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Proteins > Bacterial infection > Flashcards

Bacterial infection Flashcards

1
Q

What are the 5 qualities of bacteria

A 
Small
Prokaryotic
Unicellular
Diverse
Ubiquitous
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2
Q

What are koch formulates postulates

A

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

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3
Q

What is zoonosis

A

Infections transmitted from an animal to a human

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4
Q

How does step.pneumonaie effect the host

A

Compromises O2 movement across alveoli

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5
Q

Which viruses and bacteria regularly show synergy

A

Influenza and bacterial pneumonia

HIV and tb

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6
Q

Which diseases are caused by toxins

A 
Botulism
Cholera
Anthrax
Thyphoid
Tetanus
Dysentry
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7
Q

What is cholera caused by

A

Vibrio cholerae

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8
Q

What is the mechanism of action of cholera toxin

A

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

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9
Q

How can bacterial disease be prevented

A

Sterilisation
Aseptic technique
Decolonisation and prophylactic antibacterial a
Vaccination

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10
Q

Which organisms have a cell wall

A

Plants bacteria fungi

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11
Q

What is the plant bacterial wall made up of

A

Cellulos which is a glucose polymer

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12
Q

What is the bacterial cell wall made up of

A

Peptidoglycan- polymer of 2 sugars cross linked by peptides

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13
Q

What is the function of cell walls

A

Scaffold

Anchoring

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14
Q

What are the 2 subunits of peptidoglycan

A

NAM + NAG

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15
Q

Which monomer is the peptide bridge joined to

A

NAM

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16
Q

Which proteins catalyse transglycosylation and transpeptidation

A

Penicillin binding proteins

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17
Q

Why is there a “chlamydial paradox”

A

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

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18
Q

How does the immune system recognise peptidoglycan

A

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

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19
Q

How do enzymes disrupt peptidoglycan

A

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

20
Q

What is the mechanism of b lactams antibiotics eg penicillin

A

Inhibits peptidoglycan cross linking by inhibiting enzymes involved

21
Q

How does vancomycin work

A

Binds d ala d alas to prevent cross linking

22
Q

How does bacitracin work

A

Binds to undecaprenyldiposphate in Peptidoglycan cycle preventing dephosphorylatoon

23
Q

How does fosfomycin work

A

Inhibits MurA by binding to cysteine residue in active site

24
Q

How does D-cycloserine work

A

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

25
Q

What are antibiotics

A

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

26
Q

What are the mechanisms of antibacterial action

A

Substrate analogues
Steric hindrance
Enzyme inactivation
Disruption or subversion

27
Q

What is the basis for selective toxicity of antibacterials/antibiotics

A

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

28
Q

What is the mechanism of ionpizid and ethionamide

A

Pro drugs which block mycobacterial myolic acid synthesis

29
Q

How does daptomycin target the membrane

A

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

30
Q

What is co-trimoxazole made up of

A

SMZ and TMP

31
Q

What does co-trimoxazole target

A

Nucleotide metabolism

32
Q

How do quinolone target DNA

A

Block decatenation and supercoiling

33
Q

How does rifampicin target transcription

A

Binds B subunit of prokaryotic RNA pol

34
Q

How do most protein synthesis targeted antibiotics work

A

Act directly on 70s ribosome

35
Q

How dies linezolid interfere with protein synthesis

A

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

36
Q

What other antibiotics target protein synthesis

A

Tetracycline streptomycin chloramphenicol erythromycin

37
Q

What is the definition of antibiotic resistance

A

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

38
Q

What are the consequences of resistance

A

Increased mortality, morbidity and cost

39
Q

How can acquired resistance occur

A

Spontaneous mutation upon dividing

Horizontal gene transfer

40
Q

What are the mechanisms of resistance

A

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

41
Q

How does S aureus become resistant to rifampicin

A

Alters RNA pol

42
Q

How does s aureus become resistant to linezolid

A

Methylated ribosomal RNA

43
Q

How does s aureus become resistant to vancomycin

A

Thickening of th cell wall

44
Q

How does active efflux work

A

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

45
Q

What is an example of a multiple drug efflux system

A

AcrAB/TolC in ecoli

46
Q

How can enzymatic modification confer resistance to b lactams

A

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

Proteins (4 decks)

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