Differential Expression Levels of Agglutinin‑Like Sequence, Lipase, and Secreted Aspartyl Protease Genes in Candida tropicalis Treated with Fluconazole Alone and in Combination with Clotrimazole

Background:  The  frequency  of  opportunistic  fungal  infections  in  immunocompromised  patients,  especially by Candida  species,  has  sharply  increased  in  the  last  few  decades.  As  the  number  of  antifungal drugs available for the treatment of candidiasis is limited, combination therapy has been employed as one of the most commonly used techniques to alleviate this problem. Aims: The main aim of this study was to explore the antifungal activity of fluconazole in combination with clotrimazole on expression levels of virulence genes, agglutinin‑like sequences (ALS1 and ALS2), lipases (LIP1 and LIP4) and secreted aspartyl proteases (SAP2 and SAP4) in Candida tropicalis. Methods: Ten infected clinical isolates obtained from recurrent vulvovaginal candidiasis patients were used in this study. The broth  microdilution  assay  was  utilized  to  investigate  antifungal  susceptibilities  to  fluconazole  alone  and in combination with clotrimazole and the synergistic effects were interpreted with reference to the fractional inhibitory concentration (FIC) index model. The expression levels of ALS1, ALS2, LIP1, LIP4, SAP2 and SAP4 genes were quantified by real‑time RT–PCR. Results: Antifungal susceptibility results showed that isolates were resistant to at least one type of azole antifungals. The combination of  fluconazole  with  clotrimazole  revealed  synergistic  effects  against  C. tropicalis isolates with FIC90  index  ranging  from  0.011  to  0.43.  The  results  indicated  that  combination  of  fluconazole  with  clotrimazole could cause a down-regulation of gene expression of ALS1, SAP2, LIP4, SAP4, LIP1 and ALS2  genes,  respectively.  Conclusions: Fluconazole in combination with clotrimazole may diminish the virulence properties of C. tropicalis.