The Survival of Listeria monocytogenes on Fingertips and Factors Affecting Elimination of the Organism by Hand Washing and Disinfection

Abstract

The survival of Listeria monocytogenes applied to the fingertips was investigated using both an impression plate and an elution method. When suspended in saline, L. monocytogenes NCTC 9863 survived for up to 60 min on fingertips, but survival times were greatly extended when the inoculum was suspended in milk. Survival was not apparently affected by skin lipids, the skin's normal flora, or the fat content of the milk. Different serotypes displayed similar results for the percentage persistence over a 2-h period when suspended in milk except for an isolate of L. monocytogenes serotype 7 which had a greater percentage survival than other organisms tested. In contrast, Escherichia coli C600 failed to survive for one hour under the same conditions. Hand washing with either soap or a water-based chlorhexidine hand cleanser usually failed to decontaminate fingertips to which an inoculum of 104/CFU per fingertip suspended in milk was applied, but a solution of chlorhexidine gluconate in methanol was found to be effective.