Skin microbiome altered by swimming in the ocean

Ocean swimming can significantly alter the skin microbiome, increasing infection susceptibility and potentially influencing disease states.

In a recent study, researchers from the University of California, Irvine (CA, USA) have shown that swimming in the ocean can significantly alter the microbiome on the skin, potentially influencing disease states and leaving the individual more susceptible to infection.  

Previous studies have demonstrated links between ocean swimming and infection, something likely strongly influenced by the high prevalence of poor water quality at many beaches due to wastewater and water runoff from storms. As well as increased vulnerability to infection, exposure to these waters can potentially lead to gastrointestinal and respiratory illness as well as ear and skin infections. 

“Our data demonstrate for the first time that ocean water exposure can alter the diversity and composition of the human skin microbiome. While swimming normal resident bacteria were washed off while ocean bacteria were deposited onto the skin.” 

“Recent studies have shown that human skin microbiome plays an important role in immune system function, localized and systemic diseases, and infection,” commented lead author Marisa Chattman Nielsen. “A healthy microbiome protects the host from colonization and infection by opportunistic and pathogenic microbes.” 

“Our data demonstrate for the first time that ocean water exposure can alter the diversity and composition of the human skin microbiome,” Nielsen explained. “While swimming normal resident bacteria were washed off while ocean bacteria were deposited onto the skin.” 

Nine volunteers were sought at a beach, each meeting the criteria of infrequent ocean exposure, no sunscreen use, no bathing within the last 12 hours and no antibiotic use during the past 6 months. The participants were swabbed on the back of the calf before entering the water, after they had air dried post a 10 minute swim and at 6 and 12 hours after swimming. 

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“One very interesting finding was that Vibrio species—only identified to the genus level—were detected on every participant after swimming in the ocean, and air drying,” described Nielsen. “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,” she added. 

Though the bacterium was only identified to the level of genus, the Vibrio genus includes the species responsible for cholera. The fraction of Vibrio species that was detected in the skin microbiome of the participants was over 10-times greater than the fraction detected in a sample of the ocean water. The researchers propose this may suggest a special affinity of the bacterium for attachment to human skin. Six hours post swim they were still found on most of the volunteers, however, following 24 hours they were detected on only one participant. 

The full results of the study were presented at ASM Microbe 2019 (San Francisco, CA, USA, 20-24 June).