Did the omnipresent use of antibiotics lead to the development of resistant strains in bottle-nose dolphins? Vanshika Dhyani investigates

The World Health Organisation regards antibiotic resistance as a threat to global health and food security. In the summer of 2003, the Harbor Branch Oceanographic Institution conducted an extensive health assessment alongside Center for Coastal Environmental Health and Biomolecular Research. Scientists examined over 733 samples collected from 171 dolphins. It was concluded that 88% of the samples contained at least one pathogen that showed resistance towards an antibiotic. Data recorded over a period of thirteen years suggested that antibiotic resistance in bottlenose dolphins, mimics the antibiotic resistance developed by humans. 

Antibiotics and antibiotic resistant bacteria make their way into the seawater via untreated wastewater containing an appalling quantity nitrates and phosphates. These chemicals give the bacteria the leverage of evading antibiotics. Scientists suggest that the resistance to broad spectrum antibiotics in various strains of E. coli has increased by a factor of two from 2009 to 2015. Public Health England discovered a shocking nineteen new types of antibiotic resistant bacteria in the last decade, itself. Studies have led researchers to anticipate the ill effects of antibiotic resistance on public health. Over half of the population of the United States lives along coastal freshwater or marine ecosystems, living with a risk of developing drug-resistance. Apex predators are known to reflect the condition of the ecosystem. Their health is a direct indicator of the health of our ecosystem, since marine mammals are often laden with zoonotic pathogens that are easily transferable to other animals and humans, posing an astronomical public health risk. 

The research conducted to investigate the genetic behaviour in  Bottlenose Dolphins extricated samples from Indian River Lagoon, Florida  and Charleston Harbor area, South Carolina. Two different sites were chosen to ensure that samples were collected from an area characterized by a mix of residential, urban, agricultural, and undeveloped territory. Interestingly, the location where the sample was collected from, played an integral role in determining whether the animals showed resistant towards at least one isolated antibiotic. Upon observing the influence of antibiotic resistance in organisms cultured from the Indian River Lagoon and Charleston Harbor area, it was concluded that the results were similar. 

A Kirby–Bauer test was conducted to examine the antibiotic sensitivity of bacteria. Once standardised concentration of antibiotics were determined-by employing techniques of antibiotic resistance, screening-Antibiograms were built. (Antibiogram refers to tabulated data that depicts the susceptibility of pathogens towards antibiotics). When the data was analysed collectively, four different antibiotics were found to be ineffective in Bottlenose Dolphins from the capture sites. It was revealed that  E. coli extracted from Indian River Lagoon had a higher resistance to piperacillin, tetracycline, and trimethoprim/sulfamethoxazole as compared to isolates from Charleston Harbor area. Most samples showed antibiotic resistance towards erythromycin (91.4%), followed by clindamycin (87%), ampicillin (77.2%), cephalothin (53.3%), piperacillin (51.1%), and amoxicillin clavulanate (46.1%).

Dr. Gregory Bossart, who has been studying wildlife pathology marine mammals, for over three decades believes that “Antibiotic resistance is one of the most significant risks to public health,”.  He believes that an increase in antibiotic resistance will lead to a significant decrease in the probability of successfully treating infections. Adam Schaefer, an epidemiologist at Florida Atlantic University pin-points the adversity: “It is concerning because it means that antibiotic-resistant bacteria and antibiotics are getting into the marine environment. Once in the environment, the resistance genes are being exchanged between bacteria in the water, some of these bacteria are potential human pathogens.” The trend, he says, appears to mirror the pattern of antibiotic resistance developed in humans. In recent years, the seawater has started to operate as a massive reservoir for antibiotic resistance genes, at a global scale. Pharmaceuticals building up in the sea water lead to an extensive and chronic exposure of medicinal chemicals to aquatic life. 

“The increasing resistance is a sign that human activity is affecting the coastal environments where the dolphins live.” Adam Schaefer, told Inverse. “Unlike humans, wild dolphins are not taking antibiotics, and seeing an increase in resistance among the dolphin isolates was not expected,”

Schaefer believes that antibiotic-resistant bacteria are either being released into the water along with chemical waste or antibiotics are being discharged, transforming bacterial populations. “Both processes are likely going on,” he presumes. 

Antibiotic resistance is referred to as a ‘Silent Tsunami’ because it has become a global challenge that threatens our entire biosphere. With the ability to treat common infectious diseases at stake, antibiotic resistances puts medical advances like surgeries in jeopardy. A recent study conducted by University of Southern California found antibiotic resistance gene prevalent in groundwater. Researchers anticipate 6 out of 10 people carry multidrug-resistant bacteria along with their normal bacterial flora, in some regions. Antibiotic resistance is said to be accelerated by the abuse of antibiotics,along with inadequate infection prevention and control. In 2015 the World Health Assembly presented their global action plan which aims to tackle antimicrobial resistance by ensuring prevention and treatment of microbial diseases with safe, effective and potent medicines.