The World Health Organization has raised concerns that because of polluted sea water around the globe, we may be entering an era where antibiotics are no longer strong enough to kill once treatable bacterial infections.

The organization cited research at the University of Exeter in England, where scientists tested rectal swabs from surfers and nonsurfers to determine the kind of bacteria in their guts.

The researchers tested more than 300 people from the United Kingdom, half of whom said they regularly surfed along the UK coastline. The research team members were curious if swallowing polluted water had made the surfers more vulnerable to antibiotic-resistant E. coli bacteria.

They found that the surfers were four times more likely to carry the bacteria that contain genes that are resistant to Cefotaxime (sepho-TAX-im), which is prescribed to kill off the bacteria.

What concerns scientists the most is these genes can be passed among bacteria, eventually enabling more bacteria to survive in the presence of that antibiotic.

The spread of antibiotic-resistant bacteria would make infections that were once easily treated a greater risk. Infections such as pneumonia, tuberculosis, blood poisoning and waterborne diseases would be more difficult to treat once they stop responding to the medication.

The Exeter researchers said they are focusing on learning more about other ways in which humans are exposed to these bacteria and how they colonize the gut.

Meanwhile, they call for government officials to make greater efforts to keep the bacteria from entering coastal waters and beaches through improvements to sewage and wastewater treatment plants.