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Int J Antimicrob Agents. 2014 Jun;43(6):553-7. doi: 10.1016/j.ijantimicag.2014.02.019. Epub 2014 Apr 16.

Chromosomal location of blaCTX-M genes in clinical isolates of Escherichia coli from Germany, The Netherlands and the UK.

Author information

1
Federal Institute for Risk Assessment (BfR), Department for Biological Safety, Max-Dohrn Strasse 8-10, D-10589 Berlin, Germany. Electronic address: irodriguezf@salud.madrid.org.
2
Federal Institute for Risk Assessment (BfR), Department for Biological Safety, Max-Dohrn Strasse 8-10, D-10589 Berlin, Germany.
3
Central Veterinary Institute (CVI) of Wageningen UR, Department of Bacteriology and TSEs, P.O. Box 65, 8200 AB Lelystad, The Netherlands.
4
Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut (FLI), 31535 Neustadt-Mariensee, Germany.
5
Public Health England (PHE), 61 Colindale Avenue, London NW9 5EQ, UK.
6
Animal Health and Veterinary Laboratories Agency (AHVLA), Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
7
Central Veterinary Institute (CVI) of Wageningen UR, Department of Bacteriology and TSEs, P.O. Box 65, 8200 AB Lelystad, The Netherlands; Department of Infectious Diseases and Immunology, Utrecht University, 3584 CL Utrecht, The Netherlands.

Abstract

This study aimed to detect and characterise clinical Escherichia coli isolates suspected of carrying chromosomally encoded CTX-M enzymes. Escherichia coli (n=356) obtained in Germany, The Netherlands and the UK (2005-2009) and resistant to third-generation cephalosporins were analysed for the presence of ESBL-/AmpC-encoding genes within the European SAFEFOODERA-ESBL project. β-Lactamases and their association with IS26 and ISEcp1 were investigated by PCR. Isolates were typed by phylogenetic grouping, MLST and PFGE. Plasmids were visualised by S1 nuclease PFGE, and the location of blaCTX-M genes was determined by Southern hybridisation of XbaI-, S1- and I-CeuI-digested DNA. ESBL enzymes could not be located on plasmids in 17/356 isolates (4.8%). These 17 isolates, from different countries and years, were ascribed to phylogenetic groups D (9), B2 (6) and B1 (2), and to seven sequence types, with ST38 being the most frequent (7 phylogroup D isolates). Eleven isolates produced CTX-M-15. blaCTX-M-15 genes were associated with ISEcp1. The remaining isolates expressed the CTX-M group 9 β-lactamases CTX-M-14 (4), CTX-M-9 (1) and CTX-M-51 (1). blaCTX-M probes hybridised with I-CeuI- and/or XbaI-digested DNA, but not with S1-digested DNA, corroborating their chromosomal location. To summarise, only 4.8% of a large collection of ESBL-producing E. coli isolates harboured chromosomal blaCTX-M genes. These isolates were of human origin and belonged predominantly to ST38 and ST131, which possibly indicates the role of these sequence types in this phenomenon. However, heterogeneity among isolates was found, suggesting that their spread is not only due to the dispersion of successful E. coli clones.

KEYWORDS:

Antimicrobial resistance; CTX-M; PFGE; Plasmids

[Indexed for MEDLINE]

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