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Chapter 8 : Epidemiology of Argentinean Shiga Toxin-Producing Escherichia coli
Category: Bacterial Pathogenesis
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Shiga toxin-producing Escherichia coli (STEC) is an important food-borne pathogen that can cause nonbloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome(HUS). The first isolation of shiga toxin-producing Escherichia coli (STEC) O157 from cattle occurred in Argentina in 1977, when three E. coli O157 strains were recovered from feces of 13 calves aged 1 to 3 weeks with colibacillosis in Buenos Aires Province. In a study on STEC carriage in feedlots, four STEC O157 strains harbored the stx 2, eae, ehxA genes. In this study the prevalence of non-O157 STEC strains was 45.2%. In a study that analyzed fecal samples from steers at slaughter in order to evaluate two PCR procedures for STEC detection, non-O157 STEC strains were isolated from 15.8% of calves with diarrhea, with a majority of strains (60%) carrying the stx1 gene. With respect to the routes of contamination of the carcasses with non-O157 STEC serotypes, the study showed that identical serotypes were recovered in carcasses and feces of the same animal in 4% (3/73) of the cases. STEC strains are widespread in Argentina, and infect humans and animals and contaminate food products. Postenteric HUS is endemic, with more than 500 cases reported each year. Different serotypes and genotypes are detected, and the severity of clinical symptoms caused by STEC has been associated with its virulence profile, especially the stx genotype.
Number of HUS cases, incidence rates, and percentages of lethality in Argentina, 1999 to 2008.
Incidence rates (cases per 100,000 children under 5 years old) of HUS in different Argentinean provinces, 2008.
XbaI-PFGE patterns associated with human STEC O157 strains.
Flow chart for the phenotypic and genotypic characterization of STEC strains.
Distribution of STEC O157 (light gray, lower bars) and non-O157 (dark gray, upper bars) strains in human infections in Argentina, 2004 to 2008.
PFGE patterns yielded by STEC O157 strains of human, food, animal, and environmental origin
Outbreaks in Argentina associated with O157 and non-O157 STEC strains
Prevalent STEC O groups of strains detected in food
STEC serotypes isolated from fecal samples from young steers at the abattoir
Comparison of virulence profiles identified in non-O157 STEC isolated from fecal and carcass samples from cattle at the abattoir
Comparison of virulence profiles identified in LEE-negative STEC strains isolated from cattle and humans