Persistence Factors Augment Healthcare Personnel Handwash Efficacy

Background: Healthcare personnel hand washes/sanitizers are prominent elements of hand hygiene, serving a necessary function in the professional and consumer markets.  Many are alcohol based, providing immediate kill for a wide variety of microbes.  Few, if any, alcohol formulations have added factors for persistence or residual antimicrobial effects.

Objective: To develop and validate a formula with extended efficacy against a wide variety of pathogens, in addition to providing antimicrobial persistence with repeated use.

Methods: Following test formula development, a series of in vitro and clinical studies were performed to establish antimicrobial range, time to kill, safety, and efficacy as a surgical scrub, to establish persistence, as well as a healthcare personnel handwash. These studies were performed under GLP or GCP at a contract laboratory.

Results: In vitro studies confirmed the formula did not induce resistant bacterial strains. Excellent MIC data were obtained for the 1100 strain mix of Gram positive and negative bacteria; in time kill studies a 5-6 Log₁₀ reduction was routinely observed within 15 seconds for most organisms, including clinical and drug resistant isolates.  Extended range studies with enveloped viruses, including swine and avian influenza virus, produced not less than 4 Log₁₀ reductions with a 15 second exposure. Repeated product applications (3 or 6) to a human skin substitute, followed by a 6 hour delay to ensure alcohol evaporation prior to a viral challenge (H1N1 swine), resulted in no decrease in efficacy.  Data obtained from a panel of 219 human volunteers confirmed the formulation is not a dermal irritant nor is it sensitizing.  All FDA criteria for success in a clinical study for the surgical scrub indication were surpassed.  For the 5 day, 11 wash series the test requirements were a 1 Log₁₀ reduction on day 1, a 2 Log₁₀ reduction on day 2, and a 3 Log₁₀ reduction on day 5; respective Log₁₀ reductions were day 1 = 2.86, day 2 = 3.22, and day 5 = 3.05.  These data confirm the formulation demonstrates immediacy of kill, persistence to 6 hours post-application, and residual antimicrobial effects with repeated use. Finally, data for the healthcare handwash clinical study are presented below. Requirements are a 1 Log₁₀ reduction following application 1 and a 3 Log₁₀ reduction post application 10. The test formulation exceeded each of these requirements (application 1 Log₁₀ reduction = 4.75; application 10 Log₁₀ reduction = 5.79) by greater than 100 times the required reduction in the contaminating indicator organism Serratia marcescens.

Conclusions: The alcohol-based test formulation with persistence factors provided a very broad antimicrobial range with excellent immediate kill.  FDA requirements for the surgical scrub and handwash indications were surpassed; persistence at 6 hours post-application was confirmed for bacterial and viral species. The formulation is not irritating nor is it a sensitizer.