University of Pennsylvania Medical Center Guidelines
for Antibiotic Use
Pictured above is a graph which shows the relationship between
the MIC and the size of the zone of inhibition
in the Bauer-Kirby test for the drug-A using
the bacteria-Q. "R" represents the cutoff for the interpretation of
"resistant", and "S" represents the cutoff for the interpretation of
The portion of the curve which is red represents the region where it
would be reported that bacteria-Q is resistant to drug-A. Refection
of the curve onto the X-axis (dotted red line) show that a zone diameter less than 16 mm (red arrow) is
required for "resistant" to be reported out for this bug/drug pair.
This correlates approximately with an MIC of >64 micrograms.