What is included in the evaluation of colitis with a suspected bacterial etiology?

Updated: Jan 04, 2019
  • Author: David A Piccoli, MD; Chief Editor: Carmen Cuffari, MD  more...
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When a bacterial cause (eg, Salmonella species, Shigella species, Campylobacter species, Yersinia species, E coli, or C difficile) is suspected, stool samples must be cultured, and Gram staining and methylene blue staining of the stool are recommended. WBC counts may be elevated or normal.

Most of the organisms may be cultured from the stool by using appropriate media, but enrichment techniques may be required for Y enterocolitica. Infectious agents, such as Clostridium perfringens, E coli, and S epidermidis species, have been recovered from stool cultures in patients with colitis. Nonetheless, in most cases, no pathogen is identified.

Failure to isolate pathogenic organisms may be attributable to possible clearance of the organisms at time of isolation, inability to identify an organism, lack of suitable culture techniques, or laboratories that do not routinely test for all pathogens.

Enterohemorrhagic E coli (EHEC), including O157:H7 and O26:H11, causes hemorrhagic colitis and systemic complications, including hemolytic uremic syndrome (HUS).

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