ASM Microbe

ASM Microbe

June 22, 2019
1 min read

Ocean swimming changes skin microbiome, could raise infection risk

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Marisa Chattman Nielsen, MS
Marisa Chattman Nielsen

SAN FRANCISCO — Ocean water exposure changes the human skin microbiome and could increase the likelihood of infection after swimming, according to findings presented at ASM Microbe.

“Our research demonstrated that ocean water washed off normal bacteria and simultaneously deposited ocean-borne bacteria onto the skin,” Marisa Chattman Nielsen, MS, a PhD candidate at the University of California, Irvine, told Infectious Disease News. “These changes persisted for at least 24 hours, and this could present an opportunity for pathogenic organisms to cause infection.”

Other studies have linked ocean water activities and infection. One study found that surfers are more likely to harbor antibiotic-resistant bacteria in their gut.

In their study, Nielsen and colleagues swabbed a section of skin on participants’ calves before swimming and after swimming for 10 minutes in the ocean — once their skin was air-dried — and again at 6 hours and 24 hours post-swim. They analyzed 30 samples from nine participants using next-generation sequencing.

According to Nielsen, participants' skin microbiomes were different before swimming but were significantly similar after swimming because the water had removed normal bacteria and deposited ocean bacteria onto the skin. Over the 24-hour period post-swim, the microbial communities began to return to pre-swim status, and normal commensal flora established dominance, the researchers reported.

“I think it is important that clinicians recognize that exposure to ocean water can cause changes in the skin microbiome and possibly leave us susceptible to pathogenic organisms present in the ocean,” Nielsen said. “Some of these pathogens are only found in water and may not be in the differential diagnosis otherwise.”

Nielsen said exploring a connection between an altered skin microbiome and increased infection risk after swimming in the ocean was beyond the scope of the study. – by Joe Gramigna


Nielsen M, et al. Alterations in the human skin microbiome after ocean water exposure. Presented at: ASM Microbe; June 20-24, 2019; San Francisco.

Disclosures: The authors report no relevant financial disclosures.