Gastrointestinal Tract - Bacterial IdentificationLaboratory testing algorithm for Salmonella, Shigella, Vibrio, E. coli, Campylobacter jejuni, Yersinia enterocolitica, Enterococcus, and Bacillus cereus Hover over the animation to start / stop rotationGram Negative Rods MacConkey Agar - Lactose Negative S/S Agar Positive - Citrate Positive Salmonella S. typhi - Dulcitol(-) - S. enterica - Dulcitol(+) Gram Negative Rods MacConkey Agar - Lactose Negative S/S Agar Positive - H2S negative Shigella spp Curved Motile Gram Negative Rods MacConkey Agar - Negative Lactose Oxidase Positive - - Glucose Positive Vibrio cholerae Sucrose(+) Vibrio parahemolyticus Sucrose(-) Large Gram Negative Rods MacConkey Agar - Positive Lactose Positive Indole Test - - Green sheen on EMB Agar Escherichia coli Gram Negative Coccobacilli Growth in low O2 High CO2 Oxidase Positive - - Catalase Positive Campylobacter jejuni Gram Negative Pleomorphic Cocci MacConkey Agar - Lactose Negative Oxidase Negative Glucose - Urea - Catalase: Positive Yersinia enterocolitica Gram Positive Cocci in Chains Catalase Negative Gamma (no) Hemolysis on Blood Agar Bile Esculin Agar Positive Enterococcus Large Spore-forming Gram Positive Rods Oxidase Positive - - Catalase Positive Bacillus cereus |
Stool culture must be performed to identify specific pathogens, because stool contains an abundance of commensal bacteria. A standard stool culture identifies Salmonella, Shigella, Campylobacter, and Yersinia enterocolitica. Since E. coli constitutes a substantial amount of gut flora, then specific serotypes known to cause illness must be identified, such as serotype O157:H7 producing a shiga-like toxin that can lead to hemolytic-uremic syndrome (HUS).
|