Distribution and Virulence of Candida parapsilosis Complex Oral Isolates from Immunocompetent Subjects with and without Gingival-Periodontal Disease

The Candida parapsilosis complex comprises three genetically related species: Candida parapsilosis sensu stricto, Candida orthop- silosis and Candida metapsilosis. During the last decade, Candida parapsilosis sensu stricto has become the second most commonly isolated yeast from patients with blood stream invasive fungal infections, following Candida albicans. Despite its clinical significance, little is known about its distribution and behavior in oral cavity niches. Given this background, we intended to perform a molecular characterization of 38 isolates of the Candida parapsilosis complex collected from oral cavities of immunocompetent patients with and without gingival-periodontal disease, with the aim of determining its distribution and establishing a correlation with clinical data. Besides, we assessed the virulence of the strains by examining the in vitro biofilm-forming capacity in two different culture media: YPD and RPMI 1640. Being more frequently isolated from oral cavities with pathological conditions, 89.5% of the strains were reconfirmed to be Candida parapsilosis sensu stricto. More than 70% of the Candida parapsilosis sensu stricto strains showed biofilm- forming capacity in both culture media, reflecting a statistically significant association between biofilm-forming capacity and the clinical conditions of the subjects from whom the strains were isolated. Among the three complex species, Candida parapsilosis sensu stricto is a normal commensal in the oral cavity, being more frequently recovered in inflammatory conditions. Gingival-periodontal disease may be a factor triggering overgrowth and virulence of Candida parapsilosis sensu stricto commensal strains.