Correction to: Diagnostic performance of four SARS-CoV-2 antibody assays in patients with COVID-19 or with bacterial and non-SARS-CoV-2 viral respiratory infections

European Journal of Clinical Microbiology & Infectious Diseases -     

Long-term coexistence of SARS-CoV-2 with antibody response in COVID-19 patients

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causing coronavirus disease 2019 (COVID-19) has spread worldwide. Whether antibodies are important for the adaptive immune responses against SARS-CoV-2 infection needs to be determined. Here, 26 cases of COVID-19 in Jinan, China, were examined and shown to be mild or with common clinical symptoms, and no case of severe symptoms was found among these patients. Strikingly, a subset of these patients had SARS-CoV-2 and virus-specific IgG coexist for an unexpectedly long time, with two cases for up to 50 days. One COVID-19 patient who did not produce any SARS-CoV-2–bound IgG successfully cleared SARS-CoV-2 after 46 days of illness, revealing that without antibody-mediated adaptive immunity, innate immunity alone may still be powerful enough to eliminate SARS-CoV-2. This report may provide a basis for further analysis of both innate and adaptive immunity in SARS-CoV-2 clearance, especially in nonsevere cases.     

Diagnostic usefulness of subgenomic RNA detection of viable SARS-CoV-2 in patients with COVID-19

ObjectivesThe development of a rapid diagnostic test for viable SARS-CoV-2 is important for infection control. Real-time RT-PCR assays detect non-viable virus, and cell culture differentiates viable virus but it takes several weeks and is labour-intensive. Subgenomic RNAs may reflect replication-competent virus. We therefore evaluated the usefulness of subgenomic RNAs for diagnosing viable SARS-CoV-2 in patients with COVID-19.MethodsPatients with various severities of confirmed COVID-19 were enrolled at a tertiary hospital between February and December 2020. RT-PCR assay results for genomic and subgenomic RNA of SARS-CoV-2 from nasopharyngeal swab, sputum and saliva specimens were compared with cell culture results.ResultsA total 189 specimens from 20 COVID-19 patients were tested in genomic and subgenomic PCR assays and cultured on Vero cells. Of these 189 samples, 62 (33%) gave positive culture results, 93 (49%) negative results and the remaining 34 (18%) indeterminate results. Compared with cell culture results, the sensitivities of genomic RNA and subgenomic RNA of the N and S genes were comparable at 100%, but the specificity of subgenomic RNA (N, 65% and S, 68%) was higher than that of genomic RNA (N, 23% and S, 17%, p < 0.001). The mean durations of positive culture and subgenomic RNA were 11.39 ± 10.34 and 13.75 ± 11.22 days after symptom onset (p 0.437), respectively, while that of genomic RNA was 22.85 ± 11.83 days after symptom onset (p < 0.001).DiscussionOur comparison of subgenomic RNA detection with symptom duration and SARS-CoV-2 culture positivity provides a significant advancement on the transmissibility-based approach beyond the detection of SARS-CoV-2 genomic RNA, and warrants further studies on the development of better diagnostic strategy.     

Antibody dynamics to SARS-CoV-2 in asymptomatic COVID-19 infections

Background

The missing asymptomatic COVID-19 infections have been overlooked because of the imperfect sensitivity of the nucleic acid testing (NAT). Globally understanding the humoral immunity in asymptomatic carriers will provide scientific knowledge for developing serological tests, improving early identification, and implementing more rational control strategies against the pandemic.

Measure

Utilizing both NAT and commercial kits for serum IgM and IgG antibodies, we extensively screened 11 766 epidemiologically suspected individuals on enrollment and 63 asymptomatic individuals were detected and recruited. Sixty-three healthy individuals and 51 mild patients without any preexisting conditions were set as controls. Serum IgM and IgG profiles were further probed using a SARS-CoV-2 proteome microarray, and neutralizing antibody was detected by a pseudotyped virus neutralization assay system. The dynamics of antibodies were analyzed with exposure time or symptoms onset.

Results

A combination test of NAT and serological testing for IgM antibody discovered 55.5% of the total of 63 asymptomatic infections, which significantly raises the detection sensitivity when compared with the NAT alone (19%). Serum proteome microarray analysis demonstrated that asymptomatics mainly produced IgM and IgG antibodies against S1 and N proteins out of 20 proteins of SARS-CoV-2. Different from strong and persistent N-specific antibodies, S1-specific IgM responses, which evolved in asymptomatic individuals as early as the seventh day after exposure, peaked on days from 17 days to 25 days, and then disappeared in two months, might be used as an early diagnostic biomarker. 11.8% (6/51) mild patients and 38.1% (24/63) asymptomatic individuals did not produce neutralizing antibody. In particular, neutralizing antibody in asymptomatics gradually vanished in two months.

Conclusion

Our findings might have important implications for the definition of asymptomatic COVID-19 infections, diagnosis, serological survey, public health, and immunization strategies.

     

Viable SARS-CoV-2 in various specimens from COVID-19 patients

ObjectivesThe aim was to determine whether various clinical specimens obtained from COVID-19 patients contain the infectious virus.MethodsTo demonstrate whether various clinical specimens contain the viable virus, we collected naso/oropharyngeal swabs and saliva, urine and stool samples from five COVID-19 patients and performed a quantitative polymerase chain reaction (qPCR) to assess viral load. Specimens positive with qPCR were subjected to virus isolation in Vero cells. We also used urine and stool samples to intranasally inoculate ferrets and evaluated the virus titres in nasal washes on 2, 4, 6 and 8 days post infection.ResultsSARS-CoV-2 RNA was detected in all naso/oropharyngeal swabs and saliva, urine and stool samples collected between days 8 and 30 of the clinical course. Notably, viral loads in urine, saliva and stool samples were almost equal to or higher than those in naso/oropharyngeal swabs (urine 1.08 ± 0.16–2.09 ± 0.85 log₁₀ copies/mL, saliva 1.07 ± 0.34–1.65 ± 0.46 log₁₀ copies/mL, stool 1.17 ± 0.32 log₁₀ copies/mL, naso/oropharyngeal swabs 1.18 ± 0.12–1.34 ± 0.30 log₁₀ copies/mL). Further, viable SARS-CoV-2 was isolated from naso/oropharyngeal swabs and saliva of COVID-19 patients, as well as nasal washes of ferrets inoculated with patient urine or stool.DiscussionViable SARS-CoV-2 was demonstrated in saliva, urine and stool samples from COVID-19 patients up to days 11–15 of the clinical course. This result suggests that viable SARS-CoV-2 can be secreted in various clinical samples and respiratory specimens.     

SARS-CoV-2 antibody dynamics and B-cell memory response over time in COVID-19 convalescent subjects

ObjectivesThe worldwide spread of coronavirus disease 2019 (COVID-19) highlights the need for assessment of long-term humoral immunity in convalescent subjects. Our objectives were to evaluate long-term IgG antibody response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and B-cell memory response in COVID-19 convalescent subjects.MethodsBlood samples were collected from a cohort of subjects recovering from COVID-19 and from healthy subjects who donated blood. SARS-CoV-2 IgG antibodies were quantitatively detected by ELISA using anti-S1 spike IgG. SARS-CoV-2 spike-specific IgG memory B cells were evaluated by reversed B-cell FluroSpot based on human IgG SARS-CoV-2 receptor-binding domain in a randomly selected group of subjects recovering from COVID-19. Statistical analysis was performed with clinical variables and time post COVID-19 infection.ResultsAntibody response was not detected in 26 of 392 COVID-19 convalescent subjects (6.6%). Over a period of 9 months, the level of antibodies decreased by 50% but stabilized at 6 months, and a protective level prevailed for up to 9 months. No differences were found regarding IgG SARS-CoV-2 antibody levels for age, gender, and major blood types over time. Over time, asymptomatic COVID-19 subjects did not differ in antibody level from subjects with mild to severe disease. Repeated paired IgG SARS-CoV-2 antibody level analyses disclosed that, over 6 and 9 months, 15.3% (nine of 59) and 15.8% (three of 19) of subjects became SARS-CoV-2 IgG-seronegative, respectively, all with a low antibody level at 3 months. Rate of antibody decline was not affected by age, gender, or clinical symptomatology. In a subgroup of recovering subjects, memory B-cell response up to 9 months post-COVID-19 infection was undetectable in 31.8% of subjects (14/44), and there was no correlation with age, SARS-CoV-2 antibody level, or time post infection.ConclusionsThe majority of convalescent COVID-19 subjects develop an IgG SARS-CoV-2 antibody response and a protective level prevails over a period of up to 9 months, regardless of age, gender, major blood types or clinical symptomatology.     

The kinetics of SARS-CoV-2 viremia in COVID-19 patients receiving remdesivir

Detection of SARS-CoV-2 RNA in serum, viremia, has been linked to disease severity and outcome. The kinetics of viremia in patients receiving remdesivir has not been thoroughly studied and could help predict treatment response and outcome. We investigated the kinetics of SARS-CoV-2 viremia and factors associated with baseline viremia, viral clearance and 30-day mortality in patients receiving remdesivir. An observational study including 378 hospitalised patients (median age 67 years, 67% male) sampled with serum SARS-CoV-2 RT-PCR within ± 24 h of initiation of remdesivir treatment. Baseline viremia was present in 206 (54%) patients with a median Ct value of 35.3 (IQR = 33.3–37.1). In patients with baseline viremia, the estimated probability of viral clearance was 72% by day 5. Ct values decreased significantly during remdesivir treatment for viremic patients, indicating an increase in viral load. In total, 44 patients (12%) died within 30 days, and mortality was significantly associated with viremia at baseline (OR = 2.45, p = 0.01) and lack of viral clearance by day 5 (OR = 4.8, p =  < 0.01). Viral clearance was not associated with any individual risk factor. Viremia appears to be a prognostic marker before and during remedesivir treatment. The resolution of viremia was similar to patients not receiving remdesivir in other studies, and the decrease in Ct values during treatment questions the antiviral capacity of remdesivir in vivo. Prospective studies are warranted to confirm our findings.

     

The nasopharyngeal microbiota in patients with viral respiratory tract infections is enriched in bacterial pathogens

The nasopharynx is the primary site of colonization by respiratory pathogen that constitutes the port of entrance in the respiratory tract. The role of mucosal respiratory microbiota in infection has been recently emphasized; therefore, we aimed to assess if a specific respiratory microbiota profile was associated with symptomatic infection and/or with presence of respiratory viruses. We performed a case-control study to characterize the healthy respiratory microbiota and its alteration during acute viral infections. Next-generation sequencing of the 16S rRNA gene was applied to 225 nasopharyngeal samples from 177 patients with viral respiratory infection and 48 matched healthy controls. We evidenced an important decrease of bacterial alpha-diversity in patients with symptomatic respiratory infection and a loss of the healthy core microbiota, specifically anaerobes and Prevotella spp. Moreover, eight respiratory pathogens were enriched in these patients, including Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Dol osigranulum pigrum and Corynebacterium propinquum/pseudodiphtheriticum, whose role in respiratory infection is unclear. The asymptomatic carrier of influenza harbors a microbiota similar to healthy subjects, suggesting a critical role of microbiota in the clinical expression of viruses. These data suggest that the commensal microbiota plays a significant role in susceptibility to viral infection. The frequent co-detection of virus and bacteria raises the question of a strategy to prevent bacterial disease, focusing on the prevention of nasopharyngeal colonization through effective antibiotic treatment. In addition to antibiotics, further studies should test preventive or therapeutic interventions for maintaining or restoring a healthy nasopharyngeal microbiota.     

Identification of viral and atypical bacterial pathogens in children hospitalized with acute respiratory infections in Hong Kong by multiplex PCR assays

Acute respiratory tract infection is a leading cause of hospital admission of children. This study used a broad capture, rapid and sensitive method (multiplex PCR assay) to detect 20 different respiratory pathogens including influenza A subtypes H1, H3, and H5; influenza B; parainfluenza types 1, 2, 3, and 4; respiratory syncytial virus (RSV) groups A and B; adenoviruses; human rhinoviruses; enteroviruses; human metapneumoviruses; human coronaviruses OC43, 229E, and SARS‐CoV; Chlamydophila pneumoniae; Legionella pneumophila; and Mycoplasma pneumoniae; from respiratory specimens of 475 children hospitalized over a 12‐month period for acute respiratory tract infections. The overall positive rate (47%) was about twice higher than previous reports based on conventional methods. Influenza A, parainfluenza and RSV accounted for 51%, and non‐cultivable viruses accounted for 30% of positive cases. Influenza A peaked at March and June. Influenza B was detected in January, February, and April. Parainfluenza was prevalent throughout the year except from April to June. Most RSV infections were found between February and September. Adenovirus had multiple peaks, whereas rhinovirus and coronavirus OC43 were detected mainly in winter and early spring. RSV infection was associated with bronchiolitis, and parainfluenza was associated with croup; otherwise the clinical manifestations were largely nonspecific. In general, children infected with influenza A, adenovirus and mixed viruses had higher temperatures. In view of the increasing concern about unexpected outbreaks of severe viral infections, a rapid multiplex PCR assay is a valuable tool to enhance the management of hospitalized patients, and for the surveillance for viral infections circulating in the community. J. Med. Virol. 81:153–159, 2009. © 2008 Wiley‐Liss, Inc.     

The interface between COVID-19 and bacterial healthcare-associated infections

BackgroundA wide range of bacterial infections occur in coronavirus disease 2019 (COVID-19) patients, particularly in those with severe coronaviral disease. Some of these are community-acquired co-infections.ObjectiveTo review recent data that indicate the occurrence of hospital-onset bacterial infections, including with antibiotic-resistant isolates, in COVID-19 patients.SourcesUsing PubMed, the literature was searched using terms including: ‘COVID-19’; ‘SARS-CoV-2’; ‘bacterial infection’; ‘healthcare-associated infection’; ‘antibiotic resistance’; ‘antimicrobial resistance’; ‘multi-drug resistance’; ‘Streptococcus’; ‘Staphylococcus’; ‘Pseudomonas’; ‘Escherichia’; ‘Klebsiella’; ‘Enterococcus’; ‘Acinetobacter’; ‘Haemophilus’; ‘MRSA’; ‘VRE’; ‘ESBL’; ‘NDM-CRE’; ‘CR-Ab’; ‘VRSA’; ‘MDR’.ContentThere is a growing number of reports of bacterial infections acquired by patients with severe COVID-19 after hospital admission. Antibiotic-resistant pathogens found to cause healthcare-associated infections (HAIs) in COVID-19 patients include methicillin-resistant Staphylococcus aureus, New Delhi metallo-β-lactamase-producing carbapenem-resistant Enterobacterales, carbapenem-resistant Acinetobacter baumannii, extended-spectrum β-lactamase Klebsiella pneumoniae and vancomycin-resistant enterococci. COVID-19 has impacted bacterial HAIs in a number of ways with an increase in the incidence of New Delhi metallo-β-lactamase-producing carbapenem-resistant Enterobacterales and carbapenem-resistant A. baumannii reported at some hospital sites compared with before the pandemic. Recommended guidelines for antimicrobial stewardship in COVID-19 patient treatment are discussed regarding minimization of empiric broad-spectrum antibiotic use. Other studies have reported a decrease in methicillin-resistant S. aureus and vancomycin-resistant enterococci cases, which has been attributed to enhanced infection prevention and control practices introduced to minimize intra-hospital spread of COVID-19.ImplicationsPoorer outcomes have been observed in hospitalized COVID-19 patients with an antibiotic-resistant infection. Although heightened IPC measures have been accompanied by a reduction in some HAIs at specific sites, in other situations, COVID-19 has been associated with an increase in bacterial HAI incidence. Further research is needed to define the cost–benefit relationship of maintaining COVID-19-related infection prevention and control protocols beyond the pandemic to reduce the burden of HAIs. In addition, the longer-term impact of high usage of certain broad-spectrum antibiotics during the COVID-19 pandemic requires evaluation.