Abstract
Objectives: The purpose of this study was to characterize sets of extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae collected longitudinally from different flocks of broiler breeders, meconium of 1-day-old broilers from theses breeder flocks, as well as from these broiler flocks before slaughter.Methods: Five sets of ESBL-producing Escherichia coli were studied by multi-locus sequence typing (MLST), phylogenetic grouping, PCR-based replicon typing and resistance profiling. The blaCTX-M-1-harboring plasmids of one set (pHV295.1, pHV114.1, and pHV292.1) were fully sequenced and subjected to comparative analysis.Results: Eleven different MLST sequence types (ST) were identified with ST1056 the predominant one, isolated in all five sets either on the broiler breeder or meconium level. Plasmid sequencing revealed that blaCTX-M-1 was carried by highly similar IncI1/ST3 plasmids that were 105 076 bp, 110 997 bp, and 117 269 bp in size, respectively.Conclusions: The fact that genetically similar IncI1/ST3 plasmids were found in ESBL-producing E. coli of different MLST types isolated at the different levels in the broiler production pyramid provides strong evidence for a vertical transmission of these plasmids from a common source (nucleus poultry flocks).
Highlights
One of the currently most important antibiotic resistance mechanisms in Enterobacteriaceae is based on plasmid-mediated production of extended-spectrum β-lactamases (ESBLs) which inactivate β-lactam-antibiotics including cephalosporins and monobactams by hydrolyzing their β-lactam ring (Frère et al, 1992)
Phylogenetic grouping and multi-locus sequence typing (MLST) analysis showed that different E. coli types could be identified at the investigated production levels in all five sets, suggestive of a non-clonal bacterial composition
E. coli B1 ST1056 was isolated in all five sets either in the broiler breeder samples or in the meconium samples
Summary
One of the currently most important antibiotic resistance mechanisms in Enterobacteriaceae is based on plasmid-mediated production of extended-spectrum β-lactamases (ESBLs) which inactivate β-lactam-antibiotics including cephalosporins and monobactams by hydrolyzing their β-lactam ring (Frère et al, 1992). ESBLs are classified according to their primary sequences and substrate profiles into different families such as the TEM-, the SHV-, the OXA-, and the CTX-M -family (Bush and Jacoby, 2010). Lahey database , CTX-M-1 predominates in Escherichia coli isolated from food-producing animals and foods in Europe (EFSA, 2011). Several reports highlighted the dissemination of ESBL-producing E. coli in poultry in several countries across. A high fecal prevalence of blaCTX−M−1 -harboring E. coli has been reported for poultry flocks in Switzerland (Endimiani et al, 2012; Geser et al, 2012). CTX-M-1-producing E. coli have been found both on local and imported retail poultry meat (Abgottspon et al, 2014; Vogt et al, 2014)
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