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

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.

Bacterial Isolation Microwell-Plug (μWELLplug) for Rapid Antibiotic Susceptibility Testing Using Morphology Analysis

“…Thus, in an attempt to determine antibiotic susceptibility more quickly and precisely, many methods have been developed to observe the division of bacterial cells. Several platforms to monitor bacterial cell division have been developed and commercialized, but they still require additional equipment or specific materials. ,− …”

Performance of dRAST on Prospective Clinical Blood Culture Samples in a Simulated Clinical Setting and on Multidrug-Resistant Bacteria

“…Previously published dRAST studies focusing on its performance on Gram-positive bacteria report a lower error rate of 0–4.5% in comparison to other methods such as the MicroScan Walkaway and broth microdilution. However, it was noted that these earlier dRAST studies did not contain data regarding cefoxitin screen ( 8 , 9 ). In the present study, the dRAST achieved a 100% agreement with disk diffusion for cefoxitin screen on prospective clinical blood culture samples.…”

“…It is capable of giving phenotypic AST results directly from positive blood cultures or from colony isolates within 6 h, using automated microscopy to analyze bacteria growth in agar in the presence of a panel of antimicrobial agents that were designed based on either Clinical and Laboratory Standards Institute (CLSI) or EUCAST recommendations ( 7 ). Several published prospective studies evaluating the dRAST were focused on staphylococci and enterococci ( 8 , 9 ), and on Gram-negative bacteria ( 10 , 11 ). The reported categorical agreement (CA) between the dRAST system and various reference AST methods was over 90% ( 7 , 8 , 10 , 11 ).…”

Clinical Validation of the QMAC-DST System for Testing the Drug Susceptibility of Mycobacterium tuberculosis to First- and Second-Line Drugs

“…All drugs except PAS showed a concordance rate of more than 90% in both susceptible and resistant isolates. The microfluidic chip technique applied in QMAC-DST is efficient and highly accommodating in terms of speed and choice of drugs tested because it has adapted the same technology as the established rapid automated antimicrobial susceptibility testing systems for bacterial pathogens, QMAC-dRAST (QuantaMatrix) (Kim et al, 2018). Therefore, compared with other rapid culture-based methods like MGIT, QMAC-DST had an advantage of high throughput, less labor-intensive procedures, and wide availability of various first- and second-line drugs in a single run, similar to QMAC-dRAST.…”

“…The CCs were based on the Middlebrook 7H9 broth, which were set up for the MGIT 960 system (World Health Organization [WHO], 2009), except streptomycin, amikacin, and PAS, which were adjusted according to a previous study (Jung et al, 2018). The CCs were 0.1, 1.0, 2.0, 5.0, 2.0, 2.5, 2.5, 1.5, 0.5, 2.0, 0.5, 4.0, and 5.0 μg/mL for isoniazid, rifampin, streptomycin, ethambutol, amikacin, capreomycin, kanamycin, levofloxacin, moxifloxacin, ofloxacin, para -aminosalicylic acid (PAS), rifabutin, and ethionamide, respectively (Woodley, 1986; Kam et al, 2010; Jung et al, 2018). MTB cell suspension was inoculated as previously described (Jung et al, 2018).…”