Soap dispensers transfer bacteria
13 May 2011
Bacteria can be spread efficiently through contaminated liquid soap in refillable dispensers used in public settings, researchers have shown.
After infection outbreaks linked to bulk soap dispensers in healthcare settings, the US Centers for Disease Control and Prevention recommended nearly a decade ago against adding soap to a partially empty dispenser.
Now microbiologists have conducted the first study showing that washing hands with contaminated soap actually increases the amount of bacteria on the hands, and these bacteria can be transferred.
Lab tests of liquid soap contaminated with the bacterium Serratia marcescens at a concentration of about 10 million bacteria per millilitre showed that more than 10,000 bacteria remained on each hand after washing.
A palm print left on an agar surface by a contaminated hand transferred more than 100 bacteria.
A second study in a school with contaminated soap dispensers showed students and staff increased the load of gram-negative bacteria on their hands 26-fold when using the soap.
In contrast, hand washing with uncontaminated soap halved the number of bacteria.
The researchers recommended sealed soap dispensing systems which use a new bag or cartridge of soap that includes a new nozzle.
Last Reviewed: 13 May 2011
- 1. Zapka CA, Campbell EJ, Maxwell SL, et al. Bacterial hand contamination and transfer after use of contaminated bulk-soap-refillable dispensers. Appl Environ Microbiol 2011; 77: 2898-904. Epub 2011 Mar 18. http://aem.asm.org/cgi/reprint/77/9/2898 (accessed May 2011).
