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Does antifouling paint select for antibiotic resistance?

Flach, Carl-Fredrik, Pal, Chandan, Svensson, Carl-Johan, Kristiansson, Erik, Östman, Marcus, Bengtsson-Palme, Johan, Tysklind, Mats, Joakim Larsson, D.G.
The Science of the total environment 2016
DNA, agar, antibiotic resistance, antifouling agents, bacteria, bacterial communities, biocides, biofilm, breeding sites, copper, copper sulfate, cross resistance, gamma-Proteobacteria, gene transfer, genes, gentamicin, heavy metals, metagenomics, resistance mechanisms, risk, selection pressure, species diversity, tetracycline, zinc sulfate
There is concern that heavy metals and biocides contribute to the development of antibiotic resistance via co-selection. Most antifouling paints contain high amounts of such substances, which risks turning painted ship hulls into highly mobile refuges and breeding grounds for antibiotic-resistant bacteria. The objectives of this study were to start investigate if heavy-metal based antifouling paints can pose a risk for co-selection of antibiotic-resistant bacteria and, if so, identify the underlying genetic basis. Plastic panels with surfaces painted with copper and zinc-containing antifouling paint as well as unpainted surfaces were submerged in a Swedish marina and biofilms were harvested after 2.5–4weeks. DNA was isolated from the biofilms and subjected to metagenomic sequencing. Biofilm bacteria were cultured on marine agar supplemented with tetracycline, gentamicin, copper sulfate or zinc sulfate. Biofilm communities from painted surfaces displayed lower taxonomic diversity and enrichment of Gammaproteobacteria. Bacteria from these communities showed increased resistance to both heavy metals and tetracycline but not to gentamicin. Significantly higher abundance of metal and biocide resistance genes was observed, whereas mobile antibiotic resistance genes were not enriched in these communities. In contrast, we found an enrichment of chromosomal RND efflux system genes, including such with documented ability to confer decreased susceptibility to both antibiotics and biocides/heavy metals. This was paralleled by increased abundances of integron-associated integrase and ISCR transposase genes. The results show that the heavy metal-based antifouling paint exerts a strong selection pressure on marine bacterial communities and can co-select for certain antibiotic-resistant bacteria, likely by favoring species and strains carrying genes that provide cross-resistance. Although this does not indicate an immediate risk for promotion of mobile antibiotic resistance, the clear increase of genes involved in mobilizing DNA provides a foundation for increased opportunities for gene transfer in such communities, which might also involve yet unknown resistance mechanisms.