Sin ttulo de diapositiva

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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
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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.
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Escherichia coli

• The organism Gram negative,
• non-spore forming rod,
• Fam. Enterobacteriacea
  
• (aerobic/facultatively anaerobic)
• Serotypes O, H K antigens
• Toxins
• - ETEC produce LT and/or ST -
  EHEC produce Stx toxins

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• Generally harmless
• Pathogenic groups
• - Enteropathogenic (EPEC)
• Enterotoxigenic (ETEC)
• Enterohemorrhagic (EHEC) HC, HUS, TTP
• Enteroinvasive (EIEC)
• Enteroaggregative (EAEC)
• Diffusely adherent (DAEC)

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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
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Outbreaks associated with E. coli O157H7 in
food products
Food product
Country
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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
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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
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Incidence of E. coli O157 infection reported by
laboratories (per 100 000 population)
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Outbreaks of enterohemorrhagic E. coli reported
in Japan
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Incidence of hemolytic-uremic syndrome
in children 4 years of age or younger
(per 100 000 population)
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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 ().
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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
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Incidence of Shiga-toxin (Stx)-associated illness
in Buenos Aires, Argentina
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Children with HUS at the Hospital de Niños, Dr.
Ricardo Gutierrez, Buenos Aires, Argentina
Age (months)
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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

Veal Holstein calves
Non-O157 9 Frozen
Hamburgers 1998-2000
1
soft cheese sample
O157H7 6 Ground
beef sample 2000
Non-O157 1
O157H7 1 0
Animal and meat sample
1996-2000 Brazil O157H7 3
Healthy calves, heifers
1996-1997
and cows
Non-O157 4
O157NM 1
Calves with diarrhea Unknown
Non-O157 3
Non-O157
9 Ground beef and
1995-1996

hamburger sample
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Enterohemorrhagic E. coli O157H7 in Latin
American Countries
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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
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Escherichia coli O157 strains isolated in Mexico
1985-2003
N 263
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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.
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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)
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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
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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
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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
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Immune response of human breast milk samples
against E. coli O157 LPS
kDa
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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.
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Escherichia coli O157 isolated from Animals in
Mexico from 1995-1996
N 132
PCR
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Heterologous response of bovine serum samples
against different LPSs of E. coli
N 310
Serum dilutions
Positive samples
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Response of bovine serum samples against O157
and cross-reacting LPSs
ELISA cut-off 0.7 DO a 405nm. Serum dilution
1800
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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.