In vivo efficacy of novel alcohol-based hand rubs utilizing the standard test method ASTM E 2755 to represent in-use conditions.

BACKGROUND: The current U.S. standard for evaluating the in vivo activity of alcohol-based hand rubs (ABHR) is the Health Care Personnel Hand Wash (HCPHW) method, ASTM E 1174. The HCPHW method was developed for the evaluation of hand wash products and does not reflect the in-use conditions of ABHR. ASTM E 2755, a recently approved Standard Test Method specifically designed for evaluation of hand rubs, is more reflective of normal use conditions. OBJECTIVE: Evaluate the in vivo efficacy of two novel alcohol-based hand rubs using ASTM E 2755. METHODS: Test products were a novel ABHR gel (Product A) and a novel ABHR foam (Product B) containing 70% ethanol and formulated for optimized antibacterial efficacy and skin feel. The Control Product was an NDA approved ABHR gel based on 61% ethanol and 1% chlorhexidine gluconate (CHG). Test products were evaluated on adult human hands using ASTM E 2755. Hands were contaminated by spreading 200 ml of a concentrated suspension of Serratia marcescens for 30 seconds. Test Product A and the Control were evaluated at an application volume of 2 ml and Test Product B was evaluated at 1.6 ml. Bacterial log reductions were calculated after a single application and after ten consecutive product applications. Statistical analysis was conducted using one-way ANOVA (a50.05). RESULTS: Products A and B, and the Control achieved log reductions of 3.14, 3.54, and 3.37 respectively, after a single product application and were statistically equivalent (P.0.05). After ten consecutive hand contamination and product application cycles, Products A and B, and the Control achieved log reductions of 5.11, 3.92, and 0.75 respectively. Both test products were statistically superior to the Control after ten product applications (P,0.001). CONCLUSIONS: When tested according to E 2755 to more realistically simulate in-use conditions, two novel ABHS products were equivalent to an NDA approved product after a single use, and were superior after ten uses. Despite the presence of 1% CHG, efficacy of the Control declined after 10 uses, whereas efficacy of Test Products A and B improved. These results demonstrate that product efficacy under high frequency usage cannot be extrapolated from single use data and highlight the need to evaluate product performance after repeated use. Finally, total product formulation is a critical determinant of antibacterial efficacy. American Journal of Infection Control. Vol. 39 No. 5.