After scanning four public restrooms in San Diego recently, a team of researchers found a diverse mix of microbes that persisted for months despite regular cleaning of the facilities.
At the start of the study 4 restrooms were thoroughly cleaned with bleach solution, to kill any existing germ communities. During the following hours, days, weeks and months of human use, the researchers periodically sampled soap dispensers, floors and toilet seats for microbes using genetic sequencing technology.
Within one hour, restrooms were recolonized with microbes. Fecal bacteria dominated, including on toilet seats and on soap dispensers — about 45 percent of the bacteria there were of fecal origin. In all, the scientists found genetic traces of more than 77,000 distinct types of bacteria and viruses. Patterns of regrowth and succession, as some species waned and others replaced them, were surprisingly similar from bathroom to bathroom; within just five hours the population mix in each room stabilized.
When the team tried growing cultures from different surfaces in each room, they found one set of live bacteria in overwhelming abundance: Staphylococcus. Even after some of the bathrooms were closed, these human-generated communities of microbes continued to survive. Staph's are common on human skin and inside the nose and other orifices; they generally cause no problems, or trigger only minor skin infections. The authors noted that none of the live Staph strains showed signs of being antibiotic resistant. Although restrooms that were left open for use for up to two months were cleaned regularly with soap and water, the communities of microbes found there remained relatively unchanged for the full eight weeks of the study.
The full study can be found at http://aem.asm.org/content/early/2014/11/10/AEM.03117-14.abstract