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Category: Clinical Microbiology
Fecal and Other Gastrointestinal Cultures and Toxin Assays, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818814/9781555818814_Chap3.8-1.gif /docserver/preview/fulltext/10.1128/9781555818814/9781555818814_Chap3.8-2.gifAbstract:
Gastroenteritis can be caused by bacteria, parasites, or viruses. With such a wide array of pathogens and the need for cost containment, physician input and practice guidelines ( 1 ) can help the laboratory determine which tests are appropriate for detecting the etiological agent of diarrhea. Microbiology laboratories should review the local epidemiology of bacterial enterocolitis and implement routine stool culture methods that will allow recovery and detection of all of the major pathogens causing most of the cases in their geographic area. All microbiology laboratories should routinely test for the presence of Salmonella spp., Shigella spp., and Campylobacter spp. on all stool cultures. Other major pathogens, such as Shiga toxin-producing Escherichia coli, particularly E. coli O157 or enterohemorrhagic E. coli (EHEC), should also be routinely tested for on bloody stool samples during the spring, summer, and early fall months in geographic areas where the prevalence of these strains has been shown to be increased. Microbiology laboratories situated in or near coastal communities may also test for Aeromonas and Vibrio spp. since the prevalence of these types of infections is increased with exposure to water or contaminated food such as shellfish.
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Flowchart for the identification of oxidase-positive stool pathogens from BAP or from either TCBS or CIN. Most are also indole positive. Biochemical reactions for species identification are available for many commercial kits. Note: Growth on TCBS implies that the organism is a Vibrio sp., but not all Vibrio spp. grow on TCBS. Abbreviations: MH, Mueller-Hinton agar; ID, identification; K, alkaline; A, acid; r/o, rule out.
Flowchart for identification of stool pathogens from routine stool cultures. Set up either TSI or KIA, BAP, and urea agar (or rapid urea tube) from all lactose-negative or H2S-positive colonies on enteric selective agars. Reactions of the slant are listed with a slash before the butt reaction. Optionally for H2S-negative colonies, Andrade’s glucose tube with Durham tube for gas will eliminate most questionable production of gas and provide a broth for VP testing. Perform spot tests (indole, oxidase, PYR) only from BAP. r/o, rule out.
Campylobacter identification flowchat or minimum identification of C. jejuni from stool specimens. Abbreviations: R, no zone; S, zone.
Commonly used primary plating and broth media for isolation of Salmonella and Shigella a
Special highly selective media for specific pathogen requests
QC of specialized media for detection of fecal pathogens
Microscopic and gross observations of fecal specimens associated with various infections a
Biochemical differentiation of selected members of the Salmonella group a
Summary of detection media and identification methods for fecal pathogens a
Taxonomic position, known sources, and common disease associations of Campylobacter, Arcobacter, Helicobacter, and related species a
Human disease associations of Campylobacter species by clinical syndrome
Commercial systems for generating microaerobic environments and the approximate atmospheric content
Phenotypic reactions of clinically important Campylobacter and Helicobacter species a
Single wavelength