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.
Originally 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.
Based on their primary sequence homology ( Ambler et al., 1991) and their substrate profiles ( Bush and Jacoby, 2010), ESBLs can be categorized into classes and groups, respectively, whereby the majority of ESBLs belong to Ambler class A and to the Bush group 2be. They represent the most important mechanism of antibacterial resistance in Gram-negative bacilli. For the first time, bla CTX-M-1 genes encoded on IncHI1 plasmids were detected in isolates from cattle and from water bodies.Ĭonclusions: 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.Įxtended 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). Lineage IncN/ST1 was detected mainly in isolates from pigs. 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. 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. A selection of IncI and IncN plasmids were characterized by multilocus sequence typing in order to determine their epidemiological relatedness. 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. Objectives: The aim of this work was to determine the plasmid replicon profiles of a collection of bla CTX-M-1-positive enterobacterial strains. Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.Katrin Zurfluh, Gianna Jakobi, Roger Stephan *, Herbert Hächler and Magdalena Nüesch-Inderbinen
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