Open Access Highly Accessed Research article

Molecular characterization of multiresistant Escherichia coli producing or not extended-spectrum β-lactamases

Belén Ruiz del Castillo1*, Laura Vinué2, Elena Jesús Román1, Beatriz Guerra3, Alessandra Carattoli4, Carmen Torres2 and Luis Martínez-Martínez15

Author Affiliations

1 Service of Microbiology, Hospital Universitario Marqués de Valdecilla-IFIMAV, Av/ de Valdecilla s/n, Santander 39008, Spain

2 Área de Bioquímica y Biología Molecular, Universidad de La Rioja, Logroño, Spain

3 Federal Institute for Risk Assessment, Berlin, Germany

4 Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanita, Rome, Italy

5 Department of Molecular Biology, University of Cantabria, Santander, Spain

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BMC Microbiology 2013, 13:84  doi:10.1186/1471-2180-13-84

Published: 16 April 2013



The prevalence and type of plasmids, resistance genes and integrons carried by two collections of multiresistant E. coli producing or not extended-spectrum β-lactamases have been compared. Rep-PCR was used to determine the clonal relationship of the organisms. Plasmids were classified according to their incompatibility. Class 1 and Class 2 integrons and antibiotic resistance genes were analysed by PCR and sequencing.


Both collections of organisms contained a large diversity of unrelated strains with some clones distributed in both groups of isolates. Large plasmids were identified in the two groups of organisms. Plasmids with replicons repK and repColE were more frequent among ESBL-producing isolates, while repFIA, repFII and repA/C replicons were more frequent in isolates lacking ESBL. Conjugative plasmids with repK and repA/C replicons coded for CTX-M-14 and CMY-2 β-lactamases, respectively. No significant differences were observed in the distribution of class 1 and class 2 integrons among multiresistant E. coli producing or not ESBL, and dfrA17-ant(3″)-Ie was the cassette arrangement most commonly found.


In the concrete temporal and geographical context of this study, multiresistant E. coli producing ESBL or other mechanisms of resistance were largely clonally diverse and present some differences in the types of harboured plasmids. Still, some clones were found in both ESBL-producing and –lacking isolates.

E. coli; Plasmids; ESBL; Multiresistance