Globally, healthcare-associated infections (HAI) are the most frequent adverse outcome in healthcare delivery. Although bacterial biofilms contribute significantly to the incidence of HAI, few studies have investigated the efficacy of common disinfectants against dry-surface biofilms (DSB). The objective of this study was to evaluate the bactericidal efficacy of seven Environmental Protection Agency (EPA)-registered liquid disinfectants against DSB of Staphylococcus aureus and Pseudomonas aeruginosa. We hypothesized that overall, there will be significant differences among the bactericidal efficacies of tested disinfectants by product type and active ingredient class. We also hypothesized that depending on the species, higher bactericidal efficacies against DSB will be exhibited after 24 h of dehydration compared to 72 h. Wet-surface biofilms of S. aureus and P. aeruginosa were grown following EPA-MLB-SOP-MB-19 and dehydrated for 24 and 72 h to establish DSB. Seven EPA-registered disinfectants were tested against dehydrated DSB following EPA-MLB-SOP-MB-20. Overall, quaternary ammonium plus alcohol, sodium dichloro-s-triazinetrione and hydrogen peroxide products were more efficacious against DSB than quaternary ammoniums for both tested species. While there was no significant difference in the log10 reductions between 24 and 72 h S. aureus biofilms, significantly higher log10 reductions were observed when products were challenged with 24 h P. aeruginosa DSB compared to 72 h P. aeruginosa DSB. Species type, active ingredient class and dry time significantly impact disinfectant efficacy against DSB of S. aureus or P. aeruginosa.
Keywords: Pseudomonas aeruginosa; Staphylococcus aureus; disinfectants; dry-surface biofilms.