Quantifying the Effect of Hand Wash Duration, Soap Use, Ground Beef Debris, and Drying Methods on the Removal of Enterobacter aerogenes on Hands

Abstract

Hand washing is recognized as a crucial step in preventing foodborne disease transmission by mitigating crosscontamination among hands, surfaces, and foods. This research was undertaken to establish the importance of several keys factors (soap, soil, time, and drying method) in reducing microorganisms during hand washing. A nonpathogenic nalidixic acid-resistant Enterobacter aerogenes surrogate for Salmonella was used to assess the efficacy of using soap or no soap for 5 or 20 s on hands with or without ground beef debris and drying with paper towel or air. Each experiment consisted of 20 replicates, each from a different individual with ∼ 6 log CFU/ml E. aerogenes on their hands. A reduction of 1.0 ± 0.4 and 1.7 ± 0.8 log CFU of E. aerogenes was observed for a 5-s wash with no soap and a 20-s wash with soap, respectively. When there was no debris on the hands, there was no significant difference between washing with and without soap for 20 s (P > 0.05). Likewise, there was no significant difference in the reductions achieved when washing without soap, whether or not debris was on the hands (P > 0.05). A significantly greater reduction (P < 0.05) in E. aerogenes (0.5 log CFU greater reduction) was observed with soap when there was ground beef debris on the hands. The greatest difference (1.1 log CFU greater average reduction) in effectiveness occurred when ground beef debris was on the hands and a 20-s wash with water was compared with a 20-s wash with soap. Significantly greater (P < 0.05) reductions were observed with paper towel drying compared with air (0.5 log CFU greater reductions). Used paper towels may contain high bacterial levels (>4.0 log CFU per towel) when hands are highly contaminated. Our results support future quantitative microbial risk assessments needed to effectively manage risks of foodborne illness in which food workers' hands are a primary cause.

Surfactant concentration and type affects the removal ofEscherichia colifrom pig skin during a simulated hand wash

“…The maximum log reduction observed on the treated pig skin was when a surfactant used was higher than the maximum log reduction observed with a water treatment in the current study. A similar result was observed in Jensen et al (2015) where the maximum log reduction with soap was higher (c. 4 log CFU) than when no soap was used (c. 2 log reduction). While significant differences between plain water or surfactant solutions were not seen for most of the treatments, these findings, and those from Jensen et al (2015), would suggest that further research using inoculated pig skin with oil or grease carrier matrix could better reveal the full efficacy of a surfactant solution.…”

“…Prior research showed no statistically significant difference between a water or a water and soap wash when there was no oily/fatty debris present on the subjects' hands (Jensen et al . ). The maximum log reduction observed on the treated pig skin was when a surfactant used was higher than the maximum log reduction observed with a water treatment in the current study.…”

“…A similar result was observed in Jensen et al . () where the maximum log reduction with soap was higher ( c . 4 log CFU) than when no soap was used ( c .…”

“…While significant differences between plain water or surfactant solutions were not seen for most of the treatments, these findings, and those from Jensen et al . (), would suggest that further research using inoculated pig skin with oil or grease carrier matrix could better reveal the full efficacy of a surfactant solution. A high concentration of sodium lauryl sulphate may promote microbial reduction, due to the repulsive interaction of the anionic molecules with skin (Ginn et al .…”

“…), especially if debris is present on hands (Jensen et al . ). Many studies have addressed antimicrobial soap formulation, and how antimicrobial soaps may provide a greater bacterial reduction than plain or bland soap (Fischler et al .…”