Table 7.

Interpretive guidelines for susceptibility testing in vitro of Candida speciesa

Antifungal agentBreakpointb (μg/ml) forCandida against agent
Susceptible (S)Susceptible-dose dependent (S-DD)cIntermediate (I)Resistant (R)
Fluconazolee ≤816–32d ≥64
Itraconazolef ≤0.1250.25–0.5≥1
  • a Adapted from reference169 with permission of the publisher. The interpretive data are valid only if the methodology in M27-A is followed. The current standard may be obtained from NCCLS, 940 West Valley Road, Suite 1400, Wayne, PA 19087.

  • b Shown are the breakpoints forCandida species against the indicated agents. If MICs are measured on a scale that yields results falling between categories, the next higher category is implied. Thus, an isolate with a fluconazole MIC of 12.5 μg/ml would be placed in the S-DD category. These breakpoints were adopted at a meeting of the subcommittee held June 1, 1996 in Reston, VA. They are considered tentative for 1 year and are open for comments.

  • c Susceptibility is dependent on achieving the maximal possible level in blood. For fluconazole, doses of 400 mg/day or more may be required in adults with normal renal function and body habitus. For itraconazole, measures to ensure adequate drug absorption and concentrations of >0.5 μg/ml in plasma may be required for an optimal response.

  • d —, the susceptibility of these isolates is not certain, and the available data do not permit them to be clearly categorized as either susceptible or resistant.

  • e For fluconazole, these guidelines are based substantially on experience with mucosal infections but are consistent with the limited information for invasive infectious due toCandida spp. Isolates of C. krusei are assumed to be intrinsically resistant to fluconazole, and the MICs for these isolates should not be interpreted on the basis of this scale. It is also pertinent that the 8-μg/ml upper boundary for the range of susceptibility to fluconazole is not known with certainty; the data would permit selection of either 4 or 8 μg/ml for this cutoff.

  • f For itraconazole, the data are based entirely on experience with mucosal infections and data supporting breakpoints for invasive Candida infections are not available.