Patients older than 18 years old that are hospitalised in the Virgen Macarena University Hospital that are being treated with Ceftolozane-Tazobactam in empiric or targeted treatment.

The dose will be 1g ceftolozane + 0,5 g tazobactam every 8 hours or 2 g ceftolozane + 1 g tazobactam, it´s recommended to use this last dose regimen in patients with pneumonia or septic shock of any focus.

The patients will be followed as it´s done habitually. There will be done infection focus cultures and others according to usual clinical practice. It´ll be determined the clinical response and mortality in the days 14 and 30 after the beginning of the medicine, respectively.

The Ceftolozane-Tazobactam levels determination will always be made in state of equilibrium (after the third dose). Four samples will be collected:

1. Just before the antibiotic infusion.
2. One hour after the antibiotic infusion.
3. Three hours after the antibiotic infusion.
4. Six hours after the antibiotic infusion.

Determination of the Ceftolozane-Tazobactam seric concentration by collecting 4 blood samples and measuring its antibiotic levels and if it´s achieved an adequate therapeutic efficacy assessed by the patient´s clinical and microbiological recovery.

The dose regimens used until now are 1+0,5 g every 8 hours in case of intra-abdominal infection or complicated urinary infection and 2 +1 g every 8 hours in case of pneumonia or septic shock of any focus.

Determine if with both dose regimens are achieve the pharmacodynamic and pharmacokinetic parameters associated with the maximum therapeutic efficacy in patients that have creatinine clearance above 130 ml/min.