NEW BRUNSWICK, N.J.—Researchers at Rutgers University conducted a systematic quantitative analysis in order to determine if there is a difference between antimicrobial and non-antimicrobial soaps, and to identify the methodological factors that might affect this; and although differences in efficacy between antimicrobial and non-antimicrobial soap were small, antimicrobial soap produced consistently statistically significantly greater reductions (J Food Prot. 2011 Nov;74(11):1875-82).
Data on hand washing efficacy and experimental conditions (sample size, wash duration, soap quantity, challenge organism, inoculum size and neutralization method) from published studies were compiled and transferred to a relational database. A total of 25 publications, containing 374 observations, met the study selection criteria. The majority of the studies included fewer than 15 observations with each treatment and included a direct comparison between non-antimicrobial soap and antimicrobial soap.
The difference reported was true for any of the antimicrobial compounds investigated where n was greater than 20 (chlorhexidine gluconate, iodophor, triclosan or povidone). Average log reductions were statistically significantly greater (∼2 log CFU) when either gram-positive or gram-negative transient organisms were deliberately added to hands compared with experiments done with resident hand flora (∼ 0.5 log CFU). Their findings support the importance of using a high initial inoculum on the hands, well above the detection limit. The inherent variability in hand washing seen in the published literature underscores the importance of using a sufficiently large sample size to detect differences when they occur.