Comparison of in vitro Susceptibilities of Talaromyces marneffei in Mold and Yeast Forms in Malaysia

by Selleckchem | Apr 25 2023

Purpose: This study was aimed to determine minimum inhibitory concentration (MIC) differences between yeast and mold forms of T. marneffei in Malaysia.

Patients and methods: Ninety-seven clinical strains of T. marneffei were received from various Malaysian hospitals from the year 2020 until 2022. Their identities were determined using microscopic, macroscopic and molecular methods. Next, the susceptibility of yeast and mold forms of each isolate against amphotericin B, itraconazole, voriconazole, posaconazole, ketoconazole, isavuconazole, terbinafine, caspofungin and micafungin were tested according to the broth microdilution according to the Clinical and Laboratory Standards Institute (CLSI) M38 and M27 guidelines. The geometric means of minimal inhibitory concentration (GM MIC), MIC50, and MIC90 were determined for each antifungal. Additionally, Wilcoxon signed-rank test was used to compare the significant difference of GM MICs for each antifungal, GM MIC, MIC50 and MIC90 for the combined nine antifungals against different growth forms of T. marneffei. The significance was set at p<0.05.

Results: Micafungin had the highest GM MIC, MIC50 and MIC90 for mold form of T. marneffei. For yeast form, amphotericin B achieved the highest GM MIC and MIC50 while micafungin achieved the highest MIC90. However, the GM MIC, MIC50 and MIC90 of terbinafine and azole antifungals on T. marneffei were similar to each other, namely between 0.03 and 0.60µg/mL. The difference of GM MIC of all tested antifungals except caspofungin and micafungin was insignificant. Overall, GM MIC, MIC50 and MIC90 of the combined nine antifungals against two growth forms were insignificant.

Conclusion: The findings suggested either yeast or mold form can be used in the susceptibility testing of T. marneffei against amphotericin B, itraconazole, voriconazole, posaconazole, ketoconazole, isavuconazole and terbinafine.

Comments：

The study aimed to determine the differences in minimum inhibitory concentration (MIC) between the yeast and mold forms of T. marneffei in Malaysia. The researchers obtained 97 clinical strains of T. marneffei from various Malaysian hospitals between 2020 and 2022. The identity of each isolate was confirmed using microscopic, macroscopic, and molecular methods. The susceptibility of the yeast and mold forms of each isolate against nine antifungal drugs was tested using the broth microdilution method according to CLSI M38 and M27 guidelines. The researchers determined the GM MIC, MIC50, and MIC90 for each antifungal drug and compared the differences between the yeast and mold forms using Wilcoxon signed-rank test.

The results showed that micafungin had the highest GM MIC, MIC50, and MIC90 for the mold form of T. marneffei, while amphotericin B achieved the highest GM MIC and MIC50 for the yeast form. The GM MIC, MIC50, and MIC90 of terbinafine and azole antifungal drugs were similar for both forms of T. marneffei. The difference in GM MIC for most antifungal drugs tested was not significant, except for caspofungin and micafungin. Overall, the GM MIC, MIC50, and MIC90 of the combined nine antifungal drugs against both growth forms of T. marneffei were not significantly different.

The study concluded that either the yeast or mold form of T. marneffei could be used in susceptibility testing against amphotericin B, itraconazole, voriconazole, posaconazole, ketoconazole, isavuconazole, and terbinafine. The findings of this study may be useful in guiding the choice of antifungal drugs for the treatment of T. marneffei infections in Malaysia.