pO157_Sal, a novel conjugative plasmid detected in outbreak isolates of Escherichia coli O157:H7

Abstract

In addition to the large virulence plasmid pO157, a novel 38-kb conjugative plasmid, pO157_Sal, was identified and sequenced from an Escherichia coli O157:H7 outbreak-associated Chinese isolate that shares high similarity with a plasmid in Salmonella enterica serovar Agona. The plasmid was found in 15 of 326 isolates, 12 of which were of the same pulsed-field gel electrophoresis type.

Fig. 1.

Plasmid map and comparison with other conjugative plasmids. (A) Representational circular map of pO157_Sal. The inside circle is the G+C skew. The middle circle is the G+C content. The outside circle is the genetic organization of ORFs within the plasmid. The direction of transcription of each ORF is indicated. Genes are color coded as indicated. (B) Comparison of the tra regions of pO157_sal, R721, and pTiA6. Sequences for other plasmids were obtained from GenBank (accession numbers NC_002525 and NC_002377 for R721 and pTiA6, respectively). Filled arrows and arrowheads are T4SS-related genes. The percentages of amino acid identity (above) and similarity (below) are shown between the homologous genes.