Optimizing heat inactivation for SARS-CoV-2 at 95 °C and its implications: A standardized approach.

Background: Standardized and validated heat inactivation procedure for Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not available. For heat inactivation, various protocols were reported to prepare External Quality Assessment Programme (EQAP) samples without direct comparison between different durations. Objective: To assess the heat inactivation procedures against SARS-CoV-2. The efficacy of the optimized condition was reflected by the results from laboratories testing the EQAP samples. Study design: The SARS-CoV-2 strain was exposed to 95 °C in a water bath for three different time intervals, 5 min, 10 min and 15 min, respectively. The efficacy of inactivation was confirmed by the absence of cytopathic effects and decreasing viral load in 3 successive cell line passages. The viral stock inactivated by the optimal time interval was dispatched to EQAP participants and the result returned were analyzed. Results: All of the three conditions were capable of inactivating the SARS-CoV-2 of viral load at around cycle threshold value of 10. When the 95 °C 10 min condition was chosen to prepare SARS-CoV-2 EQAP samples, they showed sufficient homogeneity and stability. High degree of consensus was observed among EQAP participants in all samples dispatched. Conclusions: The conditions evaluated in the present study could be helpful for laboratories in preparing SARS-CoV-2 EQAP samples.

Analytical sensitivity of the Rapid Antigen Test kits for detection of SARS-CoV-2 Omicron variant BA.2 sublineage.

The severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) Omicron was classified as a variant of concern in November 2021. The sublineage BA.2 spreads rapidly worldwide. Currently, there is a lack of data for the parallel comparison of Rapid Antigen Test (RAT) Kits to detect SARS-CoV-2 Omicron BA.2. We evaluated the analytical sensitivity of 12 RAT kits to detect Omicron BA.2 in the present study. Analytical sensitivity was determined by means of the limit of detection (LOD). We prepared a dilution set using a respiratory specimen collected from a COVID-19 patient infected by Omicron BA.2. The reverse transcription-polymerase chain reaction was used as a reference method. The LOD results showed that all 12 RAT kits had comparable analytical sensitivity to detect Omicron BA.2. The RAT kits selected in the current study may be used for the first-line screening of the rapid spreading Omicron BA.2.

Evaluation of automated antigen detection test for detection of SARS-CoV-2.

RT-PCR is the gold standard to detect SARS-CoV-2, however, its capacity is limited. We evaluated an automated antigen detection (AAD) test, Elecsys SARS-CoV-2 Antigen (Roche, Germany), for detecting SARS-CoV-2. We compared the limit of detection (LOD) between AAD test, rapid antigen detection (RAD) test; SARS-CoV-2 Rapid Antigen Test (SD Biosensor, Korea), and in-house RT-PCR test. LOD results showed that the AAD test was 100 fold more sensitive than the RAD test, while the sensitivity of the AAD test was comparable to the RT-PCR test. The AAD test detected between 85.7% and 88.6% of RT-PCR-positive specimens collected from COVID-19 patients, false negative results were observed for specimens with Ct values >30. Although clinical sensitivity for the AAD test was not superior or comparable to the RT-PCR test in the present study, the AAD test may be an alternative to RT-PCR test in terms of turn-around time and throughput.

Evaluation of rapid antigen detection kit from the WHO Emergency Use List for detecting SARS-CoV-2.

BACKGROUND: Currently, there are two rapid antigen detection (RAD) kits from the WHO Emergency Use List for detecting SARS-CoV-2. OBJECTIVE: The Panbio COVID-19 Ag Rapid Test Device was selected to evaluate the performance for detecting SARS-CoV-2. STUDY DESIGN: Analytical sensitivity for the detection of SARS-CoV-2 virus was determined by limit of detection (LOD) using RT-PCR as a reference method. Clinical sensitivity was evaluated by using respiratory specimens collected from confirmed COVID-19 patients. RESULTS: The LOD results showed that the RAD kit was 100 fold less sensitive than RT-PCR. Clinical sensitivity of the RAD kit was 68.6 % for detecting specimens from COVID-19 patients. CONCLUSIONS: The RAD kit evaluated in the present study shared similar performance with another kit from the WHO Emergency Use List, the Standard Q COVID-19 Ag. Understanding the clinical characteristics of RAD kits can guide us to decide different testing strategies in different settings.

Quinolone resistance and correlation to other antimicrobial resistances in faecal isolates of Escherichia coli in Hong Kong.

In an attempt to assess the level of quinolone resistance and its association with other antimicrobial resistance in faecal Escherichia coli isolated from routine outpatient specimens in Hong Kong, ciprofloxacin-supplemented MacConkey agar was used to screen for resistant isolates. Antimicrobial susceptibility testing of the isolates was done by VITEK 2 and previous amplification-based methods were employed to characterize the genetic determinants behind some of the resistance phenotypes. One hundred and seventy-six (43%) of 409 specimens had quinolone-resistant E. coli isolated (199 isolates). Quinolone resistance was found to be associated with resistances to penicillins (>80%) and co-trimoxazole (69%). Nonsusceptibility to combinations of penicillins and clavulanic acid was above 20% and up to 50% for the aminoglycosides gentamicin and tobramycin. CTX-M-type extended-spectrum beta-lactamases were found responsible for most cephalosporin resistances but the transferable quinolone resistance determinant qnrA was not detected. Our data suggested that a high percentage of E. coli isolates as part of the alleged normal intestinal microflora in humans appeared to be resistant to quinolones. Co-resistance to various other frequently used antimicrobials was also observed. Transferable genetic determinants were found to be involved in some cases.