Plasmid-mediated quinolone resistance pump QepA2 in an Escherichia coli isolate from France

Abstract

One hundred twenty-one extended-spectrum beta-lactamse-producing enterobacterial clinical isolates were screened for the qepA gene. A single CTX-M-15-positive Escherichia coli isolate (0.8%) that produced the putative pump QepA2 was identified. This qepA2 gene was located onto a 90-kb mobilizable plasmid that conferred reduced susceptibility to hydrophilic fluoroquinolones.

FIG. 1.

Genetic environment of the qepA2 gene in plasmid pQep from E. coli BicA and comparison with related QepA-positive plasmid structures. Plasmids pHPA and pIP1206 are from E. coli C316 from Japan (19) and E. coli 1540 from Belgium (13), respectively. Recombinant plasmid pRBicAH was obtained in the present study. Open reading frames are indicated by horizontal arrows. The HindIII restriction sites used for cloning experiments are indicated. Shaded areas indicate identities between sequences.

FIG. 2.

Hypothesis of the ISCR3C-mediated mobilization of the qepA2 gene according to the model proposed by Toleman et al. (17). The process may result from several steps. (A) Insertion of ISCR3C downstream of a groEL gene. Aberrant rolling circle (RC) replication of the ISCR3C element (fused to the groEL gene) generates a transposition intermediate starting at oriTS and ending at terIS1, located inside the groEL gene. (B) This intermediate thereafter transposes into a class 1 integrase gene. A second aberrant RC replication generates a transposition intermediate starting at oriTS and ending at terIS2, located inside a dfr2 gene itself downstream of the intI1 gene. (C) This second transposition intermediate transposes upstream of the qepA2 gene. (D) A third aberrant RC replication produces circular intermediates which can then be rescued by recombination events between tnpA or intI1-groEL genes, generating the qepA2-containing complex integron (E). Boxes represent the open reading frames of the various genes, with arrows indicating the direction of their transcription. The integrase-specific recombination sites are indicated as black dots, and oriIS and terIS are represented as black and white triangles, respectively.