BACTE MODULE 4

• Escherichia

   These microbes constitute the major

  microflora of the gastrointestinal tract

   They have the ability to become

  opportunistic microbes in almost all

  species of animals

   Predisposition to septicemic diseases,

  enterotoxigenic diarrhea and edema

  disease
• Species of Escherichia associated with animal infections

  E. coli
• Morphology, staining features and cellular composition OF Escherichia

   Gram-negative rods

   Non-spore former, some strains are capsulated

   Strains are motile by means of peritrichous

  flagella (H-antigens)

   Invasive strains possess capsular polysaccharides

  (K-antigens)

   K antigens inhibit attachment of the pathogen to

  phagocytic cells and ingestion by host cells
• Growth characteristics of Escherichia

  • The organism grows on all ordinary

  media

  • Some strains are aerobes while some are

  facultative anaerobes

  • Positive for indole, nitrate and urease

  • Does not ferment sorbitol (E. coli 0157: H7)
• Reservoir of Infection of Escherichia

  • Environment infected with fecal

  materials

  • Carrier animals

  Transmission

  • Feco-oral route
• Strains of Escherichia associated with animal

  infections

  (Diarrhea and Colibacillosis)

  1. Enterotoxigenic strains (ETEC) - neonatal piglets,

  and weanlings

  2. Entero-invasive strains (EIEC) – neonates that

  received inadequate amount of colostrum

  3. Enteropathogenic strains (EPEC) – diarrhea in

  animals with attaching and effacing lesions in the

  intestinal tract

  4. Enterohemorrhagic strains (EHEC)- associated

  with Edema and enterotoxemia and it involves

  release of a vasotoxin

  5. Colibacillosis of fowls- debilitation and chronic

  diarrhea

  6. Extra-intestinal pathogenic E. coli (ExPEC)
• Colibacillosis of fowls

  • Marked by debilitation and chronic

  diarrhea

  • Fulminating septicemia

  • Complicated by respiratory

  infections

  • Associated with salpingitis,

  synovitis and panophthalmitis
• E. coli infection of swine

  (Swine Colibacillosis)

   Marked by colonic malabsorption

  3 Distinct manifestations

  • Neonatal E. coli enteritis (1-4 days old piglets)

  • Weanling enteritis (enteritis occurs shortly after

  weaning, entero-toxemia cases)

  • Edema disease (diarrhea, associated with age,

  change in feed)
• E. coli infection of cattle

  (Colibacillosis of Cattle)

   Enteric disease (white scours) in

  calves during the first week life
• E. coli infection of lambs

  (Colibacillosis of lambs)

  • Enteric form occurs in lambs 2-8

  days old

  • Caused by the proliferation of

  entero-pathogenic, non-invasive

  strains of E. coli in the upper

  small intestines
• E. coli infection of horses

  (Colibacillosis of horses)

  • Accounts for approximately 1% of

  abortion cases

  • Observed in mares and about 25%

  in infected foals
• E. coli infection of dogs

  • Bacteremia implicated in

  “fading puppy syndrome”
• E. coli infection of poultry

  E. coli is rarely implicated in avian

  diarrheal diseases
• E. coli infection of Rabbits

  • Cellulitis accompanied by

  dysentery and high mortality
• Virulence Factors of Escherichia

   Surface structures expressed as O (somatic), K

  (Capsular), H (flagellar) and F (fimbrial) antigens

  attack complement cascade

   Plasmid- encoded heat-labile (LT) and heat-stable

  (ST) enterotoxins

   Edema disease toxin

   Vasotoxin (edema disease)

   Lipopolysaccharide from the outer membrane

   Adhesins (adherence to target cells of the GI tract)

   Siderophores, Shiga-like toxins (verotoxin)

   Cytotoxic necrotizing factors

   Hemolysin
• Laboratory diagnosis of Escherichia

  Samples: Stools

  Agent identification

   Bacterial isolation (MacConkey, Minca medium and

  E media

   Quantification of E. coli in the small

  intestines

   ELISA for ST and LT enterotoxin

   DNA probes for genes encoding enterotoxins

   PCR specific for E. coli trait

   Detection of genes associated with EPEC
• Treatment of Escherichia

  • Apramycin

  • Chloramphenicol

  • Spectinomycin

  • Gentamycin

  • Trimethoprim-sulfamethazole

  • Ceftiofur

  • Correction of fluid and electrolyte imbalance

  Prevention and Control

  Vaccination of gilts and sows with

  fimbrial K88 antigens

  Administration of heat-inactivated

  bacterins

  Good husbandry practice