H2: For pneumonia, cIAI (complicated intrabdominal infection) and BSI (bloodstream infection), combination therapy with two active drugs, one of them being (if available) an "active" beta-lactam (such as meropenem or imipenem if minimum inhibitory concentration [MIC] <16 mg/L, aztreonam if isolate is susceptible as in many metallo-beta-lactamase producers, or cephalosporin if isolate is susceptible as in some OXA-48 producers). For cUTI (complicated urinary tract infection), monotherapy with an "active" beta-lactam as above, colistin or an aminoglycoside (if active in vitro) is as effective as combination therapy.