Virulence of Candida parapsilosis sensu stricto from argentinean patients with Candidemia, biofilm expression and response profile to antifungal agents

Candida parapsilosis sensu stricto had emerged as major nosocomial pathogens, being the second most frequently isolated yeast after C. albicans from candidemia. Our aim was to analyze the virulence and the response to antifungal agents, of the species C. parapsilosis sensu stricto from blood cultures of Argentinean patients with candidemia and to know how this envi- ronment impact in virulence Methods & Materials: A basic and retrospective study was designed for 75 cryopreserved isolates, 25 from blood, 28 from buc- cal cavity and 22 from skin. First they were identified based on color in chromogenic medium, micro-morphology in 1% milk agar- Tween 80, and Vitek2 (BioMérieux, Francia) systems. The molecular characterization was made by PCR with specific primers and Min- imum Inhibitory Concentration (MIC) was determined for each antifungal agent on the study strains using CLSI M27-A3. Biomass biofilm quantification was studied through crystal violet on two culture media YPD and RPMI 1640 using well microtiter plates. Isolates were categorized as high (≥0.41OD), low (0.11-0.40 OD) or non-producers (≤0.10 OD). The InfoStat 2016 statistical software was used for statistical calculation, considering a p value lower than alpha error (alpha = < 0.05) significant. Results: Out of the 75 isolates of the C. parapsilosis complex were reconfirmed to be C. parapsilosis sensu stricto. 20 strains derived from blood (80%) were sensitive to fluconazole, 100% to voricona- zole, (96%) to Caspofungin. and 100% of the strains were wild type to amphotericin. In the biofilm biomass assay, higher absorbance levels were reached with YPD medium (p≤0.05). 96% (24/25) of the blood, 82.1% (23/28) buccal and 72.7% (16/22) skin yeasts were high biofilm producers. Isolates from blood environment are likely to be more virulent than those isolated in buccal and skin conditions (Wilcoxon test p≤0.05). Conclusion: Biofilm-forming capacity of the C. parapsilosis sensu stricto species depends on the strain. However, conditions in the environment may affect or determine this species virulence potential. YPD medium is more effective and less expensive than RPMI to stimulate biofilm growth at 24 hours. Both, buccal and the skin contain highly biofilm-producing strains, both of which can be routes of infection related to health care.