Evaluation of acute diarrhea in adults

STEC: Shiga toxin-producing Escherichia coli; HIV: human immunodeficiency virus.
* Routine stool culture will identify Salmonella, Campylobacter, and Shigella. If other bacterial organisms (eg, Vibrio, Listeria, Yersinia, Aeromonas) are suspected based on exposures, the laboratory should be notified for specific plating of the specimen. Some laboratories perform multiplex molecular testing of stool to test for multiple organisms simultaneously; the indications for such testing are similar to those for stool cultures.
¶ Individuals who have had antibiotic use or hospitalization within the prior three months should be tested for C. difficile. Testing for C. difficile is also often performed in patients with inflammatory bowel disease. Testing for parasites (microscopy, antigen testing, molecular testing) is generally not warranted for acute diarrhea but is appropriate in patients with persistent diarrhea (>7 days), in patients with advanced HIV infection (CD4 cell count <200 cells/microL), in men who have sex with men, in the setting of a community waterborne outbreak, and if stool leukocytes/lactoferrin is negative in patients with bloody diarrhea.
Δ Empiric antibiotic therapy can reduce the duration of diarrhea and other symptoms by several days, but the benefits of antibiotics do not outweigh potential drawbacks in most patients with acute diarrhea. For these select patients (with or at high risk for severe disease, with dysentery, or with persistent disease) empiric antibiotic treatment is reasonable, as symptom reduction may have a greater relative benefit in such patients. When indicated, azithromycin or a fluoroquinolone is used for empiric antibiotic therapy. In particular, azithromycin is preferred for patients with fever, dysentery, or risk factors for fluoroquinolone-resistant infection. Empiric antibiotic therapy should be tailored to results of stool testing, if appropriate.
◊ We withhold empiric antibiotic therapy until stool testing has ruled out STEC or Shiga toxin production in stable patients when the likelihood of STEC is higher (eg, bloody diarrhea in the setting of an outbreak or in an afebrile patient). However, for adults with highly symptomatic or severe bloody diarrhea, the benefits of antibiotic therapy may outweigh the low risk of potential complications from treating STEC.
§ Loperamide and bismuth salicylates are both effective in reducing the duration and frequency of diarrhea, but loperamide is somewhat more effective. However, we avoid loperamide in patients with evidence of dysentery (fever, bloody or mucous stools) unless antibiotics are also given because of concern for exacerbation of disease. Loperamide is also often avoided when C. difficile is suspected. Patients taking loperamide should be cautioned not to exceed the maximum daily dose.