Why Dolphins Are Becoming Resistant To Antibiotics

Dolphins are carriers of antibiotic resistant bacteria that enter the marine ecosystem due to degradation in the environment, a new study found. Academicians at Florida Atlantic University in collaboration with the Georgia Aquarium, the Medical University of South Carolina and Colorado State University, undertook the research. 

The requirement of such study is important because there is a slow jump in antibacterial resistance among dolphins. The trend reflects the major public health concern  since two million people suffer from antibiotic-resistant infections worldwide and kills 23,000 people every year. A few studies so far have analyzed isolated pathogens from wildlife to study antibiotic resistance in wildlife species. Interestingly, most of the isolated pathogens from these dolphins were human pathogens. 

“In 2009, we reported a high prevalence of antibiotic resistance in wild dolphins, which was unexpected. Since then, we have been tracking changes over time and have found a significant increase in antibiotic resistance in isolates from these animals,”  Adam M. Schaefer, MPH, lead author and an epidemiologist at FAU's Harbor Branch, said in the press release.

What They Found

The data was collected from the Multiple Antibiotic Resistance (MAR) index and a 13-year period of data of marine mammal species from 2003 to 2015. The researchers took 733 samples of 171 bottlenose dolphins from the Indian River Lagoon. Of the isolated pathogens, 88.2 percent showed resistance to at least one bacteria.

Dolphins, manatees and other marine life perish in Indian River Lagoon 51 dolphins have perished this year in the midst of a marine death wave in Florida's Indian River Lagoon. Creative Commons

The highest resistance by a pathogen was prevalent towards the antibiotic called erythromycin at 91.6 percent. Erythromycin is commonly used to treat infections such as pneumonia, sexually transmitted infections, acne and dental abscesses. It can also be used to treat children’s ear and chest infections. 

The second most-prevalent resistance was shown towards the antibiotic called ampicillin at 77.3 percent. The drug is used to treat urinary and respiratory tract infections. Lastly, resistance to cephalothin was at 61.7 percent. This drug is generally intravenously absorbed and used to treat a broad range of health concerns. 

Besides the mentioned antibiotics, a resistance was seen to various drugs as well. In the press release, the researchers said that "resistance to ciprofloxacin among E. coli isolates more than doubled between sampling periods, reflecting recent trends in human clinical infections." 

"In addition to nosocomial infections, resistant strains associated with fish and fish farming have been reported globally. The high MAR index for this bacteria isolated from dolphins in the Indian River Lagoon represents a significant public health concern," Peter McCarthy, PhD, co-author, a research professor and an associate director for education at FAU's Harbor Branch, cited.

The bacteria entered the lake through terrestrial sources since the area is occupied by a large population, which “include septic tanks, runoff from the land, freshwater discharge from canals, to name a few,” according to Schaefer.

And now that the Health and Environmental Risk Assessment or HERA Project has established a vast database from the animals, it aims to find better solutions to treat antibiotic resistance onwards.