Resensitization of fluconazole-resistant urinary Candida spp. isolates by amikacin through downregulation of efflux pump genes

Abstract

The contribution of fluconazole-resistant Candida spp. isolates to urinary tract infections in Egypt has become a nationwide problem. A recent approach to overcome such disaster is combining conventional antifungals with non-antifungals. This study investigated the interaction of amikacin with fluconazole against resistant Candida strains isolated from the urine culture of patients admitted to Alexandria Main University Hospital. Among the collected Candida spp. isolates, 42.9% were resistant to fluconazole with MICs ranging between 128 and 1,024 µg/ml. The resistance-modifying activity of amikacin (4,000 µg/ml) was studied against fluconazole-resistant isolates where amikacin sensitized 91.7 % of resistant Candida spp. isolates to fluconazole with a modulation factor ranging between 32 and 256. The rhodamine efflux assay was performed to examine the impact of amikacin on efflux pump activity. After 120 minutes of treatment, amikacin affected the efflux pump activity of the isolates tested with a percentage of reduction in the fluorescence intensity of 8.9%. Quantitative real-time PCR was applied to assess the amikacin effect on the expression of the efflux pump genes MDR1, CDR1, and CDR2. The downregulatory effect of amikacin on the expression of the studied genes caused a percentage of reduction in the expression level ranging between 42.1 and 94%. In conclusion, amikacin resensitized resistant Candida spp. isolates to fluconazole and could be used in combination in the management of candiduria with a higher efficiency or at lower administration doses. To the best of our knowledge, this is the first study evaluating the enhancement of fluconazole activity in combination with amikacin against Candida spp.