Every morning, Heidi Wintermeyer dons a bright pink cap and swims with fellow cancer survivors as part of Manly Beach’s Bold and Beautiful swimming club. But after a big downpour, she’s wary of the risk of untreated sewage overflowing into the ocean. “Most of the people I swim with know better than to go in after heavy rain,” she says. “They’ll miss swim club rather than get sick.”
But research indicates that getting sick after a downpour is not the only risk: antibiotic-resistant bacteria can last for seven days at some Sydney beaches. If contaminated water is accidentally swallowed, the swimmer is at risk of developing future drug resistance to antibiotics, says Professor Maurizio Labbate of the school of life sciences at the University of Technology Sydney.
Research published in the Water Research journal in September 2019 showed that after intense rainfall, some antibiotic-resistant bacteria linger in Sydney’s seawater for days after other illness-causing bacteria have died. Professor Labbate said that swallowed seawater could enable drug-resistant DNA to be absorbed by the swimmer in a process called lateral gene transfer.
“It’s a bit like sharing photos via a smartphone Airdrop,” Professor Labbate says. The drug-resistant bacteria bumps against normal human gut bacteria and transfers some of its drug-resistant genes, he says. “You’re then at higher risk of treatment failure the next time you require antibiotics.”