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ENTEROBACTERIACEAE

ENTEROBACTERIACEAE. General characters: Predominant aerobic bacterial flora of large intestine. Composed of non sporing, nonacid fast, gram negative bacilli. May or may not be capsulated. Motile by peritrichate flagella or non motile.

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ENTEROBACTERIACEAE

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  1. ENTEROBACTERIACEAE

  2. General characters: • Predominant aerobic bacterial flora of large intestine. • Composed of non sporing, nonacid fast, gram negative bacilli. • May or may not be capsulated. • Motile by peritrichate flagella or non motile. • Grow readily in ordinary media. • Ferments glucose, producing acid and gas or acid only. • Reduces nitrates to nitrites. • Form catalase but not oxidase.

  3. CLASSIFICATION: • TRIBE 1: Escherchiae Genus : 1.Escherchia 2.Edwardsiella 3.Citrobacter 4.Salmonella 5.Shigella

  4. TRIBE 2: Klebsiellae Genus : 1.Klebsiella 2.Enterobacter 3.Hafnia 4.Serratia

  5. TRIBE 3: Proteae Genus : 1.Proteus 2.Morganella 3.Providencia • TRIBE 4: Erwinieae Genus : Erwinia

  6. ESCHERICHIA COLI • Parasite living only in human or animal intestine • Voided in faeces and remain viable for some days only • Detection of E.coli in drinking water – recent pollution with or human or animal faeces

  7. MORPHOLOGY: • Gram negative, straight rods • size 1-3x0.4-0.7 microns • Arrangement-singles/pairs • Motility-Peritrichious flagella some are non motile • Some strains are Capsulated and Fimbriated • Non sporing

  8. CULTURAL CHARACTERISTICS: • Aerobe and facultative anaerobe • Temp.range 10-40c optimum :37c • Good growth occurs on ordinary media • Growth inhibited on selective media-DCA/SS agar • In broth turbid growth occurs

  9. COLONY MORHOLOGY: • 2 Types of colonies are observed • 1.Smooth colonies: Large,thick,greyish white, moist,smooth or partially translucent discs. • 2.Rough colonies: colonies are irregular,dull surface and are often auto agglutinable.

  10. ON BLOOD AGAR: Hemolytic colonies seen. • ON MAC CONKEY AGAR: Bright pink colonies seen due to lactose fermentation.

  11. BIOCHEMICAL REACTIONS: • Catalase : positive • Oxidase : negative • Indole : positive • Methylred: positive • VP : negative • Citrate : negative

  12. SUGAR FERMENTATION TESTS: • Glucose : positive • Lactose : positive • Mannitol: positive • Maltose : positive

  13. Gelatin liquefaction : negative • H2s production test : negative • Urease test : negative • Growth does not occur in KCN media

  14. ANTIGENIC STRUCTURE: • Serotyping done based on 3 antigens 1.SOMATIC antigen “O” 2.CAPSULAR antigen”K” 3.FLAGELLAR antigen”H”

  15. “K” ANTIGEN: • Acid polysaccharide antigen located in envelope • Encloses “O” Ag • Contributes virulence by inhibiting phagocytosis Thermolabile ‘L’ Ag • “K” Ag ‘A’ Ag Thermostabile ‘B’ Ag

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