scholarly journals Diagnosis and Analysis of a Recent Case of Human Rabies in Canada

2002 ◽  
Vol 13 (2) ◽  
pp. 129-133 ◽  
Author(s):  
Lindsay D Elmgren ◽  
Susan A Nadin-Davis ◽  
Frances T Muldoon ◽  
Alexander I Wandeler
Keyword(s):  
Polymerase Chain Reaction ◽  
Rabies Virus ◽  
False Negative ◽  
Strain Identification ◽  
Direct Immunofluorescence ◽  
Product Analysis ◽  
Chain Reaction ◽  
Food Inspection ◽  
Polymerase Chain ◽  
Rabies Diagnosis

BACKGROUND: On September 30, 2000, staff at the Canadian Food Inspection Agency's Centre of Expertise for Rabies, located at the Animal Diseases Research Institute in Ottawa, Ontario, diagnosed rabies in a child from Quebec. This was the first case of rabies in a human in Canada in 15 years and in 36 years in the province of Quebec. After spending a week in intensive care in a Montreal hospital, the nine-year-old boy succumbed to this nearly always fatal disease. The boy had been exposed to a bat in late August 2000, while vacationing with his family in the Quebec countryside.METHODS: Antemortem specimens taken from the patient were sent to the Canadian Food Inspection Agency laboratory for rabies diagnosis. Samples included saliva, eye secretions, corneal impressions, cerebral spinal fluid and skin. Specimens were examined by direct immunofluorescence microscopy, and results were confirmed using molecular biological techniques. Virus strain identification was performed by both genetic methods and phenotypic analysis with monoclonal antibodies.RESULTS: Initial results from direct immunofluorescence staining indicated that rabies virus was present in the skin biopsy specimen but not in the corneal impressions. This diagnosis of rabies was confirmed by polymerase chain reaction product analysis from several of the submitted specimens. Virus isolation from postmortem samples was not possible because fresh brain tissue was not available. Rabies virus was isolated from saliva and was determined to be similar to a variant that circulates in populations of silver-haired bats.INTERPRETATION: Intravitam diagnosis of rabies in humans is very dependent on the samples submitted for diagnosis and the method used for testing. Upon first examination, only skin specimens were positive for rabies virus antigen; using polymerase chain reaction analysis, only saliva yielded positive results for rabies virus genome. Extensive testing and retesting of specimens submitted for rabies diagnosis in humans must be done to avoid false negative results.

scholarly journals Digital Droplet PCR for SARS-CoV-2 Resolves Borderline Cases

2021 ◽  
Author(s):  
Jing Xu ◽  
Timothy Kirtek ◽  
Yan Xu ◽  
Hui Zheng ◽  
Huiyu Yao ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Limit Of Detection ◽  
False Negative ◽  
Accurate Method ◽  
Viral Envelope ◽  
Chain Reaction ◽  
Borderline Cases ◽  
Droplet Pcr ◽  
Polymerase Chain ◽  
Digital Polymerase Chain Reaction

Abstract Objectives The Bio-Rad SARS-CoV-2 ddPCR Kit (Bio-Rad Laboratories) was the first droplet digital polymerase chain reaction (ddPCR) assay to receive Food and Drug Administration (FDA) Emergency Use Authorization approval, but it has not been evaluated clinically. We describe the performance of ddPCR—in particular, its ability to confirm weak-positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) results. Methods We clinically validated the Bio-Rad Triplex Probe ddPCR Assay. The limit of detection was determined by using serial dilutions of SARS-CoV-2 RNA in an artificial viral envelope. The ddPCR assay was performed according to the manufacturer’s specifications on specimens confirmed to be positive (n = 48) or negative (n = 30) by an FDA-validated reverse transcription–polymerase chain reaction assay on the m2000 RealTime system (Abbott). Ten borderline positive cases were also evaluated. Results The limit of detection was 50 copies/mL (19 of 20 positive). Forty-seven specimens spanning a range of quantification cycles (2.9-25.9 cycle numbers) were positive by this assay (47 of 48; 97.9% positive precent agreement), and 30 negative samples were confirmed as negative (30 of 30; 100% negative percent agreement). Nine of 10 borderline cases were positive when tested in triplicate. Conclusions The ddPCR of SARS-CoV-2 is an accurate method, with superior sensitivity for viral RNA detection. It could provide definitive evaluation of borderline positive cases or suspected false-negative cases.

scholarly journals UTILITY OF ANTIGEN DETECTION TEST AND POLYMERASE CHAIN REACTION IN THE DIFFERENTIATION OF TUBERCULOUS AND NON-TUBERCULOUS MYCOBACTERIA

2017 ◽  
Vol 10 (6) ◽  
pp. 289
Author(s):  
Yogita Singh ◽  
Raji Vasanth ◽  
Shrikala Baliga ◽  
Dhanashree B
Keyword(s):  
Polymerase Chain Reaction ◽  
False Negative ◽  
Diagnostic Methods ◽  
Clinical Samples ◽  
Chain Reaction ◽  
College Hospital ◽  
Medical College ◽  
Negative Results ◽  
Polymerase Chain ◽  
Mycobacterium Spp

Objectives: Cultivation and identification of mycobacteria to species level remains difficult and time-consuming. Hence, easy and rapid diagnostic methods are necessary for the differentiation of Mycobacterium tuberculosis (MTB) from non-tuberculous mycobacteria (NTM). The present study aims to detect and differentiate MTB from NTM isolated from clinical samples by immunochromatographic test (ICT) and polymerase chain reaction (PCR). Methods: Over a period of 1 year, clinical samples (n=496) received from suspected cases of TB, at the Department of Microbiology, Kasturba Medical College Hospital, Mangalore were cultured to isolate Mycobacterium spp. Identification of all the isolates was done by conventional biochemical technique, ICT, and PCR. Results: Among the 496 samples processed, 49 (9.87%) were acid-fast bacilli smear positive and 59 (11.89%) samples showed the growth of Mycobacterium spp. Among these, 10 were rapid growers, 49 were slow-growing mycobacteria, out of which 30 were MTB as identified by conventional biochemical reaction. Out of 59 Mycobacterial isolates subjected to ICT for the detection of MPT 64 antigen, only 28 were identified as MTB. However, all the 30 isolates were correctly identified as MTB by PCR. Conclusion: Hence, PCR is essential for rapid differentiation of non-tuberculous Mycobacterium from MTB. False negative results seen with immunochromatographic MPT 64 antigen assay could be due to mutations within the mpt64 gene. Further studies are necessary to characterize these PCR-positive and immunochromatographic assay negative MTB isolates.

scholarly journals Comparison of polymerase chain reaction and microscopy for the detection of Fasciola spp. in the fecal matter of domestic bovines in Kalasin Province, Thailand

2021 ◽  
pp. 2878-2882
Author(s):  
Sirikanda Thanasuwan ◽  
Anupong Tankrathok
Keyword(s):  
Polymerase Chain Reaction ◽  
False Negative ◽  
Economic Losses ◽  
Rrna Gene ◽  
28S Rrna ◽  
Chain Reaction ◽  
Fecal Matter ◽  
Specificity And Sensitivity ◽  
Polymerase Chain ◽  
Fasciola Spp

Background and Aim: Fasciola spp. are important foodborne trematodes and waterborne zoonotic parasites that cause health problems and economic losses worldwide, including in Thailand. Fasciola spp. are usually detected by sedimentation or the formalin-ethyl acetate concentration technique (FECT) under microscopy, which is less specific and sensitive. Accurate detection is important to detect real incidence for protection against and elimination of fasciolosis in the area. This study aimed to determine the distribution of Fasciola spp. and compare the specificity and sensitivity of FECT under microscopy to that of polymerase chain reaction (PCR) in cattle feces. Materials and Methods: The study was conducted in Kalasin Province, Thailand. Feces of 46 cattle were investigated for infection with Fasciola spp. To detect infection, FECT under microscopy and PCR amplification of the 28S rRNA gene of Fasciola spp. were used to identify egg parasites. Results: Feces of 16 of 46 (34.78%) cattle were positive for Fasciola spp. using FECT under microscopy, whereas PCR showed that 67.39% (31 of 46) were positive for Fasciola spp. False-negative results were as high as 32.61% when diagnosed under microscopy. Conclusion: This study confirmed the infection of cattle with Fasciola spp. in Kalasin Province, indicating that PCR demonstrated higher sensitivity and specificity when diagnosing infection. FECT under microscopy can still be used as a primary and traditional method for diagnosis. However, relapse cases of Fasciola spp. and Paramphistomum spp. should be diagnosed by microscopy combined with PCR. This is the first report on the molecular distribution of fecal samples in cattle in Kalasin Province.

Polymerase chain reaction detection of melanoma cells in the circulation: relation to clinical stage, surgical treatment, and recurrence from melanoma.

1998 ◽  
Vol 16 (5) ◽  
pp. 1760-1769 ◽  
Author(s):  
B J Curry ◽  
K Myers ◽  
P Hersey
Keyword(s):  
Polymerase Chain Reaction ◽  
Regional Lymph Node ◽  
Clinical Stage ◽  
False Negative ◽  
Primary Melanoma ◽  
Melanoma Cells ◽  
Early Postoperative Period ◽  
Chain Reaction ◽  
Negative Results ◽  
Polymerase Chain

PURPOSE The detection of melanoma cells in the circulation by polymerase chain reaction (PCR) assays has been shown by several investigators to correlate with the stage of the disease and possibly with prognosis. PATIENTS AND METHODS We performed prospective studies on 276 patients with primary melanoma and regional lymph node (LN) metastases to assess the predictive value of PCR detection of tyrosinase and melanoma antigen recognized by T cells-1 (MART-1) in the blood for recurrence of melanoma. RESULTS PCR tests for gp 100, Muc-18, and p97 reacted with RNA in blood from healthy subjects and were considered unsuitable for patient monitoring. The tests were most frequently positive in the first 3 months after surgery. There were 47 recurrences in 123 patients who had been followed up for 18 months. Assays within 3 months of surgery predicted recurrence from melanoma in 66% of the latter (tests for tyrosinase alone detected 51% and MART-1 alone 21% of the patients). Hence, 34% of recurrences were not predicted by tests in the early postoperative period. This did not appear to be because of marker-negative melanoma because summation of tests over the first year identified 89% of those with recurrent disease. CONCLUSION Positive tests were recorded in 35% of patients who remained disease free, but it is too early to assess whether these represent false-positive results. The false-negative results raise the question of whether the assays will provide a reliable basis for selection of patients for adjuvant therapy.

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