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July 30th: How surfactant Concentration and Type Affects the Removal of Escherichia coli from Pig Skin During a Simulated Handwash

When giving hygiene advice, we just assume that “handwashing with soap “works” – but in reality there is little or no data to show whether this is true-and how hygiene effectiveness might be  improved soap formulation, more rigorous hand rubbing and rinsing etc..  

In the is news study by Jenson Rogers and Shaffner the effect of surfactant type and concentration on a bland soap formulations ability to remove bacteria from hands is studies Several combinations of surfactants and water were combined to test bacterial removal efficacy using a handwashing device (two pieces of pig skin and a mechanical motor) to simulate a handwash. Two anionic surfactants, sodium lauryl sulfate and sodium stearoyl lactylate, and two nonionic surfactants, poloxamer 407 and sorbitan monostearate, each in concentrations of 2%, 5%, and 10% were studied. A slight positive (r2=0.17) but significant (p=0.03) correlation was observed between hydrophile-lipophile balance value and mean log reduction. No correlation was observed between pH of the treatment solution and the mean log reduction (r2=0.05, p=0.25). A 10% sodium lauryl sulfate mixture showed the highest log reduction ( = 1.1 log cfu reduction, SD=0.54), and was the only treatment significantly different from washing with water (p=0.0005). There was a correlation between increasing surfactant concentrations above the critical micelle concentration, and mean microbial reduction (r2=0.62, p=0.001).

The study can be found at http://onlinelibrary.wiley.com/doi/10.1111/lam.12777/abstract?campaign=w...