Hydrogen peroxide, chlorine, and peracetic acid disinfectants outperform quaternary ammonium compounds against Staphylococcus aureus and Pseudomonas aeruginosa wet and dry surface biofilms

Abstract Background: Wet and dry surface biofilms (WSB and DSB), are a recognized source for healthcare-associated infections (HAI), and effective cleaning and disinfection regimens are critical to reducing HAI risk for patients. Disinfectant efficacy against biofilms on dry surfaces, however, remains poorly characterized relative to that against planktonic organisms. Methods: The bactericidal efficacy of eight EPA-registered hospital-grade, one-step cleaner-disinfectants was assessed against WSB and DSB of Staphylococcus aureus (ATCC 6538) and Pseudomonas aeruginosa (ATCC 15442) . Biofilms were grown in a CDC biofilm reactor following EPA-MLB-SOP-MB-19-06 and, for DSB formation, dehydrated at 25 and 21 o C for S. aureus and P. aeruginosa respectively for 24, 48, and 72 h intervals to reflect recommended cleaning frequencies for healthcare surfaces. Biofilms were challenged with each disinfectant at its label-specified contact time following EPA-MLB-SOP-MB-20-04. Efficacy was expressed as log 10 CFU/cm 2 reduction, and experiments were performed in triplicate. Results: Hydrogen peroxide-, chlorine- and peracetic acid-based disinfectants demonstrated significantly greater efficacy than quaternary ammonium-based products against S. aureus biofilms (P < 0.05) . Desiccation time significantly impacts bactericidal efficacy of P. aeruginosa biofilms (P < 0.05) unlike biofilms of S. aureus . There is greater disinfectant efficacy against P. aeruginosa biofilms with the addition of a solvent to a quaternary ammonium product. Conclusions: Our findings indicate that current planktonic-based registration testing may overstate real-world disinfectant performance against the biofilm-embedded organisms healthcare facilities are realistically working to control, and that this gap varies by chemistry, organism, and how long a biofilm has been allowed to persist before disinfection.