Objectives: The aim of this work was to determine the plasmid replicon profiles of a collection of bla CTX-M-1-positive enterobacterial strains. The isolates originated from chicken in the production pyramid, healthy food-producing animals at slaughter (chicken, calves, and pigs), chicken retail meat, environmental isolates originating from water bodies, and isolates from humans. A selection of IncI and IncN plasmids were characterized by multilocus sequence typing in order to determine their epidemiological relatedness.
Methods: Transconjugants of 74 bla CTX-M-1-positive isolates were analyzed by PCR-based replicon typing and by PCR-based plasmid multilocus sequence typing.
Results: The incompatibility groups detected among the bla CTX-M-1-harboring plasmids included IncI1, IncN, IncHI1B, IncF, IncFIIS, IncFIB, and IncB/O, with plasmid lineage IncI1/ST3 predominating in isolates from chicken and from humans. Lineage IncN/ST1 was detected mainly in isolates from pigs. For the first time, bla CTX-M-1 genes encoded on IncHI1 plasmids were detected in isolates from cattle and from water bodies.
Conclusions: This study identifies plasmid lineages that are contributing to the dissemination of bla CTX-M-1 genes in the food chain, the environment, and humans.
Keywords: blaCTX−M−1; dissemination; food chain; human; incompatibility groups; plasmids.