WEEK 1: MICROBIAL DIVERSITY AND PATHOGENESIS Flashcards
(115 cards)
1
Q
What 4 things does Archaea have in common with bacteria?
A
- Anucleate cells (Cells without nucleus)
- Cell envelope
- Generally has a single chromosome (but some exceptions)
- Varies in shape and size
2
Q
What 3 things does Archaea have in common with eukaryotes?
A
- DNA replication, transcription and translation more like eukarya
- HISTONES in DNA
- Share similar enzymes in DNA replication of eukaryotes (DNA polymerase ,primase etc)
3
Q
What process that contributes to the greenhouse gas effect are species of archae involved in?
A
- Methane production from Cows!
4
Q
What are the 4 basic shapes of bacteria?
A
- Spherical (Cocci)
- Rod-shaped (Bacilli)
- Spiral (Spirochaete)
- Curved (Commas)
5
Q
What is an example of a spiral shaped bacteria?
A
- Helicobacter pylori
6
Q
What is an example of a curved shaped bacteria?
A
- Cholera
7
Q
What are the 5 specialised structures of MOST (but not all) bacteria?
A
- Cell wall
- Outer membrane
- Capsule
- Flagella
- Endospores
8
Q
Which part of the bacteria can contain the pathogenic aspect?
A
- The outer membrane
9
Q
Which feature of bacteria determines the shape?
A
- The cell wall
10
Q
In general, how thick is the gram positive layer of peptidoglycan?
A
- It is thick
- 20-80nm thickness
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
12
Q
What charge does a gram positive bacteria cell wall possess?
A
- Negative charge
13
Q
What is the peptidoglycan layer made up of?
A
- Peptido
- Glycan
14
Q
What does Peptido in the peptidoglycan layer consist of?
A
- Four amino acids (tetrapeptides)
- Both D and L amino acids
15
Q
What does the Glycan in the peptidoglycan layer consist of?
A
- TWO alternating sugars
- NAG (N-acetyl glucosamine)
- NAM (N-acetylmuramic acid)
16
Q
Which molecule NAG and NAM similar to structurally?
A
- Glucose
17
Q
Which type of amino acids are ONLY unique to the bacterial cell wall?
A
- The D amino acids
18
Q
What are 6 functions of the cell wall in gram positive bacteria?
A
- Maintains SHAPE of bacteria
- Provides STRUCTURAL SUPPORT
- Contributes to PATHOGENICITY
- Site of action of some antibiotics
- Attachment
- Peptidoglycan provides RIGIDNESS to cell
19
Q
How thin is the peptidoglycan sheet in gram negative bacteria?
A
- The thin sheet of peptidoglycan –> 1-3nm
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
21
Q
How many periplasmic spaces are there in gram negatvie bacteria?
A
- 2!
22
Q
What percentage of lipid makes up the OM of gram negative bacteria?
A
- 15%
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
24
Q
What are the two components of the LPS layer?
A
- Lipid A
- O specific Polysaccharide side chain –> O ANTIGEN
25
What does Lipid A function as in the LPS layer of gram negative bacteria?
- An endotoxin
| - Released in salmonella to cause nasty immune responses
26
Which part of the LPS is used to evade immune defenses via antigenic variation?
- Glycan O antigen ---> Molecular mimicary and evasion
27
What are 3 positive things that LPS does for BACTERIA?
- 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
28
What are examples of bacteria that COMPLETELY lack peptidoglycan?
- Chlamydiae (STI) and Planctomycetes
- Also intracellular parasites --> c.f. RIckettsia and Mycoplasma
- They maintain their shape despite having no peptidoglycan
- Stain gram negative
29
Are the bacteria that completely lack peptidoglycan sensitive to Penicillin and beta-lactam antibiotics?
- NO
| - They are INSENSITIVE
30
What is an example of bacteria that naturally lack a cell wall and 3 features of them?
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)
31
What types of diseases can strains of Mycoplasmataceae cause?
- Pelvic inflammatory disease as some are sexually transmitted
- Cause atypical pneumonia in humans
32
What is the name for bacteria with a unique atypical outer membrane?
- Acid Fast Bacterial Cell Wall
33
What types of lipids are contained in the Acid Fast Bacterial Cell Wall?
- Mycolic acid (main one) or Cord Factor (found in Mycobacterium TB)
34
What does the waxy nature caused by the lipids of the Acid fast cell wall cause it to be?
- Hydrophobic
- Impenetrable to most organic molecules + antibiotics
- HIGH resistance to chemicals and dyes
35
Which component of the acid fast cell wall contributes to the pathogenicity? -
- The mycolic acid as it gives it the waxy component
36
Which 5 things does the bacterial cytoplasm comprise of?
1. Cytosol
2. Nucleoid--> Chromosome
3. Ribosomes (cell wall production)
4. Inclusion (endospores)
5. Cytoskeletal components
37
Which type of bacterial ribosome does antibiotics target and why doesn't it kill our own cells?
- Targets the 70S ribosomes to STOP protein synthesis
| - Doesn't kill our cells because they have 80S ribosomes
38
What sequence does the 16S rRNA bind to?
- The Shine-dalgano sequence
39
What is the 16S rRNA a component of and what is it the scaffold for?
- Component of the 30S ribosome unit in prokaryotes
| - Scaffold for the protein component
40
Does the 16S rRNA have BOTH conserved and variable sections? **
- YES
41
Is the 16 rRNA conserved in bacteria?
- YES
42
If bacteria contains capsules are you supposed to heat fix when staining?
- NO!
| - Could denature the protein layers (glycoprotein)
43
What do the bacterial capsules (glycocalyx) contain?
- Loose polysaccharide or protein layers on OUTER surface of cell wall of SOME bacteria whether they are gram +ve or -ve
44
What are 4 functions of bacterial capsules?
1. Protects against dessication
2. Prevents bacteriophages from attachment and infection
3. Protects against phagocytosis
4. Mediate bacterial attachment to solid surfaces
45
What do the capsules of Strep. Pneumoniae and Klebsiella pneumoniae cause?
- Prevent their destruction in the respiratory tract and cause pneumonia
46
Are uncapsulated strains of Step.Pneumoniae and Klebsiella pneumoniae pathogenic?
- NO
| - Basis of vaccines
47
What are some characteristics of bacterial flagella?
- Long, whip like structures that extend beyond the surface of the bacterial cell
- Aid cell motility
48
What are 3 things things that flagella enable bacetria to do?
1. Flee from harmful environments
2. Move towards favorable environments
3. Move bacteria forward or backward -depending on direction of flagella motor
49
What are pili/fimbriae (what are they composed of) and what are their functions?
- 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
What are bacterial endospores?
- Dormant, tough, NON-REPRODUCTIVE structure in cytoplasm of certain bacteria (Bacillus and Clostridium)
51
How many bacterial cells does one spore give rise to?
- ONE!!!
52
What are bacterial spores resistant to?
- UV radiation
- Dessication
- Heat
- Freezing
- Chemical Disinfectants
53
When are spores produced?
- When environmental conditions become unfavorable
54
What is normal flora defined as?
- The mixture of microbes present on a healthy human
55
What is resident flora termed as?
- Organisms consistently found at a given site (normally) and are always present there
56
What is transient flora termed as?
- Not always present at a given site
57
In utero, are there microorganisms colonising the fetus' skin?
- No that only happens after birth
| - Different microflora based on type of birth
58
What are the two most common bacteria present in ALL humans?
- Staphylococcus epidermis
| - Escherichia coli
59
What are 5 characteristics of the Staphylococcus genus?
- 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
What does the presence of E.coli in the gut supress?
- Suppresses the growth of harmful bacteria
61
When can E.coli cause disease? (2 things)
- In debilitated and immunosuppressed people
| - When GI barriers are violated
62
What bacteria is the most common cause of a UTI?
- E.coli
63
In a healthy human, are the internal tissues such as brain, CSF, blood, kidneys and liver?
- YES!
| - But not in all cases
64
What is mutualism defined as and what is an example?
- 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
What is commensalism defined as?
- Normal flora that NEITHER hurt, harm, nor benefit the carrying host
- e.g. normal flora (residents, commensals)
66
What is paratism defined as?
- Where one organism benefits at the EXPENSE of the other
67
What kind of relationship with us is normal flora considered to be? (2 types)
- Commensalistic or Mutualistic
68
When are normal flora considered to be in a parasitic relationship?
- When they cause infection
e. g. Opportunistic pathogens
e. g. E.coli, Strep pneumoniae, Candida albicans
69
What is the carrier defined as in terms of bacteria-human relationship?
- Infected individual who is not diseased (potential source of infection)
70
What are the two types of acute carrier and what is an explanation?
- Incubatory --> incubating the pathogen but not ill yet
| - Convalescent--> Recovered but has LARGE NUMBERS OF PATHOGEN
71
What is a chronic carrier of a disease?
- 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
What is an asymptomatic carrier defined as and what is an example?
- 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
What is one thing that normal flora on the skin do?
- Produce FAs
74
What are 6 things that gut bacteria can do that is beneficial for us?
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
What is the role of vaginal lactobacilli and what kind of environment is it ?
- Acid envrionment suppresses growth of other bacterial inhabitants
- Thought to decrease thrush
76
What process do adults eliminate 3E13 microorganisms daily via?
- Peristalsis
77
What makes skin an inhospitable environment for some microorganisms?
- Slightly acidic pH
- HIGH CONCENTRATION of NaCl
- Lots of areas LOW INMOISTURE (a part from underarms where tinea fungus can grow)
78
Which inhibitory substances does skin contain?
- Lysozymes
| - Cathelicidins
79
Where is the normal flora of the nose found?
- Just inside the nostrils
80
Which enzyme does nasal mucous contain?
- Lysozyme
81
What are the main bacteria found in the nose?
- Staphylococcus spp. (Epidermis and aureus)-main one
- Aerobic corynebacteria (DIPTHEROIDS)
- SMALL NUMBERS OF : Strep. pneumoniae, Neisseria meningitidis and haemophillus influenzae in NASOPHARYNX
82
Are there normally microbiota in the lower respiratory tract (trachea, bronchi, bronchioles and alveoli-lungs)?
- NO!!
- Cilia produce mucous which removes them
- Macrophages
83
Why is saliva not a good culture medium?
- Because it contains antibacterial substances like lyzozymes
84
What is Glycoxalyx?
- A glycoprotein and polysaccharide layer that covers surface of epithelial cells
85
What are two types of baceria that are acid tolerant and thus found in the stomach?
- Lactobacilli
| - Streptococci
86
Which part of the small intestine contains the most bacterial numbers per gram which is indicated as moderate?
- The ileum
| More similar to the colon microbiota as pH more alkaline
87
Which part of the gut contains the largest number of bacteria?
- The large intestine
88
Which class of bacteria predominates the oxygen depleted area in the large intestine?
- The anaerobes--> 95-99% (Bacteriodes) and facultative anaerboes (E.coli)
89
What is disease defined as?
- When the body no longer functions properly
| - Due to genetic, metabolic, deficiency, or infection
90
What is infection defined as and what is the time frame?
- When bacteria or microorganisms penetrate the host defenses
- Invade tissues
- Multiply
- Time-frame is WEEKS e.g. Hepatitis- 14 days
91
What is intoxication and what is the timeframe?
- When the bacteria produce toxins due to food/chemicals present
- Can occur within 30mins-2hrs of consumption
92
What are pathogens defined as?
- 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
What is pathogenicity defined as?
- The CAPACITY of an organism to enter a host and CAUSE DISEASE
94
What is virulence defined as?
- A measure of pathogenicity
| - The degree of intensity of pathogenicity --> the MORE virulent, the MORE damage is caused
95
What is a virulence factor required by an organism to cause?
- Virulence factor is required by the organism to cause disease
96
What processes do virulence determinants which are expressed by pathogens mediate to cause disease?
- Adhesion (ligands for cells)
- Anti-phagocytic (Capsule)
- Damage (Toxin)
97
What are the 4 general steps in bacteria causing disease?
1. Exposure (to pathogens)
2. Adherence (to skin or mucosa)
3. Penetration/Invasion (through epithelium)
4. Colonization and Growth (Production of virulence factors)
98
What are the two types of sources where an infectious agent is acquired?
1. Inamimate
| 2. Animate
99
What are examples of Inamimate sources of infection?
- Food, soil, water
| - inanimate objects (fomites) --> hospital/industrial equipment, soiled linen, dressings
100
What are examples of animate sources of infection?
- Animals (zoonosis) --> Pets, food source
- Insects
- Humans --> patients, family members, staff, casual contacts (carriers)
101
What are the 3 types of transmission between humans?
- Respiratory or salivary spread (aerosol, saliva)
- Faecal-oral spread (good public health hygiene)
- Venereal Spread (sexually and difficult to control)
102
What are the 3 types of anthropod-borne infections and zoonoses?
- Vector (biting anthropod)e.g. malaria,typhus, sandfly
- Vertebrate reservoir e.g Rabies
- Vector-vertebrate reservoir e.g. Plague, yellow fever
103
What are the 4 general modes of transmission of pathogens?
- Airborne
- Contact
- Vehicle
- Vector borne
104
What is the droplet spread for airborne transmission and which particle is an important route of transmission, and how large are the particles?
- Travels LONG distances
- MORE than 1m
- Dust particles
- Particles are SMALL (1-4microm)
105
What is the droplet spread for contact transmission, and how large are the particles?
- Travel LESS than 1m
| - Particles are LARGE (more than 5microm)
106
What are fomites in vehicle transmission of pathogens?
- Common vehicles like surgical instruments, bedding, eating utensils
107
What are nosicomal infections?
- HOSPITAL acquired infections e.g. biofilms from own flora, catheders
- Major source of morbidity and mortality
108
What are biofilms composed of?
- "...microorganisms attached to the surface and encased in a hydrated polymeric matrix of their own synthesis"
109
What are the majority of hospital acquired infections due to?
- Biofilms
110
What are 3 examples of HAI (hospital acquired infections-nosocomial)?
- Staphylococcal infections
- Hospital acquired Legionnaires disease (from cooling towers)
- UTIs
111
What are the three sources of infection for nosocomial (HAI)?
- Self infection
- Staff/patient or patient/patient
- Environment
112
Which bacterium is the major cause of nosocomial HAI?
- S.aureus --> golden Staph
113
Which people does S.aureus manly manifest itself in?
- In immuno-compromised people
114
What is the MRSA S. aureus resistant to?
- Methicillin --> this is a semi synthetic penicillin (antibiotic)
115
What is the VRSA S.aureus resistant to?
- Vancomycin antibiotic
