18. Enterobacter aerogenes (left) – E. coli (bright red) + Reagent: Methyl red indicator identifies pH change due to mixed acid fermentation Methyl Red (MR) (IMViC tests)
19. Enterobacter aerogenes +(left) E. coli – (right) Barritt’s reagent Tests for acetoin, precursor to 2,3 butanediol fermentation Voges – Proskauer (VP) (IMViC tests)
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22. INTERPRETATION OF TUBES ABOVE TUBE 1 (UNINOCULATED) TUBE 2 TUBE 3 TUBE 4 TUBE 5 SLANT - A A K K BUTT - A A A A HYDROGEN SULFIDE - - - + + GAS - - + - - A=Acidic K=Alkaline
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33. Gastroenteritis Caused by Escherichia coli A/E, Attachment/effacement. Organism Site of Action Disease Pathogenesis Enteropathogenic E. coli (EPEC) Small intestine Infant diarrhea in underdeveloped countries; watery diarrhea and vomiting, nonbloody stools Plasmid-mediated A/E histopathology with disruption of normal microvillus structure resulting in malabsorption and diarrhea Enterotoxigenic E. coli (ETEC) Small intestine Traveler's diarrhea; infant diarrhea in developing countries; watery diarrhea, vomiting, cramps, nausea, low-grade fever Plasmid-mediated, heat-stable and/or heat-labile enterotoxins that stimulate hypersecretion of fluids and electrolytes Enterohemorrhagic E. coli (EHEC) Large intestine Initial watery diarrhea, followed by grossly bloody diarrhea (hemorrhagic colitis) with abdominal cramps; little or no fever; may progress to hemolytic uremic syndrome (HUS) Mediated by cytotoxic Shiga toxins (Stx-1, Stx-2), which disrupt protein synthesis; A/E lesions with destruction of intestinal microvillus resulting in decreased absorption Enteroinvasive E. coli (EIEC) Large intestine Disease in underdeveloped countries; fever, cramping, watery diarrhea; may progress to dysentery with scant, bloody stools Plasmid-mediated invasion and destruction of epithelial cells lining colon Enteroaggregative E. coli (EAEC) Small intestine Infant diarrhea in underdeveloped countries; traveler's diarrhea; persistent watery diarrhea with vomiting, dehydration, and low- grade fever Plasmid-mediated aggregative adherence of rods ("stacked bricks") with shortening of microvilli, mononuclear infiltration, and hemorrhage; decreased fluid absorption
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