Sequence analysis of TraE in the novel conjugative plasmid pO157_Sal detected in Escherichia coli O157∶H7 / 中华传染病杂志

ABSTRACT

Objective To analyze the sequence of the novel conjugative plasmid pO157_Sal detected in outbreak isolates of Escherichia coli O157∶H7 .Methods The traE genes of the outbreak isolates in China were amplified by polymerase chain reaction (PCR) and the products were sequenced .The TraE sequences of Escherichia coli O157 ∶ H7 strains from other sources were retrieved from GenBank . Phylogenetic tree based on the TraE sequences was constructed by Neibhor-joining analysis .The whole plasmid sequences of pO157_Sal and pEC4115 were compared .Results The sequences of traE gene were identical among the Chinese isolates . There were homologous sequences of TraE in Escherichia coli O157∶H7 isolates from different sources .Twenty-one out of the 52 pO157_Sal genes were homologous to genes of pEC4115 with amino acid level identity ranging from 28% to 51% .Conclusions Although similar TraE sequences and similar plasmid are found in Escherichia coli O157∶H7 isolates from different sources ,pO157_Sal is only observed in Chinese outbreak isolates .The TraE sequences are conservative among the outbreak isolates ,indicating they are from the same specific source .