Analysis of plasmids encoding extended-spectrum β-lactamases (ESBLs) from Escherichia coli isolated from non-hospitalised patients in Seville

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is an emerging pathogen in the community. We investigated the specific types of ESBLs in E. coli isolates from non-hospitalised patients and the plasmids harbouring these ESBLs. Forty-eight consecutive ESBL-producing E. coli were studied. All the isolates were clonally unrelated. ESBLs were characterised by sequencing. Mobility of the undigested plasmids was investigated both by conventional electrophoresis and by pulsed-field gel electrophoresis. Southern restriction fragment length polymorphism (RFLP) experiments were carried out by digesting plasmids with EcoRI and HindIII. CTX-M-14 was the most frequent ESBL (28 isolates), followed by SHV-12 (16 isolates). Plasmids encoding CTX-M-14 appeared homogeneous both in hybridisation profile and mobility. In contrast, plasmids expressing SHV-12 were more varied in size and hybridisation patterns. Our data suggest that a single type or very closely related plasmids harbouring CTX-M-14 are spreading in the community among unrelated E. coli isolates in our area.