Phenotypic and genotypic characterization of Candida species from the oral cavity of healthy individuals in Lublin province, Poland

Background Candida spp., particularly C. albicans, are commonly isolated fungi in the oral cavity. However, their prevalence in healthy participants and their genotype–phenotype relation remains elusive.Aim This study aimed to update the information on Candida species colonizing the oral cavity of healthy population, identify the most common species, and characterize the intraspecific diversity to determine the genotype-phenotype relationship.Methods Oral swabs of healthy participants who declared an absence of oral infection were analyzed. Microbiological methods: chromogenic media, sugar assimilation tests, drug susceptibility, filamentation tests, temperature tolerance analysis, and assessment of biofilm formation ability. Genotyping methods: PCR amplification of the internal transcribed spacer (ITS) region with MspI restriction enzyme digestion and 25S rDNA region.Results Of the 500 individuals tested, 130 harbored C. albicans in 77%, C. dubliniensis in 12%, Pichia kudriavzevii (previously C. krusei) in 8%, and Nakaseomyces glabrata (previously C. glabrata) in 3%. The microbiological tests yielded conflicting results. Analysis of the 25S rDNA transposable intron region contributed to the identification of individual Candida spp. and intraspecific identification of C. albicans genotypes. Genotype A accounted for 70% (n = 100) of C. albicans isolates, whereas genotypes B, C, and D (C. dubliniensis) accounted for 17%, 9%, and 4% of the isolates, respectively.Conclusion The results indicate a complex genotype–phenotype relationship in Candida spp. and recommends combining microbiological and molecular methods for the efficient typing of Candida spp.