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

현정 김¹ 현영 정²³⁴ 상권 한¹ 신훈 한¹ 정길 최¹ 봉환 진² 태근 임¹²³ 은근 김¹ 은근 김¹ 동영 김¹ 상훈 송⁵ 태수 김⁵ 상훔 권^12346*

¹ QuantaMatrix Inc.
² Institutes of Entrepreneurial BioConvergence, Seoul National University
³ Department of Electrical and Computer Engineering, Seoul National University
⁴ Department of Transdisciplinary Studies, Seoul National University
⁵ Department of Laboratory Medicine, Seoul National University Hospital
⁶ Seoul National University Hospital Biomedical Research Institute, Seoul National University Hospital, Seoul

Abstract

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 Grampositive organisms (76 Staphylococcus spp. and 39 Enterococcus spp.) were evaluated by the QMACdRAST 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 QMACdRAST 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 (falsesusceptible) 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)

Keywords

Antimicrobial drug resistance Bacteremia Bioengineering Microbial sensitivity test

Acknowledgements

This work was supported by the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI13C1468 and HI13C0866).

Figures & Tables

Table 1. Distribution of Gram-positive cocci from PBCs used in this study

Genus	Species	No. (%)
Staphylococcus spp.	Staphylococcus aureus	42 (36.5)
Staphylococcus epidermidis	23 (20.0)
Staphylococcus haemolyticus	8 (7.0)
Staphylococcus hominis	3 (2.6)
Enterococcus spp.	Enterococcus faecium	24 (20.9)
Enterococcus faecalis	14 (12.2)
Enterococcus gallinarum	1 (0.9)
Total		115 (100)