Background: 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 disinfectants against DSB of Staphylococcus aureus and Pseudomonas aeruginosa. We hypothesized that overall, hydrogen peroxides, sodium dichloro-s-triazinetrione and quaternary ammonium compounds plus alcohol disinfectants will be more bactericidal against DSB than quaternary ammonium. We also hypothesized that regardless of differences in product chemistries, higher bactericidal efficacies against DSB will be exhibited after 24 h of dehydration compared to 72 h.Methods: Wet surface biofilms of S. aureus and P. aeruginosa were grown following EPA-MLB-SOP-MB-19 and dehydrated for 24 h and 72 h to establish DSB. Seven EPA-registered disinfectants were tested against dehydrated DSB following EPA-MLB-SOP-MB-20. Results: Overall, quaternary ammonium plus alcohol, sodium dichloro-s-triazinetrione, and hydrogen peroxide products were more efficacious against DSB than quaternary ammoniums for both tested strains. While there was no significant difference in biofilm killing efficacies between 24 h 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. Conclusion: Strain type, active ingredient class, and dry time significantly impact disinfectant efficacy against DSB of S. aureus or P. aeruginosa.

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 .

Background Pre-wetted disinfectant wipes are increasingly being used in healthcare facilities to help address the risk of healthcare associated infections (HAIs). However, HAIs are still a major problem in the US with Clostridioides difficile being the most common cause, leading to approximately 12,800 deaths annually in the US. An underexplored risk when using disinfectant wipes is that they may cross-contaminate uncontaminated surfaces during the wiping process. The objective of this study was to determine the cross-contamination risk that pre-wetted disinfectant towelettes may pose when challenged with C. difficile spores. We hypothesized that although the tested disinfectant wipes had no sporicidal claims, they will reduce spore loads. We also hypothesized that hydrogen peroxide disinfectant towelettes would present a lower cross-contamination risk than quaternary ammonium products. Methods We evaluated the risk of cross-contamination when disinfectant wipes are challenged with C. difficile ATCC 43598 spores on Formica surfaces. A disinfectant wipe was used to wipe a Formica sheet inoculated with C. difficile. After the wiping process, we determined log10 CFU on previously uncontaminated pre-determined distances from the inoculation point and on the used wipes. Results We found that the disinfectant wipes transferred C. difficile spores from inoculated surfaces to previously uncontaminated surfaces. We also found that wipes physically removed C. difficile spores and that hydrogen peroxide disinfectants were more sporicidal than the quaternary ammonium disinfectants. Conclusion Regardless of the product type, all disinfectant wipes had some sporicidal effect but transferred C. difficile spores from contaminated to otherwise previously uncontaminated surfaces. Disinfectant wipes retain C. difficile spores during and after the wiping process.

There has been an increase in Candida auris healthcare-associated infections, which result from cross-contamination from surfaces and equipment. In this study, we tested the efficacies of EPA-registered disinfectant towelettes products that are increasingly used for infection control against C. auris at a range of contact times following modifications to standard EPA protocol MB-33-00. Hydrogen peroxide (HP)-based disinfectant towelettes were more efficacious against C. auris than the quaternary ammonium chloride (QAC)-alcohol-based disinfectant towelettes irrespective of tested contact times. Thirty s contact time was significantly less effective in reducing C. auris compared to 1-, 2-, 3-, and 10-min contact times. However, there were no statistically significant differences in the level of disinfection among 1-min and longer contact times regardless of product chemistry. None of the products achieved a standard six-log10 reduction at any tested contact times. Overall, the HP-based disinfectant towelette was significantly more fungicidal than the QAC-alcohol-based disinfectant towelette. For all product types, 30 s contact time did not achieve the same level of disinfection as 1-min or longer contact times. Overall, disinfectant towelette efficacy is dependent upon product formulation and contact time.

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