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Pharmacology III > Exam 3: Rose Testing Mechs > Flashcards

Exam 3: Rose Testing Mechs Flashcards

1
Q

Serology

A
  • blood testing
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2
Q

Direct detection

A
  • atigen, staining, assays
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3
Q

Culture

A
  • biochem reactions
  • antisera
  • molecular methods
  • susceptibility
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4
Q

Antimicrobial Susceptibility Testing.. what info do you want to find from this?

A

Minimum inhibitory concentration and minimum bactericidal concentration

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5
Q

Minimum inhibitory concentrations… are they set concentrations?

A
  • no they differ in each person
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6
Q

Susceptibility breakpoints

A
  • concentration that separates the populations of micro organisms
  • classifications are:
  • susceptible
  • intermediate
  • resistant
    • nonsusceptibile
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7
Q

Intermediate susceptibility

A
  • infection may be treated with higher doses or drug conectrations istes
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8
Q

Nonsusceptible

A
  • newer antimicrobials with few resistant strains
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9
Q

What is point of susceptibility breakpoint?

A
  • provide info to clinicians to select optimal antibiotic therapy
  • may be set for drug classes but unique to each organism and an antibiotic
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10
Q

MIC… low numbers next to antibiotics more or less potent?

A
  • more potent
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11
Q

MIC50

A
  • concentration at which 50% of organism population is halted by the selected antibiotic
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12
Q

MIC 90

A
  • often reported in surveillance studies
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13
Q

What other factors to consider when antibiotic with lowest mc50/mc90 is not the best

A
  • protein binding (only free drug available for activity)
  • tissue penetration
  • suceptibility breakpoints
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14
Q

Disk Diffusion Test (Kirby-Bauer) (qual vs quantitative, method, how long it takes, pros/cons)

A
  • QUALitative
  • organism streaked across surface of agar followed by antibiotic disks
  • 18-24 hour incubation, inhibition zones are measured
  • results as resistant, sensitive, or intermediate
  • advantages: speed, low cost, minimum labor
  • cons: no MBC, misinterpretation of new and rare resistance
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15
Q

Broth Dilution Test

A
  • QUANtitative
  • macrotube vs microtube
  • doesn’t tell if bacteria is killed but does show inhibition of growth if not turbid
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16
Q

Macrotube Broth dilution test

A
  • serial two-fold dilutions of antibiotic made into growth medium.. add bacteria at standard dose
  • tubes examined for turbidity 18029 horus
  • MIC defined as tube containing highest dilution of antimicrobial inhibiting visual growth
17
Q

Microtube Broth dilution Test

A
  • smaller volumes in plastic microtiter plates
  • adaptability to automation
  • pros: can determine MBCs and automated
  • cons: labor intensive and time consuming, difficult on large scale
18
Q

Automated susceptibility testing

A
  • reports susceptibility of up to 25 agents after 4-24 hours of incubation
  • pros:
  • reduced labor time/costs
  • reproducibility
  • data management
  • rapid results: most <12 hours
  • Cons
  • increased equipment costs
  • predetermined panels
  • inability to test all clinically relevant pathogens
  • inaccurate detection of resistant phenos
  • can have inducable resistance
19
Q

Epsilometer Test (ETEST) (what it does and how to read it)

A
  • QUANtitative
  • similar to disk diffusion
  • bacteria streaked on agar, place strip with gradient of antibiotic onto plate
  • incubate 18-24 hours
  • tear shaped zone of inhibition
  • MIC read as lowest point of intersection on E-strip
20
Q

Pros and Cons of Etest

A
  • pros:
  • quantify MIC
  • easy to perform, high reproducibility
  • multiple antibiotics can be tested per plate
  • cons:
  • expensive
  • MBC cannot be determined
21
Q

Minimum Bactericidal Concentration (how to get there from Broth test)

A
  • get the MICs
  • dilutions of the antimicrobial MICs (ones that didn’t grow) are subcultured onto antibiotic-free agar
  • plates incubated for 18-24 hours and then examined for growth
  • lowest conc of antibiotic able to kill >99.9 of original inoculum is MBC
22
Q

MBC fun facts

A
  • not routinely performed
  • not standardized between laboratories
  • may be determined for serious infections (meningitis, endocarditis)
23
Q

Tolerance in terms of MIC and MBC

A

MIC/MBC >/= 16 is tolerance

24
Q

MIC and clinical utility

A
  • used to determine selection of definitive antibiotic therapy
  • pathogen susceptible to antibiotic will be reported as
  • susceptible: below achievable blood [ ]
  • intermediate: approaching MIC blood [ ]
  • resistant: MIC above achievable antibiotic blood [ ]
25
Q

MBC and clinical utility

A
  • really only used when bactericidal activity required for patient to live
  • meningitis, endocarditis

Pharmacology III (18 decks)

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