Urinary tract infections are very common in pediatrics. Urinary antibiotic prophylaxis is commonly used in children with malformative uropathies. Long-term, low-dose antibiotic prophylaxis with trimethoprim-sulfamethoxazole has been associated with a decrease in the number of urinary tract infections in susceptible children, but not systematically with a decrease in the risk of renal scarring (depending of uropathy stage). Long-term antibiotic prophylaxis has implications for the acquisition of antibiotic resistance. A child receiving antibiotic prophylaxis for urinary tract infection is around 6 times more likely to develop a multidrug-resistant infection. In the general population, the microbiota of children treated with curative antibiotics is less diverse in terms of species and strains. In addition, short-term compositional changes are observed between consecutive samples of children treated with antibiotics. The gut microbiota modulates the immune system, in particular via metabolites (SCFA, polysaccharide A) produced by bacteria that modify the expansion and function of regulatory T-cells. The disturbances of the intestinal microbiota play a role in the medium and long term on the acquisition of pathologies, such as atopy. The study authors wish to describe the intestinal microbiota of children with vesico-ureteral reflux treated long-term with trimethoprim-sulfamethoxazole and compared it those not receiving antibiotic prophylaxis and to healthy children.