Cefiderocol and Ampicillin-sulbactam vs. Colistin +/- Meropenem for Carbapenem Resistant A. Baumannii

Inclusion Criteria: Adults \>18 years with bacteremia or hospital-acquired pneumonia (HAP)/ ventilator-associated pneumonia (VAP) (Table 3) caused by carbapenem-resistant A. baumannii (CRAB) (meropenem and/ or imipenem minimal inhibitory concentration (MIC) \>8 μg/mL) susceptible to cefiderocol (disc zone diameter \>=17 mm, corresponding to an MIC \<2 μg/mL). We will include CRAB regardless of colistin, ampicillin-sulbactam, minocycline, tigecycline, trimethoprim/sulfamethoxazole and/or aminoglycoside susceptibility of the isolate. Attribution of the HAP/ VAP to CRAB will be allowed with isolation of CRAB from any respiratory sample within 7 days prior to the clinical diagnosis of pneumonia. Exclusion Criteria: * More than 72 hours of therapy with in-vitro coverage against the CRAB within 96 hours of enrolment * Polymicrobial carbapenem-susceptible infections: growth of other pathogens susceptible to carbapenems, or another beta-lactam, deemed clinically-significant by the treating physicians in blood or sputum (with HAP/ VAP). We will allow recruitment of patients with other carbapenem-resistant Gram-negative bacteria * CRAB susceptible any beta-lactam other than cefiderocol * Coronavirus 2019 (COVID-19) co-infection * Immediate-type hypersensitivity to penicillin * Pregnant women * Previous participation in the trial * Lack of informed consent, considering the procedures acceptable to ethics committees per locale, including deferred consent * Infection requiring treatment for over 14 days, at the discretion of the investigators * Life expectancy less than 24 hours or expected futility of antibiotic treatment