Public bathroom bacteria uncovered, thanks to gene sequencing

We all know public bathrooms are lousy with bacteria, but what kind are they, and how did they get there? A study released Wednesday in the journal PLoS ONE uses gene sequencing to find out exactly what germs lurk in public restrooms and where they came from. And after reading this, you are definitely going to want to wash your hands. A few times.

Researchers used high-throughput genetic sequencing to detect bacteria on 10 different surfaces in 12 men’s and women’s bathrooms on a college campus. Those surfaces included door, toilet and faucet handles, soap dispensers, toilet seats and various areas of the floor. The sequencing process used allows scientists to create up to millions of sequences at the same time.

Nineteen bacterial phyla were identified. Most belonged to four phyla: Actinobacteria, Bacteriodetes, Firmicutes and Proteobacteria. Scientists were able to get an average of 3,340 gene sequences per sample.

Bacteria commonly associated with human skin were found on all surfaces -- not a big surprise, since most of the areas sampled are routinely touched. Other human bacteria, including some linked with the mouth, gut and urine were also found on all surfaces.


Bacterial communities were grouped into three categories: those found on toilet surfaces, on floors, and on surfaces usually touched by hands. Bacteria associated with the gut were common on toilet surfaces, signifying fecal contamination (and an argument for seat protectors). Bacteria linked to skin were most often found on surfaces people touched with their hands. The floor had the biggest bacteria party, revealing what the authors called “diverse bacterial communities” of organisms, including several typically found in soil.

Some toilet flush handles also had bacteria comparable to what was found on the floor. Getting the picture? It suggests some people flush the handles with their feet, a practice, the authors wrote, “well known to germophobes and those who have had the misfortune of using restrooms that are less than sanitary.”

Finding bacteria associated with the gut and female urine at various points in the restrooms may indicate that frequent toilet use distributes those germs around and about. And while on some level we all know that, even if we don’t want to admit it ourselves, the authors said this emphasizes the importance of hand washing after using the facilities, since surfaces could transmit human pathogens.

Those who used the bathrooms tapped for the study might want to take a cue from the research. “Unfortunately,” they wrote, “previous studies have documented that college students (who are likely the most frequent users of the studied restrooms) are not always the most diligent of hand-washers.”


The study was released online today in the journal PLoS ONE.