Swimming in the ocean could increase your chances of infection, study finds

Swimming in the ocean could increase people’s chances of infection, a new study has found.

Marisa Chattman Nielsen, a PhD student at the University of California in Irvine, led the research, which was presented at ASM Microbe 2019.

"Our data demonstrate for the first time that ocean water exposure can alter the diversity and composition of the human skin microbiome," she said.

“While swimming, normal resident bacteria were washed off while ocean bacteria were deposited onto the skin."

The researchers found nine volunteers at a beach who met their stringent criteria – no sunscreen, rare exposure to the ocean, no bathing in the last 12 hours, no antibiotics use in six months – and swabbed them before they swam.

They were swabbed again six hours after their 10-minute swim, and then 24 hours after.

All those who took part were found to have a similar microbe community on their skin after swimming, whereas beforehand each participant's was different.

"One very interesting finding was that Vibrio species [which includes the creature that causes cholera] – only identified to the genus level – were detected on every participant after swimming in the ocean, and air drying," said Nielsen.

She added: "While many Vibrio are not pathogenic, the fact that we recovered them on the skin after swimming demonstrates that pathogenic Vibrio species could potentially persist on the skin after swimming.”

After 24 hours, however, only one of the people analyzed had the Vibrio species present on their skin.

But when they were found on the skin, they were at 10 times the levels of those found in the ocean itself – suggesting a strong affinity for human skin among the bacteria.

"Recent studies have shown that human skin microbiome plays an important role in immune system function, localized and systemic diseases, and infection," Nielsen added.

"A healthy microbiome protects the host from colonization and infection by opportunistic and pathogenic microbes.”