Skin Microbiome Changes After Ocean Swimming, Raising Risk of Infection

Swimming in the ocean alters the skin microbiome, raising concerns about the potential for infection, according to a new study.

The data, presented recently at the annual meeting of the American Society for Microbiology (ASM Microbe 2019), found that ocean bacteria remained on the skin after drying and for as long as 24 hours after leaving the water.

“We were surprised by the significant changes in the microbiome after swimming. While we expected some change, we did not expect that all participants would have completely different microbial communities after swimming,” lead author Marisa Chattman Nielsen, MS, a PhD student at the University of California, Irvine, told Contagion^®.

Previous studies have also shown a link between ocean swimming and an increase in infections.

The new study included 9 volunteers whose skin was swabbed before they entered the water for a 10-minute swim and again after they had air dried. Post-swim samples were collected at 6 and 24 hours after leaving the water. Investigators used DNA sequencing to examine 30 samples. Before swimming, the participants had different microbial communities on their skin. Afterward, their microbiomes had changed and were similar to one another.

Among the microbes detected post-swim were bacteria from the Vibrio genus. These bacteria were present after 6 hours, but only found on 1 participant at 24 hours post-swim. Many Vibrio bacteria are harmless, but Vibrio cholerae causes the water-borne disease cholera. An outbreak was reported in Canada last year, and global cases have been climbing since 2005, according to the US Centers for Disease Control and Prevention (CDC).

“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,” Chattman said. “If pathogenic organisms are present in the water, they may persist on the skin for at least 24 hours. Patient exposure history may be important in some cases because some of these pathogens are only found in water and may not be in the differential diagnosis otherwise.”

Further research is needed to better understand the effects of ocean swimming on the microbiome.

“We would like to see how individuals respond to ocean water exposure over time, in different seasons, and at different beaches,” Chattman said. “We would also like to look at the skin microbiomes in those with frequent ocean exposure vs those with infrequent exposure.”

Risk of infection by water-borne pathogens is a consideration during summertime activities. Outbreaks of Cryptosporidosis, which is often associated with pools and water parks, increased an average of 13% each year between 2009 and 2017, according to a recent report. The CDC offers tips to prevent infection from microbes associated with recreational water, including Cryptosporidium, E coli, Giardia, Shigella, and norovirus.

The study, “Ocean swimming alters skin microbiome, increasing vulnerability to infection,” was presented on June 22, 2019, at ASM Microbe 2019 in San Francisco, California.