Antimicrobial Effect of Slightly Acidic Hypochlorous Acid Water Against Biofilm Formed by Candida parapsilosis

Background: Many of the pathogenic bacteria and fungi found in hospital environments form biofilms, which allow them to persist in the environment for long periods, posing a risk of hospital-acquired infections. Although the pathogens within biofilms often have reduced levels of drug susceptibility, the efficacy of disinfectants routinely applied against planktonic pathogens must be evaluated against biofilms as well. Our objective in this study was to determine the efficacy of treatment using slightly acidic hypochlorous acid water and to compare the results with sodium hypochlorite when both were used to disinfect Candida parapsilosis biofilms. Methods: C. parapsilosis in the planktonic or biofilm state was treated with each disinfectant. The number of viable cells that remained was determined, and scanning electron microscopy (SEM) of the disinfectant-treated biofilms was performed. Results: Compared with sodium hypochlorite, in a shorter period of time, hypochlorous acid water completely killed not only planktonic C. parapsilosis but also C. parapsilosis in a biofilm that had been formed for 72 h. SEM showed that both disinfectants were effective in removing the C. parapsilosis biofilm to some extent. Conclusions: Slightly acidic hypochlorous acid water appears to be an effective disinfectant against C. parapsilosis both in suspension and in biofilms.