Time is Survival: Early Detection of Antimicrobial Susceptibility in Bloodstream Infections

Introduction: Bloodstream infections (BSIs) are associated with morbidity and mortality, requiring timely effective antimicrobial therapy. However, conventional antimicrobial susceptibility testing (AST) from positive blood cultures generally requires 24–48 hours after culture positivity confirmation, delaying targeted treatment and sustaining broad-spectrum antibiotic use. Direct susceptibility testing (DST) from positive blood culture bottles is a rapid, cost-effective approach that may shorten turnaround time. This study compared direct and conventional AST. Materials and Methods This cross-sectional study was conducted from April 2024 to November 2025 in bacteriology at SMS&R, Sharda Hospital, Greater Noida. Positive blood culture bottles from BacT/ALERT were included; contaminated or mixed-growth samples were excluded. Direct Gram staining and susceptibility testing on flagged bottles were compared with traditional culture methods. Data were analysed using Excel and SPSS. Results Of 10,248 blood samples, 302 flagged positive and 256 with single morphotype on Gram stain were included. Gram-negative bacilli predominated (202/256, 78.90%), followed by Gram-positive cocci (54/256, 21.10%). Enterobacterales predominated (57.81%), and categorical agreement between direct susceptibility testing and conventional AST was highest for Enterococcus species (91.23%). Conclusion DST from flagged positive blood culture bottles offers rapid and reliable early susceptibility results, with high agreement and no very major errors compared with conventional AST. Its routine use can shorten reporting time by 18–24 hours, support earlier targeted therapy, and strengthen antibiotic stewardship in bloodstream infections.