The present study evaluated the effect of non-absorbable oral
polymyxin on the duodenal microflora and clinical outcome of infants with severe infectious
diarrhea.
Polymyxin was chosen because classic enteropathogenic Escherichia coli was more sensitive to this
antibiotic. Twenty-five infants were randomly assigned to a 7-day treatment with oral
polymyxin (2.5 mg/kg in 4 daily doses) or placebo. Duodenal and stool cultures were performed before and after the treatment. Five patients were excluded during the study because of introduction of parental
antibiotic therapy due to clinical
sepsis (N = 3) or rapid clinical improvement (N = 2). In the
polymyxin group, small bowel bacterial overgrowth occurred in 61.5% of the cases (8/13) before treatment and in 76.9% (10/13)
after treatment. In the placebo group these values were 71.4% (5/7) and 57.1% (4/7), respectively. By the 7th day, clinical cure was observed in 84.6% of the cases (11/13) in the
polymyxin group and in 71.4% (5/7) in the placebo group (P = 0.587). Considering all 25 patients included in the study, clinical cure occurred on the 7th day in 12/14 cases (85.7%) in the
polymyxin group and 6/11 cases (54.5%) in the placebo group (P = 0.102). Clinical
sepsis occurred in 3/11 (27.3%) of the patients in the placebo group and in none (0/14) in the
polymyxin group (P = 0.071). Oral
polymyxin was not effective in reducing bacterial overgrowth or in improving the clinical outcome of infants hospitalized with severe infectious
diarrhea. Taking into account the small sample size, the rate of cure on the 7th day and the rate of clinical
sepsis, further studies with greater number of patients are necessary to evaluate these questions.