Jack Gilbert, a microbiologist at Argonne National Laboratory in Illinois, is co-author of a 2014 study in the journal of Applied and Environmental Microbiology in which researchers tracked the microbiomes of four university restrooms over hours and days.
According to LiveScience, Gilbert and his colleagues first sampled restrooms on an hourly basis and then sterilized the locations to start with a clean slate. They then allowed 4 more hours’ use and then shut the bathrooms down for the rest of the day to see how the bacterial assortment changed with time.
People bring a lot of bacteria into bathrooms, the researcher found. LiveScience reported that within an hour of normal use, there were 500,000 bacterial cells per square inch on the bathroom surfaces, on average.
But when left undisturbed, many of these bacteria quickly perished. Gut bacteria, especially, which don’t do well tolerating oxygen, cold or lack of nutrients, did very poorly, Gilbert said, according to LiveScience.
Skin bacteria showed better survival. Some of the surviving bacteria did have the potential to be pathogenic, Gilbert said, but you’d have to try pretty hard to get sick. The skin-associated bacterium Staphylococcus aureus, for example, persisted for a long time on bathroom surfaces. But S. aureus is present on the skin in about one in five people, and generally causes problems only when people are immunocompromised or have open wounds.
Ultimately, “the only places we see significant transference of illness on a regular basis, we believe, are health care environments, because people in that environment have had their immunity stripped away,” Gilbert said. For healthy people, there is very little to fear in a public restroom.And, of course, washing your hands is important.