A study published in Applied and Environmental Microbiology showed that in some public bathrooms with refillable soap dispensers the soap in contaminated with bacteria. Apparently if the dispenser is the type that a whole new bag of soap is put into it, it is ok. It is the ones that the new soap is poured into the dispenser that can become contaminated.

I don’t know what type of bacteria can live in soap, but hopefully it is one that is killed with hand sanitizer. Bringing your own small container of liquid soap is another idea to avoid this problem, although I bet it is rare anyway. But who wants to take a chance?