Gunasena, C.Wijekoon, W.M.P.S.K.Jayatilake, J.A.M.S.Giguruwa, D.N.Senanayake, M.R.D.M.Weerasekera, H.S.K.2025-11-182025-11-182025-08-28Proceedings of the Peradeniya University International Research Sessions (iPURSE) – 2025, University of Peradeniya, P.161https://ir.lib.pdn.ac.lk/handle/20.500.14444/6721Hypochlorous acid (HOCl) is used as an antiseptic and a disinfectant. However, antimicrobial activity (AMA) of HOCl on Candida species (CS) and oral microflora (OM) is poorly investigated. This study aimed to evaluate the AMA of HOCl on some selected CS and OM in vitro. AMA of HOCl was tested against standard isolates of Candida; C. albicans (ATCC 90028), C. parapsilosis (ATCC 22019), C. krusei (ATCC 6258), C. glabrata (ATCC 90030) and C. tropicalis (ATCC 13803). Further, the effect of HOCl against OM harvested from healthy individuals was also assessed as follows. HOCl produced by Steripower® unit (Japan) was adjusted to different concentrations (200, 100 and 50 ppm). Phosphate buffered saline (PBS) and 0.2% chlorhexidine were used as negative and positive controls. CS were cultured in Tryptic Soy Broth (TSB) at 37°C for 24 h and were harvested by centrifugation, washed and suspended in PBS (108 cell/ml; 0.5 McFarland). OM was harvested from 5 healthy volunteers after rinsing the mouth with sterile PBS (10 ml) for 30 seconds. Resultant oral rinses were concentrated into 1ml PBS with centrifugation. Afterwards, 0.1 ml of the Candida suspension or concentrated oral rinse was mixed with 0.9 ml of HOCl or control solutions for 1 min. Subsequently, 0.1 ml of the resultant solutions of Candida or OM exposed to HOCl were inoculated on to Sabourauds dextrose agar or blood agar plates respectively. Candida cultures were incubated at 37°C aerobically. OM was incubated at 37°C both aerobic and anaerobic conditions. All cultures were observed up to 48 h for microbial growth. Each experiment was quadruplicated. CS (C. albicans, C. glabrata, C. krusei, C. parapsilosis, and C. tropicalis) and OM of healthy volunteers exposed to HOCl (200, 100, 50 ppm) and 0.2% chlorhexidine for 1min resulted no growth on solid agar after 48 h incubation at 37°C. Exposure to HOCl (200, 100, 50 ppm) and 0.2% chlorhexidine for 1 min completely inhibited all the tested CS (C. albicans, C. glabrata, C. krusei, C. parapsilosis, and C. tropicalis) and the OM of healthy volunteers suggesting a remarkable AMA. This could be attributed to the fact that HOCl dissociates into H+ and OCl– that are capable of denaturing and aggregating microbial proteins resulting in killing a broad spectrum of microorganisms in a brief exposure. HOCl (200, 100, 50 ppm) may be used as an effective antiseptic/disinfectant similar to 0.2% chlorhexidine against C. albicans, C. glabrata, C. krusei, C. parapsilosis, C. tropicalis and OM. Further studies are recommended to assess the in vivo effects of HOCl to explore its application for oral hygiene.en-USAMACandida speciesHOClOral hygieneOral microfloraArticle