B-283. Phenotypic Changes of Escherichia coli O157:H7 Strains after the Deletion of Plasmid O157

J. Lim, H. Sheng, C. J. Hovde;
Univ. of Idaho, Moscow, ID.

Escherichia coli O157:H7 is an important food-borne pathogen that causes hemorrhagic colitis and life-threatening sequelae in humans. Recently, many studies report that the large plasmid of E. coli O157:H7, pO157, contributes to bacterial pathogenesis; however, its role is not well-defined. Here we used the Phenotype Microarray System (Biolog, Hayward, CA) to determine the phenotypes of E. coli O157:H7 with or without pO157. These results may help to identify the function of pO157 in E. coli O157:H7 pathogenesis. Two E. coli O157:H7 strains (ATCC 43894 and Sakai) and two isogenic pO157-cured strains were analyzed to determine their metabolic capacity and stress resistance potential. Briefly, the growth performance of the four strains was assessed in duplicate for ~2000 cell phenotypes, including use of nutrient sources, replication in various environments, and antibiotic resistance. The phenotypic microarray differences were verified individually. Several phenotypic differences were found between the wild-type and isogenic pO157-cured strains, such as differences in utilization of nutrient sources or dipeptides and resistance to antibiotics. The pO157-cured strains of ATCC 43894 (277) and Sakai (Sakai-cu) showed 44 and 31 gained phenotypes, and 23 and 7 lost phenotypes, respectively. The phenotypes gained and lost between the two pO157-cured strains differed. For example, the cured 277 grew better in dipeptide nitrogen sources but not as well in carbon sources such as n-acetyl-d-glucosamine, d-mannitol, d-glucose, and mucic acid. Sakai-cu showed different phenotypes mostly in antibiotic resistance compared to the wild-type strain. This phenotypic data may add to our understanding of the role of the pO157 in different environments and ecological niches.