A new paper in the Journal of Applied and Environmental Microbiology (free full text here) describes a trial in which liquid soap was intentionally contaminated in grade school restrooms. The investigators found that when children washed their hands with contaminated soap there was a 26-fold increase in gram-negative rods on the hands. On the other hand, when uncontaminated soap was used there was a 2-fold reduction in hand contamination. It has previously been shown that soap dispensers which require refilling have been linked to outbreaks, and CDC recommends that soap not be added to partially empty dispensers (i.e., topping off). The solution to this problem is to use sealed soap-dispensing systems.