Dolphins in Florida waters are carrying potentially deadly bacteria that show increased resistance to antibiotics, according to new research published this weekend.
The presence of the resistant germs in the Indian River Lagoon, which stretches from central to south Florida along the Atlantic Coast, means human waste or antibiotics, or both, are entering the waterways and are potentially harmful to marine life and humans.
Eating fish from the area could become more risky, according to the study, which said the bacteria that causes seafood poisoning, Vibrio alginolyticus, showed a significant increase in resistance.
"If humans are swimming in the same area, they could be acquiring a resistant bacteria that would be difficult to treat," said Adam Schaefer, epidemiologist at Florida Atlantic University's Harbor Branch Oceanographic Institute in Fort Pierce, Fla.
He said antibiotics should never be disposed flushed down a toilet or sink. "Our sewage treatment plants do not break down antibiotics," Schaefer said.
Some antibiotics listed in the study also are used in agriculture and veterinary medicine.
The new data on pathogens in the lagoon comes as the area sees growing problems with toxic cyanobacteria, known as blue-green algae blooms, and massive fish kills in recent years.
The U.S. Centers for Disease Control and Prevention says antibiotic resistance is one of the biggest public health challenges of our time. At least 2 million people develop antibiotic-resistant infections each year, and at least 23,000 people die from them, the agency says.
Antibiotic-resistant pathogens were reported in 2009 after a similar shorter study. Schaefer said the findings were a big surprise at the time. The new study, published in the journal Aquatic Mammals, builds on 13 years of data.
Teams of researchers were able to sample 171 dolphins over the years and isolated 733 bacteria cultures from them. A great majority of those bacteria, 88.2 percent, showed resistance to at least one antibiotic.
Resistance was highest to erythromycin at 91.6 percent, which the U.S. National Library of Medicine says is used to treat bronchitis, pneumonia, certain skin infections and sexually transmitted diseases.
Other antibiotics noted in the study included ampicillin, to which 77.3 percent of bacteria were resistant, and cephalothin, 61.7 percent. Ampicillin is used to treat illnesses such as meningitis or infections of the lung, throat and sinuses, while cephalothin is used frequently in surgeries to treat various infections of the blood, bone and other tissue.
Resistance to ciprofloxacin among E. coli found in the dolphins had more than doubled since 2009. According to the report, that mirrors human trends.
"One of the things we found so interesting was how some resistance patterns we were seeing are very similar or the same to what we're seeing in humans," Schaefer said. "What it tells us is these animals are impacted by the same things affecting us."
The bacterium with highest resistance was one that causes respiratory or urinary tract infections, pseudomonas aeruginosa.
All bacteria showed significant increased resistance to cefotaxime, ceftazidime and gentamicin.
The study's results were published in the September 2019 issue of the journal, Aquatic Mammals. The journal says it is the oldest peer-reviewed journal publishing papers on marine mammal science. It is sponsored by the European Association for Aquatic Mammals, the Alliance of Marine Mammal Parks and Aquariums, and the International Marine Animal Trainers' Association.
Research was done by taking swabs from dolphin mouths, blowholes and feces in the lagoon. Collaborators on the study include Georgia Aquarium , the Medical University of South Carolina and Colorado State University.
"Bottlenose dolphins are a valuable sentinel species in helping us understand how this affects human and environmental health," said Gregory Bossart, a co-author and chief veterinary officer at the Georgia Aquarium.
"Antibiotic resistance is one of the most significant risks to public health. As resistance increases, the probability of successfully treating infections caused by common pathogen decreases."
The study was funded in part by the Florida specialty license plate fund and the Georgia Aquarium.
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