Comparison of The Semisolid Agar Antifungal Susceptibility Test with 1 The NCCLS M38-P Broth Microdilution Test for Scrcening of Filamentous Fungi
Antifungal susceptibility festing of pathogenic molds is being developed. A simple screening semisolid agar antifungal ssceptibility (SAAS) test accurately measures susceptibilities of yeasts. The performance of the SAAS sereeuing test for filamentous fungi was assessed by comparing MICS of four antifungals (amphotericin B [AMB], AMB lipid complex [ABEL], itraconazole (ITZ], and posaconazole [POSJ) for 54 clinical mold isolates with the results of the National Committce for Clinical Laboratory Standards (NCCLS) proposed broth microdilution method (M38-P). The SAAS test utilized inocula stabbed into fubes of 0.5% semisolid heart infusion agar. In both tests MICS were read after incubation at 35°C for 48 h. The isolates tested wvere Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, other Aspergillus spp., Fusarium spp., Penieillium sp., Mucor sp., Scedosporiun prolificans, Trichophyton sp., ad an unidentificd dematiaccous mold. Concordance of Lest 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%. Tor the Aspergillus spp., all hut one were susceptible to ITZ by SAAS test; all wvere susceptible to P'OS (MIC range, 0.25 to 4 ug/ml). Three of six non-Aspergillus molds that were resistant to AMB and ABEL by SAAS (MIC 2 2 ug/ml) were also resistant by the NCCLS test. The SAAS test compared favorably to the NCCLS broth microdilution test for molds, aud most of the clinical isolates tested were susceptible to all four drugs.