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Gastroenteritis: Multimedia
Updated: Oct 22, 2009
Multimedia
 | Media file 1: Hektoen enteric agar with Escherichia coli colonies. Different growth media are necessary for identifying different enteric pathogens, suppressing the growth of nonpathogens, and allowing for chemical reactions to assist in identification. The appearance results from the organism's ability to ferment lactose placed in the medium. This results in the production of acid, which lowers the pH and causes a change in the pH indicator placed in the medium. Salmonella and Shigella organisms do not ferment lactose. |
 | Media file 2: Example of Salmonella on Hektoen enteric agar. The medium also contains ferric ammonium citrate, which indicates the production of hydrogen sulfide by the appearance of a black precipitate. |
 | Media file 3: The MacConkey medium is commonly used and differentiates lactose fermenters, which produce acid, decrease the pH, and cause the neutral red indicator to give the colonies a pink-to-red color. |
 | Media file 4: The Christensen method is used to determine if an organism produces the enzyme urease (Yersinia) or not (Salmonella, Shigella, Vibrio). Hydrolysis of urea produces ammonia and carbon dioxide, alkalinizing the medium and turning the phenol red from light orange to magenta (pink). |
 | Media file 5: Often, a combination of methods may be used for identification. The tube on the left is triple sugar iron (TSI) agar. The alkaline slant and acid butt (K/A) indicates an organism that ferments glucose only (not lactose or sucrose). The middle tube is indole positive, as indicated by the pink ring, and indicates the organism's ability to split tryptophan to form indole. The tube on the right is urease negative. Taken together, these tests indicate the organism is likely Shigella. |
 | Media file 6: Gram stain may be helpful in identifying an etiologic agent. This stain shows gram-negative bacilli, which could be Salmonella or Shigella with 2 polymorphonucleocyte cells (PMNs). |
More on Gastroenteritis |
| Overview: Gastroenteritis |
| Differential Diagnoses & Workup: Gastroenteritis |
| Treatment & Medication: Gastroenteritis |
| Follow-up: Gastroenteritis |
 Multimedia: Gastroenteritis |
| References |
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References
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Further Reading
Keywords
gastroenteritis symptoms, gastroenteritis causes, gastroenteritis treatment, enterogastritis, stomach flu, intestinal flu, dysentery, infectious diarrhea, diarrhea, traveler's diarrhea, food poisoning, food-borne toxigenic diarrhea, shellfish poisoning, amebiasis, rotavirus, norovirus
Norwalk-like virus, Norwalk virus, Shigella dysenteriae, Salmonella, Campylobacter jejuni, C jejuni, Yersinia enterocolitica, Y enterocolitica, Escherichia coli, E coli, Vibrio cholera, V cholera, Clostridium difficile, C difficile
Clostridium perfringens, Listeria, Mycobacterium avium-intracellulare, MAI, Vibrio parahaemolyticus, Vibrio vulnificus, Giardia lamblia, Cryptosporidium, Cyclospora, Staphylococcus aureus, S aureus, dehydration, enterotoxins, rice water diarrhea, O157:H7
