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CP1 = Core Micobiology > Mechanisms of Antibiotic Resistance > Flashcards

Mechanisms of Antibiotic Resistance Flashcards

1
Q

What does ESBL stand for?

A

Extended-spectrum B-lactamase producing Enterobacteriaceae

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2
Q

How does MRSA work?

A

Produce penicillinase - destroys penicillin.

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3
Q

What does VRE/GRE stand for?

A

Vancomycin/glycopeptide resistant enterococci

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4
Q

Sensitivity Testing Reasons:

A

> Oral switch from IV
Alternative antibiotics
Explain treatment failures
Enable transition from “empiric” to “targeted”.

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5
Q

What is Horizontal transfer of resistance?

A

Plasmid to plasmid using transposons and integrin’s.

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6
Q

How are antibodies expelled from the cell?

A

By active efflux mechanisms (rare)

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7
Q

Multi-Resistant Enterobacteriaceae alternative:

A

Meropenem (Last Line)

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8
Q

What enzyme degrades Gentamicin?

A

Aminoglycoside modifying enzymes

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9
Q

Microtitre plate susceptibility testing:

A

Increase anti’b conc in wells, the more a microbe grows = more resistant it is.

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10
Q

What genetic mutation makes Trimethoprim resistant to Gram -ve bacilli?

A

Mutation in Dihydrofolate Reductase gene.

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11
Q

What is the method of passing on resistance?

A

1 . AntiB resistance on plasmid.

  1. May –> chromosome.
  2. Conjugation
  3. New organism = resistance.
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12
Q

What enzyme degrades Chloramphenicol?

A

Chloramphenicol AcetylTransferase (CAT)

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13
Q

What genetic mutation makes MRSA resistant to Flucloxacillin ?

A

Altered penicillin binding protein PBP2 (encoded by MecA) - not bind beta lactams.

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14
Q

What are the risks of empiric therapy

A

Under treatment - doesn’t cover infection.

Excessively broad-spectrum - Risk of resistance.

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15
Q

What causes an antibody to bounce around and disappear?

A

Absent Target

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16
Q

What genetic mutation makes VRE resistant to Vancomycin?

A

Altered peptide sequence in gram +ve peptidoglycan - reduce binding of Vancomycin 1000 fold.

17
Q

NDM-1 Producers Alternatives:

A

Colistin (Nephrotoxic)

18
Q

How are antibodies destroyed?

A

By bacteria produced enzymatic degradation.

19
Q

What becomes resistant to Antifungal triazoles?

A

Candida species

20
Q

How are resistance genes transmitted within a species?

A

By conjugation

21
Q

What enzymes degrade penicillins/cephalosporins?

A

B-lactamases

22
Q

What type of organisms does Gentamicin not work with?

A

Anaerobic, aminoglycosides need O2 dependent active transport mechanism.

23
Q

What does MDR-TB stand for?

A

Multi-drug resistant tuberculosis (also extreme version = XDR-TB)

24
Q

Limitations of sensitivity testing:

A

> Antimicrobial sensitivity and clinical response = not absolute.
Some micro-organisms resistant to antimicrobial agents even when in vitro = susceptibility.
- Enterobacteriacaea - AmpC B-lactamase genes.

25
Q

What causes a target to change shape?

A

Single gene mutation

26
Q

How does ESBL work?

A

Knocks out B-lactam anti’bs.

27
Q

Define: Zone of Inhbition

A

The area around the antibiotic which has no microbe growth.

28
Q

When does absent targeting occur?

A

Treating the infection with wrong anti’b.

e.g central line candida infection, treat with broad-spectrum, fungi –I peptidoglycan.

29
Q

What is Vertical transfer of resistance?

A

Chromosomal/plasmid resistance gene to daughter cell - on division.

30
Q

MRSA Alternatives:

A

Linezolid
Tigecycline
Daptomycin

31
Q

Define: Sensitivity (Microbe)

A

If it doesn’t grow in the presence of an organism.

32
Q

What does MRSA stand for?

A

Meticillin-Resistant Staphyloccocus Aureus

33
Q

What type of bacilli does Vancomycin not work with?

A

Gram -ve = impermeable.

34
Q

What can stop an antibody getting into a cell?

A

Decreased permeability.

CP1 = Core Micobiology (7 decks)

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