Rectal swabs taken from surfers and bodyboarders indicate that people who regularly recreate in the waters off the UK coastline may be three times more likely to harbor antibiotic-resistant (AR) bacteria in their intestines than those who stick to dry land.
Researchers from the University of Exeter Medical School compared samples of fecal matter from 143 frequent surfers or bodyboarders (at least 3x per month) to 130 volunteers who had low exposure to seawater (no more than once per month). Their microbiological analysis, published in Environment International, showed that 9 percent of surfers were carrying strains of E. coli that cannot be eliminated by the common antibiotic drug cefotaxime. In comparison, only 3 percent of non-surfers tested positive for these species.
"We looked for a particular type of E. coli (E. coli ST131) that is highly virulent and resistant and is spreading worldwide,” lead author Dr Anne Leonard told IFLScience. “It typically causes extra-intestinal (i.e. not gastrointestinal) infections such as urinary tract infections.”
“People taking part in the study who were carrying these bacteria were probably asymptomatic, and therefore they will not need treatment to get rid of these bacteria,” Dr Leonard continued. “However, there is the potential for anyone carrying resistant bacteria to pass them onto other members of the community that they come into contact with... and therefore [put them] at increased risk of developing an infection that is difficult to treat."
Perhaps more troublingly, Dr Leonard’s team found that surfers’ bowels were four times more likely to contain bacterial species with a mobile gene element that confers resistance to cefotaxime and other agents. Bacteria use mobile genes in the form of circular DNA molecules to rapidly share the spontaneous mutations that enable them to survive the effects of antibiotics, leading to overall decreases in the efficacy of antibiotic drugs and the creation of deadly "superbugs". These genetic swaps can occur between members of the same species or wildly different bacterial classes.
Species of terrestrial bacteria with acquired resistance to man-made drugs have been introduced into the waters through large-scale agricultural runoff, sewage, and trash dumping. The ocean is now a major reservoir of dangerous AR bacteria, such as E. coli, that can transfer resistance genes to native species or directly infect an unlucky host who is exposed to seawater – like a surfer.