Bacterial infection

Question 1

What are the 5 qualities of bacteria

Answer 1

Small
Prokaryotic
Unicellular
Diverse
Ubiquitous

Question 2

What are koch formulates postulates

Answer 2

The microorganism must be present in all cases of he disease
The organism must be isolated from the host and grown in culture
The disease must be replicated when cultured microorganism is reintroduced into a healthy susceptible host
The microorganism must be recoverable from the newly infected host and shown to be identical to original causative agent

Question 3

What is zoonosis

Answer 3

Infections transmitted from an animal to a human

Question 4

How does step.pneumonaie effect the host

Answer 4

Compromises O2 movement across alveoli

Question 5

Which viruses and bacteria regularly show synergy

Answer 5

Influenza and bacterial pneumonia

HIV and tb

Question 6

Which diseases are caused by toxins

Answer 6

Botulism
Cholera
Anthrax
Thyphoid
Tetanus
Dysentry

Question 7

What is cholera caused by

Answer 7

Vibrio cholerae

Question 8

What is the mechanism of action of cholera toxin

Answer 8

B subunit binds GMI ganglioside receptor
A subunit undergoes endocytosis
A subunit catalyses ADP-ribosylation of Gs protein
Adenylate cyclise is stimulated leading to over production of cAMP
Stimulates secretion of ions into the lumen causing large scale movement of water into lumen

Question 9

How can bacterial disease be prevented

Answer 9

Sterilisation
Aseptic technique
Decolonisation and prophylactic antibacterial a
Vaccination

Question 10

Which organisms have a cell wall

Answer 10

Plants bacteria fungi

Question 11

What is the plant bacterial wall made up of

Answer 11

Cellulos which is a glucose polymer

Question 12

What is the bacterial cell wall made up of

Answer 12

Peptidoglycan- polymer of 2 sugars cross linked by peptides

Question 13

What is the function of cell walls

Answer 13

Scaffold

Anchoring

Question 14

What are the 2 subunits of peptidoglycan

Answer 14

NAM + NAG

Question 15

Which monomer is the peptide bridge joined to

Answer 15

NAM

Question 16

Which proteins catalyse transglycosylation and transpeptidation

Answer 16

Penicillin binding proteins

Question 17

Why is there a “chlamydial paradox”

Answer 17

No detectable peptidoglycan but it’s susceptible to antibiotics that inhibit it’s synthesis, it contains pbps and genomic analysis reveals almost complete pg pathway

Question 18

How does the immune system recognise peptidoglycan

Answer 18

Uniquely bacterial so PAMPS via cd14 and tlr2
Nod receptors
Lectins, lysozyme

Question 19

How do enzymes disrupt peptidoglycan

Answer 19

Glycoside hydrolases in lysozyme cleaves bond between nag and nam
Metalloendopeptidase activity on cross link from lysostaphin

Question 20

What is the mechanism of b lactams antibiotics eg penicillin

Answer 20

Inhibits peptidoglycan cross linking by inhibiting enzymes involved

Question 21

How does vancomycin work

Answer 21

Binds d ala d alas to prevent cross linking

Question 22

How does bacitracin work

Answer 22

Binds to undecaprenyldiposphate in Peptidoglycan cycle preventing dephosphorylatoon

Question 23

How does fosfomycin work

Answer 23

Inhibits MurA by binding to cysteine residue in active site

Question 24

How does D-cycloserine work

Answer 24

Competitive inhibitor of Alr and Ddl which naturally recognise D-Ala

Question 25

What are antibiotics

Answer 25

Secondary metabolites produced by bacteria and fungi to kill competing organism or as signalling molecules

Question 26

What are the mechanisms of antibacterial action

Answer 26

Substrate analogues Steric hindrance Enzyme inactivation Disruption or subversion

Question 27

What is the basis for selective toxicity of antibacterials/antibiotics

Answer 27

Agent doesn't enter mammalian cells as easily Targets are not present in mammalian cells Pro drugs which are only activated in bacteria

Question 28

What is the mechanism of ionpizid and ethionamide

Answer 28

Pro drugs which block mycobacterial myolic acid synthesis

Question 29

How does daptomycin target the membrane

Answer 29

Interacts via acyl chain and is integrated causing aggregation and membrane depolarisation, leakage and death

Question 30

What is co-trimoxazole made up of

Answer 30

SMZ and TMP

Question 31

What does co-trimoxazole target

Answer 31

Nucleotide metabolism

Question 32

How do quinolone target DNA

Answer 32

Block decatenation and supercoiling

Question 33

How does rifampicin target transcription

Answer 33

Binds B subunit of prokaryotic RNA pol

Question 34

How do most protein synthesis targeted antibiotics work

Answer 34

Act directly on 70s ribosome

Question 35

How dies linezolid interfere with protein synthesis

Answer 35

Binds 50s subunit occupying the space normally occupied by aa residue of tRNA

Question 36

What other antibiotics target protein synthesis

Answer 36

Tetracycline streptomycin chloramphenicol erythromycin

Question 37

What is the definition of antibiotic resistance

Answer 37

Ability of bacteria to grow and survive in concentrations that can be safely achieved in patients at the site of infection so antibiotic is no longer effective for treatment

Question 38

What are the consequences of resistance

Answer 38

Increased mortality, morbidity and cost

Question 39

How can acquired resistance occur

Answer 39

Spontaneous mutation upon dividing | Horizontal gene transfer

Question 40

What are the mechanisms of resistance

Answer 40

Altered target site Decreased uptake or ef flux Inactivation or modification of an enzyme Bypass pathways

Question 41

How does S aureus become resistant to rifampicin

Answer 41

Alters RNA pol

Question 42

How does s aureus become resistant to linezolid

Answer 42

Methylated ribosomal RNA

Question 43

How does s aureus become resistant to vancomycin

Answer 43

Thickening of th cell wall

Question 44

How does active efflux work

Answer 44

Toxic compounds removed by pump which requires proton motive force or ATP arising from up regulation of endogenous pump or horizontal gene transfer

Question 45

What is an example of a multiple drug efflux system

Answer 45

AcrAB/TolC in ecoli

Question 46

How can enzymatic modification confer resistance to b lactams

Answer 46

B lactamases hydrolyse cyclic bonds of rings so it can no longer bind