Types of eae genes in non-O157 Shiga toxin-producing Escherichia coli strains / 中华微生物学和免疫学杂志

ABSTRACT

Objective To analyze the subtypes of eae genes in various non-O157 Shiga toxin-pro-ducing Escherichia coli ( STEC) strains isolated in China.Methods The complete nucleotide sequences of 10 eae genes were amplified by PCR and sequenced.The BLASTn software was used to analyze the se-quences for eae gene subtyping.A phylogenetic tree was constructed based on the10 ea e gene sequences to-gether with the gene sequences of 30 different subtypes in GenBank and those of STEC strains of 7 prevalent serotypes (O157 ∶H7, O26 ∶H11, O103 ∶H2, O111 ∶H8, O145 ∶H28, O45 ∶H2 and O121 ∶H19) using MEGA 5.0.Multilocus sequence typing (MLST) was performed on the 10 STEC strains with reference to the Escherichia coli ( E.coli) MLST website ( http//mlst.warwick.ac.uk/mlst/dbs/Ecoli) for the typing of multiple loci.A minimum spanning tree ( MST) was constructed using the BioNumerics software to inves-tigate the phylogenetic relationships between the 10 eae gene-positive STEC strains in this study and hemolyt-ic uremic syndrome-associated enterohemorrhagic E.coli ( HUSEC) strains as well as all human STEC strains of O157, O26, O45, O103, O111, O121 and O145 serotypes submitted to the E.coli MLST website data-base.Results The complete nucleotide sequences of eae genes in 10 non-O157 STEC strains were 2.8 kb in length and belonged to 3 known subtypes.The predominant subtype wasβ1, accounting for 60%of the 10 STEC strains (6/10), followed byθandγ1 subtypes with two strains in each type.The eae gene sequences in certain strains were identical to those of the prevalent serotypes.Seven sequence types ( STs) were identi-fied from the 10 STEC strains carrying eae gene.Conclusion The eae genes harbored by the non-O157 STEC strains isolated from different specimens in China were diverse and had close phylogenetic relationships with the highly pathogenic and prevalent STEC strains.This study implied that the STEC strains harboring eae gene had high pathogenic potential.