A multicenter, national, prospective, observational pharmacological study of patients with difficult-to-treat Gram-negative infections treated with ceftazidime/avibactam (CAZ/AVI) or cefiderocol (CEF) monotherapy or combination therapy with ceftazidime/avibactam associated with fosfomycin (FOS) or cefiderocol associated with fosfomycin.
Patients with infection due to a difficult-to-treat Gram-negative bacteria treated with CAZ/AVI alone, CEF alone, CAZ/AVI plus FOS, or CEF plus FOS (any age)
Signature of the informed consent (for pediatric patients: parents or guardians able to provide consent)
Premature newborns
Polymicrobial/mixed infections with the exception of cases with multiple Gram-negative bacteria susceptible to study drugs
Continuous renal replacement therapy (CRRT) applications
Age ≥18 years