Swimming in the ocean alters the skin's microbiome and may increase the likelihood of infection, according to research presented at ASM Microbe 2019, the annual meeting of the American Society for Microbiology.
"Our data demonstrate for the first time that exposure to ocean water can alter the diversity and composition of the microbiome of human skin," said Marisa Chattman Nielsen, MS, a Ph.D. student at the University of California, Irvine, the study's lead author. While swimming, normal resident bacteria were washed away, while ocean bacteria were deposited on the skin. "
The researchers detected oceanic bacteria in all participants after air drying and at six and 24 hours after swimming, but some participants acquired more oceanic bacteria and / or had to persist for longer.
The research was motivated by previous studies that showed associations between ocean swimming and infections, and by the high prevalence of poor water quality in many beaches, due to the drainage of wastewater and rainwater. Recent research has shown that changes in the microbiome may leave the host susceptible to infections and influence disease states. Exposure to these waters can cause gastrointestinal and respiratory diseases, ear infections and skin infections.
The researchers sought 9 volunteers on a beach that met criteria for not using sunscreen, little exposure to the ocean, no bathing in the last 12 hours and no antibiotics in the last six months. The researchers wiped out the participants at the back of the calf before they entered the water, and again after the participants completely dried up after a ten-minute, six-and-a-half-hour dive.
Before swimming, all individuals had different communities from each other, but after swimming, they all had similar communities on their skin, which were completely different from the "before-swim" communities. At six hours after swimming, the microbiomes began to revert to the pre-swimming composition and, at 24 hours, were very far in that process.
"A very interesting discovery was that Vibrio species – identified only at the genus level – were detected in all participants after swimming in the ocean and drying in the air," he said. Nielsen. (The genus Vibrio includes the bacteria that causes cholera.) At six hours after swimming, they were still present in most volunteers, but within 24 hours they were present only in one individual.
"Although many Vibrio are not pathogenic, the fact that we recover them on the skin after swimming demonstrates that pathogenic Vibrio species could persist in the skin after swimming," said Nielsen. The fraction of Vibrio species detected in human skin was more than 10 times greater than the fraction in the ocean water sample, suggesting a specific affinity for binding to human skin.
The skin is the body's first line of defense, both physically and immunologically, during exposure to contaminated water. "Recent studies have shown that the microbiome of human skin plays an important role in immune system function, localized and systemic diseases and infection," said Nielsen. "A healthy microbiome protects the host from colonization and infection by opportunistic and pathogenic microbes."
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