Abstract
Background: Extended-spectrum β-lactamase (ESBL)-encoding genes are frequently mapped to plasmids, yet few of these structures have been characterized at the molecular level, to date.Methods: Eighty-seven ESBL-producing Escherichia coli were isolated from fecal samples of food-producing animals and healthy humans in Switzerland from 2009 to 2011. Plasmid DNA of all isolates was purified. Broth mating assays were carried out individually for 32 isolates to determine if the ESBL marker could be transferred by conjugation. The plasmid sizes were determined by S1-nuclease pulsed-field gel electrophoresis (PFGE) and the plasmids were typed by PCR-based replicon typing. Susceptibility tests by disk diffusion followed with a re-analysis S1-nuclease PFGE and PCRs were performed to confirm plasmid transfer. Microarray was performed to detect additional antibiotic resistance markers and multi-locus sequence typing was also performed in selected donor strains. The phylotypes were identified by triplex PCR.Results: About half (n = 46) of the 87 isolates carried small (<20-kb) plasmids. All selected 32 isolates contained large plasmids (ranging in sizes from 20- to 600-kb). Eleven plasmid replicon types were detected. Of these, IncFIA (n = 5), IncFIB (n = 9), and IncK/B (n = 4) were common. Nine isolates demonstrated the ability to transfer their cefotaxime resistance marker at high transfer rates. Plasmid profile re-analysis of these transconjugants identified 16 plasmids. IncFIB and IncI1 were the most prevalent replicon types. Phylogenetic grouping showed that five of the nine donor strains belonged to phylogroup B1. Nine different sequence types were identified in nine tested donor strains.Conclusion: Characterization of these ESBL-encoding conjugative plasmids extends our understanding on these resistance markers in multi-drug resistant E. coli cultured from healthy human and animal sources.
Highlights
Global dissemination of multiple antibiotic resistance and virulence traits by plasmids poses an increasing threat to the successful treatment of bacterial infectious diseases in animals and humans alike (Bush, 2010)
The plasmid sizes were determined by S1-nuclease pulsed-field gel electrophoresis (PFGE) and the plasmids were typed by PCR-based replicon typing
Characterization of these ESBL-encoding conjugative plasmids extends our understanding on these resistance markers in multi-drug resistant E. coli cultured from healthy human and animal sources
Summary
Global dissemination of multiple antibiotic resistance and virulence traits by plasmids poses an increasing threat to the successful treatment of bacterial infectious diseases in animals and humans alike (Bush, 2010). It is acknowledged that the horizontal transfer of plasmids carrying these ESBL genes is an important contributory factor in the epidemiology of this bacterial ecosystem (EFSA Panel on Biological Hazards [BIOHAZ], 2011). Plasmids evolve as an integral part of the bacterial genome, consisting of several extra-chromosomal traits, one of which is their resistance genes, which can be exchanged among bacteria of different origins by conjugation (Carattoli, 2011). Those expressing an ESBL phenotype frequently carry genes encoding resistance to other commonly used antimicrobial drug classes (such as aminoglycosides, chloramphenicols, fluoroquinolones, or tetracycline; Harajly et al, 2010; Rogers et al, 2011). Extended-spectrum β-lactamase (ESBL)-encoding genes are frequently mapped to plasmids, yet few of these structures have been characterized at the molecular level, to date
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
