Differential expression of virulence and stress fitness genes between Escherichia coli O157:H7 strains with clinical or bovine-biased genotypes.
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.
Vanaja
Sivapriya Kailasan
SK
Microbial Evolution Laboratory, National Food Safety and Toxicology Center, 165 Food Safety and Toxicology Building, Michigan State University, East Lansing, MI 48824, USA.
Springman
Amber C
AC
Besser
Thomas E
TE
Whittam
Thomas S
TS
Manning
Shannon D
SD
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
D029968:Escherichia coli Proteins; D037521:Virulence Factors