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Updated: Jan 29, 2026

Preparation of a Blood Culture Pellet for Rapid Bacterial Identification and Antibiotic Susceptibility Testing
Published on: October 15, 2014
Rapid antimicrobial susceptibility testing by VITEK®2 directly from blood cultures in patients with Gram-negative rod
C A Hogan1, N Watz2, I Budvytiene2
1Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA; Clinical Microbiology Laboratory, Stanford University Medical Center, Palo Alto, CA, USA.
Objective:
Optimizing therapy for bacteremia is currently limited by the 1-2-day turnaround time required for antimicrobial susceptibility testing (AST). Here, we assess a rapid AST method with VITEK®2 (bioMérieux, France) directly from positive blood cultures.
Methods:
Patient-derived positive blood cultures with Gram-negative rods identified as Enterobacteriaceae and Pseudomonas aeruginosa were prospectively tested, and other blood culture bottles were spiked with carbapenem-resistant Enterobacteriaceae (CRE). Positive cultures were subjected to red blood cell lysis and centrifugation, and setup on VITEK®2.
Results:
A total of 109 patient blood cultures and 52 spiked blood cultures were tested. Overall, essential agreement was 97.7% [95% confidence interval (CI) 96.4-99.0], and categorical agreement was 96.8% (95% CI 95.0-98.6). Mean turnaround time from setup to susceptibility results for Enterobacteriaceae in the clinical cultures was 9.0 (±1.3) h.
Conclusions:
Direct susceptibility testing of blood cultures by VITEK®2 for Enterobacteriaceae is an accurate, practical, and inexpensive diagnostic strategy for rapid automated AST.
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