Evolving the EN 1500 test method for alcohol-based hand rub closer to clinical reality by reducing the organic load on hands and enabling product to be applied to dry hands

M Suchomel, FHH Brill , G Kampf , RA Leslie, DR Macinga

Journal of Hospital Infection | doi: 10.1016/j.jhin.2023.05.002.

Background: The methods currently used in Europe and North America to evaluate the bactericidal efficacy of hand hygiene products have some limitations, e.g., in the selection of test organisms or the method of contamination, and none of the methods allows prediction of actual clinical efficacy. WHO has therefore proposed to develop methods that better reflect typical clinical reality.

Methods: In a first experiment, we investigated two contamination methods (immersion according to EN 1500 and low-volume according to ASTM E2755) with the EN 1500 test organism Escherichia coli and using 60% v/v iso-propanol. The second experiment was for comparison of the two contamination methods with Enterococcus faecalis. Finally, the two test organisms were compared using the low-volume contamination method. Data within each experiment was statistically compared using the Wilcoxon test for paired samples and data from all experiments were combined and fit to linear mixed effects models.

Results: Mixed-effects analysis confirmed that the test organism and contamination method both impacted the pre-values and all three of these were factors that influenced log10 reductions. Higher pre-values resulted in significantly higher log10 reductions, immersion contributed to significantly higher log10 reductions, and E. coli affected significantly lower log10 reductions.

Conclusion: An efficacy evaluation against E. faecalis with a low-volume contamination method could be considered as an alternative to the EN 1500 standard. This could help improve the clinical relevance of the test method with including a Gram-positive organism and reducing soil load which allows a product application closer to reality.

Keywords: EN 1500; Enterococcus faecalis; Escherichia coli; alcohol-based hand rubs; bactericidal efficacy; contamination method.