Infective Endocarditis and Antimicrobial Timing: A Case for Delay?

Abstract Background In patients with suspected infective endocarditis (IE), current guidelines recommend prompt initiation of empiric antimicrobial treatment after obtaining blood cultures. However, the clinical benefit of immediate treatment in hemodynamically stable patients remains uncertain. This study assessed the impact of deferring antimicrobial treatment in patients with suspected IE. Methods We conducted a multicenter cohort study of adult patients with bacteremia and clinical suspicion of IE from two university hospitals (2015-24). Patients presenting with sepsis, intensive care unit admission, neutropenia, or a clearly identifiably focus other than IE were excluded. All cases were adjudicated by a dedicated Endocarditis Team as either IE or not IE. The primary outcome for all episodes was 30-day mortality; for confirmed IE cases, the composite outcome included 30-day mortality, new embolic events, or new bone and joint infection. Results Among 1,230 episodes, empirical antimicrobial treatment was initiated immediately (Group I) after blood culture collection in 675 episodes (55%) and deferred until preliminary blood culture results (Group D) in 555 episodes (45%). Thirty-day mortality was 5% (59 episodes), with no difference between Groups I and D (5% versus 5%; P=0.894). Of 597 confirmed IE episodes (49%) IE, 327 (55%) were in Group I and 270 (45%) in Group D. The composite primary endpoint occurred in 157 episodes (26%), with no difference between groups (28% versus 24%; P=0.304). Conclusions In clinically stable patients with suspected IE, deferring antimicrobial treatment until available blood culture results was not associated with worse clinical outcomes.