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Escherichia coil O157:H7, a toxin-producing food and waterborne bacterial pathogen, has been linked to large outbreaks of gastrointestinal illness for more than two decades. E. coil O157 causes a wide range of clinical illness that varies by outbreak, although factors that contribute to variation in disease severity are poorly understood. Several recent outbreaks involving O157 contamination of fresh produce (e.g., spinach) were associated with more severe disease, as defined by higher hemolytic uremic syndrome and hospitalization frequencies, suggesting that increased virulence has evolved. To test this hypothesis, we developed a system that detects SNPs in 96 loci and applied it to >500 E. coil 0157 clinical strains. Phylogenetic analyses identified 39 SNP genotypes that differ at 20% of SNP loci and are separated into nine distinct clades. Differences were observed between clades in the frequency and distribution of Shiga toxin genes and in the type of clinical disease reported. Patients with hemolytic uremic syndrome were significantly more likely to be infected with clade 8 strains, which have increased in frequency over the past 5 years. Genome sequencing of a spinach outbreak strain, a member of clade 8, also revealed substantial genomic differences. These findings suggest that an emergent subpopulation of the clade 8 lineage has acquired critical factors that contribute to more severe disease. The ability to detect and rapidly genotype 0157 strains belonging to such lineages is important and will have a significant impact on both disease diagnosis and treatment guidelines. pathogens| polymorphisms | population genetics

A surveillance system used different detection methods to estimate prevalence of Shiga toxin-producing Escherichia coli during 2003-2005 and 2001-2002. More non-O157 serotypes were detected by enzyme immunoassay than by evaluation [...]

Immigrants from Tibet may have active tuberculosis or a tuberculosis exposure and should be carefully screened. In 1990, 191 Tibetans migrated from India and Nepal to the Minneapolis area. Ninety-eight percent had a positive TB test, indicating that they had been exposed to TB. Sixteen had active TB and almost one-third of them had not been detected using blood cultures for Mycobacterium (M.) tuberculosis. Thirty-eight percent had a strain of M. tuberculosis that was resistant to one or more anti-tuberculosis drugs., Objective.--To study screening outcomes among a group of Tibetan immigrants at high risk for developing active tuberculosis (TB) after arrival in Minnesota. Design.--Retrospective cohort study. Participants.--A total of 191 Tibetan immigrants undergoing medical screening. Main Outcome Measures.--Occurrence and treatment outcomes of active TB. Setting.--A health maintenance organization and a public TB clinic in Minneapolis, Minn. Results.--Positive (induration, [Greater than or equal to] 10 mm) tuberculin skin test results were documented in 98% of Tibetans, compared with 44% of Vietnamese, 10% of Hmong, and 51% of Russian refugees in Minnesota (P Conclusions.--Tuberculosis infection is nearly universal among Tibetans settling in Minnesota. A single screening evaluation failed to detect the majority of TB cases among Tibetans. Even in the face of negative M tuberculosis cultures, persons with a history of active TB require particularly close follow-up. JAMA. 1997;277:785-738