Association between Bacterial Culture before Carbapenem Use and Treatment Duration and Clinical Outcomes: A Nationwide Inpatient Claims Database Study in Japan.

OBJECTIVES: To determine whether bacterial culture before carbapenem initiation is associated with shorter carbapenem exposure and better clinical outcomes in hospitalized patients in Japan. METHODS: We conducted a multicenter retrospective study using the 2022 Diagnosis Procedure Combination Study Group database. Carbapenem treatment episodes were included, excluding those from special functioning hospitals, perioperative prophylaxis, and scheduled admissions. The primary outcome was carbapenem discontinuation within 10 days, with in-hospital death and transfer treated as competing events. Exposure was defined as bacterial culture performed on or within 2 days before carbapenem initiation: at least two sets of blood cultures, at least one blood culture, or any bacterial culture. Fourteen-day in-hospital mortality was assessed during first episodes. RESULTS: Among 206,908 episodes from 167,705 patients, bacterial culture before carbapenem initiation was associated with earlier discontinuation. Adjusted hazard ratios were 1.07 for at least two blood culture sets, 1.07 for at least one blood culture, and 1.05 for any bacterial culture. Bacterial culture was associated with lower 14-day in-hospital mortality, with hazard ratios of 0.89, 0.89, and 0.81, respectively. CONCLUSIONS: Bacterial culture before carbapenem initiation was associated with shorter carbapenem treatment and lower short-term mortality, supporting further evaluation of culture collection as a potential antimicrobial stewardship quality indicator.