Reply to Widmer and Tschudin-Sutter

To the Editor—We appreciate the interest in our recent article ¹ and would like to respond to issues raised by Widmer and Tschudin-Sutter ² as possible explanations why 2 mL of a 70% alcohol handrub product did not completely eradicate methicillin-resistant Staphylococcus aureus (MRSA) from the hands of colonized patients. First, the assertion that the handrub used in the study did not meet the European Standards (EN 1500) requirements within 30 seconds of application is inaccurate. Although a product of the same brand name was evaluated by Kramer et al, ³ that was a previous formulation based on 62% (vol/vol) ethanol. The product used in the current study is based on 70% (vol/vol) ethanol and meets both the EN 1500 efficacy requirements within 30 seconds and the US Food and Drug Administration Healthcare Personnel Handwash requirements at a 2 mL application. ⁴ Therefore incomplete MRSA eradication cannot be attributed to a lack of efficacy of the handrub product. Second, we acknowledge that a larger volume of product may have been more effective because handrub efficacy is highly dependent on application volume. Further studies to investigate the impact of product volume on clinical efficacy are warranted. We point out, however, that there is a practical limit to the volume of product end users will apply, which is largely influenced by dry-time. The volume of handrub used in this study (2 mL) takes approximately 30 seconds to rub dry and is consistent with World Health Organization recommendations; in contrast, a volume of 3 mL typically remains wet longer than 30 seconds and can take as long as 90 seconds to dry on hands. ⁵ Third, as stated in our article, patients were asked to rub their hands for 30 seconds with coaching to ensure proper technique according to World Health Organization recommendations. A majority of participants studied were elderly and some displayed diminished hand dexterity, which may have impacted our results. However, there is still debate whether the 6-step technique outlined by the World Health Organization provides an efficacy benefit. ^{6 , 7} We agree that the ability of handrub products to meet established efficacy requirements, as well as product application volume and good technique to ensure adequate hand coverage, are all important variables that influence clinical efficacy. However, we caution against the generalization of the results obtained with this specific population of MRSA-colonized patients to make predictions on the ability of alcohol handrub products to eliminate transient MRSA from the hands of healthcare workers.