The role of mitochondrial deficiencies in Candida glabrata on azole susceptibility

Background: Next generation sequencing and other molecular approaches are showing that vaginal microbial populations are complex and variable over time and in health versus disease. Vaginal candidiasis (VVC) is caused by Candida, usually C. albicans, an opportunistic yeast that colonizes about 25% of women. Candida glabrata is species within the Candida genus that is less prevalent in the vaginal microbiome and less virulent but more likely to be resistant to azole drugs, thus making it more difficult to treat. The relationship between drug resistivity and mitochondrial function is unclear. Fungal mitochondrial genomes contain genes which encode RNA and other products involved in translation and encoding for protein components involved in the electron transport chain and oxidative phosphorylation. Other studies have found that fungal mitochondrial dysfunction is associated with overexpression of ABC transporter genes such as CDR1 which allows for increased drug efflux from the cell resulting in multi-drug resistance. This study asks what specific mitochondrial mutations are present in azole resistant C. glabrata, that have acquired respiration incompetency making fluconazole (FLZ), a third-generation azole used to treat vaginal fungal infections ineffective for patients colonized with C. glabrata. Methods: Presence of mitochondrial mutations were determined with the use of PCR, restriction enzyme digests and gel electrophoresis. Results: All vaginal isolates of C. glabrata from our repository were found to be resistant to fluconazole via MIC, many of the same isolates were respiratory deficient but also found to have high CDR1 expression and therefore increased drug resistance. Although, respiration deficient C. glabrata isolates may have multiple deletions in their mtDNA they are not completely devoid of mtDNA. Conclusion: Results indicate that lack of mitochondrial function in C. glabrata is associated with high resistance to FLZ in petites derived from vaginal isolates and that intermediate resistance in vaginal parent strains is not due to mutation to petite status.