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Comparative Study
. 2012;7(4):e34609.
doi: 10.1371/journal.pone.0034609. Epub 2012 Apr 5.

Comparison of human and soil Candida tropicalis isolates with reduced susceptibility to fluconazole

Yun-Liang Yang  1 , Chih-Chao Lin, Te-Pin Chang, Tsai-Ling Lauderdale, Hui-Ting Chen, Ching-Fu Lee, Chih-Wen Hsieh, Pei-Chen Chen, Hsiu-Jung Lo
Affiliations
Comparative Study

Comparison of human and soil Candida tropicalis isolates with reduced susceptibility to fluconazole

Yun-Liang Yang et al. PLoS One. 2012.

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.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Dendrogram of 18 Candida tropicalis isolates from human and soil.
The Dice coefficient was used to analyze the similarities between the PFGE band patterns. UPGMA was used for the cluster analysis. The position tolerance and optimization were set at 1%. A total of 7 isolates were recovered from human (YMs) and 11 from soil (NHUEs). MIC refers to fluconazole MIC (in mg/L). An MIC of 64 indicates isolates with reduced susceptibility.
Figure 2
Figure 2. Growth curves of different C. tropicalis isolates with different fluconazole susceptibilities.
Six isolates, ATCC13803 (rectangles), NHUE40 (diamonds), NHUE42 (triangles), NHUE48 (circles), YM990579 (crosses), and YM990649 (stars) were grown in the RPMI medium 1640 (Gibco BRL31800-022) in the absence (dot lines) or in the presence of 64 mg/L (solid lines) fluconazole.
See this image and copyright information in PMC

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