review from my seminar paper

1. HARAMAYA UNIVERSITY
COLLEGE OF VETERINARY MEDICINE
Power point presentation of REVIEW ON ESCHERICHIA
COLI O157:H7 GIVEN EMPHASIS IN ETHIOPIA: AN
EMERGING FOODBORNE PATHOGEN
Prepared by: EBA TEFERI

2. REVIEW ON ESCHERICHIA COLI O157:H7 GIVEN
EMPHASIS IN ETHIOPIA: AN EMERGING FOODBORNE
PATHOGEN
Overview
Introduction
Taxonomy
Morphology
Characteristics
Epidemiology
Pathogenesis
Clinical Significance
Diagnostic Methods
Risk Factors
Antimicrobial Resistance
Conclusion and Recommendations

3. INTRODUCTION
• Food-borne diseases are important public health and economic burden.
• Result in considerable morbidity and mortality rate.
• The severity is higher among developing countries due to:-
Changes in eating habits and widespread habit of raw beef
consumption
Poor food handling and sanitation practices
Inadequate food safety laws, weak regulatory systems,
Lack of financial resources and
Lack of awareness about proper food handling which creates a
conducive environment for the spread of food-borne and food
poisoning etiologic agents.

4. CON’T…
Escherichia coli is among the most challenging Enterobacteriaceae group of
bacterial meat contaminant worldwide.
Most E. coli strains do not cause diseases and are actually part of the normal flora.
Some strains of E. coli such as E. coli O157:H7 are capable of producing disease
when the immune system is compromised or as a result from an environmental
exposure.
Among the intestinal pathogens there are six well-described E. coli categories:
entero-pathogenic E. coli(EPEC),
entero-haemorrhagic E. coli (EHEC),
entero-toxigenic E. coli (ETEC),
entero-aggregative E. coli(EAEC),
entero-invasive E. coli (EIEC) and
diffusely adherent E. coli (DAEC).

5. CONT…
• E. coli serotype O157:H7 is:-
an enterohaemorrhagic strain.
initially recognized in the United States of America as a cause of food-
borne illness and
has now emerged as an important enteric pathogen of considerable
public health significance.
• In Ethiopia, E. coli O157:H7 was isolated from:-
 different sample sources
 humans
 food animals and
 contact surfaces
• Most of the studies also showed that E. coli O157:H7 isolated to be resistant to
varieties of antimicrobial agents.
Therefore the objective of this paper is to review on a foodborne pathogen E.
coli O157:H7.

6. ESCHERICHIA COLI O157:H7: AN EMERGING FOODBORNE
PATHOGEN
Taxonomy
• Escherichia coli is:-
The most common species of facultative anaerobe.
Belongs to family Enterobacteriaceae Genus Escherichia and Species coli
Has a number of serovars (160 antigenic types O, 56 types H, 80 types K/Vi).
Morphology
• Escherichia coli are:-
 Gram negative bacteria
 Facultative anaerobic
 Non sporulating organism
 The cells are about 2μm long and 0.5μm in diameter
 Some strains possess flagella and motile. Eg: O157: H7 strain

7. CON’T…

8. Characteristics of E. coli O157: H7
• Escherichia coli can be characterized by stereotyping.
• The serotype is defined by :-
 O-antigen (Ohne),
 Lipopolysaccharide (LPS) in the outer membrane, and
 H-antigen (Hauch) consisting of flagella protein.
• May also include the K antigen (Kapsel) and the F-antigen (Fimbriae).
• The three phenotypic differences between E. coli O157:H7 and other
E. coli are:-
 inability to ferment sorbitol,
 lack of β–glucuronidase enzyme and
 weak or no growth at temperatures above 44 °C.

9. Epidemiology of E. coli O157:H7
• Escherichia coli O157:H7 infections occur worldwide.
Reservoir of infections
• Livestock are the most important reservoir of E. coli O157:H7.
• Cattle being the principal sources, followed by sheep and goat.
Mode of Transmission
 via fecal-oral route.
Fecal contamination of other food products.
Consumption of contaminated food and water.
 direct contact with infected animals.

10. Pathogenesis
• The pathogenicity of E. coli O157:H7 is associated with a number of
virulence factors;-
 Locus of Enterocyte Effacement (LEE),
 Shiga toxins (Stx) and
 The plasmid (pO157)

11. Clinical Significance of E. coli O157:H7 in Humans and
Farm Animals
In Humans
• It forms three types of syndromes:-
hemorrhagic colitis (HC),
hemolyticuremic syndrome (HUS) and
thrombocytic thrombocytopenic purpura (TTP).
• Extra renal signs including CNS involvement with lethargy, irritability
and seizures are common.
• Adhesion of bacteria to the host bowel mucosa induces subsequent
histo-pathologic lesion defined as “attaching and effacing” (A/E).

12. In Livestock
• Escherichia coli causes, three main kinds of disease in animals:-
 urinary tract infections
 neonatal meningitis and
 diarrheal diseases.
• They are mostly associated with colibacillosis in neonate.
• In addition, EHEC O157:H7 causes:-
• more rapid and severe neurological disease in suckling neonates.
• edema disease in pig
• haemorrhagic entero colitis in calves and
• post weaning diarrhoea in pigs.
CON’T…

13. Escherichia coli O157:H7 Identified From Apparently
Health and Foods of Animal Origin
E. coli O157:H7 isolated from food animal
• Food of animal origin (milk and meat) can become contaminated with
bacteria during food processing or slaughtering.
• Contaminated raw milk and undercooked beef products were
implicated in outbreaks of E. coli O157:H7 infections.
• Cattle are the primary reservoir of E. coli O157:H7 and an important
source of human infection and
• Undercooked ground beef and unpasteurized milk being common
vehicles of the pathogen transmission.

14. CON’T…
E. coli O157:H7 isolated from poultry
• Poultry meat sometimes has E. coli O157:H7 on its surface and
• These bacteria do persist in the ceca of experimentally infected chicks
for as long as 11 months.
• Escherichia species in liquid egg products are of major public health
concern.

15. Diagnostic Methods used for identification of E. coli
O157:H7 in Ethiopia
• Researchers in Ethiopia reported the use of several bacterial isolation
procedures.
Isolation of the agent on general media.
eg. McConkey, followed by EMB and biochemical methods.
Very few of them use tests such as molecular biology based
technologies such as:
polymerase chain reaction (PCR).
• There is no single technique that can be used to isolate all EHEC
serotypes.

16. Risk Factors Associated With Occurrence of E.coli
O157:H7 in Animals and Animal Products
• Understanding the epidemiology of this organism requires knowledge
of:-
where these bacteria live and grow in nature (their reservoir)
and
how humans come into contact with them.
• Ruminants have been identified as the major reservoir of E.coli
O157:H7.
• Animals acquired these bacteria from meat, foods or water
contaminated by fecal material from ruminants.
• Raw meat and its products are commonly consumed in traditional
Ethiopian diets.

17. Antimicrobial Resistance Patterns of E. coli O157:H7
Isolates in Ethiopia
• Antibiotics are commonly used in livestock for the treatment,
prevention of disease and to increase growth.
• Antibiotic resistance is the result of inappropriate antibiotic use.
• Most of antimicrobials are not commonly used in Ethiopia in the
treatment of animals that served as a source of meat.
• The susceptibility might have contributed to the effectiveness of these
antimicrobials mostly against Gram negative bacteria.
• From recent studies all of the E. coli O157:H7 isolates were resistant
to Amoxicillin while intermediate resistance to Cefoxitine and
Nitrofurantoin.

18. CONCLUSION AND RECOMMENDATIONS
• Escherichia coli is a food borne pathogen causing a major public
health problem in Ethiopia.
• The agents was present in the feces, intestinal mucosal swab, carcasses
swab and cut board at municipal abattoir and butcher houses.
• This pathogen was isolated from carcasses, from the inside parts that
indicated the presence of carcass contamination during slaughter
operations and at the butcher house the presence of E. coli O157: H7
due to environmental contamination.
• The use of antimicrobials in food animals produces resistant bacteria.
• These type of bacteria were susceptible to most of the drugs used and
multi drug resistance was occurred obviously.

19. CON’T…
Based on the above conclusions the following recommendations are forwarded:-
 A thorough hygienic practice should be considered at the time of slaughtering of
animals.
 Hazard Analysis of Critical Control Points at every stage of the meat supply
chain, from the farm through to the abattoir, the retailer, and to those involved
with the handling to and processing of such raw food items products in the home
environment should be practiced.
 Additionally targeted intervention strategies or technologies, like E. coli vaccine
or feed additives and awareness creation to the public on sanitary practices should
be applied.
 Study on E. coli and its characteristics with an aim to reduce the human hazard
caused by this emerging pathogen is highly needed.
 Public health regulatory agency has to be in place to ensure wholesomeness and
safety of food of animal origin for human consumption.

20. THANK YOU
FOR
YOUR PATIENCE!!!.