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CMD Block 2 > Abx Resistance: Relationship to Clinical Use > Flashcards

Abx Resistance: Relationship to Clinical Use Flashcards

1
Q

A drug that kills or inhibits the growth of microorganisms

A

Abx

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2
Q

Implies that an antimicrobial will not inhibit bacterial growth at clinically achievable concentrations

A

Resistant

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3
Q

Implies that an antimicrobial will inhibit bacterial growth at clinically achievable concentrations

A

Susceptible

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4
Q

Lowest concentration of antimicrobial that inhibits growth of bacteria

A

Minimal inhibitory concentration

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5
Q

Concentration of an antimicrobial that kills bacteria

A

Minimal bactericidal concentration

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6
Q

MIC that is used to designate between susceptible and resistant

A

Breakpoint

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7
Q

How is MIC determined in test tubes?

A

100mcg/mL is given to test tubes through serial dilutions to 0.4 mcg/mL; a standard amount o bacteria is added and incubated; the lowest concentration of abx with no bacterial growth (cloudiness) is the MIC

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8
Q

How is MIC determined on a well plate, and what are some advantages?

A

1 bacterium tested on each plate; each row has serial dilutions of a distinct antibiotic
(many abx per plate, less reagent and bacteria needed)

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9
Q

How is MIC measures automatically?

A

Machine will photometrically measure growth for each antimicrobial concentration well; determines an MIC within 6-8 hours

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10
Q

What is an advantage of automated testing?

A

antimicrobial susceptibilities can be determined at the same time the organism is identified

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11
Q

Test that can determine only susceptible vs resistant and not an MIC.

A

Kirby-Bauer Disk diffusion

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12
Q

MIC test that is measuring the diameter of growth inhibition and comparing to a chart.

A

Kirby-Bauer Disk diffusion

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13
Q

Tests that can determine MICs directly.

A

agar dilution and E-test

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14
Q

MICs are _____ while susceptible and resistant are ______ determinations

A

relative; absolute

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15
Q

Susceptible or resistant: MIC is lower than the breakpoint

A

susceptible

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16
Q

Susceptible or resistant: MIC is higher than breakpoint

A

resistant

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17
Q

How is breakpoint determined?

A

arbitrarily designated by a committee

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18
Q

T/F: MICs between different antibiotics may be compared to determine efficacy or potency of antibiotic.

A

F: breakpoint is different for each antibiotic

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19
Q

Where are half of abx used in N America?

A

agriculture

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20
Q

Why do doctors overuse abx? (3)

A

Patient expectations; diagnostic uncertainty; time

21
Q

What patients are high risk for abx resistance? (3)

A

Immunocompromised, hospitalized, invasive devices (central venous catheters)

22
Q

T/F: Abx are the ONLY drug that have direct public health consequences for persons other than the one who received the abx.

A

T

23
Q

Although different antibiotics select different bacteria, they can select phenotypes that have resistance to other drugs, too. These microbes are called:

A

multidrug-resistant (MDR) organisms

24
Q

Linezolid and erythromycin inhibit

A

protein synthesis

25
Q

What 2 places would you find genes encoding resistance?

A

Plasmid or chromosome

26
Q

In what cell structure might decreased permeability improve a microbe’s drug resistance?

A

Cell wall

27
Q

What 3 reactions do microbial enzymes use to degrade drugs, especially aminoglycosides?

A

Sulfonation, phosphorylation, or esterifictation

28
Q

B-lactamases are more potent in gram (positive/negative) bacteria.

A

negative

29
Q

Type of B-lactamase most common in Klebsiella pneumoniae.

A

Carbapenemases (class A)

30
Q

Type of B-lactamase capable of hydrolysing extended spectrum cephalosporins, penicillins, and aztreonam.

A

Extended spectrum

31
Q

Type of B-lactamase most often associated with E. coli and Klebsiella pneumoniae.

A

Extended spectrum

32
Q

T/F: ESBL and resistance for Aminoglycosides, ciprofloxacin and trimethoprim-sulfamethoxazole are often on same plasmid.

A

T

33
Q

Pseudomonas spp. are often associated with what resistance mechanisms?

A
  1. Decreased Permeability

2. Efflux Pumps

34
Q

What are 2 abx commonly effluxed?

A

Tetracyclines

Macrolides

35
Q

Alterations to its gram positive cell wall protects Enterococcus from what drug?

A

vancomycin

36
Q

What 2 microbes are associated with penicillin-binding protein?

A

Methicillin-resistant S. aureus (MRSA)

Penicillin-resistant S. pneumoniae

37
Q

If altered, what enzyme in S. pneumo and many gram negative bacteria is protected from fluoroquinolones?

A

DNA gyrase

38
Q

S. pneumoniae, Staph sp., N. gonorrhoeae, and enteric gram-negative rods are protected from tetracycline and macrolides through modifications to what cell organelle?

A

Ribosomes

39
Q

T/F: MRSA is a problem that has been confined to hospitals

A

F: in communities as well

40
Q

How does abx resistance affect healthcare (2)?

A

Increased costs and mortality

41
Q

T/F: Surgical site infections with MRSA are not associated with increased mortality, but do seem to correlate with increased length of hospital stay.

A

F: Patients who have surgical sites with methicillin resistant cultures have been shown ~3x the mortality rate of those who are MSSA (and LOS is longer for those w MRSA)

42
Q

Diabetic patients with peripheral vascular disease and chronic renal failure have demonstrated high level resistance to what type of abx?

A

Glycopeptides

43
Q

Resistance to what drug has been demonstrated with prolonged vancomycin use due to persistent S.aureus infections?

A

Glycopeptides

44
Q

S. pneumo resistance to what type of abx is on the rise?

A

Macrolides (such as azithromycin)

45
Q

Resistance to fluoroquinolone correlates with:

A

its frequency of use

46
Q

What is the most common infection caused by community-acquired resistant E. Coli?

A

UTI’s

47
Q

Bacteria picks up free DNA from environment.

A

transformation

48
Q

DNA is transferred to bacterial by viral delivery.

A

Transduction

CMD Block 2 (38 decks)

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