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Clinical and Epidemiological Aspects of Escherichia coli O157:H7 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. Dr. Alejandro Cravioto (b. Mexico City,

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Clinical and Epidemiological Aspects of Escherichia coli O157:H7 in Latin America

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Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Clinical and Epidemiological Aspects of Escherichia coli O157:H7 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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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.


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

  • Generally harmless

  • Pathogenic groups

  • - Enteropathogenic (EPEC)

    • Enterotoxigenic (ETEC)

    • Enterohemorrhagic (EHEC) – HC, HUS, TTP

    • Enteroinvasive (EIEC)

    • Enteroaggregative (EAEC)

    • Diffusely adherent (DAEC)


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

E. coli O157:H7

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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Outbreaks associated with E. coli O157:H7 in food products

Food product

Country


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

E. coliO157: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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

  • 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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Incidence of E. coli O157 infection

reported by laboratories

(per 100 000 population)


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Outbreaks of enterohemorrhagic

E. coli reported in Japan


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Incidence of hemolytic-uremic syndrome in children 4 years of age or younger

(per 100 000 population)


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Comparison of EHEC isolation rates from HUS patients in North America, Europe, and South America

aNumber of children with EHEC / number of children with HUS

whose stool cultures yielded E. coli (%).


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Incidence of Shiga-toxin (Stx)-associated illness in Buenos Aires, Argentina


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Children with HUS at the

Hospital de Niños, Dr. Ricardo Gutierrez, Buenos Aires, Argentina

Age (months)


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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:H72 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 1996-2000

Brazil 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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Enterohemorrhagic E. coli O157:H7 in

Latin American Countries


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Escherichia coli O157 strains isolated in

Mexico 1985-2003

N= 263


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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.


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Human serum responses against different E. coli LPS’s by ELISA test using a cut-off point of 0.7

Serum samplesE. 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)


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Immune response of human breast milk samples against E. coli O157 LPS

kDa


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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.


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Escherichia coli O157 isolated from

Animals in Mexico from 1995-1996

N= 132

* PCR


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

Heterologous response of bovine serum samples against different LPS’s of E. coli

N= 310

Serum dilutions

Positive samples


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

N=310

LPS

Response of bovine serum samples

against O157 and cross-reacting LPS’s

ELISA cut-off: 0.7 DO a 405nm.

Serum dilution: 1:800


Clinical and epidemiological aspects of escherichia coli o157 h7 in latin america

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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