Efficacy of Disinfectants on Candida Biofilms at Different Concentrations and Contact Times

Aims: Candida species cause a wide spectrum of diseases, including hospital-acquired and device-associated infections. The biofilm formation is a major virulence factor in Candida pathogenesis and the cells in biofilm show enhanced resistance to disinfectants. Our aim was to evaluate the efficiency of the commonly used hospital disinfectants (glutaraldehyde (GLU), hydrogen peroxide (HP), peracetic acid (PA), ortho-phtalaldehyde (OPA) and sodium hypochlorite (SH) on biofilms of clinical Candida (C. albicans, C. glabrata, C. parapsilosis, C. krusei and C. tropicalis) isolates.
Study Design: An experimental study.
Place and Duration of Study: Department of Microbiology, Faculty of Medicine and Electron Microscope Laboratory, Eskisehir Osmangazi University, between January 2011 and May 2011.
Methodology: These disinfectants were selected due to their common application in hospital environment. Their concentrations were adjusted to manufacturer’s recommendations for instrument disinfection: 5% HP, 0.2% PA, 5.25% SH (5000 ppm of chlorine), 2% GLU and 0.55% OPA. They were also prepared at the 1:2 and 1:4 times of recommended concentration to evaluate the activity of lower concentrations. The biofilms were grown in microplates and treated with disinfectants at contact times 1, 5 and 10 minutes (20 min for GLU), then stained with the biomass indicator (2, 3-Bis [2-methoxy-4-nitro-5-(sulfenylamino) carbonyl-2H-tetrazolium-hydroxide]).
Results: The disinfectants reduced the biofilm for all concentrations studied, however none of them completely removed the biofilm. When they were used at low concentration, longer contact times were more effective. However, when the disinfectants were used in recommended concentration, results showed many variations depending on the disinfectant type, contact times and species.
Conclusion: Our results also emphasize the importance of regular disinfection, before the starting of biofilm formation.