A urinary tract infection requires antibiotic treatment. While this treatment is intended to eliminate bacteria from the urine, it may also facilitate the development of resistant strains in the digestive tract. Patients are asked to provide stool samples on several occasions so that any potential side effects of this treatment on the digestive flora can be analysed.

Each of us has billions of bacteria in our intestines that aid digestion (scientifically known as the gut microbiota), some of which can "mutate", i.e. adapt to resist antibiotics. Although this is usually harmless, these bacteria can sometimes cause infections.

Hence the importance of better understanding this phenomenon, known as the 'collateral effect on flora of otherwise beneficial antibiotic treatment'. The investigators already know that not all antibiotics are equivalent, with some having a stronger 'collateral effect'. However, the risk classification remains poorly understood.

Recent advances in laboratory stool analysis now make it possible to better analyse this phenomenon.

The ultimate goal is to identify treatment regimens that are both highly effective in treating urinary tract infections and have the least possible ecological impact.

Inclusion Criteria:

• Adult patient requiring hospitalisation
• Diagnosis of urinary tract infection requiring systemic antibiotic therapy with ceftriaxone, piperacillin/tazobactam or temocillin
• Collection of a stool sample possible before or within 24 hours of starting systemic antibiotic therapy
• Patient who has read and understood the information letter and given their consent to participate in the research

Exclusion Criteria:

• Minor patient
• Patient hospitalised in an intensive care unit
• Digestive stoma
• Patient not affiliated with social security
• Pregnant woman, woman in labour or breastfeeding woman
• Person deprived of liberty by administrative or judicial decision
• Person placed under judicial protection, guardianship or curatorship

Patients will be recruited via the Emergency Department (ED).