Disease of the Day - E. coli O157:H7

Background of disease

Emerging infectious disease

Caused by Escherichia coli O157:H7

Strain of E. coli that was initially isolated in Argentina in 1977

Causes of illness in 1982 during outbreak of severe bloody diarrhea

• Contaminated Hamburgers

• Sometimes referred to “Hamburger disease”

Most strains of E. coli are harmless and live in the intestines of healthy humans

• Part of Normal Microbiota

Escherichia coli O157:H7

Gram negative

Rod Shaped

Facultative anaerobe

Has Flagella

In the name Escherichia coli O157:H7

O refers to the antigen associated with the lipopolysaccharide

H refers to the flagellar antigen

Main Problem

Toxin

Strain produces a “shiga-like” toxins

Toxin starts by destroying cells which line the large intestine

Escapes into the blood stream and kills erythrocytes

Damages endothelial cells lining the blood vessels

Only need about 100 organisms to cause disease - can resist acidic conditions of stomach

Signs and Symptoms

Abdominal cramps + diarrhea

Progress to bloody diarrhea (hemorrhagic colitis)

Maybe fever and vomiting (rare)

Illness resolves in 5-10 days

Severe - Haemolytic uraemic syndrome

Haemolytic Uraemic Syndrome (HUS)

5-10% of all infections develop into this

• Children under 5 and the elderly

• Red blood cells are destroyed and the kidneys fail

Diagnosis

Isolation of E. coli in stool sample grown with Sorbitol MacConkey (SMAC) agar

• Selective - Inhibits the growth of the Gram positive microbial flora

• Differential - Cannot utilize sorbitol on plate, therefore, not red

Source

Reservoirs of this pathogen appears to be mainly cattle - can be up to 50% of feedlot cattle

• Organisms can be mixed into beef when its ground

Dried cured salami

Unpasteurized fresh-pressed apple cider

Yogurt, cheese and unpasteurized milk

Fruits and vegetables (sprouts, lettuce, coleslaw, salad)

Swimming in or drinking sewage-contaminated water

Petting zoos

Prevention

Cook meat thoroughly and do not eat undercooked meat - 72C (160F)

Avoid spreading harmful bacteria in your kitchen

Drink only pasteurized milk, juice, or cider

Wash fruits and veggies thoroughly

Importance

Estimated 73,000 cases of infections and 61 deaths yearly in the US

Effect on Jack in the Box - Blamed for E. coli outbreak, lost 140 million