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Pavšič J, Žel J, Milavec M. Digital PCR for direct quantification of viruses without DNA extraction. Anal Bioanal Chem 2015; 408:67-75. [PMID: 26483186 PMCID: PMC4706837 DOI: 10.1007/s00216-015-9109-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 10/02/2015] [Accepted: 10/08/2015] [Indexed: 12/30/2022]
Abstract
DNA extraction before amplification is considered an essential step for quantification of viral DNA using real-time PCR (qPCR). However, this can directly affect the final measurements due to variable DNA yields and removal of inhibitors, which leads to increased inter-laboratory variability of qPCR measurements and reduced agreement on viral loads. Digital PCR (dPCR) might be an advantageous methodology for the measurement of virus concentrations, as it does not depend on any calibration material and it has higher tolerance to inhibitors. DNA quantification without an extraction step (i.e. direct quantification) was performed here using dPCR and two different human cytomegalovirus whole-virus materials. Two dPCR platforms were used for this direct quantification of the viral DNA, and these were compared with quantification of the extracted viral DNA in terms of yield and variability. Direct quantification of both whole-virus materials present in simple matrices like cell lysate or Tris-HCl buffer provided repeatable measurements of virus concentrations that were probably in closer agreement with the actual viral load than when estimated through quantification of the extracted DNA. Direct dPCR quantification of other viruses, reference materials and clinically relevant matrices is now needed to show the full versatility of this very promising and cost-efficient development in virus quantification.
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Affiliation(s)
- Jernej Pavšič
- Department of Biotechnology and Systems Biology, National Institute of Biology, Večna pot 111, 1000, Ljubljana, Slovenia.
- Jožef Stefan International Postgraduate School, Jamova cesta 39, 1000, Ljubljana, Slovenia.
| | - Jana Žel
- Department of Biotechnology and Systems Biology, National Institute of Biology, Večna pot 111, 1000, Ljubljana, Slovenia
| | - Mojca Milavec
- Department of Biotechnology and Systems Biology, National Institute of Biology, Večna pot 111, 1000, Ljubljana, Slovenia
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de Vries JJC, van der Eijk AA, Wolthers KC, Rusman LG, Pas SD, Molenkamp R, Claas EC, Kroes ACM, Vossen ACTM. Real-time PCR versus viral culture on urine as a gold standard in the diagnosis of congenital cytomegalovirus infection. J Clin Virol 2011; 53:167-70. [PMID: 22177273 DOI: 10.1016/j.jcv.2011.11.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 11/09/2011] [Accepted: 11/16/2011] [Indexed: 11/29/2022]
Abstract
BACKGROUND Cytomegalovirus (CMV) infection is the most common cause of congenital infection. Whereas CMV PCR has replaced viral culture and antigen detection in immunocompromised patients because of higher sensitivity, viral culture of neonatal urine is still referred to as the gold standard in the diagnosis of congenital CMV infection. OBJECTIVE To compare real-time CMV PCR with shell vial culture on urine in the diagnosis of congenital CMV, in a multicenter design. STUDY DESIGN A series of neonatal urines (n=340), received for congenital CMV diagnostics and routinely assessed with shell vial CMV culture, was retrospectively tested by real-time CMV PCR. RESULTS The proportion of newborns found to be congenitally infected by real-time CMV PCR was 8.2% (28/340, 95%CI 5.6-11.8%), and 7.4% (25/340, 95%CI 4.9-10.8%) by rapid culture. When considering rapid culture as reference, real-time PCR was highly sensitive (100%), whereas sensitivity of rapid culture was 89.3% when considering real-time PCR as reference. CONCLUSIONS Our results, supported by analytical and clinical data on CMV DNA detection in neonatal urine, suggest enhanced sensitivity of recent PCR techniques when compared to viral culture. There is considerable rationale to favor real-time CMV PCR as a gold standard in the diagnosis of congenital CMV infection. A large-scale study combining both laboratory and clinical data is required to determine the exact time frame for sampling of neonatal urine when using real-time PCR.
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Affiliation(s)
- Jutte J C de Vries
- Department of Medical Microbiology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
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Dhuruvasan K, Sivasubramanian G, Pellett PE. Roles of host and viral microRNAs in human cytomegalovirus biology. Virus Res 2010; 157:180-92. [PMID: 20969901 DOI: 10.1016/j.virusres.2010.10.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 10/11/2010] [Accepted: 10/12/2010] [Indexed: 02/02/2023]
Abstract
Human cytomegalovirus (HCMV) has a relatively large and complex genome, a protracted lytic replication cycle, and employs a strategy of replicational latency as part of its lifelong persistence in the infected host. An important form of gene regulation in plants and animals revolves around a type of small RNA known as microRNA (miRNA). miRNAs can serve as major regulators of key developmental pathways, as well as provide subtle forms of regulatory control. The human genome encodes over 900 miRNAs, and miRNAs are also encoded by some viruses, including HCMV, which encodes at least 14 miRNAs. Some of the HCMV miRNAs are known to target both viral and cellular genes, including important immunomodulators. In addition to expressing their own miRNAs, infections with some viruses, including HCMV, can result in changes in the expression of cellular miRNAs that benefit virus replication. In this review, we summarize the connections between miRNAs and HCMV biology. We describe the nature of miRNA genes, miRNA biogenesis and modes of action, methods for studying miRNAs, HCMV-encoded miRNAs, effects of HCMV infection on cellular miRNA expression, roles of miRNAs in HCMV biology, and possible HCMV-related diagnostic and therapeutic applications of miRNAs.
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Affiliation(s)
- Kavitha Dhuruvasan
- Department of Immunology and Microbiology, Wayne State University School of Medicine, 540 East Canfield Avenue, 6225 Scott Hall, Detroit, MI 48201, USA.
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Habbal W, Monem F, Gärtner BC. Comparative evaluation of published cytomegalovirus primers for rapid real-time PCR: which are the most sensitive? J Med Microbiol 2009; 58:878-883. [PMID: 19502375 DOI: 10.1099/jmm.0.010587-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Standardization of human cytomegalovirus (CMV) PCR is highly recommended. As primer design is essential for PCR sensitivity, this study evaluated all published CMV primer pairs to identify the most sensitive for single-round real-time PCR. PubMed (1993-2004) was searched for original papers aimed at CMV PCR. Fifty-seven papers were identified revealing 82 different primer pairs. Of these, 17 primer sets were selected for empirical study, as they were either used in real-time PCR or were evaluated comparatively by conventional PCR. After optimizing the PCR conditions, these primer sets were evaluated by real-time PCR using a SYBR Green format. Analytical sensitivities were assessed by testing the reference standard CMV strain AD169. A blast search was performed to identify mismatches with published sequences. Additionally, 60 clinical samples were tested with the three primer sets showing highest analytical sensitivity and the best match to all CMV strains. Three primer sets located in the glycoprotein B (UL55) gene region were found to be the most sensitive using strain AD169. However, two of these showed a considerable number of mismatches with clinical isolates in a blast search. Instead, two other pairs from the lower matrix phosphoprotein (UL83) gene and DNA polymerase (UL54) gene showed reasonable sensitivity and no mismatches with clinical isolates. These three pairs were further tested with clinical samples, which indicated that the two primer sets from UL55 and UL54 were the most sensitive. Interestingly, the analytical sensitivity of the PCR was inversely correlated with the size of the PCR product. In conclusion, these two primer pairs are recommended for a standardized, highly sensitive, real-time PCR.
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Affiliation(s)
- Wafa Habbal
- Clinical Laboratories Department, Al-Assad University Hospital, Damascus University, PO Box 10769, Damascus, Syria
| | - Fawza Monem
- Clinical Laboratories Department, Al-Assad University Hospital, Damascus University, PO Box 10769, Damascus, Syria
| | - Barbara C Gärtner
- Department of Virology, University of Saarland Medical School, D-66421 Homburg/Saar, Germany
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Espy MJ, Uhl JR, Sloan LM, Buckwalter SP, Jones MF, Vetter EA, Yao JDC, Wengenack NL, Rosenblatt JE, Cockerill FR, Smith TF. Real-time PCR in clinical microbiology: applications for routine laboratory testing. Clin Microbiol Rev 2006; 19:165-256. [PMID: 16418529 PMCID: PMC1360278 DOI: 10.1128/cmr.19.1.165-256.2006] [Citation(s) in RCA: 800] [Impact Index Per Article: 44.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Real-time PCR has revolutionized the way clinical microbiology laboratories diagnose many human microbial infections. This testing method combines PCR chemistry with fluorescent probe detection of amplified product in the same reaction vessel. In general, both PCR and amplified product detection are completed in an hour or less, which is considerably faster than conventional PCR detection methods. Real-time PCR assays provide sensitivity and specificity equivalent to that of conventional PCR combined with Southern blot analysis, and since amplification and detection steps are performed in the same closed vessel, the risk of releasing amplified nucleic acids into the environment is negligible. The combination of excellent sensitivity and specificity, low contamination risk, and speed has made real-time PCR technology an appealing alternative to culture- or immunoassay-based testing methods for diagnosing many infectious diseases. This review focuses on the application of real-time PCR in the clinical microbiology laboratory.
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Affiliation(s)
- M J Espy
- Mayo Clinic, 200 First St. SW, Hilton 470, Rochester, MN 55905, USA.
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Mackay IM, Arden KE, Nitsche A. Real-time Fluorescent PCR Techniques to Study Microbial-Host Interactions. METHODS IN MICROBIOLOGY 2004; 34:255-330. [PMID: 38620210 PMCID: PMC7148886 DOI: 10.1016/s0580-9517(04)34010-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This chapter describes how real-time polymerase chain reaction (PCR) performs and how it may be used to detect microbial pathogens and the relationship they form with their host. Research and diagnostic microbiology laboratories contain a mix of traditional and leading-edge, in-house and commercial assays for the detection of microbes and the effects they impart upon target tissues, organs, and systems. The PCR has undergone significant change over the last decade, to the extent that only a small proportion of scientists have been able or willing to keep abreast of the latest offerings. The chapter reviews these changes. It discusses the second-generation of PCR technology-kinetic or real-time PCR, a tool gaining widespread acceptance in many scientific disciplines but especially in the microbiology laboratory.
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Affiliation(s)
- Ian M Mackay
- Clinical Virology Research Unit, Sir Albert Sakzewski Virus Research Centre, Royal Children's Hospital, Brisbane, Qld, Australia
- Clinical Medical Virology Centre, University of Queensland, Brisbane, Qld, Australia
| | - Katherine E Arden
- Clinical Virology Research Unit, Sir Albert Sakzewski Virus Research Centre, Royal Children's Hospital, Brisbane, Qld, Australia
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Abstract
Use of PCR in the field of molecular diagnostics has increased to the point where it is now accepted as the standard method for detecting nucleic acids from a number of sample and microbial types. However, conventional PCR was already an essential tool in the research laboratory. Real-time PCR has catalysed wider acceptance of PCR because it is more rapid, sensitive and reproducible, while the risk of carryover contamination is minimised. There is an increasing number of chemistries which are used to detect PCR products as they accumulate within a closed reaction vessel during real-time PCR. These include the non-specific DNA-binding fluorophores and the specific, fluorophore-labelled oligonucleotide probes, some of which will be discussed in detail. It is not only the technology that has changed with the introduction of real-time PCR. Accompanying changes have occurred in the traditional terminology of PCR, and these changes will be highlighted as they occur. Factors that have restricted the development of multiplex real-time PCR, as well as the role of real-time PCR in the quantitation and genotyping of the microbial causes of infectious disease, will also be discussed. Because the amplification hardware and the fluorogenic detection chemistries have evolved rapidly, this review aims to update the scientist on the current state of the art. Additionally, the advantages, limitations and general background of real-time PCR technology will be reviewed in the context of the microbiology laboratory.
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Affiliation(s)
- I M Mackay
- Clinical Virology Research Unit, Sir Albert Sakzewski Virus Research Centre and Department of Paediatrics, Royal Children's Hospital, Brisbane, Queensland, Australia.
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Shrestha NK, Tuohy MJ, Hall GS, Reischl U, Gordon SM, Procop GW. Detection and differentiation of Mycobacterium tuberculosis and nontuberculous mycobacterial isolates by real-time PCR. J Clin Microbiol 2004; 41:5121-6. [PMID: 14605148 PMCID: PMC262464 DOI: 10.1128/jcm.41.11.5121-5126.2003] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Mycobacteria cause a variety of illnesses that differ in severity and public health implications. The differentiation of Mycobacterium tuberculosis from nontuberculous mycobacteria (NTM) is of primary importance for infection control and choice of antimicrobial therapy. Despite advances in molecular diagnostics, the ability to rapidly diagnose M. tuberculosis infections by PCR is still inadequate, largely because of the possibility of false-negative reactions. We designed and validated a real-time PCR for mycobacteria by using the LightCycler system with 18 reference strains and 168 clinical mycobacterial isolates. All clinically significant mycobacteria were detected; the mean melting temperatures (with 99.9% confidence intervals [99.9% CI] in parentheses) for the different mycobacteria were as follows: M. tuberculosis, 64.35 degrees C (63.27 to 65.42 degrees C); M. kansasii, 59.20 degrees C (58.07 to 60.33 degrees C); M. avium, 57.82 degrees C (57.05 to 58.60 degrees C); M. intracellulare, 54.46 degrees C (53.69 to 55.23 degrees C); M. marinum, 58.91 degrees C (58.28 to 59.55 degrees C); rapidly growing mycobacteria, 53.09 degrees C (50.97 to 55.20 degrees C) or 43.19 degrees C (42.19 to 44.49 degrees C). This real-time PCR assay with melting curve analysis consistently accurately detected and differentiated M. tuberculosis from NTM. Detection of an NTM helps ensure that the negative result for M. tuberculosis is a true negative. The specific melting temperature also provides a suggestion of the identity of the NTM present, when the most commonly encountered mycobacterial species are considered. In a parallel comparison, both the LightCycler assay and the COBAS Amplicor M. tuberculosis assay correctly categorized 48 of 50 specimens that were proven by culture to contain M. tuberculosis, and the LightCycler assay correctly characterized 3 of 3 specimens that contained NTM.
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Affiliation(s)
- Nabin K Shrestha
- Department of Infectious Diseases. Section of Clinical Microbiology, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
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Gourlain K, Salmon D, Gault E, Leport C, Katlama C, Matheron S, Costagliola D, Mazeron MC, Fillet AM. Quantitation of cytomegalovirus (CMV) DNA by real-time PCR for occurrence of CMV disease in HIV-infected patients receiving highly active antiretroviral therapy. J Med Virol 2003; 69:401-7. [PMID: 12526052 DOI: 10.1002/jmv.10303] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In HIV-infected patients treated with highly active antiretroviral therapy (HAART) included in the Predivir cohort, we have evaluated the usefulness of CMV DNA quantitation by a TaqMan PCR assay from peripheral blood leukocytes (PBLs) to predict CMV disease occurrence. In parallel with the immune restoration after treatment by HAART, the percentage of positive samples decreased progressively from 7.3% at Day 0 to 3.5% at Month 12. Among the CMV markers, the smallest concordance with PBL CMV TaqMan PCR, as evaluated by kappa, was observed with pp65 antigenemia, whereas concordance with all other CMV markers was high. Among the 16 patients with CMV DNA copies at least once >100/150,000 cells, CMV disease occurred in six during follow-up, whereas among the 159 patients with CMV DNA copies always <10/150,000 cells, CMV disease occurred in three and among the seven patients with CMV DNA copies >10 and <100 occurred in only one. In univariate Cox models, all the CMV markers including PBL CMV TaqMan PCR >10/150,000 cells (RR: 27.6, IC95: 7.1-107.2), the CD4 cell count <75 cells/mm(3) and the HIV viral load >100,000 copies/ml were predictive for CMV disease. In a stepwise multivariate analysis, which should be interpreted with caution due to the small number of events (n = 10), three covariates were associated independently with CMV disease: pp65 antigenemia >100 nuclei/200,000, PBL CMV TaqMan PCR >10 copies/150,000 cells and HIV viral load remaining or increasing >100,000 copies/ml.
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Affiliation(s)
- Karine Gourlain
- Department of Virology, Pitié-Salpêtrière Hospital, Paris, France
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10
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Abstract
The use of the polymerase chain reaction (PCR) in molecular diagnostics has increased to the point where it is now accepted as the gold standard for detecting nucleic acids from a number of origins and it has become an essential tool in the research laboratory. Real-time PCR has engendered wider acceptance of the PCR due to its improved rapidity, sensitivity, reproducibility and the reduced risk of carry-over contamination. There are currently five main chemistries used for the detection of PCR product during real-time PCR. These are the DNA binding fluorophores, the 5' endonuclease, adjacent linear and hairpin oligoprobes and the self-fluorescing amplicons, which are described in detail. We also discuss factors that have restricted the development of multiplex real-time PCR as well as the role of real-time PCR in quantitating nucleic acids. Both amplification hardware and the fluorogenic detection chemistries have evolved rapidly as the understanding of real-time PCR has developed and this review aims to update the scientist on the current state of the art. We describe the background, advantages and limitations of real-time PCR and we review the literature as it applies to virus detection in the routine and research laboratory in order to focus on one of the many areas in which the application of real-time PCR has provided significant methodological benefits and improved patient outcomes. However, the technology discussed has been applied to other areas of microbiology as well as studies of gene expression and genetic disease.
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Affiliation(s)
- Ian M Mackay
- Clinical Virology Research Unit, Sir Albert Sakzewski Virus Research Centre, Royal Children's Hospital, Brisbane, Australia.
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Kearns AM, Turner AJL, Eltringham GJA, Freeman R. Rapid detection and quantification of CMV DNA in urine using LightCycler-based real-time PCR. J Clin Virol 2002; 24:131-4. [PMID: 11744437 DOI: 10.1016/s1386-6532(01)00240-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A real-time quantitative PCR-hybridisation assay was developed for the detection of human cytomegalovirus DNA in clinical material. The assay is based on a LightCycler (LC) and provides both rapid results (<1 h) and quantification over a broad dynamic range (2 x 10(3)-5 x 10(8) CMV DNA copies/ml). Given that the assay showed a 3-fold increase in sensitivity compared to detection of early antigen fluorescent foci (DEAFF) testing of urine samples, we investigated the practicality of testing surveillance such specimens from immunocompromised patients at risk of CMV disease. Over a 12-month period, CMV DNA was detected in 81 (7%) of 1154 urine samples examined. A total of 28 patients tested positive; urine viral loads were higher in 13 infants being investigated for suspected congenital infection (median 1.6 x 10(5) copies/ml) compared with 15 transplant recipients (median 9 x 10(3) copies/ml). Urine samples could be tested directly without processing such that results were available in <1h. Real-time PCR provided information on the quantification of CMV DNA in urine and proved a reliable method for the surveillance of immunocompromised patients at risk of CMV disease. This approach should facilitate a better understanding of the epidemiology and natural history of CMV disease. Moreover, LC-based quantitative PCR is a potentially valuable tool for the management of CMV disease; assisting with the prompt initiation of treatment and assessing therapeutic response.
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Affiliation(s)
- Angela M Kearns
- Newcastle Public Health Laboratory, Newcastle General Hospital, Westgate Road, Newcastle upon Tyne NE4 6BE, UK.
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