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Objective: To analyze the epidemiological characteristics and influencing factors of COVID-19 confirmed cases with viral nucleic acid re-positive in anal and/or throat swabs after discharge during the domestic imported epidemic stage in Guangdong Province in early 2020. Methods: The COVID-19 confirmed cases with the onset time before March 1, 2020 in Guangdong Province were collected to analyze the demographic data, epidemiological characteristics, and specimen collection and testing data after discharge. Logistic regression model was used for influencing factors analysis of re-positive cases. Results: A total of 1 286 COVID-19 confirmed cases were included, the M(Q1,Q3) of age was 44(32,58)years, 617 cases were male, 224 cases were re-positive in anal and/or throat swabs with the re-positive rate 17.42%. The M(Q1,Q3) of age of re-positive cases was 35(23, 50) years, which was younger than that of re-negative cases age was those 46(33, 59) years (P<0.001). With the increase of age, re-positive rate decreased (χ2trend=52.73, P<0.001). 85.27% (191/224) of re-positive cases were found in 14 d after discharge, the duration time of re-positive status was 13(7, 24) d, and 81.69% (183/224) of re-positive cases were re-tested negative in 28 d after re-positive date. No fever and other symptoms had been observed among re-positive cases during the whole follow-up. No secondary infectious cases had been found among close contacts after 14 d of centralized isolation and sampling screening. Univariate logistic regression model analysis revealed that the influencing factors of the re-positive cases included age, occupation, clusters, clinical types, and admission time. Multivariate logistic regression model analysis revealed that age was an independent risk factor. Conclusions: SARS-CoV-2 viral nucleic acid re-positive is found in COVID-19 confirmed cases after discharge in Guangdong Province. Most re-positive cases are confirmed among 14 d after discharge and re-test to negative among 28 d after re-positive date. Age is an risk factor for re-positive cases after discharge.
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Humans , Male , COVID-19 , China/epidemiology , Epidemics , Nucleic Acids , SARS-CoV-2ABSTRACT
Objective To study the serotypes,virulence features and molecular characteristics of Vibrio parahaemaolyticus isolated in food poisoning cases and surveillance program on diarrhea patients in Guangdong,2009.Methods 95 Vibrio parahaemolyticus strains from food poisoning cases and 15 strains from surveillance program on diarrhea patients were serotyped and detected for tdh(thermostable direct hemolysin,tdh)and trh(tdh-related hemolysin gene,trh)by PCR.81 sero-variant Vibrio parahaemolyticus strains were selected through PFGE subtyping.Results There were 15 Vibrio parahaemolyticus strains isolated from surveillance program on diarrhea patients and 95 strains were isolated from 11 Vibrio parahaemolyticus-caused food poisoning cases in 2009.Among these strains,O3:K6(46.67％ and 44.21％)and O4:K8(33.33％ and 28.42％)were the dominant serotypes,but not the 7 food-borne strains.There were 93(84.54％)tdh +trh-,13(11.81％)tdh-trh-,and 3(3.65％)tdh+ trh + strains.The similarity value was between 57.7％ to 100.0％ of the 81 strains after PFGE sub-typing method and 36 PFGE subtypes were identified.PFGE001 and PFGE029 appeared to be the dominant subtypes.Conclusion O3:K6 and O4:K8 were the most dominant serotypes in Vibrio parahaemolyticus-caused diarrhea and food poisoning cases in Guangdong and tdh were detected in most of the strains.Dominant PFGE subtypes were causing both sporadic and outbreak cases in different areas in Guangdong province.
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Objective To understand the distribution,molecular characteristics and virulence genes of the O1 and O139 Vibrio cholerae isolates from the Pearl River Estuary water.Methods Vibrio cholerae isolates collected from the Pearl River estuary waters from January 2009 to December 2010,were tested by PCR for eight virulence-related genes,including cholera toxin(ctxA),zonula occludens toxin(zot),accessory cholera enterotoxin(ace),hemolysin(hlyA),toxin-coregulated pilus (tcpA),outer membrane protein(ompU),and the regulatory protein genes(tcpⅠ,toxR).Genetic relation was assessed by pulsed-field gel electrophoresis(PFGE)and the patterns were clustered by BioNumerics.Results From 1152 aquatic samples,69 isolates were identified,including 41 Inaba,18 Ogawa and 10 O139.All the isolates showed ctxA negative,while the hlyA and toxR genes were positive in all the isolates.34.15％(14/41)of the Inaba strains were hlyA + toxR + ompU + ace + zot + tcpI+,while 66.67％(12/18)belonged to Ogawa strains and 70％(7/10)of the O139 strains were hlyA + toxR+.Through PFGE analysis,the O1 isolates formed three clusters in this study.The patterns of O1 isolates differed widely,with the similarity as 72.8％-100.0％,while the patterns of O139 isolates having the similarity of 69.9％-95.5％.Conclusion The non-toxigenic O1 and O139 V.cholerae had a wide distribution in the environment of Pearl River estuary water during the nonepidemic period of cholera.All the aquatic isolates presented diversities on the related virulent genes.
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Objective To understand the phenotypic characteristics of foodbome Vibrio parahaemolyticus in Guangdong province through carrying out a comprehensive comparison including pulse field gel electrophoresis,ribotyping and serotyping.Methods 74 different Vibrio parahaemolyticus strains isolated from seafood and cases due to food poisoning in Guangdong province were under serotyping and susceptibility testing,in addition to the testing of direct heat hemolysin(tdh)and the heat hemolysin-related hemolysin hormone(trh)via PCR.Ribosomal genotyping(ribotyping)with EcoR Ⅰ restriction enzyme was utilized on 74 different Vibrio parahaemolyticus isolates,whereas pulsed-field gel electrophoresis(PFGE)with the Not Ⅰ restriction enzyme was used on 74 different Vibrio parahaemolyticus isolates.BioNumerics software was used to compare the isolates from different sources,times and places in order to elicit the correlation between different strains.Results Although Vibrio parahaemolyticus was 100.00％ sensitive to chloramphenicol,it still presented different levels of resistance against 13 other antibiotics.Among the 74 different strains of Vibrio parahaemolyticus under testing,24.32％ showed positive for the tdh virulence gene,whereas 4.05％ positive for trh.74 different Vibrio parahaemolyticus strains were found to belong to 26 serotypes,where the O5:K17 and O2:K28 serotypes were dominant in those isolates that causing seafood-poisoning.The O3:K6 serotype was found to be the dominant of those isolates that causing food-poisoning.Based on ribosomal genotyping,the 74 Vibrio parahaemolyticus isolates were divided into 62 different ribotypes,whereas the 74 strains of Vibrio parahaemolyticus were divided into 67 different PFGE types,thus exhibiting considerable genetic diversities of the strains.Conclusion Majority of the isolates causing food-poisoning carried tdh virulence gene.PFGE was shown to have the highest resolution,followed by ribotyping with serotyping being the lowest,where the combination of the three could improve the resolution.
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<p><b>OBJECTIVE</b>Through systematic monitoring of the number and strain types of O1 and O139 Vibrio cholerae in the Pearl River estuary waters to analyze it's relevance with the temperature of environment, and the relevance between strains in water and isolates during outbreaks and epidemics as well as to estimate the methods used for environmental water detection and the potential role in cholera surveillance program.</p><p><b>METHODS</b>Twenty-four stations along the Pearl River were selected and the water samples were collected monthly from March 2006 to February 2007. V. cholerae O1 and O139 strains were isolated from the samples. Real-time PCR established in our laboratory was used to detect V. cholerae O1 and O139. Air temperature and water temperature were collected during sampling. Pulsed field gel electrophoresis (PFGE) was applied in molecular typing of the isolates.</p><p><b>RESULTS</b>862 water samples were collected during the study period. A total number of 77 O1 and O139 V. cholerae were isolated in 67 water samples and the positive rates were 7.77% for isolation and 26.33% for real-time PCR. Seasonal trend of positive rates by month were approximately coincident with the change of water temperature. The positive rates in the stations in urban area were higher than those in other areas. Toxigenic O139 strains were found in one station located in downstream of a marine market. Most of the O1 and O139 isolates were non-toxigenic. No trend of seasonal variation of the strains was noticed. Within these 75 isolates, 49 PFGE patterns were identified and the patterns differed widely with the similarity of 57.4% - 100%.</p><p><b>CONCLUSION</b>V. cholerae existed as the natural habitat in estuary water of the Pearl River and showed obvious genetic diversity. Data from monitoring waters might show the separation of strains with certain seasonal association. But the crowd did not show the relationship between the infections. Results from water surveillance program might provide indicators on the appearance of cholera pathogen which might be used in assessing the environmental risk of cholera epidemics as well as the alert of cholera.</p>
Subject(s)
Electrophoresis, Gel, Pulsed-Field , Environmental Monitoring , Phylogeny , Polymerase Chain Reaction , Seasons , Temperature , Vibrio cholerae O1 , Classification , Genetics , Vibrio cholerae O139 , Classification , GeneticsABSTRACT
<p><b>OBJECTIVE</b>To develop a real-time SYBR Green polymerase chain reaction (PCR) for detection of Vibrio cholerae serogroups O1 and O139, and to evaluate its reliability through detection of estuary water samples.</p><p><b>METHODS</b>O antigen rfb genes specific for O1 and O139 were used for the design of PCR primers. The real-time SYBR Green PCR system in detecting O1 and O139 specific rfb genes in one tube was developed, and its sensitivity, specificity and reproducibility were evaluated. The ability of the real-time PCR in detection of estuary water samples was compared with the routine PCR and bacteria isolation.</p><p><b>RESULTS</b>The amplification of O1 or O139 specific target gene could be detected according to the melt curve temperature of amplicons. No amplification was observed in the templates of other 10 non-cholerae vibrios. When comparing to the real-time PCR to bacteria isolation in detection of 524 estuary water samples, it showed high sensitivity, plus also positive in real-time PCR detection among all the samples in which bacteria of O1 or O139 were isolated.</p><p><b>CONCLUSION</b>The real-time SYBR Green PCR could be used as the first step of rapid environment screen of V. cholerae in water samples thus might enhance the efficiency of isolation in screening of large amount of water samples.</p>