Susceptibility Testing 7.4

  1. This is when an organism is affected by the inhibitory action of an antimicrobial
  2. this is the ability of an organism to withstand the inhibitory effects of antimicrobials.
  3. this term is synonymous with antimicrobial agent.
  4. this is a natural or synthesized substance used to inhibit or kill infecting pathogens.
    antibiotic (antimicrobial agent)
  5. what are the four types of susceptibility testing?
    • Disk-diffusion test
    • Broth dilution
    • Agar dilution
    • Specific resistance test
  6. these are a battery of filter paper disks that are impregnated with an antimicrobial agent. They are placed in an agar medium and incubated.
    disk diffusion test
  7. Disk diffusion tests have to follow what guidelines?
  8. disk diffusion tests are limited to ______ growers.
  9. what are the special requirements to test for strep on a disk diffusion test?
    MH + 2-5% horse blood
  10. what are the special requirements for neisseria on a disk diffusion test?
    5-7% CO2 and MH + 2-5% horse blood
  11. what medium is required to test for H. influenzae with a disk diffusion test?
    Haemophilus test medium
  12. what special requirements are needed to test for N. gonorrhoeae with a disk diffusion test.
    GC agar + CO2
  13. this is the smallest amount of medication required to inhibit growth.
    Minimum inhibitory concentration (MIC)
  14. what unit of measurement is used for Minimum inhibitory concentration (MIC)?
  15. Minimum Inhibitory Concentration is correlated with what test?
    disk diffusion test
  16. This is part of a broth dilution test?
    Minimum inhibitory concentration
  17. what was developed to standardize the Kirby-Bauer System?
    Minimum Inhibitory Concentration
  18. this has the same principle as the broth MIC but the agent is implanted into usually six medias.
    MIC agar version
  19. which version of MIC is labor intesnive?
    MIC agar version
  20. what is an advantage of the MIC agar version?
    • can test multiple isolates per plate
    • fastidious organism
  21. what technique should be used when streaking a MIC agar?
    sprial technique
  22. what are the two automation techniques used for MIC testing?
    • VITEK
    • Microscan
  23. this is the lowest concentration that kills 99.9% of organisms
    Minimum Bacterial Concentration
  24. in Minimum bacterial concentration, samples from _____ and higher are cultured.
  25. Minimum Bacterial Concentration is a _____________ procedure, not routine.
  26. Minimum bacterial concentration is used for what patients?
    • Cancer
    • AIDS
  27. thest tests an enzyme that binds to beta lactam ring.
    beta lactamase test
  28. beta lactamase test is similar to what?
  29. what are the two enzyme conversions in the beta lactamase test?
    • penicillin to penicilloic acid
    • cephalosporins to cephalosporanic acid
  30. this is an in vitro test, which tests patient's serum against patient's own infecting organism.
    schlichter's test
  31. in which susceptibility test do you collect two samples (peak and trough) which are placed on ice.
    schlichter's test
  32. when is the trough sample collected for schlichter's test?
    0-30 min before dose
  33. for IV when is the peak sample collected for schlichter's test?
    30-60 minutes after dose
  34. for IM when is the peak sample drawn for schlichter's test?
    60 minutes after dose
  35. for oral when is the peak sample drawn for schlichter's test?
    90 minutes after
  36. what are the three indications of susceptibility testing?
    • effectiveness of antimicrobial
    • aid for clinicians
    • ID organism
  37. what are two deficiencies of susceptibility testing (KBS)?
    • qualitative
    • some inaccuracies
  38. what are four factors for antimicrobial selection?
    • hospital formulary
    • medical staff
    • CLSI
    • similar activity
  39. this is the size of an area arounds disc that prevents growth, measured in mm.
    zone of inhibition
  40. zone of inhibition is based on previous _____ patterns.
  41. this is an antibiotic agar diffusion method where concetration decreases as distance increases.
    modified kirby-bauer principle
  42. what media is used for a modified kirby-bauer?
    mueller-hinton agar
  43. a pH outside of 7.2-7.4 alters what two things on a modified kirby-bauer?
    • antibiotic activity
    • size of zone
  44. a 150mm plate will have how much medium which produces what depth?
    • 60-70 mL
    • 4 mm depth
  45. a 100mm plate will have how much medium which producesw what dpeth?
    • 25-30 mL
    • 4 mm depth
  46. true or false
    MH plates should be incubated for 10-20 minutes before using the media to evaporate excess moisture.
  47. antimicorbial disks are made out of ____________ and supplied in cartridges.
    filter paper
  48. how are antimicrobial discs stored?
    refrigerate unopened at 4-8oC
  49. which two antimicrobial discs should be frozen at -20oC?
    • penicillin
    • cephalosporin
  50. doing this prior to use will minimize condensation on antimicrobial discs.
    warm 1-2 hours prior to use
  51. what standard should be used to control inoculum size.
    McFarland standard
  52. how many isolates should be used to inoculate broth in inoculum preparation?
    4 or 5
  53. when performing susceptibility testing you should alternate _______ prep/suspension.
  54. for saline prep/suspension 4-5 colonies should be placed in what percent NaCl.
  55. susceptibility testing suspension should not sand longer than ________ minutes.
  56. insufficient inoculum in susceptibility testing could create a false ______ zone.
  57. too heavy susceptibility testing coul cause a false _____ zone.
  58. when performing plate inoculation for susceptibility testing, a ___ direction mat-streak should be used.
  59. how long should a plate inoculation for susceptibility testing be allowed to dry? no more than?
    • 3-5 minutes
    • 15 minutes
  60. a 150mm plate can hold how many antimicrobial disks?
    12 disks
  61. a 100 mm plate can hold how many antimicrobial disks
    5 disks
  62. how far should antimicrobial disks be placed from each other (center to center)?
    24 mm
  63. how far should antimicrobial disks be placed from the edge of the plate?
  64. plates that have been inoculated should be incubated within ___ minutes.
  65. CO2 should be avoided in inoculated plates except for what three genuses?
    • Neisseria
    • Haemophilus
    • Streptococcus
  66. when reading inoculated media, reflected light should be used in what two situations?
    • for most organisms
    • blood containing plates
  67. when reading inoculated media, transmitted light should be used when?
    haze from staph and enterocci
  68. what are the three results for susceptibility testing?
    • susceptible (sensitive, inhibited)
    • resistant (not inhibited)
    • intermediate (may require higher concentration of antibiotics)
  69. what are the four(ATCC standard control strains for susceptibility testing.
    • Pseudomonas aeruginosa
    • Streptococcus faecalis
    • E. coli
    • S. aureus
  70. guidelines for susceptibility testing quality control are provided by who?
  71. this is a quantitative dilution test using microtube wells.
  72. what are the three steps for the MIC procedure?
    • ioculate
    • incubate
    • interpret
  73. how is growth interpreted on MIC?
    large button or turbidity
  74. the MIC is the ______ tube for no growth.
Card Set
Susceptibility Testing 7.4
Microbiology susceptibility testing 7.4