Performance evaluation of microfluidic microplate-based fluorescent ELISA for qualitative detection of SARS-CoV-2-specific IgG and IgM.

We evaluated the diagnostic performance of newly developed microfluidic microplate-based fluorescent ELISA for anti-SARS-CoV-2 antibody detection: the Veri-Q opti COVID-19 IgG and IgM ELISAs (hereafter, "Opti IgG/M"; MiCo BioMed, Gyeonggi-do, Republic of Korea), in comparison with conventional ELISAs. A total of 270 serum samples were analyzed, among which 90 samples were serially obtained from 25 COVID-19 patients. Another 180 samples were collected from 180 SARS-CoV-2-negative individuals. As comparative assays, we used SCoV-2 Detect IgG/M ELISA (hereafter, "InBios IgG/M"; InBios, Seattle, WA, USA) and Veri-Q COVID-19 IgG/IgM ELISA (hereafter, "Veri-Q IgG/M"; MiCo BioMed). Compared with conventional ELISAs, the Opti IgG yielded 97.1-100.0% positive percent agreement, 95.2-98.0% negative percent agreement, 96.3-97.8% total percent agreement, and kappa values of 0.90-0.94. Between the Opti IgM and the InBios IgM, the values were 93.7%, 96.6%, 95.9%, and 0.89, respectively. For the Opti IgG, sensitivities for the samples collected from 0-7, 8-14, 15-21, and ≥ 22 days after symptom onset were 40.0, 58.3, 94.1, and 100.0%, respectively. The values for the Opti IgM were 30.0, 54.2, 88.2, and 80%, respectively. The diagnostic specificities of the Opti IgG and IgM were 99.4 and 97.2%, respectively. The microfluidic microplate-based fluorescent ELISAs showed comparable diagnostic performance to conventional ELISAs for detecting anti-SARS-CoV-2 antibodies. With the combination of high throughput, a simplified workflow, and the ability to analyze reduced volumes, this new technology has great potential for improving SARS-CoV-2 serologic testing.

Comparison of new and old BacT/ALERT aerobic bottles for detection of Candida species.

PURPOSE: A new version of aerobic blood culture media has been developed for the BacT/ALERT (bioMérieux) blood culture system. We evaluated the time to detection and yeast cell counts in positive blood cultures for each Candida spp. according to changes in media. METHODS: Isolates from defibrinated horse blood were inoculated into three types of bottles: the old version of aerobic bottle, new version of aerobic bottle, and anaerobic bottle. All bottles were incubated in the BacT/ALERT Virtuo blood culture system. The time to detection was monitored for each bottle, and yeast cell counts were performed immediately after testing positive, determined via the plate count method. Clinical retrospective data of the candidemia samples before and after aerobic bottle change also were analyzed. RESULTS: The median time to detection was 52.47 hours in the old aerobic bottles versus 19.92 hours in the new aerobic bottles (P < 0.001) for Candida glabrata, and standard and clinical strains showed similar results. C. albicans (27.6 to 24.95 hours) and C. guilliermondii (28.92 to 26.9 hours) had shorter time to detection. However, C. auris (25.43 to 28.25 hours) had a longer time to detection in the new aerobic bottle. The retrospective clinical analysis showed a significant decrease in time to detection (45.0 to 19.4 hours) for C. glabrata, which is consistent with our simulated study result for C. glabrata. As a result of analysis including all blood specimens, C. tropicalis showed a significant delay in time to detection in new aerobic bottles. In an analysis limited to peripheral blood specimens, the time to detection of C. parapsilosis was longer in new aerobic bottles than in old aerobic bottles. CONCLUSION: Most Candida species did not show remarkable TTD differences, but TTD of C. glabrata was markedly reduced in the New FA Plus bottle. The reduction of time to detection enables faster detection and therapeutic approach for C. glabrata infections.

Performance Evaluation of Bruker Biotyper, ASTA MicroIDSys, and VITEK-MS and Three Extraction Methods for Filamentous Fungal Identification in Clinical Laboratories.

Filamentous fungi are a major cause of life-threatening infections in immunocompromised patients; thus, rapid and accurate identification is critical. Filamentous fungal identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been demonstrated with high sensitivity and reproducibility; however, its wider application has been limited in clinical laboratories because of practical challenges such as database availability or lack of standardization. In this study, we compared the performance of the Bruker Biotyper, ASTA MicroIDSys, and Vitek MS for 84 clinical filamentous fungal isolates. Moreover, the sensitivity of three independent sample preparation methods (direct, on plate, in tube) was compared. Bruker Biotyper identified 71.43% (60/84) of isolates correctly (species, genus, or complex/group level). ASTA MicroIDSys and Vitek MS showed accuracy rates of 70.24% (59/84) and 55.95% (47/84), respectively. We found that any difference in sensitivity may be attributed to the database of the systems. In addition, the "in tube" method showed the highest sensitivity among the three methods; however, there was no statistical difference among them. For the broader application of MALDI-TOF MS for filamentous fungal identification, further studies from multiple perspectives are required.