Bacteriology Flashcards
(194 cards)
1
Q
What are Koch’s postulates?
A
A specific bacterium causes a specific disease so
- Bacterium must be present in every case of the disease
- Must be able to isolate the bacterium from the disease and grow it in pure culture
- Specific disease must be reproduced from pure culture in healthy susceptible host
- Bacterium must again be recovered
2
Q
How big are bacteria and how big are mammalian cells?
A
About 0.5-3 x 0.5 micrometers
Anthrax is big, 8-10 micrometers
Human 10-100micrometers
3
Q
What are nosocomial infections?
A
Hospital-borne
4
Q
Who was Mary Mallon?
A
A carrier of typhoid
small percentage of salmonella typhi remained in her gallbladder, periodically shed in faeces
5
Q
What is an endemic disease
A
A disease that occurs regularly at low or moderate frequency
e.g. dental caries
6
Q
What is epidemic disease?
A
A sudden appearance of disease, or increase above the endemic level
e.g. diphtheria
7
Q
What is pandemic disease?
A
Global epidemic
e.g. cholera
8
Q
What are the modes of transmission?
A
Direct:
- Horizontal (sexual, respiratory tract via droplets, contamination from own flora, contact with skin and eyes)
- Vertical (transplacental, parturition)
Indirect:
- Inanimate objects (nosocomial, food intoxication or infection, water faecal-oral or air-con respiratory, animals, soil via spores)
9
Q
Legionnaire’s
A
Legionella pneumophilia
Pneumonic disease
Contracted indirectly via water droplets in air con units
10
Q
Name an obligate intracellular parasite bacterial infection
A
Chlamydia
11
Q
How many genes do bacteria and mammals cause?
A
4500 genes, humans 22K gnees
12
Q
What is the cytoskeleton like in bacteria and mammals?
A
Bacteria = rudimentary, ancient homologue of actin Mammals = extensive
13
Q
How do bacteria move?
A
Rotating flagella
Extending/retracting pili
14
Q
How do bacteria divide?
A
Binary fission
15
Q
What are bacterial genomes like? What are mammalian?
A
Haploid usually single and circular + plasmids, bacteriophage
Mammalian: diploid, haploid gametes. Multiple (linear) + mitochondria
16
Q
What are bacterial and mammalian mRNAs like?
A
Bacterial: polycistronic (co-linear), unstable
Mammalian: spliced introns out, 3’ polyA, 5’ cap, often stable, single genes
17
Q
How do you regulate transcription in bacteria and mammalian cells?
A
Bacteria transcription initiation
Mammals often post-transcriptional
18
Q
How do bacteria divide?
A
Binary fission:
Rods = divide on terminal axis –> get chains
Cocci = divide in all planes –> cluster
19
Q
What shape are salmonella?
A
Rods
20
Q
What shape are E coli?
A
Rods
21
Q
What shape is vibrio cholera?
A
Curved rods
22
Q
What shape is trepanoma?
A
Syphilis
Spiral
23
Q
What shape is helicobacter?
A
Gastric ulcer
Spiral
24
Q
Which bacteria produce endospores?
A
Clostridium tetani
Clostridium perfringens
Clostridium botulinum
Bacillus anthraxis
25
How do you gram stain bacteria?
Crystal violet and iodine
Ethanol wash
Counterstain with safranin (pink)
26
What is the difference between gram positive and gram negative?
```
+ = thicker peptidoglycan wall
- = extra membrane so LPS, porins in it
```
27
Which bacteria don't gram stain and why? What do you use instead?
Mycobacteria = waxy lipid coat so called acid fast
Ziehl-Neelsen stain
Chlamydia and mycoplasma = non-gonococcal urethritis = no cell wall, difficult to culture
28
What is the structure of bacterial cell walls?
Peptidoglycan]NAG and NAM cross linked by short oligopeptides (pentapeptides), and also cross links vertically to link the sheets into a thick layer
29
What is the periplasm?
Space between two membranes of gram -ve bacteria
| Contains hydrolytic enzymes and components of transport
30
What is in the outer membrane of gram - bacteria?
Porins
Channels essential to import and export
LPS
31
What are the components of LPS?
O antigen. Highly variable, generates different antigens and therefore serotypes. Important defence against host attack against complement and macrophages.
Core polysaccharide.
A antigen. Endotoxin. Released from dying bacteria. Triggers wide ranging immune response. Recognised by TLR4.
32
What is the function of the capsule?
Prevents drying during droplet infection
| Protects from complement and macrophage
33
What is the clinical effect of lipid A?
Have to judge when to give antibiotics for patients with bacteraemia- otherwise massive endotoxin release could lead to shock
34
How do proteins cross the inner cell membrane in bacteria?
N-terminal secretion signal and Sec pathway
| Then additional export pathways across periplasm and outer membrane
35
What is TolC?
An exit duct for large toxin proteins and noxious molecules like antibiotics
36
How often do E. Coli numbers double in lab culture?
20-30mins
37
What concentration of bacteria can you just about see in a practical?
10^5/ml
38
How do bacteria physically divide after chromosome duplication?
FtsZ, a tubulin ancestor involved in cell division localises at midcell, forms ring that tightens, then new membrane and peptidoglycan form at division site
39
Name 2 facultative anaerobes
```
Staphylococcus (aureus, epidermidis)
Streptococcus (pyogenes, pneumonia, viridans)
E coli
Enterococcus faecalis
Salmonella
```
40
Name 2 strict anaerobes
Clostridium
| Bacteriodes
41
Discuss the structure of the mechanism that rotates the flagellum
Universal joint motor that rotates 360 degrees
H+ switch (H+ into cell)
Rings around motor that stop the rotation from damaging the cell membrane
42
How do bacteria choose where to go?
Chemotaxis
Chemoreceptors at nose of cell --> histidine-aspartate phosphorelay --> flagellar motor switch --> CCW to swim, CW to 'tumble' and randomly change direction
43
How fast can bacteria move?
30 microns/s
44
Define operon
Contiguous genes whose transcription is coupled
45
What is HAP?
Histidine-aspartate phosphorelay signalling pathways
46
What is global regulation?
Co-regulation of expression of regulons
47
Define regulon
A set of operons switched on and off by the same phosphorelays
48
What is quorum sensing?
Where some pathogens switch on their virulence genes when its population reaches a specific density
49
How does quorum sensing work?
Bacteria release small signal molecules and sense its concentration
50
What does pseudomonas aeruginosa switch on with quorum sensing?
Genes for swarming, polysaccharide production, biofilm formation, virulence
51
What are K antigens of Salmonella and E Coli?
Capsular polysaccharide
52
How does the bacterial genome change?
1. Mutations
2. DNA rearrangements due to random capture and insertion of insertion sequences (through their own recombination system)
3. Transposons (often have IS at their ends)
53
What can transposons encode that is useful to the pathogen? And necessary for itself?
Antibiotic/heavy metal resistance, virulence genes
DNA transfer genes
Plasmid replication genes
54
What are pathogenicity islands?
Genes required for infection and survival in the host are found in groups within the genome
55
What is the evidence for pathogenicity islands having joined recently?
Differing GC content of surrounding chromosomal DNA
56
What does salmonella encode on its pathogenicity islands?
SP1 - entry to non-phagocytic cells
| SP2 - survival in macrophages
57
How do bacteria acquire and transfer DNA?
1. Transduction - bacteriophage viruses transfer DNA
2. Transformation - uptake DNA released from dead lysed bacteria
3. Conjugation - direct transfer between two bacteria via a sex pilus
58
How was transformation discovered?
Released that dead capsulated Strep Pneumoniae transformed live non-capsulated bacteria into capsulated agents that could kill mice
59
Where is lactobacillus found?
Oral cavity, urethra/vagina
60
TLR2
Recognises peptidoglycan
61
TLR4
Recognises LPS
62
TLR5
Recognises flagellin
63
TLR9
Recognises unmethylated DNA
64
Discuss virulence genes
- Specialised: not constitutively expressed but switched on in response to host environmental signals, global regulation
- carried on plasmids, bacteriophage and/or pathogenicity islands
- encode proteins or other molecules that are exported and secreted or are delivered into host cells
65
How do uropathogenic E Coli colonise the host?
P-pilus adhesin binds a kidney glycolipid receptor
66
What is the most common cause of UTIs?
E coli from the host's own colon flora ascending
67
How does UPEC cause disease?
Haemolysin forms pores
| LPS triggers inflammation
68
How does proteus cause infection?
Urease cleaves urea to ammonia, increases pH, salt precipitates out, causes kidney stones
69
How are type 1 and P-pili assembled on UPEC?
1. Pilus subunits pumped across inner membrane by SEC
2. Chaperones transfer across to usher proteins with an adhesin at the top
3. Another system pushes the pili out through the usher proteins far enough to interact with the kidney cell
70
Why does UPEC recur?
superficial epithelial cells undergo exfoliation due to urine flow, UPEC can invade underlying immature cells where they persist as quiescent reservoirs and aren’t reached by antibiotics. Can then resurge and enter bladder lumen --> further acute infection
71
How does EPEC colonise the colon?
* Interaction with host cytoskeleton
* Injects effector cells using specialised needles – including Tir (translocated intimin receptor)
* Bacterial surface protein intimin binds Tir
* Subverts host cell signal transduction
* Induces actin polymers to form a pedestal
72
Name some bacteria that form biofilms
Streptococcus mutans - caries
Staphylococci that colonise catheters
Pseudomonas aeruginosa tat colonise contact lenses
73
What can pseudomonas aeruginosa cause?
Burns
Wounds
Eye infections
Nosocomial UTI
74
Pseudomonas biofilms: where and what do they release?
Cystic fibrosis sufferers lungs
| Alginate polysaccharide - protect biofilm from host immune response and antimicrobials
75
How does listeria colonise the host?
ZIPPER: bind, invasins mimic eukaryotic ligands like fibronectin (in host ECM that binds integrins), cytoskeletal rearrangement, receptor mediated endocytosis
76
What type of bacterium is listeria?
Gram +ve rod
Can cross BBB and can endanger fetus
Food borne
77
How does salmonella colonise the host? Where are the genes for this found?
TRIGGER: bacterial needles, bacterial effector proteins SipA SipC, some bind to actin, some subvert signalling pathways SptP, cytoskeletal rearrangement, internalisation
Genes found on SPI-1
78
How do listeria escape their entry vacuole?
Listeriolysin phospholipase
79
How do listeria move?
COMET TAIL!!!!
| ActA at one pole polymerises and so pushes the bacterium forwards
80
What causes infectious blindness?
Chlamydia trachomatis
81
What can chlamydia trachomatosis cause urogenitally?
Non-gonococcal urethritis
Acute prostatitis (inflammation caused by LPS)
Chronic pelvic inflammatory disease and infertility
82
How big is the chlamydia genome?
900 genes
1.04Mbp
`
83
How big is the salmonella genome?
4450 genes
| 4.85Mbp
84
What is an EB?
Infectious elementary body of chlamydia
| Low metabolic activity and cant replicate
85
What is an RB?
Reticulate body
| Replicates inside host cells
86
What is the chlamydia replication cycle?
1. EB attaches to host epithelial cell
2. Injects Tarp with virulence needle
3. Rearranges host cell cytoskeleton so endosome uptake
4. EB differentiates into RB
5. RB replicates
6. RB-containing vacuole segregates from normal endosome pathway to become an inclusion
7. RB produce EB and Rb
8. Host cell lyses, release EB, infect more cells
87
What is tarp?
translocated actin recruiting phosphoprotein
| Triggers uptake of EB of chlamydia
88
What is an inclusion?
A protective, nutrient rich vacuole that RB replicates in in the chlamydia life cycle
89
Discuss staphylococcal and streptococcal enzymes
```
Collagenase
Hyaluronidase
Staphylokinase
Coagulase
DNAse
```
90
What does streptococcus pyogenes form?
Pharyngitis
Other acute suppurative infections (tonsillitis, scarlet fever, puerperal fever, necrotzing fasciitis, erysipelas, impetigo, mastitis in cattle)
91
How do bacteria counteract lactoferrin and transferrin iron sequestration?
Bind iron at a higher affinity than the host using iron-binding siderophores and reimporting them loaded into cells. Example pyoverdine secreted by pseudomonas aeruginosa
92
How do bacteria counteract low pH caused by gastric acid, or bile salts?
Shingella and helicobacter pump H+ out of their cell, and/or produce NH3 by urease action
Eject bile salts from membrane by MDR pumps
93
What is YopT and YopP?
Yersinia injects YopT protease, which targets small GTPases to disrupt the cytoskeleton, and YopP acetyltransferase that inhibits signalling, triggering apoptosis
94
Which bacteria release cytolysins to kill mphages and what are the enzymes called?
```
B pertussis
E coli - haemolysin
Pneumococcus - pneumolysin
Strep pyogenes - streptolysins O and S
Helicobacter pylori - VacA
```
95
Where does legionella pneumophilia live?
Obligate intracellular parasite of amoebae
| Within air conditioning water and macrophages
96
How do bacteria counteract macrophages?
1. Prevent uptake: paralyse macrophage by subverting function, inhibit chemotaxis by cleaving C5a, shield with antiphagocytic capsules, kill with secreted cytolysisn
2. Survive inside mphage: interfere with phagosome maturation, resist oxidative burst
97
How does salmonella use phase variation to evade the host immune system?
Swaps gene for flagellin
First state has a promoter that allows transcription of flagellin 1 and a repressor for flagellin 2.
Promoter flanked by recombination sequences, so gets inverted
Second state doesn't allow transcription, so no repressor, and flagellin 2 synthesised
98
What is the organism morphology of Neisseria gonorrhoea?
Gram - diplococci
99
How does salmonella evade the host immune system?
1. Interfere with phagosome maturation in macrophages
2. Resist oxidative burst as waxy cell wall deflects lysosomal enzymes
3. Phase variation of flagellin
100
What does 'toxoided' mean?
Denaturing and so inactivating exotoxins
101
What are the two groups of exotoxins?
1. Cytolysins
| 2. Enzymatic intracellular toxins
102
What does C. perfringens alpha toxin do?
secreted for enzymatic degradation of membrane phospholipids
103
What are AB toxins? Why are they called that?
Enzymatic intracellular toxins
Poison host cells by specific catalytic activity
B subunit = receptor-binding
A subunit = intracellularly active components
104
```
Which AB toxins are single polypeptides, which are multimeric?
Anthrax
Tetanus
Botulinum
Cholera
Pertussis
Diphtheria
```
Single: diphtheria, tetanus, botulinum
Multimeric: anthrax, pertussis, cholera
105
Discuss bordetella pertussis AB toxins
1. ADP-ribosylate regulators of AC, disturb cAMP, signalling and ion balance
2. Produce ACs that mimic mammalian enzymes
106
How can AB toxins act?
1. ADP-ribosylating
2. Mimic mammalian AC
3. Glycosidases that depurinate 28s rRNA, blocks protein synthesis
4. Glucosylate small GTPases involved in signal transduction, disrupt actin cytoskeleton and tight junctions
5. Cleave DNA with cytolethal distending toxins
6. Deaminate host cell GTPases so disrupts signal transduction to reorganise actin cytoskeleton
107
How does cholera toxin work?
ADP-ribosylates regulators of AC, disturb cAMP signalling and ion balance
108
How does shinga toxin work?
Glycosidase that depurinates 28S rRNA so blocks protein synthesis
109
How does diphtheria toxin work?
Targets translation elongator factor 2 by ADP-ribosylating it, so blocks protein synthesis
110
How do E coli toxins work?
LT Labile toxin ETEC: ADP-ribosylates regulators of AC, disturb cAMP signalling and ion balance
Another one: Cytolethal distending toxin cleaves DNA
Another one: for E coli that causes meningitis. Deaminates host cell GTPases, disrupts signal transduction to reorganise the actin cytoskeleton
111
How does bacillus anthraxis toxin work?
Produces AC that mimics mammalian enzymes
| Disturb cAMP, signalling and ion balance
112
How does pertussis toxin work?
ADP-ribosylates regulators of AC, disturb cAMP signalling and ion balance
113
How does salmonella typhi toxin work?
Cytolethal distending toxin CDT, cleaves DNA
114
How does C diff toxin work?
Glucosylates Rho/Ras GTPases involved in signal transduction. Disrupts actin cytoskeleton and tight junctions.
115
How does UPEC toxin work?
Cytotoxic necrotising factor
Deaminase of host cell GTPases
Disrupts signal transduction to reorganise the actin cytoskeleton
116
How does campylobacter toxin work?
Cytolethal distending toxin, cleaves DNA
117
How does tetanus toxin work?
TeNT B chain binds to receptor on peripheral nerve membranes
A chain internalised and undergoes retrograde transport to CNS inhibitory interneurons
A chain cleaves synaptobrevin
Blocks release of inhibitory neurotransmitters
Uncontrollable muscle contraction, spastic paralysis
118
How does botulinum toxin work?
BoNT binds to receptor on peripheral nerve terminals
Receptor mediated endocytosis
Proteolytic action on synaptobrevin on peripheral nerves
Prevents release of stimulatory neurotransmitters
Flaccid paralysis
119
Discuss the pathogenesis of toxic shock syndrome
TSST S aureus in highly absorbent tampons
| Superantigen
120
What type of pathogen is Neisseria meningitides?
gram -ve coccus
121
What type of pathogen is haemophilus influenza type B (hib)?
Gram -ve rod
122
What type of granuloma forms for mycobacterium?
Th2 CD4
123
What causes leprosy?
Mycobacterium leprae
124
What causes syphilis?
Treponema pallidum (sperochaete)
125
What causes Lyme's disease?
Borrelia burgdorferi
126
What causes diphtheria? What kind of bacterium is it?
Corynebacterium diphtheria
| Gram + rod
127
What kind of vaccination is used for diphtheria?
Toxoid vacccination
128
What controls the diphtheria toxin?
Controlled by a bacterial TF DtxR, represses gene expression when bound by iron, so in the host (where iron is sequestered), turned on
129
Where does corynebacterium diptheriae colonise?
Nasopharyngeal epithelium
130
Which disease is associated with a respiratory pseudomembrane?
Diphtheria
131
What is the mechanism of action of diphtheria?
1. AB polypeptide binds to HB-EGF via B
2. AB polypeptide nicked by host protease furin, but two remain covalently bound
3. Toxin taken up by endocytosis
4. V-ATPase proton pump acidifies endosome
5. Triggers B-dependent translocation of A across vesicle membrane into cytosol
6. Disulfide bond reduced in cytosol
7. A released
8. Blocks protein synthesis by ADP-ribosylating transcription elongation factor-2
132
What causes pharyngitis?
Streptococcus pyogenes
133
What are the virulence factors of streptococcus pyogenes?
1. Colonisation
Adhesins
2. Damage causing
a. polysaccharide capsule
b. Surface M protein binds complement factor H
c. C5a peptidase - inhibit mphage chemotaxis
d. Streptolysisn O and S - pore-forming toxins
e. Pyogenic toxins - superantigens
f. Hyaluronidase - breaks down tissue (spread)
g. streptokinase - lyses clots (spread)
h. DNAse - depolymerises DNA in puss (reduces abscess viscosity)
134
What complications can acute pharyngitis lead to?
Rheumatic fever. Believed to involve autoimmunity e.g. to M protein. Heart and joint granulomas, plus fever
Glomerulonephritis. Type III hypersensitivity. Accumulation of Ab-Ag complexes that lodge in kidney glomeruli --> inflammation
135
What does streptococcus equi cause?
Causes strangles in horses. Purulent nasal discharge and abscesses in the lymph nodes of the head and neck
Can become systemic --> lymph to lungs, abdomen, brain
136
What lansfield group is streptococcus pyogenes?
A
137
What lansfield group is streptococcus equi?
C
138
What is the iron binding siderophore of streptococcus equi called?
Equibactin
139
What causes the black plague?
Yersinia pestis
140
How does Yersinia pestis spread through the body?
```
Flea bites skin
Lymphatics
Lymph nodes (enlarges - buboes)
Blood stream
Lung (pneumonic plague)
Meningitis
Septicaemia
Multi-organ failure
```
141
What are the virulence factors of Yersinia pestis?
* Antiphagocytic capsule
* Protein toxins including injected effector proteins called Yops that subvert mphage function to prevent engulfment
* YopT targets small GTPases to disrupt cytoskeleton
* YopP acetyltransferase inhibits signalling, triggering apoptosis
* Inflammatory damage by LPS lipid A
142
Pneumolysin
Enzyme secreted by streptococcus pneumonia
Resists removal by mucous and ciliated cells
Avoids phagocytosis
Causes lung damage
143
How is tuberculosis caused by M Bovis controlled?
Widespread slaughter of infected cattle
| Pasteurisation
144
Why might control of M Bovis not work by slaughter?
Could be animal reservoir of badgers
145
Why is mycobacterium TB called acid fast?
Difficult to destain with Gram stain due to mycolic acid waxy impermeable cell envelope
146
What type of bacterium is mycobacterium Tb?
Obligate anaerobe
| Grows slowly
147
How does mycobacterium TB spread?
Small droplets
148
How does mycobacterium TB survive in macrophages?
Establish a safe uptake pathway where they arrest trafficking and inhibit phagosome-lysosome fusion
149
What is the pore forming toxin of mycobacterium TB? What does it do?
ESAT6 interferes with macrophage signalling pathways, so ROS downregulated
150
What is the test for mycobacterial infection?
Tuberculin skin test
| Inject mycobacterial protein --> CD4 Th1 --> IFNgama --> macrophages --> TNFalpha --> red, swelling.
151
What happens when M. tuberculosis persists?
Swap from Th1 to Th2 response
Type IV granulomatous inflammation
Aggregates of activated mphages (may differentiate into epitheloid or multi-nucleate giant cells) surrounded by fibroblasts and a few lymphocytes 'wall off' the pathogen
Ongoing tissue destruction (necrosis) and repair (fibrosis, scarring)
Caseating granuloma
152
What can result in a BoNT intoxication?
Home canned food
153
What do you eat to get staph aureus food intoxication?
Custard, processed meats at room temperature
154
How does cholera toxin work?
* B binds to host receptor GM1-ganglioside
* Receptor mediated endocytosis
* Retrograde transport to ER
* A translocates to host cell cytosol
* A ADP-ribosylates the stimulatory Gs protein (GTP-hydrolysing), fixes in on state
* AC levels elevated
* Uncontrolled high levels of cAMP
* Disturbs CFTR (Cl-) and Na+ membrane pumps
* Water/electrolyte loss up to 20l a day
* Copious rice water diarrhoea
* Shock collapse, sometimes cardiac failure
155
What is the subunit composition of CTX?
AB5
156
Does salmonella typhi have an animal reservoir?
No
157
What mediates the symptoms of salmonella typhi?
Typhoid toxin CDT cleave DNA (cytolethal distending toxin)
158
How do you test for intestinal bacteria?
MacConkey agar - has bile salts in
159
Is salmonella lac+ or -?
-
160
Is E coli lac + or -?
+
161
What is the toxin of ETEC?
LT labile toxin
| ADP-ribosylates regulators of AC, disturb cAMP signalling and ion balance
162
What type of E. Coli is 0157 serotype?
Enterohermorrhagic
163
What is the toxin of EHEC?
Shinga like toxin
| N-glycosidase that depurinates 28S rRNA so blocks protein synthesis
164
Why is listeria such a problem?
Can become systemic: can cross placenta, and BBB (meningitis)
165
When does C diff invade the colon?
After antibiotic eradication of the normal human gut microflora
166
What are the C diff toxins?
TcdA TcdB
Glycosylate small GTPases in intracellular signalling pathways – subversion of actin cytoskeleton and disruption of tight junctions. Epithelium leak, cell destruction
167
How do you treat C diff infection?
Vancomycin and rehydration therapy
| Recurrent infections faecal transplants
168
How and where does helicobacter pylori colonise the gut?
* Colonises mucin layer near gastic mucosal cells in gastric antrum
* Neutralises acid by urease, which also makes gastric mucous less viscous, which along with the highly motile flagellum makes it easy for helicobacter to swim towards the epithelium
169
Which cytokine is associated with H pylori infection?
IL8 released by epithelial cells
| Neutrophil chemotaxis
170
What toxin does H pylori secrete and what does it do?
VacA – pore-forming vacuolating. Inserts into host cell membrane, anion selective channels, endocytosed, pore disturbs ion balance in late endosomes, water flows in, swells to form characteristic vacuoles. Induces apoptosis
171
What is the structure of the VacA toxin?
Hexameric
172
What is CagA?
H pylori
| CagA bacterial effector also interferes with signalling pathways, leading to increased cell proliferation
173
What mechanism may link H pylori to gastric cancer?
Chronic inflammation exposes proliferating mucosal stem cells to dietary carcinogens + generates mutagenic ROS
CagA bacterial effector also interferes with signalling pathways, leading to increased cell proliferation
174
What are the forms of vaccination used against bacteria?
1. Killed
2. Live attenuated
3. Subunit - toxin, adhesins, caspules (to block colonisation or toxin binding to receptors)
175
Which vaccine is used against diphtheria?
Toxoid DPT
176
Which vaccine is used against tetanus?
Toxoid DPT
177
Which vaccine is used against whooping cough?
Killed bordetella pertussis DPT
178
Which vaccine is used against pneumonia?
Polysaccharide from S pneumonia, H influenzae (subunit)
179
Which vaccine is used against meningitis?
Purified polysaccharide from Neisseria meningitides
| Capsular polysaccharide of Hib coupled to tetanus toxin (carrier)
180
Which vaccine is used against cholera?
Killed whole cell or crude fraction of vibrio cholerae
181
Which vaccine is used against tuberculosis?
BCG, attenuated strain of mycobacterium bovis
182
Which vaccine is used against typhoid fever?
Live attenuated Ty21A
| Vi capsular polysaccharide
183
How do bacteria counteract penicillins?
- Enzyme-mediated inactivation: beta lactamases break open the lactam ring
184
How do bacteria counteract chloramphenicol and aminoglycosides?
- Enzyme-mediated inactivation: produce acetyltransferases that modify chloramphenicol and aminoglycosides to prevent ribosomes from binding
185
How do bacteria counteract tetracycline?
- Alteration of target: some resistant bacteria produce ribosomal protection proteins that have structural similarity to translation elongation factors. Dislodge tetracycline from ribosome.
186
How do bacteria counteract fluoroquinolones like ciprofloxacin?
- R plasmid encoded quinolone resistance protein Qnr binds topoisomerase to physically block binding of the antibiotic
187
How do bacteria counteract vancomycin?
- Resistant gram + pathogens produce different peptidoglycan enzymes that synthesise D-Ala-D-Lac alternative peptide crosslinks
188
What are the different mechanisms to counteract antibiotics?
1. Enzyme mediated inactivation
2. Alteration of target
3. Metabolic bypass
4. Efflux pumps
189
How do bacteria counteract trimethoprim and sulphonamide?
- Metabolic bypass: for both trimethoprim and sulphonamides. R-plasmid encoded DHPS and DHFR have a much lower binding affinity for the antibiotics than the normal bacterial enzymes.
190
What is TolC?
An efflux pump which conveys multidrug resistance to gram -ve bacteria
191
What is the structure of an efflux pump?
Drugs bind to inner membrane transporter (ATPase or proton antiporter), ejected through TolC exit duct spanning the periplasm and outer membrane (this is tripartite)
192
How do we counteract increasing drug resistance?
1. Selective antibiotic use to minimise selective pressure
2. Develop new antibiotics against different targets (e.g. against lipid A synthesis, bacterial cell division, efflux pumps)
3. Develop new antibiotics against pathogen-specific processes (quorum sensing signals, adhesion assembly)
4. Combination therapies
5. Use antibiotic potentiators e.g. clavulanic acid that inhibit resistance enzymes
193
Name the obligate aerobes
P aeruginosa
Corynebacterium diphtheria
Neisseria pharynges
194
How do superantigens work?
Bridges weakly interacting MHC Class II and TCR by binding outside the normal Ag-binding pocket. Activates useless T cells by promoting tighter binding and stronger signalling. Results in cytokine storm (IL1,2,TNF). Diverts T cell function.
