GENOTYPIC IDENTIFICATION OF CANDIDA PARAPSILOSIS COMPLEX SPECIES ISOLATED FROM DIFFERENT CLINICAL SAMPLES

Project no. 21088 · Status: Kapanmış (Yayın bekleniyor) · 2019

Summary

In recent years, the Candida parapsilosis species complex (C. parapsilosis sensu lato) has emerged as the second most frequently isolated fungal pathogen from clinical specimens worldwide. Challenges in identifying species within the Candida parapsilosis complex through phenotypic methods have led to unclear isolation rates, geographical distribution, and clinical significance of these yeasts. Moreover, this species complex exhibits variations in some virulence factors, including in vitro susceptibility to antifungal agents, proteinase and phospholipase activity, and biofilm-forming ability, which are crucial pathogenicity determinants in disease development. Therefore, this study aimed to initially identify these complex species (C. parapsilosis sensu stricto (C. parapsilosis), C. orthopsilosis, and C. metapsilosis) using genotypic methods and subsequently evaluate important virulence factors.           A total of 84 strains of the C. parapsilosis complex, phenotypically diagnosed as C. parapsilosis and collected from various clinics at SBU Tepecik Training and Research Hospital in Izmir province between January 2015 and January 2019, were included in this study.           Firstly, species-specific PCR was conducted to confirm the phenotypic diagnosis. Subsequently, to accurately distinguish the species forming the Candida parapsilosis species complex, the SADH gene region was amplified by PCR, and the resulting PCR amplicons (716 base pairs) were subjected to digestion with the restriction enzyme BanI followed by PCR-RFLP analysis. The findings indicated that all 84 isolates formed two bands (196bp and 521bp), confirming their classification as C. parapsilosis sensu stricto (C. parapsilosis).            Our study also investigated the virulence factors, including proteinase and phospholipase activities, and the biofilm-forming ability of the strains. Proteinase activity examination revealed that 51 (61%) of the 84 strains exhibited positive proteinase enzyme activity, while 33 (39%) had negative proteinase enzyme activity. Phospholipase activity analysis showed that only two C. parapsilosis strains exhibited phospholipase enzyme activity. Additionally, 68 (81%) of the 84 strains were found to form biofilms, with 16 (19%) strains not forming biofilms. Among the non-biofilm-forming strains, only 2 (12%) were isolated from catheter blood cultures, while 14 (87%) were obtained from venous blood cultures. Notably, biofilm formation was positive in 26 (93%) of the strains isolated from catheter blood cultures.           According to these results, comparing the biofilm-forming ability of C. parapsilosis strains isolated from blood cultures and catheter blood cultures, it was observed that strains from catheter blood cultures exhibited significantly higher biofilm-forming ability (p < 0.05).           Considering these results, the absence of C. orthopsilosis and C. metapsilosis in the study suggests that these species are rare in blood culture samples. Additionally, additional studies with more isolates are needed to prevent inadequacies in the identification of the C. parapsilosis species complex. Our study is valuable for examining three factors believed to play a role in the virulence of C. parapsilosis sensu stricto.

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