Hand washing, rubbing, and posters

Every now and then one sees something that is obviously well intentioned and potentially even effective, but that is problematic nonetheless. A case in point is the poster shown at the right, proclaiming that "Alcohol-based handrubs kill bacteria more effectively than soap and water." Certainly they do, but that's not the point of handwashing with plain soap and water.

The purpose of handwashing with plain soap is to mechanically remove foreign material and microorganisms from the surface of the skin. It is not to kill microbes. Plain soaps have minimal, if any, antimicrobial activity. The purpose of alcohol-based handrubs (ABHRs) is to reduce the microbial burden on the skin to a safe level through the antimicrobial action of alcohol. Because handrubs do not remove organic material, they are not a substitute for washing visibly soiled hands. Moreover, ABHRs don't kill spore forming microorganisms such as Clostridium difficile or certain other pathogens of public health importance. Handwashing with soap and water is needed to remove such contamination. Antimicrobial soap combines the cleaning action of regular soap with antiseptic activity. 

These and related issues, such as when the different approaches are best used, are well covered by Manfred Rotter in chapter 91 of the 4th edition (2012) of the expansive text Hospital Epidemiology and Infection Control. Additional information can be found in the WHO guidelines on hand hygiene in healthcare and at a related CDC website. 

In the case of the poster above, it is available at a URL that is part of an interactive education module on hand hygiene for professional HCWs. The training itself, consistent with the poster, advises (on slide #19) that plain soaps are "good" at killing bacteria whereas ABHRs are "best" and antimicrobial soaps fall in between. I can't find evidence that plain soap kills bacteria or any other pathogen. Rather, plain soap removes pathogens by acting as a surfactant or detergent, and this seems to be well established in the literature. Perhaps "Remember to wash your hands -- Soap removes germs!" or "Alcohol-based hand rubs are often an effective alternative to soap for making your hands safe!" would have been more evidence-based, defensible, and constructive messages for a poster.

More importantly, if the overarching objective of hand hygiene -- preventing transmission of microorganisms via the hands -- is to be achieved, an awareness of the issues involved in the various approaches is needed. Knowing when to wash versus rub, and why, seems relevant to communicate widely.

(image source: CDC)