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SA Micro > Antimicrobials > Flashcards

Antimicrobials Flashcards

1
Q

Classes of antimicrobials used in veterinary medicine?

A 
Aminoglycosides
Cephalosporins
Macrolides
Penicillins
Phenicols (NOT USED IN HUMANS)
Quinolones
Sulfonamindes
Tetracyclines
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2
Q

Most commonly prescribed antibiotic?

A

Clavamox

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3
Q

Why is antibiotics resistance considered a “not new event”?

A

Most antibiotics have a natural origin

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4
Q

What is the MIC?

A

Minimum Inhibitory Concentration

Lowest concentration of an antimicrobial agent that prevents visible growth in agar or broth dilution susceptibility test

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5
Q

What is the MBC?

A

Minimum Bactericidal Concentration

Lowest dilution where NO bacteria survives

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6
Q

What is the breakpoint?

A

MIC or zone diameter value used to indicate susceptible (S), intermediate (I), and resistant (R)

Some labs report not interpretable (NI) if no established breakpoint

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7
Q

Which groups of antibiotics target the bacterial cell wall?

A

Beta lactams
Glycopeptides
Bacitracin

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8
Q

Which groups of antibiotics target bacterial DNA?

A

Fluroquinolones
Novobiocin
Nitromidazoles
Nitrofurans

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9
Q

Which groups of antibiotics target bacterial protein synthesis?

A 
tetracyclines
Aminoglycosides
Lincosamides
Macrolides
Streptograminns
Chloramphenicol
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10
Q

What is intrinsic resistance?

A

Innate ability to resist activity of an antimicrobial

Natural insensitivity

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11
Q

What are causes of intrinsic resistance?

A

Lack of affinity of drug for bacterial target

Inaccessibility of drug into bacterial cell

Extrusion of drug by chromosomally-encoded active exporters

Innate production of enzymes that inactivate drug

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12
Q

What is acquired resistance?

A

Where a previously susceptible microbe obtains ability to resist activity of a drug

Involves 1) mutation of chromosomal genes involved with bacterial physiology/cell structures, 2) acquisition of foreign resistance genes, 3) both

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13
Q

By which methods can resistance be acquired?

A

Conjugation
Transformation
Transduction
Mutation

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14
Q

How do bacteria become resistant to beta lactam antibiotics?

A

Have beta-lactamase or penicillin binding proteins

Block cross-linking of enzymes if peptidoglycan layer of cell wall

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15
Q

How does clavamox overcome bacterial resistance?

A

Clavulanate inactivates beta-lactamase by forming slowly hydrolysing acyl enzyme intermediate

Amoxicillin blocks cell wall cross-linking transpeptidase, and by forming a slowly hydrolysing covalent acyl enzyme intermediate

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16
Q

Resistance by efflux affects which antibiotics?

A

Erythromycins

Teteracyclines

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17
Q

How does resistance to macrolides/lincosamides/streptogramins form?

A

Target modification by rRNA methylases

Dug efflux

Inactivation by enzymes

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18
Q

Which groups of antibiotics are typically broad-spectrum?

A

Tetracyclines

Phenicols

Fluoroquinolones

3rd and 4th generation cephalosporins

19
Q

Beta-lactam mechanism of action

A

Target and bind to penicillin binding protein

Inhibit bacterial cell wall synthesis

20
Q

Bacterial mechanism of resistance to beta-lactams

A

Enzymatic destruction of beta-lactam rings

Target (PBP) modification

Reduced intracellular accumulation

21
Q

Glycopeptide antibiotic mechanism of action

A

Inhibit the last stages of cell wall assembly by preventing ross-linking reactions

22
Q

Bacterial mechanism of resistance to glycopeptide antibiotics

A

Target modification

Production of false targets

23
Q

Quinolone mechanism of action

A

Targets DNA gyrase and topoisomerase IV of the bacteria and inhibits the necessary step of supercoiling

24
Q

Bacterial mechanism of resistance to quinolones

A

Target modification (mutation of DNA gyrases and DNA topoisomerase IV genes)

Efflux pump (reduced intracellular accumulation)

25
Q

Aminoglycoside mechanism of action

A

Target and bind to the 30s ribosomal subunit to cause misreading of the genetic code which results in inhibition of protein synthesis

Targets peptidyl transferase

26
Q

Bacterial mechanism of resistance to aminoglycosides

A

Antibiotic (structural) modification

Target modification (rRNA methylation)

Reduced uptake

Enzymatic inactivation

Efflux pump

27
Q

Macrolide mechanism of action

A

Targets and binds to 50s ribosomal subunit to inhibit translocation and transpeptidation process, resulting in inhibition of protein synthesis

28
Q

Bacterial mechanism of resistance to macrolides

A

Reduced intracellular uptake

Target modification

29
Q

Mechanism of action of tetracyclines

A

Target and bind to 30s ribosomal subunit to prevent aminoacyl-tRNA to attach to RNA-ribosome complex, inhibiting protein synthesis

30
Q

Bacterial mechanism of resistance to tetracyclines

A

Reduced intracellular accumulation

Drug efflux

Target modification (ribosome protective proteins with homology to elongation factor)

31
Q

Mechanism of action of rifampin

A

Interacts with the beta-subunit of the bacterial RNA polymerase to block RNA synthesis

32
Q

Bacterial mechanism of resistance to rifampin

A

Target modification

33
Q

Mechanism of action of sulfonamindes

A

Targets dihydropteroate synthase (DHPS) and prevents addition of para-aminobenzoic acid (PABA), inhibiting folic acid synthesis

34
Q

Bacterial mechanism of resistance to sulfonamindes

A

Target modification

35
Q

Contraindication of aminoglycoside use

A

Creatinine >5

36
Q

Which antibiotics are not effective against anaerobes?

A

Fluoroquinolones

37
Q

Which antibiotics are especially particularly effective against Gram negative enteric pathogens an Pseudomonas spp?

A

Fluoroquinolones

38
Q

Why should you avoid using fluoroquinolones in immature animals?

A

Can result in cartilagenous erosion leading to permanent lameness

39
Q

Mechanism of action of lincosamindes

A

Targets 23s part of 50s subunit of bacterial ribosomes, causing premature dissociation of peptidyl-tRNA from ribosome

40
Q

Most frequently prescribed antibiotics overall

A

Dogs: cephalexin

Cats: clavamox

41
Q

Most frequently prescribed antibiotic for skin infection

A

Dog: cephalexin

Cat: clavamox

42
Q

Most frequently prescribed antibiotic for urinary tract infections

A

Dogs and cats: clavamox

43
Q

Most frequently prescribed antibiotics for GI

A

Dogs and cats: metronidazole

44
Q

Most commonly prescribed antibiotic for respiratory infection

A

Clavamox

SA Micro (5 decks)

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