Clinical and Epidemiological Aspects of Escherichia coli
O157:H7 in Latin America
Alejandro Cravioto, M.D., Ph.DRosario Morales, M.D., Ph.D
Armando Navarro, B.Sc., M.Sc.Faculty of Medicine, UNAM
Mexico City
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.
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
• Generally harmless
• Pathogenic groups
- Enteropathogenic (EPEC)
– Enterotoxigenic (ETEC)
– Enterohemorrhagic (EHEC) – HC, HUS, TTP
– Enteroinvasive (EIEC)
– Enteroaggregative (EAEC)
– Diffusely adherent (DAEC)
E. coli O157:H71982 – First recognized as a pathogen1985 – Associated with hemolytic uremic syndrome1990 – Outbreak from drinking water1991 – Outbreak from apple cider1993 – Multi-state outbreak from fast food hamburgers1995 – Outbreak from fresh produce1996 – Outbreak in Japan – Multi-state outbreak from
unpasteurized apple juice
Meat
General
foods
Lacteous
Ground beef
Hamburger
Roast Beef
Cooked beef products
Fermented sausage
Turkey roll
Apple cider
Mayonnaise
Vegetables
Raw milk
Pasteurised milk
Yoghurt
Cheese
USA, Brasil, Argentina,
Uruguay
USA, Canada, England, Japan
USA
Scotland
USA
England
USA
USA
USA, England, Japan
USA, Canada, England and
Scotland
Scotland
England
Scotland
Outbreaks associated with E. coli O157:H7 in food products
Food product Country
E. coli O157:H7
- 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
Pathogenesis - EHEC (O157:H7) – 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
1990 1991 1992 1993 Scotland 3.4
(2.9-3.9) 4.0
(3.4-4.6) 2.3
(1.9-2.7) 2.4
(2.0-2.8) Wales 1.1
(0.7-1.5) 1.4
(0.96-1.8) 1.4
(0.96-1.8) 1.1
(0.7-1.5) England 0.5
(0.44-0.56) 0.7
(0.62-.078) 0.9
(0.82-.098) 0.7
(0.62-.078) (95% confidence interval)
Incidence of E. coli O157 infection reported by laboratories
(per 100 000 population)
City Cases HUS
Oku-cho, Okayama (May, 1996)
468 2
Sakai City, Osaka (July, 1996)
6561 101
Kyoto (July, 1996)
47 3
Outbreaks of enterohemorrhagic E. coli reported in Japan
Incidence of hemolytic-uremic syndrome in children 4 years of age or younger
(per 100 000 population)
Country HUS patients Controls P
Canada
Argentina
United Kingdom
Chile
12 / 40 (30)
4 /51 (8)
52 / 196 (26.5)
6 / 20 (30)
0 / 40 (0)
0 /25 (0)
2 /51 (3.9)
2 / 38 (5.3)
0.00019
0.30
0.00012
0.0158
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 (%).
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
Period No. of Cases
Mean Range Cases Admitted
1957-1961 32 12.8 4.5-36 6
1962-1966 130 12.2 2-60 26
1967-1972 16 13.2 2-180 86
1982-1986 273 20.4 3-84 55
1987-1996 897 14.8 6-36 50
1997-1998 80 20.8 5-108 40
Children with HUS at the Hospital de Niños, Dr. Ricardo Gutierrez,
Buenos Aires, ArgentinaAge (months)
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
O157:H7 2 Healthy and diarrheic 1998-1999
Veal Holstein calves Non-O157 9 Frozen Hamburgers 1998-2000 1 soft cheese sample O157:H7 6 Ground beef sample 2000 Non-O157 1 O157:H7 1 0 Animal and meat sample 1996-2000Brazil O157:H7 3 Healthy calves, heifers 1996-1997 and cows Non-O157 4 O157:NM 1 Calves with diarrhea Unknown Non-O157 3 Non-O157 9 Ground beef and 1995-1996 hamburger sample
Country Cases Brazil (2002)
First case of HUS
Brazil (1990, 2001)
3 Sporadic cases
Colombia (1996-1997)
3/39 (8% ) cases HUS 20/307 (7.0% ) from cattle
Costa Rica
5 Isolated from chicken giblets and raw milk
Enterohemorrhagic E. coli O157:H7 in Latin American Countries
In Mexico, there have been no reports of HC or HUS associated with O157:H7 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
Origin Number of isolation
Serotype Sorbitol Vero-toxin
SLT1-2
Children < 2 years of
age 1985-1987
18 4 1
O157:NM O157:H10 O157:H28
+ + -
- ¼ -
- - -
Children < 5 years of
age 1988
2
O157:NM
+
-
-
Adult emigrant BCN 1995
1
O157:H7
-
+
+
Children < 5 years of
age 1996-2003
8
O157:NM
+
N/D
+
TOTAL 34/263 (13)
ND Not determinated
Escherichia coli O157 strains isolated in Mexico 1985-2003
N= 263
The responses of 605 human serumsamples against O157 LPS and its two cross-reacting LPSs, O7 and O116, were analyzed by ELISA.
Of the 605 samples, 562 came fromadolescents or adults and 43 from children of different age groups.
Human serum responses against different E. coli LPS’s 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)
05
101520253035404550
O7 O116 O157
>0.4
>0.7
Comparative responses of sera from children against different E. coli LPS’s
determined by ELISA test using a cut-off point of >0.4-0.69 and >0.7
E. coli LPS
(%)
0
5
10
15
20
25
O7 O116 O157
>0.4
>0.7
Comparative responses of sera from adults against different E. coli LPS’s determined by ELISA test using a cut-off point of >0.4-0.69
and >0.7
E. coli LPS
(%)
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
Western blotting analysis of the serum samples with a positive ELISA result (using a cutoff point of >0.7) 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.
Origin strain isolation
(%)
Serotype Sorbitol VERO-toxin
SLT1-2
Pork 1995
1/36 (3) O157:NM + - -
Bovine 1996
3/96 (3)
O157:NM
-
2/3
+
Escherichia coli O157 isolated from Animals in Mexico from 1995-1996
N= 132
Heterologous response of bovine serum samples against different LPS’s of E. coli
N= 310 LPS
80 160 320 640 1280 TOTAL (%)
O7 91 91 57 20 1 259 (84)
O116 59 133 82 19 3 296 (96)
O157 108 84 28 220 (71)
Serum dilutions
Positive samples
O7 (%)
90 (29)
O116 (%)
38 (12)
O157 (%)
70 (23)
TOTAL
198
Response of bovine serum samples
against O157 and cross-reacting LPS’s
LPSN=310
ELISA cut-off: 0.7 DO a 405nm.
Serum dilution: 1:800
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