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Escherichia coli. Named for Theodor Escherich a German physician (1885) Normal flora of the mouth and intestine. Protects the intestinal tract from bacterial.

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Presentation on theme: "Escherichia coli. Named for Theodor Escherich a German physician (1885) Normal flora of the mouth and intestine. Protects the intestinal tract from bacterial."— Presentation transcript:

1 Escherichia coli

2 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 Colonizes newborns GI tract within hours after birth.

3  Properties:  Gram-negative short rod.  Facultative anaerobe  Member of the Enterobacteriaceae family.  It is present normally in high concentrations (10 8 /g) in normal human feces.  Motile and ferments lactose.

4  It has three antigens 1. O, or cell wall, antigen 2. H, or flagellar, antigen 3. 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

7  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.

8  It causes pathogenesis by. I. Pili and capsule II. Endotoxin. III. Three exotoxins (enterotoxins). 1. Labile toxin 2. Stable toxin 3. Verotoxin that causes bloody diarrhea and hemolytic-uremic syndrome.

9  Clinical disease:  Intestinal:  Caused by four different strains A. Enteropathogenic E coli  Watery diarrhea primarily in infants by endotoxin. B. Enterotoxigenic Escherichia Coli Causes traveler's diarrhea in all age-groups.  Two enterotoxins are responsible for traveler diarrhea. 1. The heat-labile toxin (LT) stimulates adenylate cyclase.

10 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. C. Enterohemorrhagic Escherichia Coli Causes Hemorrhagic Colitis and Hemolytic-Uremic Syndrome.  Verotoxin (a cytotoxin) responsible for hemorrhagic colitis and hemolytic uremic syndrome.

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

12 D. Enteroinvasive E. coil  Cause a dysentery-like syndrome with fever and bloody stools.  Extraintestinal disease: 1. UTI. E. coil is the most common cause of cystitis and pyelonephritis. Women are particularly at risk for infection. 2. Neonatal meningitis: E. coli is a major cause of disease occurring within the first month of life.

13  The K (capsular) antigen is particularly associated. 3. Nosocomial (hospital-acquired) infections: These include sepsis endotoxic shock, and pneumonia.

14  Laboratory Diagnosis:  Specimens suspected of containing E. coli, are grown on 1. A blood agar plate and 2. 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.

15 Pure culture of E.coli.

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


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