Intro to Enterobacteriaceae - Morphological characteristics - Classification - Biochemical properties - Determinants of pathogenicity - Mediums used - Biochemical tests - Treatments
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Gram staining & Morphology
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Gram-negative non-sporing bacilli
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Motile or non-motile
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Flagella
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Peritrichous or Monotrichous
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Well-defined capsule
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Negatively stained
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Attachment
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Fimbrae or Pili
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Complex cell wall
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Outer Membrane and Thick Peptidoglycan
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Family
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Enterobacteriaceae
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Genus
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Escherichia, Shigella, Salmonella, Citrobacter, Klebsiella, Enterobacter, Erwinia, Serratia, Hafnia, Edwardsiella, Proteus, Providencia, Morganella, Yersinia
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ENDOTOXIN
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Lipopolysaccharide
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- O polysaccharide
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- Lipid A (toxic)
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EXOTOXIN
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1. ENTEROTOXIN
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Subunit A induces cAMP formation
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- Normal contractions -> severe diarrhea
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Subunit B attaches to plasma membrane of epithelial cells in small intestine
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2. SHIGA TOXIN
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Subunit A modifies RNA to inactivate it
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- Inhibits protein synthesis by inactivation of 60S ribosomes
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Subunit B binds to globotriaosylceramide (GB3)
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3. VEROTOXIN (Shiga-like)
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Facultative Anaerobes
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Ferments Glucose to Acid
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Lactose Fermenters or Non-Lactose Fermenters
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No Cytochrome Oxidase
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Oxidase Test
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Oxidase negative (colorless)
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tetramethyl-p-phenylenediamine dihydrochloride -> bacterial colonies -> colorless (-)
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positive reaction = formation of purple ring
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Reduces Nitrate to Nitrite
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Red color (+)
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