Investigation of antifungal activities of some disinfectants on Candida albicans

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Disinfectants may have fungicidal or fungistatic effects against fungal cells. The mechanism of action of disinfectants on fungal cells believed to be similar to the antibacterial activity. The aim of this study was to demonstrate the efficacy of some disinfectants against Candida albicans and to investigate the relationship between virulence and disinfectant resistance. In this study, the susceptibility of 417 clinical C.albicans and reference isolates against disinfectants were determined. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of disinfectants were obtained by using broth microdilution (BMD) assay. Epidemiological cut-off values (ECVs) were determined by using the MIC and MFC values. Crystal violet assay was carried out to investigate membrane permeability in disinfectant resistant and susceptible isolates. Rhodamine 6G (R6G) flourescence stain was used to show the increase in the number of efflux pumps among selected isolates. The relationship between virulence and disinfectant resistance was determined by in vitro and in vivo investigations. Virulence factors secretory acid proteinase (SAP), phospholipase, esterase, hemolytic activity and slime factor production were examined in vitro. In vivo virulence assay was performed by infecting Galleria mellonella larvae. The relationship between virulence factors and disinfectant resistance was evaluated according to the mortality rates of G.mellonella larvae. The range of MIC values for benzalkonium chloride (BZC) and chlorhexidine digluconate (CHX), triclosan (TRC) and sodium hypochlorite (SHC) were 0.25-8 mg/L, 0.06-4 mg/L and 256-16.384 mg/L, respectively. ECV values for BZC, CHX, TRC and SHC were determined as 4, 2, 1 and 4096 mg/L, respectively. The rate of crystal violet uptake was found between 26.5-57.6% for disinfectant susceptible isolates, and between 33-79.2% for resistant isolates. It is concluded that the disinfectant resistance was related with efflux pumps. Due to the lack of number of isolates that were used in this assay, the relationship between disinfectant resistance and virulence factors could not be assessed. There was no difference in the mortality of larvae infections caused by disinfectant resistant and susceptible isolates. As a result, in this study, resistant isolates against BZC, CHX, SHC and TRC were found among 417 isolates. Input and output of disinfectants were found to be associated with the cell membrane efflux pumps of C.albicans.