Impact of Specific Antimicrobials and MIC Values on the Outcome of Bloodstream Infections Due to Extended-spectrum Beta-lactamase (ESBL) or Carbapenemase-producing Enterobacteriaceae: an Observational Multinational Study

Main objective: to observationally assess the efficacy of different antimicrobials in Bloodstream Infection (BSI) due to Enterobacteriaceae producing ESBLs or carbapenemases. Specific objectives: Bacteraemic infections due to ESBL-producing Enterobacteriaceae:

• To demonstrate that β-lactam/β-lactam inhibitors are not associated with worse cure rate and mortality than carbapenems after controlling for confounders, both as empirical and definitive therapy.
• To demonstrate that fluoroquinolones as definitive therapy are not associated with worse cure rate and mortality than carbapenems after controlling for confounders.
• To demonstrate that empirical cephalosporins in monotherapy are associated with worse cure rate and mortality than carbapenems after controlling for confounders in infections others than urinary tract infections.
• To demonstrate that the association of active aminoglycosides with cephalosporins or fluoroquinolines is not associated with worse cure rate and mortality than carbapenems after controlling for confounders.
• To demonstrate that combination empirical and definitive therapy is not associated with better cure rate than monotherapy after controlling for confounders.
• For tigecycline, colistin, and fosfomycin, no hypothesis. The objective is to provide adjusted estimations of their association with outcome variables in comparison with carbapenem monotherapy according to clinical situation and infection. Bacteraemic infections due to carbapenemase-producing Enterobacteriaceae:
• To demonstrate that combination therapy is associated with worse cure rate and mortality than monotherapy after controlling for confounders.
• To show that carbapenems are associated with worse cure rate and mortality when used in infections other than urinary tract caused by isolates showing MIC \<2 µg/mL for imipenem or meropenem in comparison to those caused by isolates with higher MIC, after controlling for confounders.
• To show that colistin used at a dose \>6 million IU per day is associated with improved outcomes in comparison with lower dose, after controlling for confounders.