Time filter

Source Type

Divis P.C.,University Malaysia Sarawak | Shokoples S.E.,Provincial Laboratory for Public Health | Singh B.,University Malaysia Sarawak | Yanow S.K.,Provincial Laboratory for Public Health | Yanow S.K.,University of Alberta
Malaria Journal

Background: The misdiagnosis of Plasmodium knowlesi by microscopy has prompted a re-evaluation of the geographic distribution, prevalence and pathogenesis of this species using molecular diagnostic tools. In this report, a specific probe for P. knowlesi, that can be used in a previously described TaqMan real-time PCR assay for detection of Plasmodium spp., and Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale, was designed and validated against clinical samples. Methods. A hydrolysis probe for a real-time PCR assay was designed to recognize a specific DNA sequence within the P. knowlesi small subunit ribosomal RNA gene. The sensitivity, linearity and specificity of the assay were determined using plasmids containing P. knowlesi DNA and genomic DNA of P. falciparum, P. knowlesi, P. malariae, P. ovale and P. vivax isolated from clinical samples. DNA samples of the simian malaria parasites Plasmodium cynomolgi and Plasmodium inui that can infect humans under experimental conditions were also examined together with human DNA samples. Results. Analytical sensitivity of the P. knowlesi-specific assay was 10 copies/L and quantitation was linear over a range of 10-106 copies. The sensitivity of the assay is equivalent to nested PCR and P. knowlesi DNA was detected from all 40 clinical P. knowlesi specimens, including one from a patient with a parasitaemia of three parasites/L of blood. No cross-reactivity was observed with 67 Plasmodium DNA samples (31 P. falciparum, 23 P. vivax, six P. ovale, three P. malariae, one P. malariae/P. ovale, one P. falciparum/P. malariae, one P. inui and one P. cynomolgi) and four samples of human DNA. Conclusions. This test demonstrated excellent sensitivity and specificity, and adds P. knowlesi to the repertoire of Plasmodium targets for the clinical diagnosis of malaria by real-time PCR assays. Furthermore, quantitation of DNA copy number provides a useful advantage over other molecular assays to investigate the correlation between levels of infection and the spectrum of disease. © 2010 Divis et al; licensee BioMed Central Ltd. Source

Bright A.T.,University of California at San Diego | Manary M.J.,University of California at San Diego | Tewhey R.,Scripps Research Institute | Arango E.M.,University of Antioquia | And 5 more authors.
PLoS Neglected Tropical Diseases

Plasmodium vivax infects a hundred million people annually and endangers 40% of the world's population. Unlike Plasmodium falciparum, P. vivax parasites can persist as a dormant stage in the liver, known as the hypnozoite, and these dormant forms can cause malaria relapses months or years after the initial mosquito bite. Here we analyze whole genome sequencing data from parasites in the blood of a patient who experienced consecutive P. vivax relapses over 33 months in a non-endemic country. By analyzing patterns of identity, read coverage, and the presence or absence of minor alleles in the initial polyclonal and subsequent monoclonal infections, we show that the parasites in the three infections are likely meiotic siblings. We infer that these siblings are descended from a single tetrad-like form that developed in the infecting mosquito midgut shortly after fertilization. In this natural cross we find the recombination rate for P. vivax to be 10 kb per centimorgan and we further observe areas of disequilibrium surrounding major drug resistance genes. Our data provide new strategies for studying multiclonal infections, which are common in all types of infectious diseases, and for distinguishing P. vivax relapses from reinfections in malaria endemic regions. This work provides a theoretical foundation for studies that aim to determine if new or existing drugs can provide a radical cure of P. vivax malaria. © 2014 Bright et al. Source

Manage D.P.,University of Alberta | Chui L.,Provincial Laboratory for Public Health | Chui L.,University of Alberta | Pilarski L.M.,University of Alberta
Microfluidics and Nanofluidics

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is a common human disease that is prevalent in resource-deprived areas of the world. Current detection techniques for TB require expensive conventional instruments in a laboratory setting, preventing accessible and low cost diagnosis of the disease. Using a loop-mediated isothermal amplification (LAMP) assay, we have amplified and detected TB in a 6 × 8 semisolid polyacrylamide gel post array using an inexpensive prototype instrument. Each post contains 670 nL of volume, minimizing the need for large quantities of reagents. Amplified DNA is detected via fluorescence of the dye LCGreen Plus+, which is polymerized into the gel along with other reagents. The prototype device contains a Peltier element for heating, a diode laser as an excitation source, and a CCD camera for detecting fluorescence in real-time. About 12 Mycobacterium tuberculosis genomes per gel post can be detected within 75 min of amplification. This sensitivity is similar to that obtained by conventional methods using a commercial thermocycler. We achieved comparable LAMP amplification when the template is added externally or when the template is polymerized in the gel. This rapid isothermal amplification technology, with its simple thermal requirements, has the potential to be integrated into micro-devices and serves as a model for implementing future low-cost point of care diagnostics. © 2012 Springer-Verlag Berlin Heidelberg. Source

Pang X.L.,Provincial Laboratory for Public Health | Pang X.L.,University of Alberta | Preiksaitis J.K.,University of Alberta | Lee B.E.,University of Alberta
Journal of Medical Virology

Viral gastroenteritis causes significant mortality and morbidity worldwide. Identifying the etiology of viral gastroenteritis is a challenge as most enteric viruses (EVs) are non-culturable. This study is to develop an EV testing panel using real-time PCR (EVPrtPCR) to simultaneously detect rotavirus, norovirus, sapovirus, astrovirus, and enteric adenovirus in stool samples. EVPrtPCR using universal amplification conditions was run in a single instrument run. EVPrtPCR was used to test 2,486 sporadic gastroenteritis samples submitted for EV testing using electron microscopy (EM) between July 2008 and July 2009. Retesting spiked negative stool samples and Salmon DNA as internal control were used to evaluate inhibition. EVPrtPCR detected viruses in significantly more samples: 748 (34%) as compared to 94 (3.8%) by EM. EM did not detect any norovirus, sapovirus, and mixed infection, and detected only 39% of rotavirus and 38.2% of enteric adenovirus positive samples. Four samples that tested positive for rotavirus and two for adenovirus and for small-round-structured viruses by EM were negative by EVPrtPCR. Norovirus was the most common virus detected (17.6%) with 92.4% as genogroup II, followed by rotavirus (6.8%), sapovirus (4.2%), astrovirus (2.0%), and enteric adenovirus (1.4%) with 9% samples positive for mixed infection. Overall, EV identification followed a U-shaped age distribution; positive samples were more common in children ≤5 years old and adults >60 years old. Norovirus, sapovirus and astrovirus showed winter predominance and rotavirus peaked in the spring. No inhibition was observed. Molecular technology significantly enhanced the identification of EV causing sporadic gastroenteritis in Alberta. © 2013 Wiley Periodicals, Inc. Source

Hawan A.,Armed Forces Hospital | Drews S.J.,Provincial Laboratory for Public Health | Drews S.J.,University of Calgary | Richardson S.E.,University of Toronto
Clinical Microbiology and Infection

This study compares the performance of four commercial multiplex PCR assays (Resplex II Panel v2.0, Seeplex RV15, xTAG RVP and xTAG RVP Fast) and direct fluorescent antibody (DFA) staining and viral isolation. Seven hundred and fifty nasopharyngeal swabs were tested for 17 viral agents. In each assay, the sensitivity and specificity for each target were determined against a composite reference standard. Two hundred and eighty-eight out of 750 (38.4%) specimens were positive by DFA or viral isolation, while an additional 214 (28.5%) were positive by multiplex PCR, for a total positivity rate of 66.9%. Of 502 positive specimens, one virus was detected in 420 specimens (83.7%), two in 77 (15.3%), three in four (0.8%) and four in one case (0.2%). Compared with a composite reference standard, the inter-assay accuracy of the multiplex PCR assays varied, but all were superior to conventional diagnostic methods in detecting a broad range of respiratory viral agents in children. In addition, the sensitivity of two commercial assays, Resplex II Plus PRE and Seeplex Influenza A/B Subtyping, was determined relative to the Astra influenza Screen & Type assay for detection of influenza A viruses, including seasonal influenzas and pandemic H1N1 2009 influenza A virus. Using 75 positive and 55 negative nasopharyngeal swabs for influenza A by the Astra assay, the sensitivity of Seeplex and Resplex was 95.9% and 91.8%, respectively, with a specificity of 100% for both. © 2011 The Authors. Clinical Microbiology and Infection © 2011 European Society of Clinical Microbiology and Infectious Diseases. Source

Discover hidden collaborations