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Widespread occurrence of mobile colistin resistance genes in Brazilian marine environments
Summary
This study investigated the presence and diversity of mobile colistin resistance genes (mcr) in bacteria isolated from water, floating plastic litter, and marine sponges across Brazilian marine environments ranging from heavily polluted to preserved sites, finding mcr variants in all environments with prevalence ranging from 12% to 44%. Over one-third of mcr-positive strains also carried other antimicrobial resistance genes, with floating plastic debris showing the highest mcr prevalence and underscoring plastic as a potential vector for antimicrobial resistance dissemination in marine ecosystems.
The spread of colistin resistance in marine environments is an emerging concern, particularly due to the role of mobile colistin resistance genes (mcr) in conferring resistance to this last-resort antibiotic. Marine ecosystems, influenced by anthropogenic activities, may act as hotspots of mcr-positive bacteria, yet their distribution remains poorly understood. This study investigated the presence and diversity of mcr variants in bacterial strains isolated from water, floating plastic litter, and marine sponges across distinct Brazilian marine environments, ranging from heavily polluted to preserved sites. Our findings confirmed the presence of mcr variants across all sampled environments, with prevalence ranging from 12% in water-isolated strains from the pristine Fernando de Noronha Archipelago to 44% in bacteria from floating plastic in the polluted Bom Jesus Cove (Rio de Janeiro city). Notably, over one-third of strains from Arraial do Cabo, Ilha Grande Bay, and the Cagarras Islands also harbored mcr genes. Of all 101 mcr-positive strains, 46.5% also carried other antimicrobial resistance genes, mainly those encoding resistance to sulfonamides, beta-lactams, as well as integron-integrases. This study provides novel insights into the spread of mcr variants in Brazilian marine ecosystems, emphasizing the role of human activity and pollution in colistin resistance spread. The detection of mcr-positive strains in floating plastic underscores the role of plastic debris as a potential vector and reservoir for antimicrobial resistance in marine ecosystems. Moreover, the presence of mcr genes in these ecosystems highlights the urgency of global surveillance and conservation strategies to mitigate the spread of antimicrobial resistance in marine environments. Widespread occurrence of mobile colistin resistance genes (mcr) in Brazilian marine environments. The charts illustrate the distribution of mcr gene variants in bacteria isolated from sponges, seawater, and floating plastic across Rio de Janeiro and the Fernando de Noronha Archipelago. Co-occurrence with other antimicrobial resistance genes is also depicted