| Title |
Phenotypic Diversity of Escherichia coli O157:H7 Strains Associated with the Plasmid O157 |
| Author |
Ji Youn Lim1, Joon Bae Hong1, Haiqing Sheng1, Smriti Shringi2, Rajinder Kaul3, Thomas E. Besser2, and Carolyn J. Hovde1* |
| Address |
1Department of Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow, Idaho 83844, USA, 2Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164, USA, 3Department of Medicine, University of Washington Genome Center, Seattle, Washington 98195, USA |
| Bibliography |
Journal of Microbiology, 48(3),347-357, 2010,
|
| DOI |
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| Key Words |
E. coli O157:H7, pO157, phenotype microarray, phenotypic diversity |
| Abstract |
Escherichia coli O157:H7, a food-borne pathogen, causes hemorrhagic colitis and the hemolytic-uremic syndrome. A putative virulence factor of E. coli O157:H7 is a 60-MDa plasmid (pO157) found in 99% of all clinical isolates and many bovine-derived strains. The well characterized E. coli O157:H7 Sakai strain (Sakai) and its pO157-cured derivative (Sakai-Cu) were compared for phenotypic differences. Sakai-Cu had enhanced survival in synthetic gastric fluid, did not colonize cattle as well as wild-type Sakai, and had unchanged growth rates and tolerance to salt and heat. These results are consistent with our previous findings with another E. coli O157:H7 disease outbreak isolate ATCC 43894 and its pO157-cured (43894-Cu). However, despite the essentially sequence identical pO157 in these strains, Sakai-Cu had changes in antibiotic susceptibility and motility that did not occur in the 43894-Cu strain. This unexpected result was systematically analyzed using phenotypic microarrays testing 1,920 conditions with Sakai, 43894, and the plasmid-cured mutants. The influence of the pO157 differed between strains on a wide number of
growth/survival conditions. Relative expression of genes related to acid resistance (gadA, gadX, and rpoS) and flagella production (fliC and flhD) were tested using quantitative real-time PCR and gadA and rpoS expression differed between Sakai-Cu and 43894-Cu. The strain-specific differences in phenotype that resulted from the loss of essentially DNA-sequence identical pO157 were likely due to the chromosomal genetic diversity between strains. The O157:H7 serotype diversity was further highlighted by phenotypic microarray comparisons of the two outbreak strains with a genotype 6 bovine E. coli O157:H7 isolate, rarely associated with human disease. |
