Impact of Long-Term Low Dose Antibiotic Prophylaxis on Gut Microbiota in Children.

We evaluated the effect of long-term low dose antibiotic prophylaxis on children's gut microbiota. We conducted 16S ribosomal RNA gene sequencing using stool samples from 35 patients younger than 3 years old (median age 5.2 months; male-to-female ratio 17:18) who underwent antibiotic treatment during the acute phase of febrile urinary tract infection. Samples were collected at 5 time points, ie before, during and at 1 to 2, 3 to 4, and 5 to 6 months after febrile urinary tract infection onset and antibiotic treatment. Continuous antibiotic prophylaxis using trimethoprim-sulfamethoxazole was initiated in 23 patients with grade III or higher vesicoureteral reflux and was not administered in 12 patients without reflux. Within 2 weeks after initiation of treatment for febrile urinary tract infection almost all enteric bacteria belonged to the order Lactobacillales, and gut microbiota diversity decreased compared to the pretreatment level (average Shannon index 2.9 before treatment, 1.4 during treatment). The diversity recovered within 1 to 2 months after febrile urinary tract infection onset in both groups. Diversity was maintained during the study period in both groups (p=0.43). A smaller proportion of gut microbiota component belonged to the order Enterobacteriales (p=0.002) in the antibiotic prophylaxis group. Our results revealed that patients receiving continuous antibiotic prophylaxis had normal gut microbiota diversity, indicating that the effect of trimethoprim-sulfamethoxazole on gut microbiota was insignificant. Furthermore, prophylaxis with trimethoprim-sulfamethoxazole might selectively suppress the growth of bacteria belonging to the order Enterobacteriales, such as Escherichia coli and Klebsiella species, which are the main causative bacteria of febrile urinary tract infections.