Accelerate PhenoTestTM BC Kit Versus Conventional Methods for Identification and Antimicrobial Susceptibility Testing of Gram-Positive Bloodstream Isolates: Potential Implications for Antimicrobial Stewardship.

BACKGROUND

The Accelerate PhenoTestTM BC kit (AXDX) provides rapid organism identification (ID) and antimicrobial susceptibility testing (AST) results. Its potential role for antimicrobial stewardship is unknown.

OBJECTIVE

To compare the diagnostic accuracy of AXDX with conventional methods (CMs) and assess AXDX's potential role for antimicrobial stewardship in patients with Gram-positive bloodstream infections (BSIs).

METHODS

This retrospective cohort study included adults with Staphylococcus aureus or Enterococcus spp BSIs from July 2014 to January 2016 at a tertiary care medical center. Available isolates were tested on AXDX, and ID and AST results from AXDX were compared with those from CMs (VITEK 2 or ETEST). The following antibiotics were assessed for categorical agreement (CA) and essential agreement (EA) between the methods: ampicillin and daptomycin ( Enterococcus spp only), erythromycin and cefoxitin ( S aureus only), linezolid, and vancomycin. Potential role of AXDX for stewardship was assessed via a retrospective audit by infectious diseases clinicians.

RESULTS

We included 231 patients with S aureus (n = 112) or Enterococcus spp (n = 119) BSIs, and 106 unique isolates were available for ID and AST performance analyses. Sensitivity and specificity of AXDX for ID were 98.0% and 99.5%, respectively. CA and EA for the tested antibiotics were >97%. In Monte Carlo simulations, AXDX coupled with stewardship personnel (either 24/7 or Monday to Friday) would have allowed unnecessary therapy to be stopped and active/targeted therapy to be started ≥24 hours sooner in >50% of patients.

CONCLUSIONS

Compared with CMs, AXDX had similar diagnostic accuracy and can potentially optimize therapy sooner in patients with Gram-positive BSIs.