The general assumption is that a whole other world exists beyond a bathroom sink. An unsavory one, home to all sorts of micro-organisms, capable of causing vile and unpleasant illnesses to its victim. Well, those assumptions are true. A new study has shown that sink drains in public restrooms are home to a host of microorganisms capable of causing life-threatening infections.

Although this hardly comes as a surprise seeing as public restrooms are generally known to be a haven for everything contagious, sinks are one part of public restrooms that are often overlooked and according to researchers from the University of Reading, they harbor fungal organisms capable of causing deadly diseases.

According to the project leader Dr. Soon Gweon, results from the study can be of great help to immunocompromised patients as it could help, in his words “avoid infections by some of the opportunistic pathogens that may be lurking in sinks”

Study Methodology

Samples for the study were obtained from over 250 restrooms, both male and female in 20 different buildings across the University of Reading. Samples were collected using sterile cotton swabs inserted into P-traps of restrooms with the entire circumference of the pipe swabbed for five seconds.

Details on the qualities of each sink including its location, purpose, gender designation, and temperature of water flowing down the drain were recorded.

The organisms encountered were then identified using DNA extraction. Next, genomic DNA was isolated from the swabs and amplified using polymerase chain reaction (PCR) and bioinformatic processing, all of which helped the researchers identify the sink’s microbial residents. 


Results from the study reported a fungal community so diverse yet so similar. The sinks used mostly for handwashing housed about 375 different genera of fungi from a wide range of classes, orders, and families. Fungal organisms from seven different phyla were also discovered in the sample sinks. 

The highly diverse organisms observed across the various sinks still shared similar taxonomic profiles, implying a similar roster of organisms from skink to sink and from building to building. 

According to researchers, the similarity in taxonomy encountered could be a result of the sinks being used for a similar purpose by individuals in the community. 

Due to the nature of the habitat they dwell in, having fast running water, high temperatures, low pH (acidic conditions), and little or no nutrients available, researchers believe these fungal organisms to be extremely resilient, making them potentially more threatening. The researchers also suggest that some of these organisms feed off of the rich carbon content of soaps and detergents. 

Genus Exophiala, a saprotrophic ‘black yeast’ that includes both terrestrial and aquatic species was also found to be the most abundant and ubiquitous. 

Exophiala species can be considered opportunistic pathogens causing cutaneous and superficial infections, however, fatal systemic infections have been documented,” the study authors write in the paper.

This study was published in the journal Environmental DNA

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