIVAL
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28
Q

What are examples of bacteria that COMPLETELY lack peptidoglycan?

A
  • Chlamydiae (STI) and Planctomycetes
  • Also intracellular parasites –> c.f. RIckettsia and Mycoplasma
  • They maintain their shape despite having no peptidoglycan
  • Stain gram negative
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29
Q

Are the bacteria that completely lack peptidoglycan sensitive to Penicillin and beta-lactam antibiotics?

A
  • NO

- They are INSENSITIVE

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30
Q

What is an example of bacteria that naturally lack a cell wall and 3 features of them?

A

Mycoplasmataceae

  1. VERY SMALL (0.1-0.5 microm)
  2. Pleomorphic (Ability to alter shape and size) e.g. coccus, donut shaped, filamentous
  3. INSENSITIVE to Penicillins or other Beta lactams (because of no peptidoglycan)
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31
Q

What types of diseases can strains of Mycoplasmataceae cause?

A
  • Pelvic inflammatory disease as some are sexually transmitted
  • Cause atypical pneumonia in humans
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32
Q

What is the name for bacteria with a unique atypical outer membrane?

A
  • Acid Fast Bacterial Cell Wall
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33
Q

What types of lipids are contained in the Acid Fast Bacterial Cell Wall?

A
  • Mycolic acid (main one) or Cord Factor (found in Mycobacterium TB)
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34
Q

What does the waxy nature caused by the lipids of the Acid fast cell wall cause it to be?

A
  • Hydrophobic
  • Impenetrable to most organic molecules + antibiotics
  • HIGH resistance to chemicals and dyes
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35
Q

Which component of the acid fast cell wall contributes to the pathogenicity? -

A
  • The mycolic acid as it gives it the waxy component
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36
Q

Which 5 things does the bacterial cytoplasm comprise of?

A
  1. Cytosol
  2. Nucleoid–> Chromosome
  3. Ribosomes (cell wall production)
  4. Inclusion (endospores)
  5. Cytoskeletal components
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37
Q

Which type of bacterial ribosome does antibiotics target and why doesn’t it kill our own cells?

A
  • Targets the 70S ribosomes to STOP protein synthesis

- Doesn’t kill our cells because they have 80S ribosomes

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38
Q

What sequence does the 16S rRNA bind to?

A
  • The Shine-dalgano sequence
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39
Q

What is the 16S rRNA a component of and what is it the scaffold for?

A
  • Component of the 30S ribosome unit in prokaryotes

- Scaffold for the protein component

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40
Q

Does the 16S rRNA have BOTH conserved and variable sections? **

A
  • YES
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41
Q

Is the 16 rRNA conserved in bacteria?

A
  • YES
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42
Q

If bacteria contains capsules are you supposed to heat fix when staining?

A
  • NO!

- Could denature the protein layers (glycoprotein)

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43
Q

What do the bacterial capsules (glycocalyx) contain?

A
  • Loose polysaccharide or protein layers on OUTER surface of cell wall of SOME bacteria whether they are gram +ve or -ve
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44
Q

What are 4 functions of bacterial capsules?

A
  1. Protects against dessication
  2. Prevents bacteriophages from attachment and infection
  3. Protects against phagocytosis
  4. Mediate bacterial attachment to solid surfaces
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45
Q

What do the capsules of Strep. Pneumoniae and Klebsiella pneumoniae cause?

A
  • Prevent their destruction in the respiratory tract and cause pneumonia
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46
Q

Are uncapsulated strains of Step.Pneumoniae and Klebsiella pneumoniae pathogenic?

A
  • NO

- Basis of vaccines

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47
Q

What are some characteristics of bacterial flagella?

A
  • Long, whip like structures that extend beyond the surface of the bacterial cell
  • Aid cell motility
48
Q

What are 3 things things that flagella enable bacetria to do?

A
  1. Flee from harmful environments
  2. Move towards favorable environments
  3. Move bacteria forward or backward -depending on direction of flagella motor
49
Q

What are pili/fimbriae (what are they composed of) and what are their functions?

A
  • Hairlike structures on the outside of bacteria
  • Smaller than flagella
  • Higher number than flagella
  • Composed of pilin (protein subunuits)
  • AID IN BACTERIAL ADHESION AND IMPORTANT VIRULENCE FACTORS–> Sex pili (transfer of genetic material)
  • also virulence factors to host cells –> E.coli
50
Q

What are bacterial endospores?

A
  • Dormant, tough, NON-REPRODUCTIVE structure in cytoplasm of certain bacteria (Bacillus and Clostridium)
51
Q

How many bacterial cells does one spore give rise to?

A
  • ONE!!!
52
Q

What are bacterial spores resistant to?

A
  • UV radiation
  • Dessication
  • Heat
  • Freezing
  • Chemical Disinfectants
53
Q

When are spores produced?

A
  • When environmental conditions become unfavorable
54
Q

What is normal flora defined as?

A
  • The mixture of microbes present on a healthy human
55
Q

What is resident flora termed as?

A
  • Organisms consistently found at a given site (normally) and are always present there
56
Q

What is transient flora termed as?

A
  • Not always present at a given site
57
Q

In utero, are there microorganisms colonising the fetus’ skin?

A
  • No that only happens after birth

- Different microflora based on type of birth

58
Q

What are the two most common bacteria present in ALL humans?

A
  • Staphylococcus epidermis

- Escherichia coli

59
Q

What are 5 characteristics of the Staphylococcus genus?

A
  • Gram Positive cocci
  • Form IRREGULAR clusters-divide in multiple planes (grapes)
  • NON-motile
  • Facultative anaerobes (grow in presence OR absence of O2)
  • Catalase positive
60
Q

What does the presence of E.coli in the gut supress?

A
  • Suppresses the growth of harmful bacteria
61
Q

When can E.coli cause disease? (2 things)

A
  • In debilitated and immunosuppressed people

- When GI barriers are violated

62
Q

What bacteria is the most common cause of a UTI?

A
  • E.coli
63
Q

In a healthy human, are the internal tissues such as brain, CSF, blood, kidneys and liver?

A
  • YES!

- But not in all cases

64
Q

What is mutualism defined as and what is an example?

A
  • Two independent organisms living together to theri MUTUAL BENEFIT
  • e.g. E.coli in colon produces Vit K and some B vitamins
  • bacteria break down WASTE
  • BACTERIA benefit by having food supply and sheltered environment
65
Q

What is commensalism defined as?

A
  • Normal flora that NEITHER hurt, harm, nor benefit the carrying host
  • e.g. normal flora (residents, commensals)
66
Q

What is paratism defined as?

A
  • Where one organism benefits at the EXPENSE of the other
67
Q

What kind of relationship with us is normal flora considered to be? (2 types)

A
  • Commensalistic or Mutualistic
68
Q

When are normal flora considered to be in a parasitic relationship?

A
  • When they cause infection
    e. g. Opportunistic pathogens
    e. g. E.coli, Strep pneumoniae, Candida albicans
69
Q

What is the carrier defined as in terms of bacteria-human relationship?

A
  • Infected individual who is not diseased (potential source of infection)
70
Q

What are the two types of acute carrier and what is an explanation?

A
  • Incubatory –> incubating the pathogen but not ill yet

- Convalescent–> Recovered but has LARGE NUMBERS OF PATHOGEN

71
Q

What is a chronic carrier of a disease?

A
  • Harbors pathogen for LONG PERIODS
  • Multiplication and shedding occur at LOW levels
  • Capable of transmitting infection
  • SOMETIMES THERE IS ABSENCE OF SYMPTOMS OF DISEASE
72
Q

What is an asymptomatic carrier defined as and what is an example?

A
  • Harbors pathogen for LONG PERIODS
  • Multiplication and shedding occur at LOW levels
  • Capable of transmitting infection
  • COMPLETE ABSENCE OF ANY SYMPTOMS OF DISEASE
    e. g. Typhoid Mary
73
Q

What is one thing that normal flora on the skin do?

A
  • Produce FAs
74
Q

What are 6 things that gut bacteria can do that is beneficial for us?

A
  1. Aid digestion (dietary fibre)
  2. Ferment unused energy substrates
  3. Produce bacteriocins and colicins (antibacterial) 3=
  4. Synthesize and excrete vitamins (B12)
  5. train immune system
  6. Boost immunity (antigenic stimulation by gut flora)
75
Q

What is the role of vaginal lactobacilli and what kind of environment is it ?

A
  • Acid envrionment suppresses growth of other bacterial inhabitants
  • Thought to decrease thrush
76
Q

What process do adults eliminate 3E13 microorganisms daily via?

A
  • Peristalsis
77
Q

What makes skin an inhospitable environment for some microorganisms?

A
  • Slightly acidic pH
  • HIGH CONCENTRATION of NaCl
  • Lots of areas LOW INMOISTURE (a part from underarms where tinea fungus can grow)
78
Q

Which inhibitory substances does skin contain?

A
  • Lysozymes

- Cathelicidins

79
Q

Where is the normal flora of the nose found?

A
  • Just inside the nostrils
80
Q

Which enzyme does nasal mucous contain?

A
  • Lysozyme
81
Q

What are the main bacteria found in the nose?

A
  • Staphylococcus spp. (Epidermis and aureus)-main one
  • Aerobic corynebacteria (DIPTHEROIDS)
  • SMALL NUMBERS OF : Strep. pneumoniae, Neisseria meningitidis and haemophillus influenzae in NASOPHARYNX
82
Q

Are there normally microbiota in the lower respiratory tract (trachea, bronchi, bronchioles and alveoli-lungs)?

A
  • NO!!
  • Cilia produce mucous which removes them
  • Macrophages
83
Q

Why is saliva not a good culture medium?

A
  • Because it contains antibacterial substances like lyzozymes
84
Q

What is Glycoxalyx?

A
  • A glycoprotein and polysaccharide layer that covers surface of epithelial cells
85
Q

What are two types of baceria that are acid tolerant and thus found in the stomach?

A
  • Lactobacilli

- Streptococci

86
Q

Which part of the small intestine contains the most bacterial numbers per gram which is indicated as moderate?

A
  • The ileum

More similar to the colon microbiota as pH more alkaline

87
Q

Which part of the gut contains the largest number of bacteria?

A
  • The large intestine
88
Q

Which class of bacteria predominates the oxygen depleted area in the large intestine?

A
  • The anaerobes–> 95-99% (Bacteriodes) and facultative anaerboes (E.coli)
89
Q

What is disease defined as?

A
  • When the body no longer functions properly

- Due to genetic, metabolic, deficiency, or infection

90
Q

What is infection defined as and what is the time frame?

A
  • When bacteria or microorganisms penetrate the host defenses
  • Invade tissues
  • Multiply
  • Time-frame is WEEKS e.g. Hepatitis- 14 days
91
Q

What is intoxication and what is the timeframe?

A
  • When the bacteria produce toxins due to food/chemicals present
  • Can occur within 30mins-2hrs of consumption
92
Q

What are pathogens defined as?

A
  • MICROORGANISM WITH THE POTENTIAL TO CAUSE DISEASE
  • Bacteria that are never part of the normal flora e.g. Mycobacerium TB
  • Or can be normal flora that acquire virulence or antibiotic resistance determinants (E.coli or Staph.aureus)
93
Q

What is pathogenicity defined as?

A
  • The CAPACITY of an organism to enter a host and CAUSE DISEASE
94
Q

What is virulence defined as?

A
  • A measure of pathogenicity

- The degree of intensity of pathogenicity –> the MORE virulent, the MORE damage is caused

95
Q

What is a virulence factor required by an organism to cause?

A
  • Virulence factor is required by the organism to cause disease
96
Q

What processes do virulence determinants which are expressed by pathogens mediate to cause disease?

A
  • Adhesion (ligands for cells)
  • Anti-phagocytic (Capsule)
  • Damage (Toxin)
97
Q

What are the 4 general steps in bacteria causing disease?

A
  1. Exposure (to pathogens)
  2. Adherence (to skin or mucosa)
  3. Penetration/Invasion (through epithelium)
  4. Colonization and Growth (Production of virulence factors)
98
Q

What are the two types of sources where an infectious agent is acquired?

A
  1. Inamimate

2. Animate

99
Q

What are examples of Inamimate sources of infection?

A
  • Food, soil, water

- inanimate objects (fomites) –> hospital/industrial equipment, soiled linen, dressings

100
Q

What are examples of animate sources of infection?

A
  • Animals (zoonosis) –> Pets, food source
  • Insects
  • Humans –> patients, family members, staff, casual contacts (carriers)
101
Q

What are the 3 types of transmission between humans?

A
  • Respiratory or salivary spread (aerosol, saliva)
  • Faecal-oral spread (good public health hygiene)
  • Venereal Spread (sexually and difficult to control)
102
Q

What are the 3 types of anthropod-borne infections and zoonoses?

A
  • Vector (biting anthropod)e.g. malaria,typhus, sandfly
  • Vertebrate reservoir e.g Rabies
  • Vector-vertebrate reservoir e.g. Plague, yellow fever
103
Q

What are the 4 general modes of transmission of pathogens?

A
  • Airborne
  • Contact
  • Vehicle
  • Vector borne
104
Q

What is the droplet spread for airborne transmission and which particle is an important route of transmission, and how large are the particles?

A
  • Travels LONG distances
  • MORE than 1m
  • Dust particles
  • Particles are SMALL (1-4microm)
105
Q

What is the droplet spread for contact transmission, and how large are the particles?

A
  • Travel LESS than 1m

- Particles are LARGE (more than 5microm)

106
Q

What are fomites in vehicle transmission of pathogens?

A
  • Common vehicles like surgical instruments, bedding, eating utensils
107
Q

What are nosicomal infections?

A
  • HOSPITAL acquired infections e.g. biofilms from own flora, catheders
  • Major source of morbidity and mortality
108
Q

What are biofilms composed of?

A
  • “…microorganisms attached to the surface and encased in a hydrated polymeric matrix of their own synthesis”
109
Q

What are the majority of hospital acquired infections due to?

A
  • Biofilms
110
Q

What are 3 examples of HAI (hospital acquired infections-nosocomial)?

A
  • Staphylococcal infections
  • Hospital acquired Legionnaires disease (from cooling towers)
  • UTIs
111
Q

What are the three sources of infection for nosocomial (HAI)?

A
  • Self infection
  • Staff/patient or patient/patient
  • Environment
112
Q

Which bacterium is the major cause of nosocomial HAI?

A
  • S.aureus –> golden Staph
113
Q

Which people does S.aureus manly manifest itself in?

A
  • In immuno-compromised people
114
Q

What is the MRSA S. aureus resistant to?

A
  • Methicillin –> this is a semi synthetic penicillin (antibiotic)
115
Q

What is the VRSA S.aureus resistant to?

A
  • Vancomycin antibiotic

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