This case report describes a patient with a pyelonephritis due to a fluoroquinolone-resistant E. coli. The prevalence and the risk factor associated with the resistance of E. coli to fluoroquinolones have been assessed from recently published data. Several studies performed in patients with urinary tract infections have shown that the increase of fluoroquinolone-resistant strains was associated with an increased prescription of these antibiotics. Indiscriminate use of fluoroquinolones, in particular for respiratory tract infections, may lead to the dissemination of resistant strains among the general population.