Abstract
Objectives: The aim of this work was to determine the plasmid replicon profiles of a collection of blaCTX-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 blaCTX-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 blaCTX-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, blaCTX-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 blaCTX-M-1 genes in the food chain, the environment, and humans.
Highlights
Extended spectrum β-lactamases (ESBLs) are bacterial enzymes that catalyze the hydrolysis of the amide bond in ß-lactam ring of extended-spectrum cephalosporins and monobactams (Matagne et al, 1998)
The incompatibility groups detected among the blaCTX−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
This study identifies plasmid lineages that are contributing to the dissemination of blaCTX−M−1 genes in the food chain, the environment, and humans
Summary
Extended spectrum β-lactamases (ESBLs) are bacterial enzymes that catalyze the hydrolysis of the amide bond in ß-lactam ring of extended-spectrum cephalosporins (ceftazidime or cefotaxime) and monobactams (aztreonam) (Matagne et al, 1998). Detected in human clinical isolates associated with nosocomial infections in the early 1990’s (Paterson and Bonomo, 2005), the classical plasmid-mediated TEM- and SHV-ESBLs which derived from point mutations in the structural genes of their precursors TEM-1, TEM-2, and SHV-1, were predominant over the following decade. Their rapid spread within and between bacterial species promoted their dissemination beyond the hospital setting, with extensive use of cephalosporins in human medicine generally considered to be a major selective force. In recent years there has been an alarming spread of CTX-M-enzymes throughout the human population, food animals, wildlife and the environment (Cantón et al, 2012)
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