Comparison of the semisolid agar antifungal susceptibility test with the NCCLS M38-P broth microdilution test for screening of filamentous fungi.

Antifungal susceptibility testing of pathogenic molds is being developed. A simple screening semisolid agar antifungal susceptibility (SAAS) test accurately measures susceptibilities of yeasts. The performance of the SAAS screening test for filamentous fungi was assessed by comparing MICs of four antifungals (amphotericin B [AMB], AMB lipid complex [ABEL], itraconazole [ITZ], and posaconazole [POS]) for 54 clinical mold isolates with the results of the National Committee for Clinical Laboratory Standards (NCCLS) proposed broth microdilution method (M38-P). The SAAS test utilized inocula stabbed into tubes of 0.5% semisolid heart infusion agar. In both tests MICs were read after incubation at 35 degrees C for 48 h. The isolates tested were Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, other Aspergillus spp., Fusarium spp., Penicillium sp., Mucor sp., Scedosporium prolificans, Trichophyton sp., and an unidentified dematiaceous mold. Concordance of test results was determined as the percent agreement of MICs +/- 1 dilution. The overall agreement between the tests for each drug was as follows: AMB, 94%; ABEL, 83%; ITZ, 94%; POS, 94%. For the Aspergillus spp., all but one were susceptible to ITZ by SAAS test; all were susceptible to POS (MIC range, 0.25 to 4 micro g/ml). Three of six non-Aspergillus molds that were resistant to AMB and ABEL by SAAS (MIC >/= 2 micro g/ml) were also resistant by the NCCLS test. The SAAS test compared favorably to the NCCLS broth microdilution test for molds, and most of the clinical isolates tested were susceptible to all four drugs.

Real-time antifungal susceptibility screening aids management of invasive yeast infections in immunocompromised patients.

We examined the utility of a semi-solid agar antifungal susceptibility screening (SAAS) test in real-time management of eight immunocompromised patients with invasive yeast infections. Tests of amphotericin B and fluconazole concentrations of 0.5 and 2 mg/L and 1, 8 and 40 mg/L, respectively, were performed on Candida albicans (two), Candida tropicalis (two), Candida krusei (one), Candida glabrata (one) and Trichosporon species (spp.) (two). All but the Trichosporon spp. and C. glabrata isolates were resistant to fluconazole at > or = 40 mg/L, and patients were successfully managed accordingly. Real-time antifungal susceptibility screening can assist in clinical management of invasive yeast infections.