Phenotypic diversity of Emphasis Type="Italic"Es

Authors: Ji Youn Lim Joon Bae Hong Haiqing Sheng Smriti Shringi Rajinder Kaul Thomas E Besser Carolyn J Hovde

Publish Date: 2010/06/23

Volume: 48, Issue: 3, Pages: 347-357

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Abstract

Escherichia coli O157H7 a foodborne pathogen causes hemorrhagic colitis and the hemolyticuremic syndrome A putative virulence factor of E coli O157H7 is a 60MDa plasmid pO157 found in 99 of all clinical isolates and many bovinederived strains The well characterized E coli O157H7 Sakai strain Sakai and its pO157cured derivative SakaiCu were compared for phenotypic differences SakaiCu had enhanced survival in synthetic gastric fluid did not colonize cattle as well as wildtype Sakai and had unchanged growth rates and tolerance to salt and heat These results are consistent with our previous findings with another E coli O157H7 disease outbreak isolate ATCC 43894 and its pO157cured 43894Cu However despite the essentially sequence identical pO157 in these strains SakaiCu had changes in antibiotic susceptibility and motility that did not occur in the 43894Cu strain This unexpected result was systematically analyzed using phenotypic microarrays testing 1920 conditions with Sakai 43894 and the plasmidcured 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 realtime PCR and gadA and rpoS expression differed between SakaiCu and 43894Cu The strainspecific differences in phenotype that resulted from the loss of essentially DNAsequence identical pO157 were likely due to the chromosomal genetic diversity between strains The O157H7 serotype diversity was further highlighted by phenotypic microarray comparisons of the two outbreak strains with a genotype 6 bovine E coli O157H7 isolate rarely associated with human disease

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