Systematic Evaluation of the Accelerate Pheno System for Susceptibility Testing of Gram-Negative Bacteria Isolated from Blood Cultures

ABSTRACT Bacteremia is a major cause of morbidity and mortality. Rapid identification of pathogens for early targeted antimicrobial therapy is crucial for detecting emergence of antibiotic resistance and improving outcomes. However, there are limited data regarding the analytical performance of a rapid identification (ID) and antimicrobial susceptibility testing (AST) method like Accelerate Pheno blood culture detection system compared with the conventional methods routinely used in microbiology laboratories. We undertook a systematic quality improvement (QI) study to compare AST results obtained with Accelerate Pheno system rapid ID/AST system with a standard reference method in a university hospital microbiology laboratory. This was a single center, retrospective (5/10/19 to 8/1/19) and prospective (8/1/19 to 1/31/20) study that evaluated all blood cultures growing Gram-negative rods (GNR). We compared AST results obtained using the reference disk diffusion (DD) susceptibility method with those obtained by the Accelerate Pheno system. We calculated the error rates and categorical agreement between the Accelerate Pheno system and DD for each organism and specific drug tested. We evaluated 355 blood cultures growing GNR, of which 284 met the inclusion criteria. We grouped all Enterobacterales (n = 263) for analysis (156 Escherichia coli, 60 Klebsiella spp., 20 Proteus mirabilis, 17 Enterobacter spp., and 10 Serratia marcescens). Twenty-one Pseudomonas aeruginosa isolates were analyzed separately. For Enterobacterales, categorical agreement (CA) was ≥90% for amikacin (AMK), aztreonam (ATM), cefepime (FEP), ceftriaxone (CRO), ertapenem (ETP), gentamicin (GEN), meropenem (MEM), and tobramycin (TOB); and very major error (VME) was