Phenotypic and genotypic traits of Shiga toxin-negative E. coli O157:H7/H(-) bovine and porcine strains.
Enterohemorrhagic E. coli (EHEC) O157:H7/H(-) (nonmotile) exist as Shiga toxin gene (stx)-positive and stx-negative variants in patients and the environment. We analyzed molecular characteristics, phenotypes, and the phylogenetic background of three stx-negative E. coli O157:H7/H(-) strains isolated from cattle and a pig and compared them with those of human EHEC and stx-negative E. coli O157:H7/H(-). All three animal strains contained fliCH7 and two contained eae. One eae-positive strain (O157:H(-)) was sorbitol-fermenting (SF) and the other (O157:H7) was non-sorbitol-fermenting (nSF). These two strains shared a spectrum of non-stx putative virulence and fitness genes with human nSF and SF EHEC and stx-negative E. coli O157:H7/H(-) and belonged, similar to the vast majority of human isolates, to sequence type (ST) 11 in multilocus sequence typing. In contrast, the eae-negative O157:H7 animal isolate, which was SF, differed in spectrum of virulence genes and also differed phylogenetically (ST717) from the two eae-positive strains and the human EHEC and stx-negative E. coli O157:H7/H(-). In contrast to efforts with human stx-negative E. coli O157:H(-), attempts to transduce the two stx-negative/eae-positive animal O157:H7/H(-) strains with stx(2)-encoding phages from human SF and nSF EHEC O157:H7/H(-) failed, despite the animal strains having intact loci where such phages integrate in human EHEC O157 (wrbA and yecE). The role of animal stx-negative/eae-positive and stx-negative/eae-negative E. coli O157:H7/H(-) in their natural source and in human infections needs further investigation.
Stephan
Roger
R
Institute for Food Safety and Hygiene, University of Zurich, Switzerland. stephanr@fsafety.uzh.ch
Zhang
Wenlan
W
Bielaszewska
Martina
M
Mellmann
Alexander
A
Karch
Helge
H
D018829:Adhesins, Bacterial; D000818:Animals; D002417:Cattle / Q000382:microbiology; D019453:Escherichia coli O157 / Q000145:classification* / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D029968:Escherichia coli Proteins; D005408:Flagellin; D005517:Foodborne Diseases / Q000382:microbiology / Q000517:prevention & control; D005838:Genotype; D010641:Phenotype; D010802:Phylogeny; D022621:Shiga Toxin / Q000096:biosynthesis*; D015398:Signal Transduction; D013012:Sorbitol / Q000378:metabolism*; D013552:Swine / Q000382:microbiology; D037521:Virulence Factors / Q000235:genetics*
D018829:Adhesins, Bacterial; D029968:Escherichia coli Proteins; C516095:FliC protein, E coli; D037521:Virulence Factors; D005408:Flagellin; C073819:eaeA protein, E coli; D013012:Sorbitol; D022621:Shiga Toxin