2 Antibiotic resistance Flashcards

1
Q

What is ESBL?

A

extended spectrum beta-lactamase-producing Enterobacteriacae

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2
Q

What is VRE/GRE?

A

Vancomycin/glycopeptide-resistant enterococci

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3
Q

Why do sensitivity testing?

A

Target therapy.
Explain Rx failures.
Provide alternatives.
Provide oral not IV.

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4
Q

How is sensitivity testing carried out?

A

Culture micro-organism in presence of differing strengths of agent and determine if MIC is above breakpoint level.

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5
Q

What is clinical resistance?

1 example.

A

Resistance genes are only expressed in vivo - so Rx is ineffective.
AmpC beta-lacatamase genes in enterobacteriacae.

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6
Q

What are the 6 mechanisms of antibiotic resistance?

A
No target.
Reduced permeability.
Altered target.
Over-expression of target.
Enzymatic degradation. 
Efflux pump.
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7
Q

Why do these combinations not work?

Vancomycin and g-ve bacilli.
Gentamicin and anaerobes.

A

Impermeable outer membrane.

Gentamicin requires O2 dependant active transport.

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8
Q

Why is MRSA resistant to flucloxacillin?

A

Altered penicillin binding protein won’t bind B lactams.

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9
Q

Which antibiotics do beta-lactamases degrade?

A

Penicillins and cephalosporins.

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10
Q

What is horizontal transfer?

A

Circular DNA sequences exchanged via plasmids by conjugation. Using transposons and integrons.

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11
Q

How do you avoid antibiotic resistance?

A

Never use unless necessary.
Use most narrow-spectrum available.
Use combination therapy if indicated.
Consult expert sources.

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12
Q

Why are VRE resistant to vancomycin?

A

Altered peptide sequence. D-ala D-lac.

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13
Q

Why are G-ves resistant to trimethoprim?

A

Dihydrofolate reductase gene (dhr) mutations.

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14
Q

Which enzyme enables bacterial resistance to gentamicin?

A

Aminoglycoside modifying enzymes.

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15
Q

Which enzyme enables bacterial resistance to chloramphenicol?

A

Chloramphenicol acetyltransferase.

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