SARS-CoV-2 real-time reverse-transcription PCR (rRT-PCR) is the most effective testing system currently available to counter COVID-19 epidemics when potent treatments and vaccines are unavailable. Therefore, four SARS-CoV-2 rRT-PCR kits have been approved by the emergency-use-authorization (EUA) without clinical validation in Korea until March 15, 2020. This study evaluated the analytical and clinical performance of these kits. Allplex 2019-nCoV Real-time PCR (Seegene, Seoul, Korea), PowerChek 2019-nCoV (KogeneBiotech, Seoul), Real-Q 2019-nCoV Real-Time Detection (BioSewoom, Seoul), and StandardM nCoV Detection (SD BIOSENSOR, Osong, Korea) were evaluated. The limit of detection (LODs) of Allplex, PowerChek, and Real-Q was determined by testing the transcribed RNA of SARS-CoV-2 E and the RNA of SARS-CoV Frankfurt1. A total of 27 consecutive samples comprising 13 sputum, 12 nasopharyngeal swab (NPS), 1 urine and 1 stool sample were collected from 2 COVID-19 patients for sensitivity analysis. Precision was assessed via daily tests of positive and negative controls in each kit for 5 d. Reproducibility was examined by repeating 21 samples and 10-fold dilutions of 14 samples in pairs using Allplex. Specificity was evaluated with 24 other respiratory virus-positive samples. LOD of Allplex, PowerChek, and Real-Q were 153.9, 84.1, and 80.6 copies/mL, respectively. The degrees of association between Cts and log viral concentrations by Allplex and PowerChek was expressed as y = −3.319 log (x) + 42.039 (R = 0.96) and y = −3.392 log(x) + 43.113 (R = 0.98), respectively. One or more of the 4 kits detected 20 out of 27 clinical samples positive. Of the 20 positive samples, the detection rates of positives for Allplex, PowerChek, Real-Q, and StandardM were 90.0, 82.3, 75.0, and 100.0%, respectively, but those of PowerChek and Real-Q would be 100% if out-of-cutoff Cts were counted as positives. Precision was 100%. Interpretation Hur et al. Evaluation of SARS-CoV-2 rRT-PCR Kits of Allplex results was reproducible when Ct of E ≤33. All 4 kits showed no cross-reactivity with other respiratory viruses. Performance of the 4 kits indicated the suitability of these for diagnosis and follow-up testing of COVID-19. Laboratory doctors who initially implement these EUA kits must be able to interpret quality control parameters.

This study investigated resistance mechanisms and epidemiology of emerging linezolidnonsusceptible Enterococcus faecalis (LNSEF) in a tertiary care hospital. LNSEF isolated from clinical samples were collected from November 2017 to June 2019. The isolates were investigated for linezolid resistance and the associated molecular mechanisms, including mutations of 23S rRNA domain V and acquisition of the cfr or optrA resistance gene. We used pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing for the molecular typing of the isolates. Among 4,318 E. faecalis isolates, 10 (0.23%) were linezolid-nonsusceptible. All LNSEF isolates were optrA-positive and cfr-negative. Of these isolates, five were sequence type (ST) 476, two ST585, one ST16, one ST16-like, and one ST480. Six LNSEF isolates obtained in the first year clustered to three types in the PFGE analysis: two ST476 isolates of type A, two ST585 isolates of type B, and two ST16 or ST16-like isolates of type C. Seven cases were of community-onset and three were hospital acquired, but total of eight were healthcare-associated including five community-onset. None of the patients had a history of linezolid treatment, and in one patient, we detected linezolid-susceptible E. faecalis one month before LNSEF detection. In conclusion, heterogenous clones of optrA-positive LNSEF emerged in the hospital mainly via communityonset. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.