M27,-a In Vitro Micro-determination Of Our Common Pathogens Of Antifungal Sensitivity

Objective (i) To test the susceptibility of our country's clinical isolates to six kinds of antifungal agents which are often used in clinical practice. To evaluate whether the isolates resistant to fluconazole were cross-resistant to other antifungal agents. (ii) To estabilish antifungal susceptibility testing of filamentous fungi include Aspergillus spp. and Dermatophytes. (iii)To evaluat antifungal susceptibility testing of yeasts and filamentous fungi reproductively and correctively. Methods In the study, M27-A microdilution method (NCCLS) was employed to detect the MICs of six current available antifungal agents which included 5-flucytocine (5-FC), fluconazole (FCZ), ketoconazole (KCZ), itraconazole(ICZ), amphotericin B (AmB) and Terbinafine(TBF). Pathogenic Fungi included Candida spp.80 , Aspergillus spp. 31 and Dermatophytes 31. Their inoculum sizes were 0.5×103～2.5×103CFU/ml,0.5×104～2.5×104CFU/ml and 0.5×105～2.5×105CFU/ml ,and incubation time were 2, 2 and 5～7 days respectively. The tested media were RPMI-1640 with he MOPS buffer and SDB. The drugs diluted into the final concentration was 0.0313-16(g/ml(KCZ, ICZ, AmB and TBF) and 0.125-64(g/ml (FCZ and 5-FC).In the test of Dermatophytes, the final concentrations of TBF were 0.00025-0.128 (g/ml. Results It was showed that (i) Candida spp. had high susceptibility to ICZ(MIC=0.1070(g/ml) and KCZ(MIC=0.1412(g/ml), while some of the tested strains seemed less sensitive to FCZ(MIC=0.7581(g/ml), AmB(MIC=0.5454(g/ml) and 5-FC(MIC=0.7983(g/ml). For TBF, most strains of Candida albicians were not sensitive while some of non-Candida albicians were sensitive ,especially Candida parapsilosis. (ii)Aspergillus had high susceptibility to ICZ(MIC=0.2989(g/ml) and TBF(MIC=0.3057(g/ml) , while MIC=1(g/ml were 3 stains and 4 stains respectively. Some of Aspergillus strains seemed not sensitive to KCZ and AmB while most of them seemed sensitive to FCZ and 5-FC . (iii) Dermatophytes was high sensitive to TBF. Their arrange of MIC was merely 0.001-0.032(g/ml(MIC=0.0044(g/ml). It was much lower than other five antifungal agents. Dermatophytes was also sensitive to azole agents, included ICZ, KCZ and FCZ. But they were not sensitive to AmB and 5-FC. Conclusion NCCLS method is accuracy and reproducibility. It appears that the microdilution method may have clinical utility in laboratories in antifungal susceptibility testing of yeast. In the meantime, our results suggested that drug-resistant strains also existed in our country's clinical practice, so attention must be paid to such cases. Meanwhile M27-A standards could be applied to antifungal susceptibility tests of filamentous fungi such as Aspergillus and Dermatophytes.