Your showerhead and toothbrush are teeming with viruses. But don’t panic – these microbes could save lives

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The warm, damp environments of your showerhead and toothbrush are the perfect breeding ground for microbes, and a new study has identified hundreds of viruses that live there, showing the vast biodiversity to be found in the average home. 

These viruses, however, are not the kind that will give you the common cold or flu (or worse). Called bacteriophages, or phages for short, they are the natural enemy of bacteria. Each tiny, tripod-looking phage has evolved to hunt, attack and gobble up a specific bacterial species.

“The number of viruses that we found is absolutely wild,” Erica Hartmann, an associate professor at Northwestern University’s McCormick School of Engineering who led the study, said in a statement. “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.”

Researchers from the university studied samples of biofilms – the glue-like communities of microorganisms attached to a surface – from 34 toothbrushes and 92 showerheads to reach their conclusions, which were published Wednesday in the journal Frontiers in Microbiomes.

They had already collected the samples from a previous study that investigated the types of bacteria inhabiting these items we use every day.

“One of things … that we’ve started to be able to do is, from those same types of samples, look at not just which bacteria are there, but actually which bacteriophages,” Hartmann told CNN.

Bacteriophages are already being used in clinical trials as a potential solution to the growing problem of antibiotic resistance. By infecting and replicating inside a host bacterium, phages could kill pathogens and form the basis of new drugs to treat antibiotic-resistant or superbugs.

“There’s also interest in designing maybe more sophisticated drugs, so that instead of taking a broad-spectrum antibiotic and wiping out your entire microbiome, you would be able to take this drug that would only affect the pathogen and leave the rest of your microbiome intact,” Hartmann said.

In the United States alone, more than 2.8 million antimicrobial-resistant infections occur each year, while the World Health Organization labels the problem as one of the biggest global public health threats since it could make standard medical treatments like surgery, caesarean sections and chemotherapy much riskier.

By sequencing the bacteria’s DNA, and then examining their corresponding phages using some “fairly complicated computer analyses,” the researchers “have been able to tell us a massive amount about what’s actually in there,” said Joe Parker, a senior research fellow at the UK’s National Biofilms Innovation Centre, who wasn’t involved in the study.

In total, researchers say they identified 614 different viruses on the samples, though Hartmann added that there were probably many more present, since almost every sample contained a unique constellation of microbes.

Parker notes that researchers probably identified a “minimum of 22 different bacterial viruses (phages) across these samples and … depending on where you draw the line in terms of believing the data analysis, which is a computer model, there could be upwards of 600 different types of phages.”

On the showerheads, many of the microbes originated from water sources, while those on toothbrushes came from a mixture of the human mouth and the surrounding environment.  

“There’s just an enormous amount of microbial diversity. And for every bacterium, there’s potentially tens or hundreds or even thousands of viruses that infect it,” Hartmann said, noting that viruses mutate very quickly, too.

She hypothesized that a bacterium in your mouth could transfer to your toothbrush, taking its viruses with it – and these could keep evolving on the toothbrush.

“And so, it’s possible that there are viruses that are basically endemic to your toothbrush and are found nowhere else on earth,” she said. “We don’t know that, that’s just one hypothesis that might explain the enormous amount of variety.”

While the idea that our homes are harboring so many tiny creatures may seem unsettling, Hartmann believes we should learn to appreciate our little guests.

“Microbes are everywhere all the time … We wouldn’t be able to digest our food or fend off infection if we didn’t have our microbes,” Hartmann said. “As much as we might initially react with a little ick factor, I think it’s really important to approach the microbial world with a sense of wonder and curiosity that these are actually things that do an enormous amount of good and potentially harbor an enormous potential for biotechnology.”

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