The emergence of resistance to fluoroquinolone (FQ) and is a major problem worldwide. The commensal flora is the main reservoir for antibiotic resistance. Understanding the factors (environmental, patient-related, dosis-related, drug-related…) involved in the emergence of resistance to fluoroquinolones in the commensal flora of patients treated with a FQ, may help prevent it and preserve the efficiency of these important antibiotics. Samples of digestive flora will be collected from hospitalized patients before receiving a FQ or Ceftriaxone, at the end of the treatment and 3 month after the end of treatment. Clinical data will be collected.