"Absolutely crazy"

Toothbrush turns out to be a true virus paradise

It's not just bacteria that feel right at home in the bathroom: viruses also think they are in paradise on shower heads and, above all, toothbrushes. An immense variety of viruses can be found there - more than 600, as samples have shown.

"The number of viruses we found is absolutely crazy," said study leader Erica Hartmann from Northwestern University in Evanston, whose team published the study results in the journal "Frontiers in Microbiomes". "We found many viruses that we know very little about and many others that we have never seen before." There was also very little overlap between two samples. "Each shower head and toothbrush is like its own little island."

Bacteria as "hosts"
The good news is that the viruses are not dangerous for humans, but attack bacteria and multiply in them. These so-called bacteriophages have recently been the subject of increased research into the treatment of antibiotic-resistant bacterial infections.

The researchers assume that newly discovered virus species could be a treasure trove for this. Many phages were found in the samples that specifically infect mycobacteria - the cause of diseases such as leprosy, tuberculosis and lung infections. "It's amazing how much untapped biodiversity there is around us," said Hartmann. "And you don't even have to go far to find it, it's right under our noses."

Microbes are everywhere, and the vast majority of them don't make us sick.

Studienleiterin Erica Hartmann

More than 100 samples taken
For the study, the researchers asked people to send them used toothbrushes and swabs from their shower heads. Previous analyses had already shown a large variety of bacteria in the samples. For the virus analysis, 34 samples from brushes and 92 from shower heads were analyzed.

"This project started out of curiosity," explained Hartmann. "We wanted to know which microbes live in our homes." Surfaces such as tables and walls are difficult for microbes to colonize because they prefer environments with water. "And where is there water? In our shower heads and on our toothbrushes."

Changing toothbrushes regularly is enough
The diversity of microbes in the bathroom is by no means a reason to reach for antimicrobial cleaning agents, the research team also emphasized. It is sufficient to change your toothbrush regularly. Special antimicrobial toothbrushes are also not necessary, especially as they could lead to antibiotic-resistant germs. Cleaning the shower head with soap and, if necessary, descaler is sufficient.

"Microbes are everywhere, and the vast majority of them don't make us ill," explained Hartmann. "The more you fight them with disinfectants, the more likely it is that they will develop resistance or become more difficult to treat."