Comparative evaluation of the QMAC-dRAST V2.0 system for rapid antibiotic susceptibility testing of Gram-negative blood culture isolates

J Microbiol Methods. 2020 May;172:105902. doi: 10.1016/j.mimet.2020.105902. Epub 2020 Mar 20.

Abstract

To comparatively evaluate the performance of the rapid antimicrobial susceptibility testing (AST) system QMAC-dRAST V2.0 and of standard disk diffusion in agar, AST was performed directly from 100 positive blood culture bottles with Gram-negative bacilli. AST results provided by QMAC-dRAST showed 92.9% agreement with disk diffusion method results. Discrepancies observed between results obtained with QMAC-dRAST and disk diffusion method conducted to 10 very major errors (0.8%, S with QMAC-dRAST vs R with disk diffusion method), 40 major errors (3.2%, R vs S, respectively), 15 minor errors (1.2%, S vs I or I vs R, respectively) and 23 very minors errors (1.8%, I vs S or R vs I, respectively). For very major and major errors, in only 36% of the cases did the repeat QMAC-dRAST confirm the initial result, whereas a repeat AST using disk diffusion method confirmed the initial result in 92% of cases. AST results obtained using microdilution in liquid medium confirmed those obtained with QMAC-dRAST and disk diffusion method in 4% and 89%, respectively. Repeatability and reproducibility tests performed on QMAC-dRAST using reference strains showed 94% to 100% of R/S/I categorical agreement.

Keywords: Antimicrobial susceptibility testing; Automated susceptibility testing; Bacteremia; Blood culture; Gram-negative bacteria.

MeSH terms

  • Anti-Bacterial Agents*
  • Bacteremia / diagnosis
  • Bacteremia / microbiology
  • Blood Culture / methods*
  • Culture Media
  • Disk Diffusion Antimicrobial Tests / methods*
  • Gram-Negative Bacteria / classification
  • Gram-Negative Bacteria / isolation & purification*
  • Humans
  • Prospective Studies
  • Reproducibility of Results
  • Time Factors

Substances

  • Anti-Bacterial Agents
  • Culture Media