Fluconazole susceptibility and multi locus sequence typing of Candida glabrata and Candida tropicalis Isolated from environment

Objective To understand the drug susceptibility and molecular epidemiological characteristics of Candida glabrata and Candida tropicalis strains isolated from leaves, barks and humus, compare the phylogenetic relationship between environmental isolates and clinical isolates and provide evidence for epidemiological investigation and effective control of invasive Candida infection.

Methods A total of 200 environmental samples were collected in Yunnan province. The samples were inoculated on Sabouraud dextrose agar plate for Candida culture and isolation. The genomic DNA of the isolates was extracted, and the isolate species were identified through Internal Transcribed Spacer (ITS) region amplification and sequencing; Antifungal susceptibility testing was performed for each C. glabrata or C. tropicalis isolate by using broth micro dilution reference method; Multi locus sequence typing (MLST) was performed for the genotyping of the isolates. The phylogenetic relationship was analyzed by using eBURST V3 package.

Results A total of 3 C. glabrata strains (1.5%) and 10 C. tropicalis strains (5.0%) were isolated from 200 environmental samples. All the isolates were sensitive to fluconazole. MLST indicated that ST3 was the only sequence type of C. glabrata. Among 10 C. tropicalis strains, 7 DSTs were identified by MLST, including 4 new DSTs (DST813–DST816). CC3 was the major clonal complex of environmentalC. glabrata strains. CC730 was the major clonal complex of environmental C. tropicalis strains.

Conclusion The environmental isolates might share the same origin strain with clinical isolates. C. glabrata and C. tropicalis isolated from leaves, barks and humus might be the potential source of human infection, posing a serious health threaten to human health.