Recreational users of coastal waters such as swimmers and surfers are at risk of exposure to antibiotic resistant bacteria, according to new research published this week.

In the first study of its kind, scientists at the University of Exeter Medical School have assessed the amount of water ingested during different water sports and combined this with water sampling data to estimate people's exposure to bacteria resistant to antibiotics.

Using data gathered across England and Wales in 2012, they estimated that over 6.3 million water sport sessions resulted in one type of resistant bacteria being swallowed.

The research, which is being presented today at the Society for General Microbiology's Annual Conference, focused on the prevalence of Escherichia coli and specifically considered those resistant to an important class of antibiotics known as third-generation cephalosporins - or 3GCs.

The team considered surfers, sea swimmers, divers and kayakers and found that while only 0.12% of E. coli found in coastal waters and rivers running into beaches were resistant to 3GCs, this number was enough to present a potential risk of exposure to water users. Surfers and sea swimmers were among those at highest risk of exposure, due to their tendency to swallow more water.

The project was led by microbiologist Dr William Gaze, who believes these findings represent just part of the story:

"We know very little about how the natural environment can spread antibiotic resistant bacteria to humans, or how our exposure to these microbes can affect health. People are exposed to antibiotic resistant bacteria in many ways, through person-to-person contact, via food and as a result of international travel. Our research establishes recreational use of coastal waters as an additional route of exposure. With millions of people visiting beaches in England and Wales each year, there is a risk of people ingesting 3GC resistant E. coli, and it looks like water-users' exposure to all resistant bacteria could be even higher."

The study also showed that people's risk of exposure to resistant bacteria is closely related to water quality at a given beach, demonstrating the importance of the EU Bathing Water Directive, which aims to ensure good water quality standards.

Antibiotic resistant bacterial infections pose a serious threat to human health and the study's authors are currently working to investigate the link between recreational exposure in the sea, colonisation in the body and infection. They hope that their findings will increase the understanding of the health risks that water users might face. Another of the study's authors, Anne Leonard, said:

"Although this research has established that coastal waters are a potential source of exposure to antibiotic resistant bacteria, we're not recommending that people stop visiting the beach. Exercise and enjoyment of the natural environment has many established benefits for health and wellbeing, and this kind of research will help us ensure people can still make the most our coastal resources."

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More information: 'Human recreational exposure to antibiotic resistant bacteria in coastal bathing waters' is published in the journal Environment International. Journal information: Environment International 'Human recreational exposure to antibiotic resistant bacteria in coastal bathing waters' is published in the journal