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AimSARS-CoV-2 has been detected in stool samples of COVID-19 patients, with potential implications for faecal-oral transmission. Compared to swab samples, the complexity of the stool matrix poses a challenge in the detection of the virus that has not yet been solved. The aim of this study was to establish a sensitive and reliable method for detecting SARS-CoV-2 in stool samples. MethodsStool samples from individuals free of SARS-CoV-2 were homogenised in saline buffer and spiked with a known titre of inactivated virus ranging from 50 to 750 viral particles per 100 mg stool. Debris was removed via centrifugation and supernatants were concentrated by ultrafiltration. RNA was then extracted from the concentrated material using a commercial kit and SARS-CoV-2 was detected via real-time reverse-transcription polymerase chain reaction (RT-qPCR) using the CDC primers and probes. ResultsThe RNA extraction procedure we used allowed the detection of SARS-CoV-2 via RT-qPCR in most of the stool samples tested. We could detect as few as 50 viral particles per 100 mg of stool. However, high variability was observed across samples at low viral titres. The primer set targeting the N1 region provided more reliable and precise results and for this primer set our method had a limit of detection of 1 viral particle per mg of stool. ConclusionsHere we describe a sensitive method for detecting SARS-CoV-2 in stool samples. This method can be used to establish the persistence of SARS-CoV-2 in stool and ensure the safety of clinical practices such as faecal microbiota transplant (FMT).
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Objective@# To apply DNA barcoding to identifying the rodents in Zhejiang Province. @*Methods @#Rodents were captured from Jiashan,Longyou,Yunhe and Ninghai counties in Zhejiang Province. The DNA was extracted from ears of rodent samples,and was amplified and sequenced with mitochondrial cytochrome C oxidase subunit I（COI）genes. The obtained sequences were compared with the related sequences in GenBank,and neighbour-joining evolutionary tree was constructed. Then the results by DNA barcoding and by morphological identification were compared. @*Results @#A total of 22 COI gene samples were amplified. The evolutionary tree constructed by 18 samples was consistent with the morphological identification results and 4 samples were different：Suncus murinus should be Crocidura lasiura,infant rats of Rattus losea and Rattus tanezumi was re-identified as Rattus rattus,infant rats of Microtus fortis（sample number：NH-1）needs further identification. @*Conclusion @#DNA barcoding can effectively correct the errors of morphological identification,thus combining the two methods could improve the accuracy of rodent identification.
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Background Leber hereditary optic neuropathy (LHON) is a maternally inherited disease caused by mitochondrial DNA (mtDNA) mutation with the common mutation sites of m.3460 G＞A,m.11778 G＞A and m.14484 T＞C,and other mutation sites are rare.Understanding the mutation type of mtDNA in LHON patients has an important clinical significance.Objective This study was to analyze the clinical features of LHON and detect the mitochondrial mutation.Methods Twelve unrelated Chinese patients who was diagnosed as LHON were included in Peking University People's Hospital from 2010 to 2014.The visual acuity,perimetry,ocular segment,visual evoked potential,fundus were binocularly examined.The peripheral blood of 4 ml was collected from each patient and mtDNA was amplified and sequenced by using PCR.Three common genetic mutation sites for LHON and other mutation sites were determined and analyzed.This study protocol was approved by Ethic Committee of Peking University People's Hospital and complied with Helsinki Declaration.Written informed consent was obtained from each patient prior to any medical examination.Results Of the 12 patients,11 were male and 1 was female.The visual acuity of both eyes reduced simultaneously in 7 patients,and the visual acuity of left eye and the right eye first reduced in 3 patients and 1 patient,respectively.There was no significant correlation in the visual impairment between the left and right eyes (P＞0.05).In the near vision of the patients,J7 was invisible in 18 eyes,and J7 were obtained in 3 eyes,J6 were obtained in 2 eyes and J2 was obtained in 1 eye.In the distant vision of the patients,hand movement was obtained in 1 eye,light perception was obtained in 1 eye,0.01-0.1 were obtained in 18 eyes and 0.12-0.3 were obtained in 2 eyes.The visual field defect of nasal lateral was found in 7 eyes,visual field defect of temporal lateral was found in 3 eyes and the visual field defect of central was found in 8 eyes.mtDNA sequencing revealed that m.3460 G＞A mutation was seen in 3 patients,m.11778 G＞A mutation was seen in 5 patients and m.14484 T＞C mutation was seen in 2 patients.In addition,other 2 mutations were found in 2 patients,which were m.3497 C＞T and m.10663 T＞C mutations at the MT-ND1 and MT-ND4L genes,respectively.Conclusions LHON is more common in male.Visual impairment shows the varying degrees between both eyes of patients and appears to be severe in near vision.Central visual field defect is common in LHON patients.This study detects m.3497 C＞T and m.10663 T＞C mutation in Chinese LHON patients.