The Role of FKS1 and ERG11 Gene Variation in Multidrug Resistance among Candida spp. Isolated from Immunocompromised Patients

Abstract

Candidiasis is an infection caused by Candida species, mostly by Candida albicans. Some strains of Candida are resistant to the antifungals used to treat them. The current study was aimed to investigate the genetic variations in FKS1 and ERG11 genes that correlates with Candida spp. isolates resistance to antifungal drugs. with cancer, diabetes, and breastfeeding infants.

The study included a collection of 157 clinical samples from immunocompromised patients, these samples were subjected to several steps of diagnosis techniques to identify the isolates to the species level. The antifungal drug sensitivity was determined by disk division method, and the genetic variation and mutations correlated with the drug resistance were detected by analyzing the DNA sequences of the FKS1 and ERG11 genes, by amplifying those genes from the drug resistance and sensitive isolates with a polymerase chain reaction (PCR) and performing a Sanger sequencing technique for the PCR amplicons which followed by conducting an alignment analysis to investigate the posable gene variation and mutations. The culture results detected a positive Candida species growth in 53 out of 157 samples (33.7%), and the drug susceptibility test results for these isolates to seven antifungal drugs included in the study detected a variable drug resistance among these isolates for each drug tested. The highest percentage of resistant isolates was 16.98% for Caspofungin followed by 11.32% for Fluconazole, 5.66% for Ketoconazole and 3.77% for Clotrimazole. While there was no resistant isolate for Itraconazole, Nystatin and Amphotericin-B. The results of the DNA sequencing analysis of the HS1 region of FKS1gene detected the presence of amino acid substitution F640L mutation in in the Caspofungin resistant isolates. And S642L mutation in all of the resistant and susceptible isolates. While the sequencing analysis of the ERG11 gene detected 7 different amino acid substitution mutations, F126L, I131F, C134F, F145I, A149S and V159F were observed only in resistant isolates, while E266D was observed in sensitive and resistant isolates. All mutations were previously reported except for I131F, C134F, A149S and V159F were reported only in the present study. In conclusion the amino acids substitution mutations in FKS1 and ERG11 genes were responsible for the reduced susceptibility of Candida isolates to Caspofungin and Azoles respectively.