title: Differential expression of virulence and stress fitness genes between Escherichia coli O157:H7 strains with clinical or bovine-biased genotypes.
abstract: Escherichia coli O157:H7 strains can be classified into different genotypes based on the presence of specific Shiga toxin-encoding bacteriophage insertion sites. Certain O157:H7 genotypes predominate among human clinical cases (clinical genotypes), while others are more frequently found in bovines (bovine-biased genotypes). To determine whether inherent differences in gene expression explain the variation in infectivity of these genotypes, we compared the expression patterns of clinical genotype 1 strains with those of bovine-biased genotype 5 strains using microarrays. Important O157:H7 virulence factors, including locus of enterocyte effacement genes, the enterohemolysin, and several pO157 genes, showed increased expression in the clinical versus bovine-biased genotypes. In contrast, genes essential for acid resistance (e.g., gadA, gadB, and gadC) and stress fitness were upregulated in bovine-biased genotype 5 strains. Increased expression of acid resistance genes was confirmed functionally using a model stomach assay, in which strains of bovine-biased genotype 5 had a 2-fold-higher survival rate than strains of clinical genotype 1. Overall, these results suggest that the increased prevalence of O157:H7 illness caused by clinical genotype 1 strains is due in part to the overexpression of key virulence genes. The bovine-biased genotype 5 strains, however, are more resistant to adverse environmental conditions, a characteristic that likely facilitates O157:H7 colonization of bovines.
authors.affiliation: Microbial Evolution Laboratory, National Food Safety and Toxicology Center, 165 Food Safety and Toxicology Building, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Sivapriya Kailasan
authors.initials: SK
authors.lastname: Vanaja
authors.forename: Amber C
authors.initials: AC
authors.lastname: Springman
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Besser
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Whittam
authors.forename: Shannon D
authors.initials: SD
authors.lastname: Manning
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D003090:Coliphages / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology* / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics; D005750:Gastric Juice / Q000382:microbiology; D020869:Gene Expression Profiling; D005838:Genotype; D006801:Humans; D050296:Microbial Viability; D008962:Models, Theoretical; D020411:Oligonucleotide Array Sequence Analysis; D039002:Prophages / Q000235:genetics; D013270:Stomach / Q000382:microbiology; D037521:Virulence Factors / Q000096:biosynthesis / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D037521:Virulence Factors