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Several commercial nucleic acid amplification tests (NAAT) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed. We used six kits available in Japan in 13 NAAT-positive specimens with crossing point values >36 and 7 NAAT-negative specimens from patients with coronavirus disease (COVID-19); their results were compared. Specimens positive in ≥2 assays were considered true positive and examined for concordance with specimen results. The SARS-CoV-2 Detection Kit -Multi- (Toyobo M) (Toyobo, Osaka, Japan) using extracted RNA had the highest concordance (κ 1.00). This was followed by the cobas® SARS-CoV-2 (Cobas) (Roche, Basel, Switzerland) (κ 0.79). There was a weak correlation between number of negative results for each kit and days between onset and testing (Spearman rank correlation: ρ= 0.44; p

The quantitative reverse transcription polymerase chain reaction method using nasopharyngeal swabs (NPS RT-qPCR) is regarded as the reference standard for diagnosing coronavirus disease 2019 (COVID-19). However, when using NPS RT-qPCR at busy airport quarantine stations, there are constraints on testing capacity, time, travelerstolerance, and availability of personal protective equipment for quarantine officers. A feasible alternative is therefore needed to test incoming travelers, especially when passenger numbers increase with the resumption of business, tourism, and economic activities. To explore alternatives to NPS RT-qPCR, we collected nasopharyngeal, anterior nasal, and saliva samples chronologically over days 1-7 from asymptomatic COVID-19 air travelers who were under quarantine at a designated facility, and we then compared test results for 9 different methods, comprising RT-qPCR (including the reference method), loop-mediated isothermal amplification (LAMP), and qualitative and quantitative antigen testing. We evaluated sensitivity for 97 person-day samples independently to evaluate asymptomatic travelers regardless of their testing date and period of asymptomatic status upon entry. Sensitivity of the different tests varied from 46.6% to 81.0%, but this was improved from 72.7% to 100.0% when the viral load was > 10 4 copies/sample on NPS RT-qPCR. Thus, most high-risk asymptomatic travelers with higher viral load would be detected by the tests evaluated. Quantitative antigen testing using saliva samples showed 90.9% sensitivity and provided quicker results, and should be an acceptable alternative to NPS RT-qPCR at busy airport quarantine stations. We discuss the implications of our exploratory findings for establishing a comprehensive and feasible testing strategy for COVID-19 among air passengers.

Background The current gold standard in coronavirus disease (COVID-19) diagnostics is the real-time reverse transcription–polymerase chain reaction (RT-PCR) assay for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in nasopharyngeal swab (NPS) samples. Alternatively, nasal swab (NS) or saliva swab (SS) specimens are used, although available data on test accuracy are limited. We examined the diagnostic accuracy of NPS/NS/SS samples for this purpose. Methods Ten patients were included after being tested positive for SARS-CoV-2 RT-PCR in NPS samples according to the National Institute of Infectious Disease guidelines. In comparison with this conventional diagnostic method, NPS/NS/SS samples were tested using the cobas 6800 systems RT-PCR device. To investigate the usefulness of the cobas method and the difference among sample types, the agreement and sensitivity were calculated. Five to six samples were collected over a total period of 5–6 d from each patient. Results Fifty-seven sets of NPS/NS/SS samples were collected, of which 40 tested positive for COVID-19 by the conventional method. Overall, the concordance rates using the conventional method were 86.0%/70.2%/54.4% for NPS/NS/SS samples (cobas); however, for samples collected up to and including on Day 9 after disease onset (22 negative and one positive specimens), the corresponding rates were 95.7%/87.0%/65.2%. The overall sensitivity estimates were 100.0%/67.5%/37.5% for NPS/NS/SS samples (cobas). For samples up to 9 d after onset, the corresponding values were 100.0%/86.4%/63.6%. Conclusions NS samples are more reliable than SS samples and can be an alternative to NPS samples. They can be a useful diagnostic method in the future.

Little is known about the prevalence of β-lactamase production in penicillin-susceptible Staphylococcus aureus isolates under high-susceptibility conditions. We analyzed S. aureus isolates with penicillin G minimum inhibitory concentration (MIC) ≤ 0.12 μg/ml that were recovered from in-/outpatients (n = 108) between 2016 and 2017 in Japan. β-Lactamase production was detected by nitrocefin-based and Clinical and Laboratory Standards Institute penicillin zone edge testing and blaZ PCR. All isolates were categorized as having penicillin G MIC ≤0.03 μg/ml using an automated system; MICs determined based on the microdilution method were 0.016 μg/ml (2%), 0.03 μg/ml (44%), and 0.06 μg/ml (54%). Notably, no isolates harbored the blaZ gene. The results from the nitrocefin-based and zone edge tests were consistent with those obtained by PCR. S. aureus isolates with penicillin G MIC ≤0.03 μg/ml exhibited a low frequency of β-lactamase production. Thus, screening for β-lactamase production may be unnecessary for isolates showing such high susceptibility.