The coronavirus disease 2019 pandemic, elicited by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is ongoing. Currently accessible antigen-detecting rapid diagnostic tests are limited by their low sensitivity and detection efficacy due to evolution of SARS-CoV-2 variants. Here, we produced and characterized an anti-SARS-CoV-2 nucleocapsid (N) protein-specific monoclonal antibody (mAb), 2A7H9. Monoclonal antibody 2A7H9 and a previously developed mAb, 1G10C4, have different specificities. The 2A7H9 mAb detected the N protein of S clade, delta, iota, and mu but not omicron, whereas the 1G10C4 antibody recognized the N protein of all variants under study. In a sandwich enzyme-linked immunosorbent assay, recombinant N protein bound to the 1G10C4 mAb could be detected by both 1G10C4 and 2A7H9 mAbs. Similarly, N protein bound to the 2A7H9 mAb was detected by both mAbs, confirming the existence of dimeric N protein. While the 1G10C4 mAb detected omicron and mu with higher efficiency than S clade, delta, and iota, the 2A7H9 mAb efficiently detected all the strains except omicron, with higher affinity to S clade and mu than others. Combined use of 1G10C4 and 2A7H9 mAb resulted in the detection of all the strains with considerable sensitivity, suggesting that antibody combinations can improve the simultaneous detection of virus variants. Therefore, our findings provide insights into the development and improvement of diagnostic tools with broader specificity and higher sensitivity to detect rapidly evolving SARS-CoV-2 variants.

Background: Long-term trends in influenza-related hospitalizations, critical care resource use, and hospital outcomes since the 2009 H1N1 influenza pandemic season have been rarely studied for adult populations. Materials and Methods: Adult patients from the Korean Health Insurance Review and Assessment Service who were hospitalized with influenza over a 10-year period (2009–2019) were analyzed. The incidence rates of hospitalization, critical care resource use, and in-hospital death were calculated using mid-year population census data. Results: In total, 300,152 hospitalized patients with influenza were identified (men, 35.7%; admission to tertiary hospitals, 9.4%). Although the age-adjusted hospitalization rate initially decreased since the 2009 H1N1 pandemic (52.61/100,000 population in 2009/2010), it began to increase again in 2013/2014 and reached a peak of 169.86/100,000 population in 2017/2018 (p < 0.001). The in-hospital mortality rate showed a similar increasing trend as the hospitalization, with a peak of 1.44/100,000 population in 2017/2018 (vs. 0.35/100,000 population in 2009/2010; p < 0.001). The high incidence rates of both hospitalization and in-hospital mortality were mainly attributable to patients aged ≥60 years. The rate of intensive care unit admission and the use of mechanical ventilation, continuous renal replacement therapy and vasopressors have also increased from the 2013/2014 season. The incidence of heart failure was the most frequent complication investigated, with a three-fold increase in the last two seasons since 2009/2010. In multivariate analysis adjusted for covariates, among hospitalized patients, type of hospitals and 2009 H1N1 pandemic season were associated with in-hospital mortality. Conclusions: We confirmed that the rates of hospitalization, critical care resource use, and in-hospital mortality by influenza have increased again in recent years. Therefore, strategies are needed to reduce infections and optimize resource use with a greater focus on older people.

Carbapenemase-producing Enterobacterales (CPE) are of serious concern worldwide due to high morbidity and mortality. To evaluate the impact of the result of a subsequent polymerase chain reaction (PCR) test for carbapenemase after serial negative surveillance cultures on positive culture conversion in patients with three consecutive negative surveillance cultures for CPE, and to identify risk factors for conversion. A retrospective study of patients with positive CPE cultures on CHROMagar KPC medium was performed in a Korean tertiary hospital from October 2018 to December 2022. PCR for bla_KPC, bla_NDM, bla_IMP, bla_VIM, bla_GES, and bla_OXA-48 was performed after three consecutive negative rectal swab cultures. Clinical characteristics and outcomes of patients were compared according to whether follow-up PCR was positive (CNPP) or negative (CNPN). Of 1075 patients with positive CPE cultures, 150 (14.0%) yielded three consecutive negative rectal swab cultures. Of these, 50 (33.3%) were CNPP, and 100 (66.7%) were CNPN. Risk factors associated with a positive PCR result on multivariate analysis were: age, central venous catheter, and Escherichia coli infection. CNPP patients were more likely to have positive culture conversion for CPE than CNPN patients (39/44 (88.6%) vs 21/50 (42.0%), P<0.001). In multivariate analysis, independent risk factors for culture conversion were: a positive PCR result after surveillance cultures, diabetes mellitus, central venous catheter, and Klebsiella pneumoniae. CNPP patients have higher rates of culture conversion than CNPN patients, and a follow-up PCR test after serial negative surveillance cultures is useful in deciding whether or not to discontinue contact precautions.