Development of a Multiplex PCR Short Tandem Repeat Typing Scheme for Candida krusei

Candida krusei is a human-pathogenic yeast that can cause candidemia with the lowest 90-day survival rate in comparison to other Candida species. Infections occur frequently in immunocompromised patients, and several C. krusei outbreaks in health care facilities have been described. Here, we developed a short tandem repeat (STR) typing scheme for C. krusei to allow the fast and cost-effective genotyping of an outbreak and compared the identified relatedness of 10 isolates to single nucleotide polymorphism (SNP) calling from whole-genome sequencing (WGS). From a selection of 14 novel STR markers, 6 were used to develop two multiplex PCRs. Additionally, three previously reported markers were selected for a third multiplex PCR. In total, 119 C. krusei isolates were typed using these nine markers, and 79 different genotypes were found. STR typing correlated well with WGS SNP typing, as isolates with the same STR genotype varied by 8 and 19 SNPs, while isolates that differed in all STR markers varied by at least tens of thousands of SNPs. The STR typing assay was found to be specific for C. krusei, stable in 100 subcloned generations, and comparable to SNP calling by WGS. In summary, this newly developed C. krusei STR typing scheme is a fast, reliable, easy-to-interpret, and cost-effective method compared to other typing methods. Moreover, the two newly developed multiplexes showed the same discriminatory power as all nine markers combined, indicating that multiplexes M3-1 and M9 are sufficient to type C. krusei.