Molecular characterization reveals three distinct clonal groups among clinical shiga toxin-producing Escherichia coli strains of serogroup O103.
Shiga toxin-producing Escherichia coli (STEC) is one of the most important groups of food-borne pathogens, and STEC strains belonging to the serotype O103:H2 can cause diarrhea, hemorrhagic colitis, and hemolytic-uremic syndrome in humans. STEC O103:non-H2 strains are also sometimes isolated from human patients, but their genetic characteristics and role in significant human enteric disease are not yet understood. Here, we investigated 17 STEC O103:non-H2 strains, including O103:H11, O103:H25, O103:HUT (UT [untypeable]), and O103:H- (nonmotile) isolated in Japan, and their characteristics were compared to those of STEC O103:H2 and other serotype STEC strains. Sequence analyses of fliC and eae genes revealed that strains possessed any of the following combinations: fliC-H2/eae-epsilon, fliC-H11/eae-beta1, and fliC-H25/eae-theta, where fliC-H2, -H11, and -H25 indicate fliC genes encoding H2, H11, and H25 flagella antigens, respectively, and eae-epsilon, -beta1, and -theta indicate eae genes encoding epsilon, beta1, and theta subclass intimins, respectively. Phylogenetic analysis based on the sequences of seven housekeeping genes demonstrated that the O103:H11/[fliC-H11] and O103:H25/[fliC-H25] strains formed two distinct groups, different from that of the O103:H2/[fliC-H2] strains. Interestingly, a group consisting of O103:H11 strains was closely related to STEC O26:H11, which is recognized as a most important non-O157 serotype, suggesting that the STEC O103:H11 and STEC O26:H11 clones evolved from a common ancestor. The multiplex PCR system for the rapid typing of STEC O103 strains described in the present study may aid clinical and epidemiological studies of the STEC O103:H2, O103:H11, and O103:H25 groups. In addition, our data provide further insights into the high variability of STEC stains with emerging new serotypes.
Interdisciplinary Research Organization, University of Miyazaki, Miyazaki, Japan. iguchi@med.miyazaki-u.ac.jp
Atsushi
A
Iguchi
Sunao
S
Iyoda
Makoto
M
Ohnishi
D018829:Adhesins, Bacterial / Q000235:genetics; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D005408:Flagellin; D014644:Genetic Variation; D006801:Humans; D007564:Japan / Q000453:epidemiology; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D054323:Shiga-Toxigenic Escherichia coli / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
D018829:Adhesins, Bacterial; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C516095:FliC protein, E coli; D005408:Flagellin; C073819:eaeA protein, E coli