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Escherichia coli

Escherichia coli. Escherichia coli . Named for Theodor Escherich a German physician (1885) Normal flora of the mouth and intestine. Protects the intestinal tract from bacterial infection. Produces small amounts of vitamins B 12 and K

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Escherichia coli

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  1. Escherichia coli

  2. Escherichia coli • Named for Theodor Escherich a German physician (1885) • Normal flora of the mouth and intestine. • Protects the intestinal tract from bacterial infection. • Produces small amounts of vitamins B12 and K • Colonizes newborns GI tract within hours after birth.

  3. Properties: • Gram-negative short rod. • Facultative anaerobe • Member of the Enterobacteriaceaefamily. • It is present normally in high concentrations (108/g) in normal human feces. • Motile and ferments lactose.

  4. It has three antigens • O, or cell wall, antigen • H, or flagellar, antigen • K, or capsular, antigen. • Diseases in general: • Urinary tract infection (UTI), Sepsis, Neonatal meningitis, and "traveler's diarrhea" are most common.

  5. E.coli

  6. Pathogenesis: • Reservoir: • Humans and animals( cattle). • The source of E. coli that causes UTI is the patient's own colonic flora. • The source of E. coli that causes neonatal meningitis is the mother's birth canal. • E. coli that causes traveler's diarrhea is acquired by ingestion of contaminated food or water.

  7. It causes pathogenesis by. • Piliand capsule • Endotoxin. • Three exotoxins (enterotoxins). • Labile toxin • Stable toxin • Verotoxin that causes bloody diarrhea and hemolytic-uremic syndrome.

  8. Clinical disease: • Intestinal: • Caused by four different strains • Enteropathogenic E coli • Watery diarrhea primarily in infants by endotoxin. • Enterotoxigenic Escherichia Coli Causes traveler's diarrhea in all age-groups. • Two enterotoxins are responsible for traveler diarrhea. • The heat-labile toxin (LT) stimulates adenylate cyclase.

  9. It in turn causes increased cyclic AMP which causes outflow of chloride ions and water, resulting in diarrhea. • The heat-stable toxin (ST) causes diarrhea by stimulating guanylate cyclase. • Enterohemorrhagic Escherichia Coli Causes Hemorrhagic Colitis and Hemolytic-Uremic Syndrome. • Verotoxin (a cytotoxin) responsible for hemorrhagic colitis and hemolytic uremic syndrome.

  10. Hemorrhagic colitis: A severe form of bloody diarrohea. • Hemolytic uremic syndrome. A potentially life-threatening acute renal failure.

  11. D.Enteroinvasive E. coil • Cause a dysentery-like syndrome with fever and bloody stools. • Extraintestinal disease: • UTI. E. coil is the most common cause of cystitis and pyelonephritis. Women are particularly at risk for infection. • Neonatal meningitis: E. coli is a major cause of disease occurring within the first month of life.

  12. The K (capsular) antigen is particularly associated. • Nosocomial (hospital-acquired) infections: These include sepsis endotoxic shock, and pneumonia.

  13. Laboratory Diagnosis: • Specimens suspected of containing E. coli, are grown on • A blood agar plate and • On a differential medium, such as EMB agar or MacConkey's agar. • E. coli, which ferments lactose, forms pink colonies, whereas lactose-negative organisms are colorless.

  14. Pure culture of E.coli. 

  15. Detection from stool is difficult but easier from specimens like CSF and urine

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