Question:
With regard to Minimal Inhibitory Concentration (MIC) measurements for fungi, what is generally considered the cutoff between “susceptible” and “resistant?” What do specific numbers actually mean?
Answer:
MIC values by themselves have no meaning.
One must know which organism is being tested and against what drug.
For organisms with no defined endpoints (and there are many), one would like to see a drug level concentration above the MIC.Standardized susceptibility testing for selected organism-drug combinations has demonstrated that correlations between MIC and clinical outcome do exist, especially with the Candida species and the azole antifungal agents.For mould, susceptibility testing has been standardized but clinical correlation is limited.
Antifungal susceptibility testing is now increasingly and appropriately used as a routine adjunct to the treatment of serious fungal infections.
For MICs of various antifungal drugs for a variety of fungi, see our N/A(L):susceptibility database.
Reference:
Rex JH, Pfaller MA. Has antifungal susceptibility testing come of age? Clin Infect Dis. 2002 Oct 15;35(8):982-9. Epub 2002 Sep 24
Rex JH, Pfaller MA, Galgiani JN, Bartlett MS, Espinel-Ingroff A, Ghannoum MA, Lancaster M, Odds FC, Rinaldi MG, Walsh TJ, Barry AL.
Development of interpretive breakpoints for antifungal susceptibility testing: conceptual framework and analysis of in vitro-in vivo correlation data for fluconazole, itraconazole, and Candida infections.
Subcommittee on Antifungal Susceptibility Testing of the National Committee for Clinical Laboratory Standards. Clin Infect Dis. 1997 Feb;24(2):235-47.