2.3. Definition

Hospital-acquired BSI was considered as the isolation of pathogens from at least one blood culture specimen after 48 hours of admission to hospital. The onset of BSI was defined as the collection date of a positive blood culture sample. Neutropenia was defined as an absolute neutrophil count (ANC) < 500 neutrophils/μl at the time of BSI onset. Corticosteroid therapy was defined as the administration of prednisone (dose ≥ 20mg/day, duration ≥ 5 days) or its equivalent. Immunosuppressive therapy referred to the use of at least one of cyclosporine, tacrolimus, rituximab, and ATG/ALG. Hypoproteinemia was defined as a serum albumin value of less than 30 g/L on the day (or within 24 hours) of the collection of a positive blood culture specimen. Mucosal barrier damage was defined as gastrointestinal mucositis or oropharyngeal mucositis. Antimicrobial agent exposure was defined as the use of antibiotics for more than 72 hours within 30 days before BSI. Typical antimicrobial agents administered within 30 days prior to BSI in this study included carbapenems (imipenem and meropenem), aminoglycosides (etimicin, amikacin and kanamycin), quinolones (levofloxacin and moxifloxacin), tigecyclines, penicillins/β-lactamase inhibitor combinations (piperacillin-tazobactam) and cephalosporins/β-lactamase inhibitor combinations (cefoperazone-tazobactam, cefoperazone-sulbactam, ceftazidime-tazobactam and ceftriaxone-tazobactam). The diagnosis of septic shock followed the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) clinical criteria (Singer et al., 2016). Carbapenem resistance was defined as resistance to one or more of meropenem, imipenem, and ertapenem. Empirical antimicrobial therapy was considered appropriate when receiving at least one antimicrobial agent with in vitro activity within 48 hours after the episode of BSI. The final clinical outcome was determined by the survival status on the 28th day after the onset of GNB BSI. If a patient was discharged from a hospital within 28 days of the onset of BSI, the clinical outcome was determined by telephone follow-up.