Variability in the Occupancy of O157 Integration Sites by Shiga Toxin-Encoding Prophages.

O157:H7 strains often produce Shiga toxins encoded by genes on lambdoid bacteriophages that insert into multiple loci as prophages. O157 strains were classified into distinct clades that vary in virulence. Herein, we used PCR assays to examine Shiga toxin (Stx) prophage occupancy in , , , and among 346 O157 strains representing nine clades.

Effect of feeding a direct-fed microbial on total and antimicrobial-resistant fecal coliform counts in preweaned dairy calves.

Objective: To determine whether feeding a direct-fed microbial (DFM) to dairy calves would reduce total and antimicrobial-resistant coliform counts in feces and affect average daily gain (ADG).

Animals: 21 preweaned Holstein heifer calves.

Procedures: The study had a randomized complete block design.

Increased adherence and expression of virulence genes in a lineage of Escherichia coli O157:H7 commonly associated with human infections.

Background: Enterohemorrhagic Escherichia coli (EHEC) O157:H7, a food and waterborne pathogen, can be classified into nine phylogenetically distinct lineages, as determined by single nucleotide polymorphism genotyping. One lineage (clade 8) was found to be associated with hemolytic uremic syndrome (HUS), which can lead to kidney failure and death in some cases, particularly young children. Another lineage (clade 2) differs considerably in gene content and is phylogenetically distinct from clade 8, but caused significantly fewer cases of HUS in a prior study.

Differences in adherence and virulence gene expression between two outbreak strains of enterohaemorrhagic Escherichia coli O157 : H7.

The Escherichia coli O157 : H7 TW14359 strain was implicated in a multi-state outbreak in North America in 2006, which resulted in high rates of severe disease. Similarly, the O157 : H7 RIMD0509952 (Sakai) strain caused the largest O157 : H7 outbreak to date. Both strains were shown to represent divergent phylogenetic lineages.