Treatment of Acute Pyelonephritis With Gram Negative Strains in Infants and Children Less Than 3 Years Old

The purpose of this study is to demonstrate the equivalence of the therapeutic efficacy of cefixime by mouth (PO) 10 days (d) and ceftriaxone intravenous route(IV) 4d followed by cefixime PO 6d on renal scars 6 months after a first acute pyelonephritis episode. The investigators hypothesize that treatment with cefixime PO will allow no more renal scars than intravenous route (IV) treatment of pyelonephritis in infants and children less than 3 years old, 6 months after the first episode. If it is true, treatment will no longer need hospitalisation and the advantages for children, families and the health system will be very important.