Microbiologists have found that toothbrushes and showerheads are covered in an extremely diverse collection of viruses - most of which have never been seen before.

Northwestern University's study, published in Frontiers in Microbiomes, revealed that viruses don’t target people; they target bacteria.

The microorganisms collected in the study are bacteriophage, or ‘phage’, a type of virus that infects and replicates inside of bacteria.

Although researchers know little about them, phage have garnered attention for their potential use in treating antibiotic-resistant bacterial infections. The previously unknown viruses found in bathrooms could become useful for exploring those applications.

Erica M. Hartmann, study lead and indoor microbiologist, said, “The number of viruses that we found is absolutely wild. We found many viruses that we know very little about and many others that we have never seen before. It’s amazing how much untapped biodiversity is all around us.”

‘Operation Pottymouth’

The study builds on previous research in which Erica and her colleagues at the University of Colorado asked people to submit used toothbrushes and swabs with samples collected from their showerheads.

Inspired by concerns that a flushing toilet might generate a cloud of aerosol particles, Erica called the toothbrush study ‘Operation Pottymouth’.

She said, “This project started as a curiosity. We wanted to know what microbes are living in our homes. If you think about indoor environments, surfaces like tables and walls are really difficult for microbes to live on. Microbes prefer environments with water. And where is there water? Inside our showerheads and on our toothbrushes.”

Diversity and opportunities

After characterising bacteria, the researchers used DNA sequencing to examine the viruses in the samples. Altogether, the samples comprised more than 600 different viruses. No two samples were alike.

Erica said, “We saw basically no overlap in virus types between showerheads and toothbrushes.

“We also saw very little overlap between any two samples at all. Each showerhead and each toothbrush is like its own little island. It just underscores the incredible diversity of viruses out there.”

While they found few patterns among all the samples, the researchers noticed more mycobacteriophage than other types of phage. Mycobacteriophage infect mycobacteria, a pathogenic species that causes diseases like leprosy, tuberculosis and chronic lung infections.

Erica predicted that, someday, researchers could harness mycobacteriophage to treat these infections and others.

She added, “We could envision taking these mycobacteriophage and using them as a way to clean pathogens out of your plumbing system.

“We want to look at all the functions these viruses might have and figure out how we can use them.”

Most microbes ‘will not make us sick’

Erica cautioned people not to worry about the invisible wildlife. She advised that people should regularly replace toothbrush heads and warned that antimicrobial toothbrushes can lead to antibiotic-resistant bugs.

She concluded, “Microbes are everywhere, and the vast majority of them will not make us sick.

“The more you attack them with disinfectants, the more they are likely to develop resistance or become more difficult to treat. We should all just embrace them.”

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