The mcr-1 (mobile colistin resistance 1) gene, which encodes phosphoethanolamine transferase, has been recently identified as a source of acquired resistance to polymyxins in Escherichia coli. Using the SuperPolymyxin selective medium, we prospectively screened 100 pigs at 2 farms in Portugal for polymyxin-resistant Enterobacteriaceae and recovered 98 plasmid-mediated MCR-1–producing isolates. Most isolates corresponded to nonclonally related E. coli belonging to many sequence types; we also found 2 Klebsiella pneumoniae sequence types. The mcr-1 gene was carried on IncHI2 or IncP plasmid backbones. Our finding of a high rate of MCR-1 producers on 2 pig farms in Portugal highlights the diffusion of that colistin-resistance determinant at the farm level. The fact that the pigs received colistin as metaphylaxis in their feed during the 6 weeks before sampling suggests selective pressure.
CITATION STYLE
Kieffer, N., Aires-de-Sousa, M., Nordmann, P., & Poirel, L. (2017). High rate of MCR-1–producing Escherichia coli and Klebsiella pneumoniae among pigs, Portugal. Emerging Infectious Diseases, 23(12), 2023–2029. https://doi.org/10.3201/eid2312.170883
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