P293 Development of a multiplex PCR short tandem repeat typing scheme for Candida tropicalis

Abstract

Candida tropicalis is a clinically relevant yeast that causes candidemia in humans with a high mortality rate. The yeast primarily infects immunocompromised patients and causes outbreaks in health care facilities. Antifungal-resistant isolates have been reported. Here, we report a short tandem repeat (STR) typing scheme, for C. tropicalis to enable fast, cost-effective, and high-resolution genotyping. This novel typing approach was applied to 117 clinical isolates. For the development of the typing scheme six novel STR markers were selected, combined into two multiplex PCRs, and used to type 117 C. tropicalis isolates, resulting in the identification of 104 different genotypes. The outcome of STR typing of 10 isolates was then compared to single nucleotide polymorphism (SNP) calling from whole genome sequencing (WGS). Isolates with >111 SNPs were also differentiated by the STR assay. Two isolates that were identical according to SNP analysis were separated by STR typing in one marker. To test specificity, STR typing was applied to 15 related yeast species and we found no amplification of these targets. For reproducibility testing, two isolates were typed independently 5-times, which showed identical results in each experiment. In summary, we developed a reliable, rapid, and high-resolution STR genotyping for C. tropicalis, which was found to correlate well to SNP calling by WGS.