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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 coli1
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.
slide3

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.
slide4

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.
slide7

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.
slide8

It causes pathogenesis by.

  • Piliand capsule
  • Endotoxin.
  • Three exotoxins (enterotoxins).
  • Labile toxin
  • Stable toxin
  • Verotoxin that causes bloody diarrhea and hemolytic-uremic syndrome.
slide9

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.
slide10

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.
slide11

Hemorrhagic colitis: A severe form of bloody diarrohea.

  • Hemolytic uremic syndrome. A potentially life-threatening acute renal failure.
slide12

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.
slide13

The K (capsular) antigen is particularly associated.

  • Nosocomial (hospital-acquired) infections: These include sepsis endotoxic shock, and pneumonia.
slide14

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.