Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology


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Clinical Evaluation of QMAC-dRAST for Direct and Rapid Antimicrobial Susceptibility Test with Gram-Positive Cocci from Positive Blood Culture Bottles

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2018 March, Volume 21, Issue 1, pages 12-19.

Clinical Evaluation of QMAC-dRAST for Direct and Rapid Antimicrobial Susceptibility Test with Gram-Positive Cocci from Positive Blood Culture Bottles

Hyunjung Kim1, Hyun Yong Jeong2,3,4, Sangkwon Han1, Shinhun Han1, Jungil Choi1, Bonghwan Jin1, Taegeun Lim1,2,3, Eun-Geun Kim1, Dong Young Kim1, Sang Hoon Song5, Taek Soo Kim5, Sunghoon Kwon1,2,3,4,6
1QuantaMatrix Inc., 2Institutes of Entrepreneurial BioConvergence, Seoul National University, 3Department of Electrical and Computer Engineering, Seoul National University, 4Department of Transdisciplinary Studies, Seoul National University, 5Department of Laboratory Medicine, Seoul National University Hospital, 6Seoul National University Hospital Biomedical Research Institute, Seoul National University Hospital, Seoul, Korea


Background: Timely intervention in the treatment of bloodstream infection is important for prescription of appropriate antimicrobials. With prompt determination of the antimicrobial susceptibility of a causative agent, rapid antimicrobial susceptibility test (AST) can help select the appropriate antimicrobial therapy. This clinical study is for evaluation of the clinical performance of the QMAC-dRAST for rapid AST directly from positive blood culture (PBC)s with Gram-positive cocci.

Methods: A total of 115 PBC samples with Gram- positive organisms (76 Staphylococcus spp. and 39 Enterococcus spp.) were evaluated by the QMAC- dRAST system, and their pure culture isolates were evaluated by the MicroScan WalkAway (Beckman Coulter, USA) as the comparative AST system. Thirteen antimicrobial agents were included, and the agreement and discrepancy rates of the QMAC- dRAST system (Quantamatrix Inc., Republic of Korea) compared to the MicroScan WalkAway were calculated. To resolve discrepancies, the broth microdilution method was performed.

Results: The QMAC-dRAST system exhibited a categorical agreement rate of 94.9% (1,126/1,187) and an essential agreement rate of 98.3% (1,167/1,187). The QMAC-dRAST system yielded very major (false- susceptible) errors at 1.0% (5/485), major (false-resistant) errors at 1.3% (9/693), and minor errors at 4.0% (47/1,187) compared to the MicroScan WalkAway. The QMAC-dRAST system significantly eliminated 30 hours of total turnaround time by combination of direct inoculation of PBC and an image-based approach.

Conclusion: The results of the QMAC-dRAST system were highly accurate. Thereby, the QMAC-dRAST may provide essential information to accelerate therapeutic decisions for earlier and adequate antibiotic treatment and patient management in clinical settings. (Ann Clin Microbiol 2018;21:12-19)


Antimicrobial drug resistance, Bacteremia, Bioengineering, Microbial sensitivity test