1 Clinical and Epidemiological Aspects of Escherichia coli O157H7 in Latin America Alejandro Cravioto M.D. Ph.D Rosario Morales M.D. Ph.D Armando Navarro B.Sc. M.Sc. Faculty of Medicine UNAM Mexico City 2 Dr. Alejandro Cravioto (b. Mexico City 1947) In 1973 Dr. Cravioto received his Medical Degree with honors from the Faculty of Medicine at the National Autonomous University of Mexico. Between 1973 and 1976 he continued his studies in Pediatrics at the National Institute of Pediatrics in Mexico City. In 1977 he received a Diploma in Tropical Public Health and in 1981 a Ph.D. from the London School of Hygiene and Tropical medicine at the University of London. 3 Escherichia coli
The organism Gram negative
non-spore forming rod
Serotypes O H K antigens
- ETEC produce LT and/or ST - EHEC produce Stx toxins
- Enteropathogenic (EPEC)
Enterohemorrhagic (EHEC) HC HUS TTP
Diffusely adherent (DAEC)
5 E. coli O157H7 1982 First recognized as a pathogen 1985 Associated with hemolytic uremic syndrome 1990 Outbreak from drinking water 1991 Outbreak from apple cider 1993 Multi-state outbreak from fast food hamburgers 1995 Outbreak from fresh produce 1996 Outbreak in Japan Multi-state outbreak from unpasteurized apple juice 6 Outbreaks associated with E. coli O157H7 in food products Food product Country 7 E. coli O157H7 - incubation 3 to 9 days - bloody diarrhea renal failure thrombocytopenia - infective dose small to large number of organisms - the young the elderly - dialysis fluid balance hypertension 8 Pathogenesis - EHEC (O157H7) HC HUS TTP - Causes adherence effacing lesions on intestinal cells (HC) - Systemic complications (HUS) acute renal failure - toxin causes death of endothelial cells of glomeruli afferent arterioles narrowing of blood vessels hemolytic anemia thrombocytopenia reduced glomerular filtration kidney tissue necrosis 9 (No Transcript) 10 (No Transcript) 11 Incidence of E. coli O157 infection reported by laboratories (per 100 000 population) 12 Outbreaks of enterohemorrhagic E. coli reported in Japan 13 Incidence of hemolytic-uremic syndrome in children 4 years of age or younger (per 100 000 population) 14 Comparison of EHEC isolation rates from HUS patients in North America Europe and South America a Number of children with EHEC / number of children with HUS whose stool cultures yielded E. coli (). 15 Argentina has one of the highest recorded HUS rates (300 cases/year) in Latin America The risk of HUS in Stx-EC associated bloody diarrhea is about 4-5 with 14 of children developing incomplete HUS A total of 80 of Stx-EC isolated from patients with diarrhea belonged to non-0157 serogroups such as O26 O91 0103 O111 O113 O128 O145 16 Incidence of Shiga-toxin (Stx)-associated illness in Buenos Aires Argentina 17 Children with HUS at the Hospital de Niños Dr. Ricardo Gutierrez Buenos Aires Argentina Age (months) 18 Origin of Shiga toxin-producing Escherichia coli strains Country Serotype Number of Origin Time of Strains
Isolation Argentina Non-O157 8 Healthy steers 1997-1998 7 Healthy calves 1999-2000 O157H7 2 Healthy and diarrheic 1998-1999
hamburger sample 19 Enterohemorrhagic E. coli O157H7 in Latin American Countries 20 In Mexico there have been no reports of HC or HUS associated with O157H7 strains However studies from our laboratory conducted between 1985 and 2003 isolated O157 non-motile or non-H7 strains in approx. 10 of the children studied 21 Escherichia coli O157 strains isolated in Mexico 1985-2003 N 263 22 The responses of 605 human serum samples against O157 LPS and its two cross-reacting LPSs O7 and O116 were analyzed by ELISA. Of the 605 samples 562 came from adolescents or adults and 43 from children of different age groups. 23 Human serum responses against different E. coli LPSs by ELISA test using a cut-off point of 0.7 Serum samples E. coli LPS n() O7 () O116 () O157 () Children 43 1 (2) 5 (12) 2 (5) Adults 562 7 (1) 27 (5) 28 (5) Total 605 8 (1) 32 (5) 30 (5) 24 Comparative responses of sera from children against different E. coli LPSs determined by ELISA test using a cut-off point of gt0.4-0.69 and gt0.7 () E. coli LPS 25 Comparative responses of sera from adults against different E. coli LPSs determined by ELISA test using a cut-off point of gt0.4-0.69 and gt0.7 () E. coli LPS 26 Immune response of human serum samples against E. coli O157 LPS by Western blotting using E. coli O157 LPS developed with rabbit and human serum samples. kDa 27 Immune response of human breast milk samples against E. coli O157 LPS kDa 28 Western blotting analysis of the serum samples with a positive ELISA result (using a cutoff point of gt0.7) showed that 86 (24 of 28) reacted with the O157 LPS. Further studies with breast milk and bovine serum samples showed that 71 and 23 respectively had a similar LPS response to that found in human serum studies. 29 Escherichia coli O157 isolated from Animals in Mexico from 1995-1996 N 132 PCR 30 Heterologous response of bovine serum samples against different LPSs of E. coli N 310 Serum dilutions Positive samples 31 Response of bovine serum samples against O157 and cross-reacting LPSs ELISA cut-off 0.7 DO a 405nm. Serum dilution 1800 32 These results suggest that early colonization by a non-pathogenic E. coli with an LPS that cross-reacts with O157 could be related to a low incidence of HC or HUS in children or adults from developing countries.
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