Replicon typing of plasmids carrying bla(CTX-M-1) in Enterobacteriaceae of animal, environmental and human origin

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.