Antimicrobial Persistence and Residual Effect in Healthcare Personnel Handwashes

Abstract

BACKGROUND: Alcohol-based hand sanitizers can reduce nosocomial infections by >30.0%. The Food and Drug Administration (FDA) via the Tentative Final Monograph assesses efficacy immediately post wash. Antimicrobial persistence and residual effect are not evaluated. Recently a novel water-optional, alcohol-based formulation preserved with zinc pyrithione has been developed that provides antimicrobial persistence and residual activity, while surpassing the FDA criteria as a healthcare personnel handwash in both the waterless and water-aided modes. METHODS: This formulation was compared to common handwashes containing various antimicrobials (0.5% triclosan, 61.0% ethanol, 2.0% chlorhexidine gluconate [CHG], and 4.0% CHG) in waterless and/or water-aided modes to assess immediacy of kill, persistence, and residual effects in a 5-day study employing >60 subjects. Following collection of baseline data, the participants were instructed to wash with each product four times within 1 hour per label instructions and then glove. Representative samples were taken by the glove juice method at selected post-wash intervals that included immediate, 4-hour (except 4.0% CHG), and 8-hour. Post-wash samples were compared to baseline and log10 reductions were calculated. RESULTS: When tested waterless, the water-optional product consistently produced log10 reductions of nearly 3.5 or greater at every point over the entire study period, demonstrating vastly superior efficacy over the CHG and other alcohol-based products. In the water-aided configuration, similar results were obtained, as log10 reductions of 2.5 were observed, thus demonstrating vastly superior efficacy over triclosan. CONCLUSIONS: The new formulation exceeds FDA criteria for classification as a healthcare personnel handwash and demonstrates exceptional persistence and residual effects.