Antimicrobial Susceptibility

Question 1

What 4 things must culture interpretation assume?

Answer 1

1. sample was appropriately collected
2. sample was appropriately transported to lab
3. clinical evidence of inflammation in pt
4. significant growth isolated (not a contaminant and must make sense with clinical signs present)

Question 2

__________ is the lowest concentration of drug that completely inhibits growth of the bacteria.

Answer 2

MIC

Question 3

________ is the maximum bacterial MIC that predicts successful therapy and is specific for each source species, drug, bug, and site combination.

Answer 3

breakpoint

Question 4

What are the 4 steps to determining a breakpoint?

Answer 4

1. evaluate population MIC (if small –> empiric tx ok; if large, intrinsic resistance present)
2. consider PK/PD parameters for each
3. use statistical modeling to predict population response
4. use clinical data (does it work in pt?)

Question 5

If the breakpoint MIC is high, what does this mean?

Answer 5

that the drug is NOT a good empiric choice for treatment for that particular bacteria in that particular site.

You desire a LOW MIC.

Question 6

what happens if breakpoint information is not available for your source species, drug, bug, and site combination?

Answer 6

that antibiotic will NOT be reported on the c/s report or reported as ‘NI’
breakpoints for similar organisms can be used (ex. e. coli for klebsiella)

Question 7

what are the 3 possible culture reports?

Answer 7

1. susceptible
2. intermediate
3. resistant

Question 8

Can you adjust teh dose/route/frequency to make an ‘I’ an ‘S’?

Answer 8

yes – example: enterococcus faecalis in dog
use ampicillin MORE frequently