Typing of eae gene in Escherichia coli strains with LEE pathogenicity island isolated in China
Objective To understand molecular epidemiological characteristic of LEE pathogenicity island of Escherichia coli strains isolated in China. Methods In 20 Shiga toxin negative E. coli strains harboring LEE (locus of enterocyte effacement) pathogenicity island, eae types were determined by PCR with specific primers basing on the eae 3′ terminal sequences and restriction endonuclease analysis of the PCR products. The LEE insertion sites in chromosomes of the strains were identified. In addition, fingerprints of the 20 strains were showed by ERIC PCR. Results The most eae type was found as β (45.0%) which could be typed into two subtypes. The restriction endonuclease patterns of eae γ found in these strains were different to the one of EHEC O157∶H7 strain EDL933. In 3 strains which eae 3′ terminal could not be typed by the PCR, their putative intimin C terminal amino acid sequences showed that the eae types of strain 96 1, C130 1, and 97 3, were γ2 (identity to type γ2= 99.3% ), a new subtype of type e(identity to type e=83.4%), and a new type λ (highest identity to type α= 58.1% ), respectively. Moreover, in strain 97 3, a variant of IS200 was inserted into the intergenic space between eae and escD. In 9 strains the LEE insertion site on chromosome was selC, in two of which there was another intact selC while a selC was split by LEE insertion. In other 11 strains, there might be other unknown insertion site except selC and pheU. The ERIC PCR fingerprints among almost all of the 20 strains were different at various degrees. The same eae type was found in strains with distinct fingerprints, and there were a few strains belonging to common clone group with same eae type too. Conclusion Among Shiga toxin negative E.coli strains harboring LEE pathogenicity island isolated in China, there are high diversities in eae type, which are independent of the phylogeny of E.coli strains, and there might be new insertion site of LEE in their chromosome. [