Factors Impacting Bactericidal and Fungicidal Efficacy of Disinfectants on Hard, Non-Porous Surfaces

Maxwell Voorn, Purdue University

Abstract

Disinfectant products are used frequently on environmental surfaces (e.g. medical equipment, countertops, patient beds) and patient care equipment within healthcare facilities. Contaminated environmental surfaces are considered a major vector for the transmission of bacterial and fungal pathogens. Multidrug-resistant pathogens are becoming more prevalent within acute care settings, highlighting the importance of developing robust pre-preventative barriers to limit colonization on environmental surfaces where immunocompromised populations preside. Ready-to-use (RTU) disinfectant wipes are one of the primary barriers against the contamination of environmental surfaces which is why the evaluation of disinfectant efficacy and the factors that impact it should be validated to ensure hygiene and sterility. Disinfectant application on environmental surfaces is generally accepted to be effective against vegetative pathogens. Disinfectant wipes are chosen based on whether they qualify for EPA disinfectant claims, and this determination is made for each kind of pathogen. All though this might seem comprehensive, several important application considerations are not being evaluated by the EPA wipe testing method. The goal of the first study was to (i) evaluate the risk of disinfectant towelettes transferring S. aureus or P. aeruginosa from an inoculated zone to otherwise not contaminated surfaces and (ii) detect levels of S. aureus or P. aeruginosa on disinfectant towelettes after the wiping process. Six disinfectant towelette were tested against S. aureus ATCC CRM-6538 and P. aeruginosa strain ATCC-15442 on Formica surfaces. Each disinfectant was evaluated on a hard nonporous surface and efficacy was measured every 0.5 m2 using a modified version of EPA MLB SOP-MB-33 to study the risk of cross-contamination. We found that all of the wipes used in this study transferred S. aureus and P. aeruginosa from an inoculated surface to previously uncontaminated surfaces. Disinfectant towelettes with certain chemistries also retained a high level of viable bacteria after disinfection of the surface area. The cross-contamination risk also varied by product chemistry and bacterial strain. Overall, it was shown that disinfectant wipes can cross-contaminate hard nonporous surfaces and retain viable bacterial cells post-disinfection, especially over larger surface areas. The objectives of the second study were to (i) evaluate the efficacy of selected disinfectants on a hard, non-porous surface contaminated with Candida auris and (ii) determine if 1 minute of contact time significantly impacted the reduction of Candida auris compared to other selected contact times (30 s, two min, three min, 10 min). Five disinfectants were tested against Candida auris ATCC MYA-5001. Each disinfectant was evaluated on a hard, nonporous surface and the efficacy was measured using a modified version of EPA MLB SOP-MB-33 to study the risk of cross-contamination combined with EPA MLB SOP-MB-35 to effectively assess the fungicidal activity of disinfectants. Overall, The product type had varying impacts on the fungicidal efficacy of disinfectant wipes. 30 seconds of disinfection was significantly less effective than other contact times and no other disinfection time (two min, three min, 10 min) significantly impacted the fungicidal efficacy compared to one minute of disinfection. Irrespective of the product used, one minute of contact time showed significant disinfection of Candida auris but none of the products tested were able to achieve a five-log reduction of fungal pathogens after disinfection.

Degree

M.Sc.

Advisors

Oliver, Purdue University.

Subject Area

Chemistry|Atmospheric Chemistry|Environmental Health|Materials science|Microbiology|Pathology|Pharmacology

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