Inclusion Criteria:  Admission to the medical ICU with severe pneumonia defined as per IDSA/ATS 2019 criteria on mechanical ventilation: presence of signs, symptoms and confirmatory chest imaging consistent with pneumonia (e.g. fever, cough and pulmonary infiltrate by chest radiograph) requiring mechanical ventilation due to respiratory failure Age ≥18 years Positive rapid identification test and respiratory culture for Gram-negative bacteria including, but not limited to, P. aeruginosa, K. pneumoniae, E. coli, S. marcescens, H. influenzae, Enterobacter spp., M. catarrhalis, A. baumannii, Achromobacter spp., P. mirabilis, and/or B. cepacia Received within the last 48 hours or will receive meropenem, cefepime, or piperacillin/tazobactam therapy  Exclusion Criteria:  Pregnancy Prisoners Allergy to the beta-lactams to be administered in this study On renal replacement therapy at the time of randomization Gram-negative bacteria identified by rapid testing only with negative respiratory culture at baseline COVID patients enrolled in other trials