Stool Cultures (LAB223)

Stool cultures are routinely performed to detect common bacterial causes of diarrhea. These include species of Salmonella, Shigella, Campylobacter, toxin-producing Escherichia coli, Yersinia, and more. Enteric infection with these organisms is acquired in community settings.

Stool specimens collected from patients who have been hospitalized for greater than three days are not acceptable for stool culture, as it is unlikely that the patient has contracted an enteric pathogen during the course of their hospital stay.  The presence of gastrointestinal symptoms in these patients is more likely due to etiologic agents acquired in the hospital or non-infectious causes.  

Patients with prolonged diarrhea often have a complex clinical history with a wide differential diagnosis. In these cases, careful consideration should be given to any testing in addition to stool culture that may be of benefit (e.g. microsporidium molecular testing in immunosuppressed patients, or ova/parasite examination in patients with a history of travel outside the US, or Norovirus testing if there is a local outbreak).

• Stool cultures detect community-acquired pathogens. New diarrhea in patients who have been hospitalized for 3 or more days is highly unlikely to be caused by a community-acquired pathogen.
• Culture does not detect viral causes of gastrointestinal illness.

• Stool cultures are routinely screened for Salmonella, Shigella, Campylobacter, Shiga-toxin-producing E. coli, Aeromonas, Plesiomonas, and Yersinia spp. Screening for Vibrio spp. is available upon request.
• In patients with negative stool cultures and persistent diarrhea, consider other infectious causes such as Norovirus, Giardia, or Cryptosporidium.

1. Humphries RM, Linscott AJ. Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Bacterial Gastroenteritis. Clin Microbiol Rev. 2015 Jan;28(1):3-31. doi:10.1128/CMR.00073-14. PMID: 25567220; PMCID: PMC4284301.