Abstract:

Objective To test the susceptibility of Penicilliosis marneffei （PM） isolates from Guangxi bamboo rats and patients to voriconazole and several commonly used antifungal agents. Methods According to the Clinical and Laboratory Standards Institute （CLSI） M27-A2 and M38-A document, a microdilution method was used to determine the minimum inhibitory concentration（MIC） of voriconazole, itraconazole，terbinafine, amphotericin B, and fluconazole against mycelial phase （25 ℃） and yeast phase （37 ℃） of 14 PM isolates from Guangxi Bamboo rats and 25 PM isolates from patients. The difference in MIC of the antifungals was assessed by two-sample t test between Bamboo rat PM isolates and clinical PM isolates, and by paired t test between the mycelial and yeast phase of PM isolates. Results The MIC ranges of voriconazole, itraconazole, terbinafine, amphotericin B and fluconazole were 0.0313－0.1250, 0.1250－1.0000, 0.0313－0.5000, 0.2500－4.0000, 2.0000－8.0000 mg/L, respectively for mycelial phase of Bamboo rat PM isolates, 0.0078－0.2500, 0.0313－0.5000, 0.0313－1.0000, 0.2500－2.0000, 1.0000－8.0000 mg/L, respectively for yeast phase of Bamboo rat PM isolates, 0.0313－0.2500, 0.0625－1.0000, 0.0313－1.0000, 0.2500－4.0000, 2.0000－32.0000 mg/L, respectively for mycelial phase of clinical PM isolates, 0.0039－0.2500, 0.0313－0.5000, 0.0313－2.0000, 0.1250－2.0000, 2.0000－16.0000 mg/L, respectively for yeast phase of clinical PM isolates. None of the PM isolates was resistant to any of the antifungals. The MIC of voriconazole was found to be the lowest for PM isolates from both Bamboo rats and patients at the same temperature （37 ℃ or 25 ℃）, followed by itraconazole, terbinafine, amphotericin B and fluconazole. Statistical difference was found in the MIC values of itraconazole, terbinafine, amphotericin B between the yeast and mycelial phase of the same PM isolate, but not found in antifungal MIC values between Bamboo rat isolates and clinical isolates at the same phase. Conclusions Of the tested drugs, voriconazole shows the strongest antifungal potency. The PM isolates from Guangxi Bamboo rats are similar to clinical PM isolates in the sensitivity to voriconazole, itraconazole, terbinafine, amphotericin B and fluconazole. The phase of PM isolates may affect their susceptibility to itraconazole, amphotericin B and terbinafine.

Key words: in vitro susceptibility test