Millions of tons of plastic end up in the oceans every year. The negative impact of plastic on marine ecosystems, especially marine life, is well known. But recently, Irish scientists discovered another problem posed by plastic debris drifting with ocean currents: it spreads antibiotic-resistant bacterial genes around the world.

Researchers from Belfast collected plastic waste from 18 locations along the Northern Ireland coast and cultured bacteria from it, identifying a total of 10 genera and 13 species. The bacteria were treated with 10 different modern antimicrobial agents to determine their susceptibility. Ninety-eight percent of the plastic pieces harbored bacteria resistant to beta-lactams (ampicillin, ceftazidime, and cefpodoxime), and 16% harbored bacteria resistant to minocycline. The rate of resistance to other antibiotics fell between these two levels.

The identification of bacteria showed that among them there are both completely harmless ones and those that cause diseases in plants, fish and even people.

Scientists say that ocean bacteria readily use any surface for colonization. This means that by filling the ocean with plastic, humanity is creating countless breeding grounds for bacteria. Human bacteria are unlikely to survive in the ocean for long, but they may pass antibiotic resistance genes to other species that thrive in seawater (bacteria of different species can exchange genetic information, a process known as horizontal gene transfer). These bacteria, along with the plastic, could travel thousands of kilometers across the ocean, thus contributing to the spread of antibiotic resistance worldwide.

Furthermore, plastic particles floating in the seas and oceans can be consumed by marine animals, such as fish and crustaceans, which are consumed by humans. Therefore, it's worth taking a closer look at how safe such foods are for humans.

Read also: Even low doses of antibiotics are harmful for children

Reducing plastic pollution in the world's oceans is the only way to preserve this fundamental ecosystem for the Earth and an important step in the fight against antibiotic resistance.

* Moore RE, Millar BC, Moore JE et al. Antimicrobial resistance (AMR) and marine plastics: Can food packaging litter act as a dispersal mechanism for AMR in oceanic environments? // Marine Pollution Bulletin, 2020, 150: 110702. https://doi.org/10.1016/j.marpolbul.2019.110702.