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Pharmacology 1 > Antimicrobial Introduction, Bacteria, Susceptibility Testing > Flashcards

Antimicrobial Introduction, Bacteria, Susceptibility Testing Flashcards

1
Q

What two bacteria are of greatest public health concern relative to food poisoning as it relates to
veterinary use of antimicrobials?

A

Salmonella and Campylobacter

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2
Q

What is the connection between veterinary antimicrobial use and
resistance in these bacteria?

A

Resistance development by vertical transmission

- fecal matter from infected animal gets in the food product –> consumer becomes infected due to improper cooking

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3
Q

Explain what the term “four quadrant coverage” implies relative to antimicrobial utility for a patient.

A

Gram positive
- aerobes/facultative anaerobes: strep, staph, corynebacteria, enterococci
- obligate anaerobes: clostridia
Gram-negative
- aerobes/facultative anaerobes: pasteurella, E coli, klebsiella, proteus
- obligate anaerobes: bacteroides, fusobacter

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4
Q

There are no _____ of importance in vet med

A

Gram-negative cocci

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5
Q

Explain the differences between constitutive versus acquired resistance.

A

Constitutive resistance: resistance contained in the DNA that can be passed on to daughter cells, cannot be transmitted to other species
Acquired resistance
- inactivating enzyme
- change in target site
- development of active efflux pump
- impermeability of bacteria
- development of bypass mechanisms in metabolic pathways
- increasing production of competitive metabolites

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6
Q

Vertical transmission

A

Mutation occurs and clone reproduces

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7
Q

Horizontal transmission

A

Predominate mechanism, transfer of genetic material between bacteria

  • same species: plasmid
  • across species: transposon
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8
Q

Genes for multiple antimicrobial resistance often occur in

A

Packets

- much greater impact

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9
Q

_____ has a huge problem with antimicrobial resistance

A

Pseudomonas

  • gram-neg rod, extracellular
  • aggressive in tissue destruction
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10
Q

Which pathogens have relatively predictable susceptibilities to certain
antibiotics such that in vitro susceptibility testing is often not performed:

A
  • rickettsia
  • leptospirosis
  • streptococci
  • most anaerobes
  • mycoplasma
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11
Q

Regardless of gram stain, most anaerobes are similar as to which antimicrobials they are susceptible to except:

A
  • fusobacteria: very sensitive to a wide range of antibiotics
  • bacteriodes fragilis: resistant to many antimicrobials that other obligate anaerobs are sensitive to
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12
Q

Which organism is often deemed as one of the most aggressive relative to tissue destruction?It
produces a collagenase

A

Pseudomonas

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13
Q

Which one cannot be removed by filtration for sterilization of liquids?

A

Mycoplasma

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14
Q

Which gram‐negative obligate anaerobe tends to be the most susceptible to antimicrobials?

A

Fusobacterium

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15
Q

Where do enterococci normally reside in the body?

A

Commonly found in feces

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16
Q

How do enterococci compare to beta‐hemolytic streptococci relative to their antibiotic
susceptibility?

A

Enterococci have a huge problem with antimicrobial resistance compared to sensitive beta-hemolytic strep

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17
Q

What is enterococci relative pathogenicity in surface wounds?

A

Not aggressively pathogenic in surface wounds

- problem in septicemia, endocarditis, UTIs, peritonitis

18
Q

Of the two major species of enterococci, which is the most common and which is the most
likely to have multiple drug resistance

A
  • enterococcus faecalis: most commonly isolated

- enterococcus faecium: more prone to resistance problems (need in vitro susceptibility results)

19
Q

What are the primary staphylococcal species causing infection in man, dog, cow, horse, and pig?

A

Staphylococcus aureus

20
Q

Goal of antimicrobial susceptiblity testing

A

To find an in vitro test that will predict in vivo efficacy

- uses MBC and MIC

21
Q

MBC

A

Minimum bactericidal concentration

  • amount of antibiotic necessary to kill 99.9% of all organisms
  • used when treating immunocompromised patients
22
Q

MIC

A

Minimum inhibitory concentration

  • amount of antibiotic necessary to inhibit growth of an organism
  • most commonly used in vitro technique
23
Q

Rule of thumb

A
  • for bactericidal antimicrobials, the MBC is within 1 or 2 dilutions of the MIC
  • for bacteriostatic antimicrobials the MBC is often > 100X the MIC
24
Q

Tube dilution MIC

A

Broth inoculated with bacteria

  • turbidity = growth
  • looking for lowest concentration that shows no growth
25
Q

MIcrotiter panel

A
  • column: different dilutions
  • row: different antibiotics
  • looking for MIC
26
Q

Etest

A

Contains more dilutions than microtiter, leading to a more precise MIC
- where the ellipse stops is the MIC

27
Q

Kirby Bauer Diffusion

A

Looking for zone of inhibition

- diameter does not determine resistance/susceptibility!! Is based on molecular weight, etc

28
Q

What are the 4 interpretations of MICs

A
  • S: susceptible
  • I: intermediate
  • R: resistant
  • NI: no interpretation
29
Q
A

Susceptible

30
Q

>

A

Resistant

31
Q

Breakpoint panel

A

Does not test the whole range

  • only looking at 3 dilutions (R, S, I)
  • similar to Kirby Bauer
  • does not determine how resistant or susceptible something is (qualitative)
32
Q

MIC has advantages in the following:

A
  • tracking resistance patterns over time

- when the PK-PD relationship is known

33
Q

______ is quantitative, while _____ and ______ are qualitative

A

MIC; KB and BP

34
Q

______ and ______ suffice for most clinical situations

A

KB and BP

35
Q

What are the 3 pharmacodynamic of bacterial killing

A
  • concentration-dependent killing
  • area under the inhibitory curve (AUIC)
  • time-dependent killing
36
Q

Concentration dependent killing

A

You want a high peak concentration, looking at how high a drug goes above the MIC
- aminoglycosides

37
Q

Time dependent dynamic

A

Looking at time above MIC

- beta lactams

38
Q

AUC/MIC dynamic

A

Fluoroquinolones

39
Q

Enteric gram neg bacteria

A
  • E coli
  • Klebsiella
  • Proteus
  • Salmonella
  • Enterobacter
  • Citrobacter
  • Serratia
40
Q

Nonenteric gram neg bacteria

A
  • Pasteurella
  • Mannheimia
  • Haemophilus
  • Bordetella

Pharmacology 1 (15 decks)

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