Related Experiment Video
Updated: May 23, 2026
Whole Genome Sequencing of Candida glabrata for Detection of Markers of Antifungal Drug Resistance
Published on: December 28, 2017
Comparison of human and soil Candida tropicalis isolates with reduced susceptibility to fluconazole
Yun-Liang Yang1, Chih-Chao Lin, Te-Pin Chang
1Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan.
Abstract:
Infections caused by treatment-resistant non-albicans Candida species, such as C. tropicalis, has increased, which is an emerging challenge in the management of fungal infections. Genetically related diploid sequence type (DST) strains of C. tropicalis exhibiting reduced susceptibility to fluconazole circulated widely in Taiwan. To identify the potential source of these wildly distributed DST strains, we investigated the possibility of the presence in soil of such C. tropicalis strains by pulsed field gel electrophoresis (PFGE) and DST typing methods. A total of 56 C. tropicalis isolates were recovered from 26 out of 477 soil samples. Among the 18 isolates with reduced susceptibility to fluconazole, 9 belonged to DST149 and 3 belonged to DST140. Both DSTs have been recovered from our previous studies on clinical isolates from the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) program. Furthermore, these isolates were more resistant to agricultural azoles. We have found genetically related C. tropicalis exhibiting reduced susceptibility to fluconazole from the human hosts and environmental samples. Therefore, to prevent patients from acquiring C. tropicalis with reduced susceptibility to azoles, prudent use of azoles in both clinical and agricultural settings is advocated.
Insights
Treatment-resistant Candida tropicalis strains, a growing threat in fungal infections, were found in Taiwanese soil. These environmental strains are genetically linked to clinical fluconazole-resistant isolates, highlighting the need for careful azole use.
Area of Science:
- Medical Mycology
- Environmental Microbiology
- Antimicrobial Resistance
Background:
- Increasing prevalence of treatment-resistant non-albicans Candida species, particularly Candida tropicalis, poses a significant challenge in managing fungal infections.
- Genetically similar strains of Candida tropicalis with reduced susceptibility to fluconazole have been widely observed in Taiwan.
Purpose of the Study:
- To investigate the potential environmental source of widespread, genetically related, fluconazole-resistant Candida tropicalis strains in Taiwan.
- To determine if soil environments harbor these challenging fungal strains.
Main Methods:
- Isolation and identification of Candida tropicalis from soil samples.
- Characterization of isolates using pulsed-field gel electrophoresis (PFGE) for genetic relatedness.
- Diploid sequence typing (DST) to identify specific sequence types.
- Antifungal susceptibility testing against fluconazole and agricultural azoles.
Main Results:
- Fifty-six Candida tropicalis isolates were recovered from 477 soil samples.
- Eighteen isolates exhibited reduced susceptibility to fluconazole, with DST149 (9 isolates) and DST140 (3 isolates) being predominant.
- These fluconazole-resistant strains were also found to be more resistant to agricultural azoles.
- Genetic linkage was established between environmental and previously identified clinical isolates.
Conclusions:
- Genetically related Candida tropicalis strains with reduced fluconazole susceptibility exist in both human clinical settings and the environment (soil) in Taiwan.
- The findings suggest a potential environmental reservoir for these resistant strains.
- Prudent use of azoles in both clinical and agricultural applications is recommended to prevent the spread of azole-resistant Candida tropicalis.
