Analysis of antifungal susceptibility, virulence factors, and biofilm genes of Candida species isolated from urine samples

Objective: This study aimed to investigate the frequency, virulence factors, biofilm formation, and antifungal susceptibility profiles of Candida species isolated from urine samples. Materials and Methods: VITEK 2 device was used for antifungal susceptibilities of 100 Candida species isolated from urine samples, and conventional methods and VITEK 2 device were used for their identification. For the assessment of virulence factors, 5% sheep blood SDA was used for hemolytic activity, egg yolk agar for phospholipase activity, 1% bovine serum albumin agar for proteinase activity, and Tween 80 agar for esterase activity. Phenotypic biofilm formation was determined by the modified tube adherence method, while the expression levels of the ALS1, ALS3, and HWP1 genes were genotypically assessed using real-time PCR. Results: Among the isolates, Candida isolates, 53% were isolated from intensive care units, 24% from outpatient clinics, and 23% from inpatient services. The isolates were obtained from 61% female and 39% male patients. Candida albicans (C. albicans) was the most frequently isolated species (57%), followed by Candida tropicalis (17%), Candida glabrata (12%), and other non-albicans Candida (NAC) species (14%). Among C. albicans isolates, hemolytic (100%), esterase (98.2%), phospholipase (92.9%), and proteinase (73.6%) activities were observed at high rates. In NAC species, hemolytic activity was equal to C. albicans (100%), proteinase activity was similar (69.7%), whereas phospholipase (67.4%) and esterase (62.7%) activities were significantly lower (p=0.001). In phenotypic biofilm assessment, strong adherence was significantly higher in NAC isolates (44.1%) compared to C. albicans isolates (p<0.001). While HWP1 (94.7%) and ALS3 (96.4%) gene expressions were found higher in C. albicans isolates compared to NAC isolates (p<0.001), no difference was observed in terms of ALS1 gene expression. No significant association was observed between biofilm formation and gene expression in C. albicans isolates, whereas HWP1 and ALS3 gene expressions were associated with biofilm formation in NAC isolates (p=0.048). Antifungal susceptibility tests revealed resistance rates of 2% against fluconazole and micafungin in C. albicans isolates. Candida tropicalis isolates resistance rates were 6% against micafungin. Candida parapsilosis isolates resistance rates were 50% against fluconazole and voriconazole, 40% against amphotericin B, and 20% against micafungin. Candida krusei isolates, resistance to amphotericin B was found at 33%. Conclusion: Accurate species-level identification, phenotypic and genotypic evaluation of virulence factors, and routine implementation of antifungal susceptibility tests in Candida infections will contribute to effective clinical management. Additionally, although further studies are needed, HWP1 and ALS3 genes may be considered potential molecular biomarkers for the diagnosis of urinary tract infections caused by C. albicans.