Culturable plastisphere from the 75°N subArctic transect as a potential vector of pathogens and antibiotic-resistant bacteria

Plastic pollution is a global emerging concern, but in the Arctic Ocean the role of plastisphere as a potential carrier of pathogens and antibiotic-resistant bacteria is unknown yet. A first recognition of the spread of these target bacteria through their colonization of plastic particles referable to the micro-sized fraction (less than 5 mm, named microplastics, MPs) was carried out across the 75°N transect (Greenland Sea). To fill the knowledge gaps regarding the bacterial community associated to microplastics (MPs) - belonging to the so-called “plastisphere” - and the potential risks related to their spread, our study focused on the abundance and taxonomic composition of the plastisphere, including potential pathogenic and antibiotic-resistant bacteria, using a culture-dependent approach. MPs particles were collected using a Manta net; decimal dilutions were cultured on Marine agar plates to estimate the abundance of culturable heterotrophic bacteria. For the search of target pathogenic bacterial species (Escherichia coli, Enterococcus spp., Salmonella spp., potentially pathogenic Vibrio spp., Staphylococcus aureus), small volumes were inoculated into selective culture media by spread plate directly or after enrichment. The screening of the antibiotic-susceptibility profiles of the bacterial isolates was performed to assess the presence of antibiotic-resistant bacteria. The culturable heterotrophic bacterial community was dominated by members of the phyla Gammaproteobacteria and Actinobacteria, with bacterial isolates assigned to the genera Psychrobacter, Pseudoalteromonas, Shewanella and Arthrobacter. Selective enrichments resulted in the detection in the examined samples of target bacterial pathogens mostly referable to potentially pathogenic Vibrio spp. The antibiotic susceptibility profiles pointed out that multiple antibiotic-resistant bacteria were also isolated, suggesting that the need to shed light on potentials risks for human and animal health deriving from plastisphere also in remote cold regions.