Viral RNA level, serum antibody responses, and transmission risk in discharged COVID-19 patients with recurrent positive SARS-CoV-2 RNA test results: a population-based observational cohort study

SummaryO_ST_ABSBackgroundC_ST_ABSManaging discharged COVID-19 (DC) patients with recurrent positive (RP) SARS-CoV-2 RNA test results is challenging. We aimed to comprehensively characterize the viral RNA level and serum antibody responses in RP-DC patients and evaluate their viral transmission risk. MethodsA population-based observational cohort study was performed on 479 DC patients discharged from February 1 to May 5, 2020 in Shenzhen, China. We conducted RT-qPCR, antibody assays, neutralisation assays, virus isolation, whole genome sequencing (WGS), and epidemiological investigation of close contacts. FindingsOf 479 DC patients, the 93 (19%) RP individuals, including 36 with multiple RP results, were characterised by young age (median age: 34 years, 95% confidence interval [CI]: 29-38 years). The median discharge-to-RP length was 8 days (95% CI: 7-14 days; maximum: 90 days). After readmission, RP-DC patients exhibited mild (28%) or absent (72%) symptoms, with no disease progression. The viral RNA level in RP-DC patients ranged from 1{middle dot}9-5{middle dot}7 log10 copies/mL (median: 3{middle dot}2, 95% CI: 3{middle dot}1-3{middle dot}5). At RP detection, the IgM, IgG, IgA, total antibody, and neutralising antibody (NAb) seropositivity rates in RP-DC patients were 38% (18/48), 98% (47/48), 63% (30/48), 100% (48/48), and 91% (39/43), respectively. Regarding antibody levels, there was no significant difference between RP-DC and non-RP-DC patients. The antibody level remained constant in RP-DC patients pre- and post-RP detection. Virus isolation of nine representative specimens returned negative results. WGS of six specimens yielded only genomic fragments. No clinical symptoms were exhibited by 96 close contacts of 23 RP-DC patients; their viral RNA (96/96) and antibody (20/20) test results were negative. After full recovery, 60% of patients (n=162, 78 no longer RP RP-DC and 84 non-RP-DC) had NAb titres of [≥]1:32. InterpretationRP may occur in DC patients following intermittent and non-stable excretion of low viral RNA levels. RP-DC patients pose a low risk of transmitting SARS-CoV-2. An NAb titre of [≥] 1:32 may provide a reference indicator for evaluating humoral responses in COVID-19 vaccine clinical trials. FundingSanming Project of Medicine in Shenzhen, China National Science and Technology Major Projects Foundation, Special Foundation of Science and Technology Innovation Strategy of Guangdong Province of China, and Shenzhen Committee of Scientific and Technical Innovation grants.

Epidemiologic and etiologic characteristics of diarrheagenic Escherichia coli infection in population in Shenzhen / 中华流行病学杂志

<p><b>OBJECTIVE</b>To understand the epidemiologic and etiologic characteristics of diarrheagenic Escherichia (E.) coli infections in Shenzhen.</p><p><b>METHODS</b>Stool samples were collected from acute diarrheal patients in four sentinel hospitals in Shenzhen and diarrheagenic E. coli strains were isolated and identified with multiplex real-time PCR. Serotyping and pulsed-field gel electrophoresis (PFGE) typing were conducted for the diarrheagenic E. coli isolates.</p><p><b>RESULTS</b>A total of 74 diarrheagenic E. coli strains were isolated from 1 823 stool samples (4.06%). The patients were mainly young children aged <3 years and adults aged 20-39 years, and the infections mainly occurred during May-September of a year. Enterotoxigenic E. coli (ETEC) and enteropathognic E. coli (EPEC) were predominant (45.9% and 31.1%). Serogroups and PFGE patterns varied among the diarrheagenic E. coli isolates. However, serogroup O159 were predominant in ETEC and there were 5 clusters with ≥2 strains sharing same PFGE patterns.</p><p><b>CONCLUSIONS</b>ETEC and EPEC were predominant in diarrheagenic E. coli strains isolated from diarrheal patients in Shenzhen. Age and season specific characteristics of diarrheagenic E. coli infections were observed. The serotypes and PFGE patterns of diarrheagenic E. coli strains varied. Close attention should be paid to the possible ETEC outbreak.</p>

Etiological and molecular characteristics of diarrhea caused Proteus mirabilis / 中华流行病学杂志

<p><b>OBJECTIVE</b>To analyze the etiological characteristics, virulence genes and plasmids that carrying diarrhea-causing Proteus mirabilis and to assess their relationship with drug resistance and pathogenicity.</p><p><b>METHODS</b>Proteus mirabilis coming from six different sources (food poisoning, external environment and healthy people) were analyzed biochemically, on related susceptibility and pulsed-field gel electrophoresis (PFGE). Virulence genes were detected by PCR. Plasmids were extracted and sequenced after gel electrophoresis purification.</p><p><b>RESULTS</b>The biochemical characteristics of Proteus mirabilis from different sources seemed basically the same, and each of them showed having common virulence genes, as ureC, rsmA, hpmA and zapA. However, the PFGE patterns and susceptibility of these strains were different, so as the plasmids that they carried. Plasmid that presented in the sequenced strain showed that the 2 683 bp length plasmid encodes qnrD gene was associated with the quinolone resistance.</p><p><b>CONCLUSION</b>Etiological characteristics and molecular characteristics of Proteus mirabilis gathered from different sources, were analyzed. Results indicated that traditional biochemical analysis and common virulence gene identification might be able to distinguish the strains with different sources. However, PFGE and plasmids analysis could distinguish the sources of strains and to identify those plasmids that commonly carried by the drug-resistant strains. These findings also provided theoretical basis for further study on the nature of resistance and pathogenicity in Proteus mirabilis.</p>

Etiological and molecular characteristics of diarrhea caused Proteus mirabilis / 中华流行病学杂志

Objective To analyze the etiological characteristics,virulence genes and plasmids that carrying diarrhea-causing Proteus mirabilis and to assess their relationship with drug resistance and pathogenicity. Methods Proteus mirabilis coming from six different sources (food poisoning,external environment and healthy people) were analyzed biochemically,on related susceptibility and pulsed-field gel electrophoresis (PFGE). Virulence genes were detected by PCR. Plasmids were extracted and sequenced after gel electrophoresis purification. Results The biochemical characteristics of Proteus mirabilis from different sources seemed basically the same,and each of them showed having common virulence genes,as ureC,rsmA,hpmA and zapA. However,the PFGE patterns and susceptibility of these strains were different,so as the plasmids that they carried. Plasmid that presented in the sequenced strain showed that the 2 683 bp length plasmid encodes qnrD gene was associated with the quinolone resistance. Conclusion Etiological characteristics and molecular characteristics of Proteus mirabilis gathered from different sources,were analyzed. Results indicated that traditional biochemical analysis and common virulence gene identification might be able to distinguish the strains with different sources. However,PFGE and plasmids analysis could distinguish the sources of strains and to identify those plasmids that commonly carried by the drug-resistant strains. These findings also provided theoretical basis for further study on the nature of resistance and pathogenicity in Proteus mirabilis.

Etiological and molecular characteristics of diarrhea caused Proteus mirabilis / 中华流行病学杂志

Objective To analyze the etiological characteristics,virulence genes and plasmids that carrying diarrhea-causing Proteus mirabilis and to assess their relationship with drug resistance and pathogenicity. Methods Proteus mirabilis coming from six different sources (food poisoning,external environment and healthy people) were analyzed biochemically,on related susceptibility and pulsed-field gel electrophoresis (PFGE). Virulence genes were detected by PCR. Plasmids were extracted and sequenced after gel electrophoresis purification. Results The biochemical characteristics of Proteus mirabilis from different sources seemed basically the same,and each of them showed having common virulence genes,as ureC,rsmA,hpmA and zapA. However,the PFGE patterns and susceptibility of these strains were different,so as the plasmids that they carried. Plasmid that presented in the sequenced strain showed that the 2 683 bp length plasmid encodes qnrD gene was associated with the quinolone resistance. Conclusion Etiological characteristics and molecular characteristics of Proteus mirabilis gathered from different sources,were analyzed. Results indicated that traditional biochemical analysis and common virulence gene identification might be able to distinguish the strains with different sources. However,PFGE and plasmids analysis could distinguish the sources of strains and to identify those plasmids that commonly carried by the drug-resistant strains. These findings also provided theoretical basis for further study on the nature of resistance and pathogenicity in Proteus mirabilis.

Establishment and application of a molecular typing system of Staphylococcus aureus based on resolution melting / 国际检验医学杂志

Objective To establish a molecular typing system of Staphylococcus aureus by using resolution melting for food-poi-soning fast tracing.Methods Primers were designed and synthesized according to the literature of VNTR in Staphylococcus au-reus ,and were used to perform molecular typing on the strains which had detected by PFGE,then 4 types of VNTRs were with higher discriminatory power were selected.On this basis,we established a molecular typing system for the detection of 59 Staphy-lococcus aureus isolated from food poisoning.Results The molecular typing system has good precision for detection.The standard deviation(s)of within-batch repetitive experiments were 0.03 -0.05 ℃,between-batch repetitive experiments were 0.04 -0.06℃,between-day repetitive experiments were 0.04-0.06 ℃.At the same time,the 59 strains of Staphylococcus aureus were divided into 19 types which were 11 epidemic clones and 8 sporadic clones.The correlation coefficient of Simpson was 0.916 4.Conclusion The molecular typing system for Staphylococcus aureus based on resolution melting was simple,fast and repeatable.It can be ap-plied to fast tracing and screen of Staphylococcus aureus in food poisoning.