Impact of Disinfectant Type, Concentration, and Contact Time on Bactericidal Efficacy against Healthcare-associated Pathogens

Alyssa M West, Purdue University


Transmission of healthcare-associated infections caused by antibiotic- and multi-drug resistant (MDR) pathogens, (e.g. Methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa) are a major concern in patient care facilities. Disinfectant usage is critical to control and prevent pathogen transmission, yet the relationships among strain, disinfectant type, contact time, and concentration are not well-characterized. Furthermore, many healthcare facilities use pre-wetted disinfectant towelettes for surface disinfection, as they are an easy-to-use solution. Yet, there is a limited consensus as to whether a surface needs to remain wet for the full label contact time after the disinfectant towelette has been used, in order for complete efficacy to be achieved. The purpose of this study was to quantify the effect of disinfectant concentration and contact time on the bactericidal efficacy of clinically relevant strains of S. aureus and P. aeruginosa. Additionally, this study examined the impact of wet versus dry contact time on bactericidal efficacy of disinfectant towelette products. Accelerated hydrogen peroxide (AHP), quaternary ammonium compounds (Quat), and sodium hypochlorite spray products were tested at label and reduced contact times and concentrations against four MDR P. aeruginosa strains and four MRSA strains. Six additional EPA-registered towelette products had complete dry time gravimetrically measured and bactericidal efficacy calculated. Both off-label disinfectant concentrations and contact times significantly affected the efficacy of the three spray disinfectants tested. Bactericidal efficacy varied among both MRSA and P. aeruginosa strains. There were also determined to be significant differences in dry times among the towelette products tested, but contact time did not have a significant effect on bactericidal efficacy. Furthermore, there was no longitudinal effect observed when a disinfectant towelette’s contact time was extended past its defined label contact time, whether the product remained wet on the surface or not. The quantitative disinfectant efficacy method used in this study highlights the inter-strain variability that exists within a bacterial species. This study also showed there was no additional bactericidal efficacy of EPA-registered disinfectant towelettes post-surface drying or beyond the label contact time.




Oliver, Purdue University.

Subject Area

Food Science|Entrepreneurship

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