Scientists have found antibiotic-resistant bacteria in seven species of sharks and redfish captured in waters off Belize, Florida, Louisiana and Massachusetts. Most of these wild, free-swimming fish harbored several drug-resistant bacterial strains.
The study, published in the Journal of Zoo and Wildlife Medicine, found antibiotic-resistant bacteria in every fish species sampled.
The researchers also found multidrug-resistant bacteria in fish at nearly all of the study sites, said Mark Mitchell, a professor of veterinary clinical medicine at the University of Illinois and a senior author of the paper.
"Ultimately the idea of this study was to see if there were organisms out there that had exposures or resistance patterns to antibiotics that we might not expect," Mitchell said. "We found that there was resistance to antibiotics that these fish shouldn't be exposed to."
Among the animals sampled, nurse sharks in Belize and in the Florida Keys had the highest occurrence of antibiotic-resistant bacteria. These sharks feed on crustaceans, small fish and other animals living in shallow waters close to shore.
Random mutations may account for drug-resistant bacteria in marine environments, Mitchell said, but there is a lot of evidence for a human origin.
"The shark population in Belize, for example, is a big tourist area, so there are people in the water right there," he said. "The sampling site is not far from a sewage plant, and so all those exposures we think are playing a role."
Sewage also is a problem in the Atlantic coastal waters of the United States, he said. Previous studies have shown that sewage outflows can leak antibiotic-resistant bacteria into the environment.
In the new study, the researchers looked for and found bacterial resistance to 13 antibacterial drugs in the fish. Patterns of resistance varied among the sites.
Bacteria from sharks off Martha's Vineyar
|Contact: Diana Yates|
University of Illinois at Urbana-Champaign