Sulfamethoxazole- trimethoprim versus ampicillin in treatment of acute invasive diarrhea in adults.

Twenty-seven Navajo adults with moderate to severe acute inflammatory diarrhea were hospitalized and randomly given ampicillin or sulfamethoxazole-trimethoprim. All patients had invasive diarrhea as defined by sheets of fecal leukocytes, seen on methylene blue wet-slide preparations, and significant clinical symptoms, including postural hypotension from dehydration or fever (temperature greater than 100 degrees F [or 37.8 degrees C]). Patients were followed daily for 5 days in the hospital. Responses of symptoms in all 13 patients who were given sulfamethoxazole-trimethoprim were comparable to or better than those 14 patients randomly assigned to receive ampicillin. Nineteen (73%) of the 27 patients had culture-proven shigellosis, 6 of whom had ampicillin-resistant Shigella isolates. All isolates were susceptible to sulfamethoxazole-trimethoprim in vitro. The eight patients with culture-proven shigellosis treated with sulfamethoxazole-trimethoprim responded as well as the eight patients with ampicillin-susceptible infections treated with ampicillin. Three of the eight patients successfully treated with sulfamethoxazole-trimethoprim had ampicillin-resistant organisms. The three patients with ampicillin-resistant organisms who were treated with ampicillin appeared to do less well; one was a clinical and bacteriological failure at 72 h and subsequently improved after sulfamethoxazole-trimethoprim therapy. As predicted by in vitro susceptibility studies and by studies in children, sulfamethoxazole-trimethoprim was highly effective in treating adult patients with shigellosis and appears to be the treatment of choice in areas where ampicillin resistance among Shigella is common.