Comparative Antimicrobial Efficacy of Current Alcohol-Based Hand Rubs: Formulation, Dose, and Test Methods All Matter

Abstract

Background: Alcohol-based hand rubs (ABHRs) are the primary form of hand hygiene in healthcare settings globally. Many developed countries, and most US hospitals utilize wall-mounted ABHR dispensers throughout the facility. The adoption of automated touch-free dispensers is increasing. However, data on the efficacy of ABHRs when used at dispensed amounts are limited. The evidence is strong, showing that formulation matters (not just alcohol concentration) and that agent volume impacts efficacy. Objective: We evaluated the efficacy of ABHR foams on human hands using 2 controlled test methods at variable volumes (ie, typical doses and realistic volumes that healthcare personnel could use in patient care practice). Methods: We tested 8 commercially available ABHR products, the WHO hand-rub formulation, (P1–P9) and a nonantibacterial foam handwash control (P10) on human participants at 2 different application frequencies (“1 application” and “10 applications”) using 2 different ASTM test methods (E1174 and E2755). Studies using ASTM-E1174 evaluated 3 different application volumes (0.7 mL, 1.1 mL, and 2.0 mL) of the 10 products, each tested on 12–13 subjects. Studies using ASTM-E2755 evaluated a single 1.1 mL volume for the 9 ABHR products (P1–P9), each on 2–12 subjects. A linear mixed-effects model was fit separately to log reductions with random effects for subject and date, and a fixed effect for product. Results: Four different foam formulations (P1–P4) consistently outperformed all other formulations by the E1174 method, especially with increasing volumes and after 10 product applications (Fig. 1). When tested with E2755, all formulations performed similarly, with only P1 and P2 differentiating after 10 applications (Fig. 2). ABHR efficacy consistently increased with larger application volumes, whereas the handwash control (P10) achieved a similar efficacy (∼2 log reduction) at all volumes. Efficacy for some ABHR formulations increased, whereas others decreased with repeated applications. Alcohol concentration did not correlate with log reduction. Conclusions: Formulation and the product application volume affect the antimicrobial efficacy of ABHR; therefore, those data should be critically assessed by healthcare personnel assessing ABHR product performance. Test methods matter: when E1174 was used, greater differentiation between formulations was observed. This may be due to the larger contamination volume and greater soil load used in E1174.

Funding: GOJO Industries, Inc., provided Funding: for this study.

Disclosures: James W. Arbogast and David R. Macinga report salary from GOJO Industries.