Analysis of extended-spectrum-β-lactamase-producing Escherichia coli isolates collected in the GERM-Vet monitoring programme.

OBJECTIVES: The aims of this study were (i) to detect extended-spectrum β-lactamase (ESBL) genes among 1378 Escherichia coli isolates from defined disease conditions of companion and farm animals and (ii) to determine the localization and organization of ESBL genes.

METHODS: E. coli isolates from the German resistance monitoring programme GERM-Vet were included in the study. Plasmids were transferred by conjugation or transformation and typed by PCR-based replicon typing. ESBL genes were detected by PCR; the complete ESBL genes and their flanking regions were sequenced by primer walking. Phylogenetic grouping and multilocus sequence typing (MLST) were performed for all ESBL-producing E. coli isolates.

RESULTS: Of the 27 ESBL-producing E. coli isolates detected, 22 carried blaCTX-M-1 genes on IncN (n = 16), IncF (n = 3), IncI1 (n = 2) or multireplicon (n = 1) plasmids. A blaCTX-M-3 gene was located on an IncN plasmid and a blaCTX-M-15 gene was located on an IncF plasmid. A multireplicon plasmid and an IncHI1 plasmid harboured blaCTX-M-2. A blaTEM-52c gene was identified within Tn2 on an IncI1 plasmid. The blaCTX-M genes located within the same or related genetic contexts showed differences due to the integration of insertion sequences. Various MLST types were detected, with ST10 (n = 7), ST167 (n = 4) and ST100 (n = 3) being the most common.

CONCLUSIONS: This study showed that the blaCTX-M-1 gene is the predominant ESBL gene among E. coli isolates from diseased animals in Germany and a considerable structural heterogeneity was found in the regions flanking the blaCTX-M-1 gene. Insertion sequences, transposons and recombination events are likely to be involved in alterations of the ESBL gene regions.