Molecular mechanisms of azole resistance in Candida glabrata isolated from oropharyngeal candidiasis in head and neck cancer patients.

OBJECTIVE: The aim of the current work was to assess the molecular mechanisms of fluconazole-resistant Candida glabrata strains isolated from oropharyngeal candidiasis (OPC) in head and neck patients, as well as evaluation of virulence factors. DESIGN: Antifungal susceptibility pattern of sixty six clinical isolates of C. glabrata were evaluated by broth-microdilution method. The expression of ERG11, CDR1, CDR2, PDR1 genes as well as ERG11 gene capable of possible mutations was also detected in 21 fluconazol-resistant C. glabrata isolates. Phospholipase and proteinase activity of these isolates was estimated, too. The correlation between the virulence factors, antifungal susceptibility patterns and cancer type was also analyzed. RESULTS: Seven synonymous and four non-synonymous mutations were found in 21 fluconazole-resistant C. glabrata isolates; subsequently, four amino acid substitutions including H257P, Q47H, S487Y and I285N were then reported for the first time. High expression of CDR1 and PDR1 in related to other gene findings were tested in these isolates. Additionally, there was no significant difference between stage of cancer and MIC of all antimicrobial drugs. Significant differences between MIC of fluconazole, voriconazole and cancer types were also, found. The proteinase activity (92.4%) was higher than phospholipase activity in the isolates. Further, no significant difference between proteinase (rs: 0.003), phospholipase (rs: -0.107) activity and fluconazole MICs was observed. CONCLUSION: C. glabrata isolated from OPC in head and neck patients represented high capacities for proteolytic enzymes activity and high mRNA level of CDR1 and PDR1 gene and ERG11 mutations play an important role in azole drug resistance.

Evaluation of virulence factors and azole resistance mechanisms of Candida tropicalis isolates from head and neck cancer patients with OPC.

Background and Objectives: Candida tropicalis is one of the major non-albicans species causing nosocomial infection. There is limited data about mechanisms of azole-resistance and virulence factors of Candida tropicalis. This study was designed to investigate molecular mechanism of azole-resistance and major virulence factors of C. tropicalis isolated from oropharyngeal candidiasis in head and neck cancer patients. Materials and Methods: After collecting 38 C. tropicalis clinical isolates, antifungal susceptibility pattern and the expression levels of ERG11, CDR1, CDR2 and MDR1 were evaluated. Moreover, proteinase and phospholipase activity and biofilm formation of the isolates were investigated as virulence factors. Results: We detected fluconazole resistance in 7 C. tropicalis isolates. The expression levels of CDR1, ERG11 and MDR1 were increased respectively. Protease activity and biofilm formation were seen in all isolates. Five isolates did not exhibit phospholipase activity. Conclusion: Taken together, the overexpressions of ERG11, CDR1 and MDR1 genes were found in fluconazole resistant C. tropicalis, isolated from oropharyngeal candidiasis patients. Also, voriconazole was an effective antifungal against C. tropicalis isolates. The observed high protease enzyme activity and biofilm formation suggested strong pathogenicity of these isolates.