Microplastics in the insular marine environment of the Southwest Indian Ocean carry a microbiome including antimicrobial resistant (AMR) bacteria: A case study from Reunion Island

ABSTRACT Background: Marine pollution by plastics poses environmental and health risks by contaminating ecosystems and the marine food chain. Indeed, microplastics harbor microbial communities (plastisphere), including numerous pathogenic bacteria. The role of marine plastic pollution in the dispersal of these pathogens, many of which are resistant to antimicrobial agents, is a cause for concern. We present here an initial study on the assessment of plastic pollution and its associated microbiome on Reunion Island, located in the southwestern Indian Ocean.Objective: To analyze plastic pollution in the coastal waters of Reunion Island and understand the associated microbiome and antibiotic-resistant bacteria.Methods: A comprehensive assessment of plastic pollution in the coastal waters and beaches of Reunion Island was carried out including the nature of the plastic debris. The composition of the bacterial microbiome was analyzed by 16SrDNA NGS sequencing. The search for viable bacteria was carried out to quantify bacterial presence on microplastics. In addition, the search for antibiotic-resistant bacteria was carried out.Results: The study revealed significant plastic pollution on the coast of Reunion Island, with up to 10,000 plastic items per km2, mainly polyethylene (70%) and polypropylene (27%). The plastic debris harbored dense microbiomes composed of Proteobacteria (79%), including the dominant genera Psychrobacter, Photobacterium, Pseudoalteromonas and Vibrio. Cultures revealed high numbers of viable bacteria on the microplastics (up to 107 bacterial CFU / g plastic), including the dominant genera Exiguobacterium and Pseudomonas. In addition, the plastics contained antimicrobial-resistant bacteria (AMR), including strains of genera Bacillus, Enterococcus and Pantoea resistant to β-lactamins and various other antibiotics such as ampicillin and penicillin.Conclusion: The results confirm the importance of the plastic pollution crisis in the southwest Indian Ocean, which poses a threat to ecosystems. The presence of an extensive plastisphere, including antimicrobial-resistant bacteria, underlines the need for vigilant monitoring to protect marine environments and potential risks to human health. Reference : Sababadichetty L, Miltgen G, Vincent B, Guilhaumon F, Lenoble V, Thibault, Bureau S, Tortosa P, Bouvier T, Jourand P. Microplastics in the insular marine environment of the Southwest Indian Ocean carry a microbiome including antimicrobial resistant (AMR) bacteria: A case study from Reunion Island. Marine Pollution Bulletin, 2024, 198:115911.https://doi.org/10.1016/j.marpolbul.2023.115911.