5.3 Lab

Question 1

methods of antimicrobial susceptibility testing: categories and subcategories?

Answer 1

phenotypic methods:
-Dilution
-Diffusion
-gradient test
-chromogenic media
-automated devices

molecular-based methods
-PCR
-Cycle sequencing
-NGS

Mass spectrometry
-MADLI-TOF

Question 2

how does the kirby bauer disc diffusion method work? what is it for?

Answer 2

1. innoculated agar plate
2. addition of antibiotic discs
3. measure the zone of inhibition

> qualitative test only
-measure the zones of inhibition and compare with charts to verify susceptibility

Question 3

what information do we gain from a gradient test (E-test)?

Answer 3

qualitative and quantitative measurement of antimicrobial susceptibility
-measure MIC

Question 4

How do we know that a certain MIC means the bacterium is resistant or susceptible?

Answer 4

-clinical laboratory standards institute has breakpoints chart
-EUCAST has info about susceptibility testing as well

Question 5

what is the dilution method for antimicrobial testing?

Answer 5

-most used method nowadays
-test tubes of different dilutions, see where bacteria grow

Question 6

when treating a bacterial infection due to a commensal, how should we proceed?

Answer 6

always consider what is the primary cause/ predispoing factor, eg. mites, allergy, etc.
>else, may see resistances develop