Multicenter evaluation of rapid antimicrobial susceptibility testing by VITEK®2 directly from positive blood culture.

Study Objective: To compare the antimicrobial susceptibility testing (AST) performance of positive blood cultures (PBC) VITEK®2 off-label use (D0) and traditional VITEK®2 workflow using isolated colonies after overnight (D1).

Methods: Patient samples with monomicrobial Gram-negative rod or Gram-positive cocci in clusters bacteremia were tested on D0 and compared to D1 AST results in 7 laboratories in France.

Results: Overall, categorical and essential agreement rates were 98.4% and 96.7%, respectively. Very major discrepancy and major discrepancy rates for Enterobacterales and Staphylococci satisfied the NF EN ISO 20776-2 (2007) criteria for sepsis-relevant drugs. Very major discrepancies were >3% for amoxicillin-clavulanate (4.9%, 6/122), piperacillin-tazobactam (7.5%, 4/53) and meropenem (33%,1/3) for Enterobacterales and gentamicin for Staphylococci (4.6%, 4/87).

Conclusion: Direct AST from PBC broths by VITEK®2 for Enterobacterales and Staphylococci is reliable and fast and may positively influence antimicrobial stewardship.