Analysis of <i>bla</i> _CTX-M -Carrying Plasmids from Escherichia coli Isolates Collected in the BfT-GermVet Study

<jats:title>ABSTRACT</jats:title> <jats:p> In this study, 417 <jats:named-content content-type="genus-species">Escherichia coli</jats:named-content> isolates from defined disease conditions of companion and farm animals collected in the BfT-GermVet study were investigated for the presence of extended-spectrum β-lactamase (ESBL) genes. Three ESBL-producing <jats:named-content content-type="genus-species">E. coli</jats:named-content> isolates were identified among the 100 ampicillin-resistant isolates. The <jats:named-content content-type="genus-species">E. coli</jats:named-content> isolates 168 and 246, of canine and porcine origins, respectively, harbored <jats:italic>bla</jats:italic> <jats:sub>CTX-M-1</jats:sub> , and the canine isolate 913 harbored <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> , as confirmed by PCR and sequence analysis. The isolates 168 and 246 belonged to the novel multilocus sequence typing (MLST) types ST1576 and ST1153, respectively, while isolate 913 had the MLST type ST410. The ESBL genes were located on structurally related IncN plasmids in isolates 168 and 246 and on an IncF plasmid in isolate 913. The <jats:italic>bla</jats:italic> <jats:sub>CTX-M-1</jats:sub> upstream regions of plasmids pCTX168 and pCTX246 were similar, whereas the downstream regions showed structural differences. The genetic environment of the <jats:italic>bla</jats:italic> <jats:sub>CTX-M-15</jats:sub> gene on plasmid pCTX913 differed distinctly from that of both <jats:italic>bla</jats:italic> <jats:sub>CTX-M-1</jats:sub> genes. Detailed sequence analysis showed that the integration of insertion sequences, as well as interplasmid recombination events, accounted for the structural variability in the <jats:italic>bla</jats:italic> <jats:sub>CTX-M</jats:sub> gene regions. </jats:p>