An Optimized Real-Time qPCR Method for the Effective Detection of Human Malaria Infections

Polymerase chain reaction, although an expensive method for the detection of human Plasmodium spp., is still considered the finest for the diagnosis of malaria. The conventional diagnostic PCR is an inexpensive process but consumes a lot of time, reagents and lacks sensitivity. On the other hand, real-time PCR assays currently being used are mostly probe-based expensive methods and sometimes not feasible to detect all the species in a single amplification reaction condition. Here we have established a real-time PCR method that is time and cost effective with a single protocol to detect and distinguish five human Plasmodium species using the existing primers efficiently. The primers used here are being used in the conventional method and the sensitivity as well as specificity of this method has also been immensely improved (100%). The lower limit of detection for Plasmodium falciparum, Plasmodium vivax and Plasmodium malariae are 0.064 parasites/µL, 1.6 parasites/µL, and 0.32 parasites/µL respectively and no cross reactivity was observed. Besides, we have analyzed melt curves that can be used for further species confirmation and validation purposes using multiplex systems. This method, therefore, can be considered as an alternative to the existing lineup for molecular diagnosis of malaria in endemic countries.

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Comparison and Recommendations for Use of Dientamoeba fragilis Real-Time PCR Assays

Journal of Clinical Microbiology ◽

10.1128/jcm.01466-18 ◽

2019 ◽

Vol 57 (5) ◽

Cited By ~ 5

Author(s):

Rory Gough ◽

John Ellis ◽

Damien Stark

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Limit Of Detection ◽

Cross Reactivity ◽

Content Type ◽

Prevalence Studies ◽

Dientamoeba Fragilis ◽

Stool Samples ◽

Pcr Method ◽

Genetic Signatures

ABSTRACT Dientamoeba fragilis is a gastrointestinal trichomonad parasite whose pathogenicity is yet to be determined. The difficulty involved in microscopically diagnosing D. fragilis in feces led to the development of real-time PCR methodologies for the detection of D. fragilis in stool samples. Prevalence studies in Europe show much higher levels of infection where a laboratory-developed real-time assay is the predominant assay for the detection of Dientamoeba fragilis than in regions that use the EasyScreen assay for detection of gastrointestinal pathogens. The aim of this study was to compare a commercially available Dientamoeba fragilis assay (Genetic Signatures EasyScreen assay) to a widely used laboratory-developed real-time PCR method. Two hundred fifty fecal samples were screened using the laboratory-developed real-time assay on four real-time PCR platforms producing a number of discrepant results. Limit-of-detection studies were undertaken to attempt to resolve sensitivity for each platform tested. The presence or absence of Dientamoeba fragilis DNA in discrepant samples was shown using PCR amplicon next-generation sequencing. Eukaryotic 18S diversity profiling was conducted on discrepant samples to identify the presence or absence of additional protozoan species in samples that may be responsible for cross-reactivity seen in these samples. The results revealed the potential for multiple false-positive results when using the laboratory-developed real-time assay across multiple real-time platforms using manufacturer default settings. This report provides recommendations to resolve these issues where possible and suggestions for future prevalence studies, and it emphasizes the EasyScreen assay as the molecular method of choice as well as the need for standardization of detection assays across all nations screening for D. fragilis.

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Development and evaluation of duplex TaqMan real-time PCR assay for detection and differentiation of wide-type and MGF505-2R gene-deleted African swine fever viruses

10.21203/rs.3.rs-59710/v2 ◽

2020 ◽

Author(s):

zhenhua Guo ◽

Kunpeng Li ◽

Songlin Qiao ◽

Xinxin Chen ◽

Ruiguang Deng ◽

...

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Large Scale ◽

Limit Of Detection ◽

African Swine Fever ◽

Economic Losses ◽

Clinical Samples ◽

Diagnosis Method ◽

Pcr Method ◽

And Control

Abstract Background: African swine fever (ASF) is the most important disease to the pigs and cause serious economic losses to the countries with large-scale swine production. Vaccines are recognized as the most useful tool to prevent and control ASF virus (ASFV) infection. Currently, the MGF505 and MGF360 gene-deleted ASFVs or combined with CD2v deletion were confirmed to be the most promising vaccine candidates. Thus, it is essential to develop a diagnosis method to discriminate wide-type strain from the vaccines used.Results: In this study, we established a duplex TaqMan real-time PCR based on the B646L gene and MGF505-2R gene. The sequence alignment showed that the targeted regions of primers and probes are highly conserved in the genotype II ASFVs. The duplex real-time assay can specifically detect B646L and MGF505-2R gene single or simultaneously without cross-reaction with other porcine viruses tested. The limit of detection was 5.8 copies and 3.0 copies for the standard plasmids containing B646L and MGF505-2R genes, respectively. Clinical samples were tested in parallel by duplex real-time PCR and a commercial ASFV detection kit. The detection results of these two assays against B646L gene were well consistent.Conclusion: We successfully developed and evaluated a duplex TaqMan real-time PCR method which can effectively distinguish the wide type and MGF505 gene-deleted ASFVs. It would be a useful tool for the clinical diagnosis and control of ASF.

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A Real-Time PCR Method for the Authentication of Common Cuttlefish (Sepia officinalis) in Food Products

Foods ◽

10.3390/foods9030286 ◽

2020 ◽

Vol 9 (3) ◽

pp. 286 ◽

Cited By ~ 2

Author(s):

Amaya Velasco ◽

Graciela Ramilo-Fernández ◽

Carmen G. Sotelo

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Food Products ◽

Polymerase Chain Reaction Method ◽

Cross Reactivity ◽

Sepia Officinalis ◽

Base Pairs ◽

Mitochondrial Coi ◽

Fresh Frozen ◽

Pcr Method

Cephalopods are very relevant food resources. The common cuttlefish (Sepia officinalis) is highly appreciated by consumers and there is a lack of rapid methods for its authentication in food products. We introduce a new minor groove binding (MGB) TaqMan real-time PCR (Polymerase Chain Reaction) method for the authentication of S. officinalis in food products to amplify a 122 base pairs (bp) fragment of the mitochondrial COI (Cytochrome Oxidase I) region. Reference and commercial samples of S. officinalis showed a threshold cycle (Ct) mean of 14.40, while the rest of the species examined did not amplify, or showed a significantly different Ct (p < 0.001). The calculated efficiency of the system was 101%, and the minimum DNA quantity detected was 10−4 ng. No cross-reactivity was detected with any other species, thus, the designed method differentiates S. officinalis from other species of the genus Sepia and other cephalopod species and works for fresh, frozen, grilled, cooked and canned samples of Sepia spp. The method has proved to be reliable and rapid, and it may prove to be a useful tool for the control of fraud in cuttlefish products.

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Multicenter Clinical Validation of a Cartridge-Based Real-Time PCR System for Detection of Coccidioides spp. in Lower Respiratory Specimens

Journal of Clinical Microbiology ◽

10.1128/jcm.01277-17 ◽

2017 ◽

Vol 56 (2) ◽

Cited By ~ 9

Author(s):

Michael A. Saubolle ◽

Bette R. Wojack ◽

Anne M. Wertheimer ◽

Atehkeng Z. Fuayagem ◽

Stephen Young ◽

...

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Limit Of Detection ◽

Fungal Species ◽

Cross Reactivity ◽

Clinical Test ◽

Target Sequence ◽

Fungal Culture ◽

Content Type ◽

Bronchial Wash

ABSTRACT Available methods for the diagnosis of coccidioidomycosis have significant shortcomings relative to accuracy and timeliness. We retrospectively and prospectively evaluated the diagnostic performance and reproducibility of a new cartridge-based real-time PCR assay for Coccidioides spp. directly in lower respiratory secretions and compared them to today's “gold standard,” fungal culture. The GeneSTAT Coccidioides assay uses a 106-bp target sequence repeated multiple times (∼60×) per genome, thus lowering the limit of detection (LOD) for extracted DNA to 10 genome equivalents/ml. A total of 332 prospective and retrospective individual patient specimens were tested. The retrospective samples consisted of 100 bronchoalveolar lavage or bronchial wash (BAL/BW) (51 positive and 49 negative by culture) specimens that had been collected previously and stored at −70°C. These samples were tested by the GeneSTAT Coccidioides assay across three clinical test sites. The sensitivity was 100%, and the specificity ranged between 93.8% and 100%. There was minimal variance in the percent agreement across the three sites, 95.6% to 100%. Additionally, a total of 232 fresh (prospective) deidentified BAL/BW specimens were tested across the three clinical sites, which included a number of specimens from Southern California to provide a diversity of isolates. Specimens were tested by fungal culture, with any isolates of Coccidioides, except for one, being confirmed by molecular means (AccuProbe). The sensitivity of the GeneSTAT Coccidioides assay across the three sites was 100% (4/4) for positive fresh specimens, and the overall specificity of the assay was 99.6% (227/228), ranging from 98.1% to 100%. In testing for cross-reactivity, the assay was 100% specific when screened against 47 different bacterial, viral, and fungal species.

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Comparative evaluation of two commercial real-time PCR kits (QuantiFast™ and abTES™) for the detection of Plasmodium knowlesi and other Plasmodium species in Sabah, Malaysia

10.21203/rs.3.rs-30644/v3 ◽

2020 ◽

Author(s):

Nor Afizah Nuin ◽

Angelica Fiona Tan ◽

Yao Long Lew ◽

Kim A Piera ◽

Timothy William ◽

...

Keyword(s):

Diagnostic Accuracy ◽

Real Time ◽

Real Time Pcr ◽

Limit Of Detection ◽

Plasmodium Knowlesi ◽

Plasmodium Species ◽

Detection Methods ◽

Clinical Samples ◽

Public Health Issue ◽

Gene Target

Abstract Background : The monkey parasite Plasmodium knowlesi is an emerging public health issue in Southeast Asia. In Sabah, Malaysia, P. knowlesi is now the dominant cause of human malaria. Molecular detection methods for P. knowlesi are essential for accurate diagnosis and in monitoring progress towards malaria elimination of other Plasmodium species. However, recent commercially available PCR malaria kits have unpublished P. knowlesi gene targets or have not been evaluated against clinical samples. Methods : Two real-time PCR methods currently used in Sabah for confirmatory malaria diagnosis and surveillance reporting were evaluated: the QuantiFast™ Multiplex PCR kit (Qiagen, Germany) targeting the P. knowlesi 18S SSU rRNA; and the abTES™ Malaria 5 qPCR II kit (AITbiotech, Singapore), with an undisclosed P. knowlesi gene target. Diagnostic accuracy was evaluated using 52 P. knowlesi, 25 P. vivax , 21 P. falciparum , and 10 P. malariae clinical isolates, and 26 malaria negative controls, and compared against a validated reference nested PCR assay. The limit of detection (LOD) for each PCR method and Plasmodium species was also evaluated. Results : The sensitivity of the QuantiFast™ and abTES™ assays for detecting P. knowlesi was comparable at 98.1% (95%CI 89.7-100) and 100% (95%CI 93.2-100) respectively. Specificity of the QuantiFast™ and abTES™ for P. knowlesi was high at 98.8% (95%CI 93.4-100) for both assays. The QuantiFast™ assay demonstrated falsely-positive mixed Plasmodium species at low parasitaemias in both the primary and LOD analysis. Diagnostic accuracy of both PCR kits for detecting P. vivax , P. falciparum , and P. malariae was comparable to P. knowlesi . The abTES™ assay demonstrated a lower LOD for P. knowlesi of ≤0.125 parasites/µL compared to QuantiFast™ with a LOD of 20 parasites/µL. Hospital microscopy demonstrated a sensitivity of 78.8% (95%CI 65.3-88.9) and specificity of 80.4% (95%CI 67.6-89.8) compared to reference PCR for detecting P. knowlesi . Conclusion : The QuantiFast™ and abTES™ commercial PCR kits performed well for the accurate detection of P. knowlesi infections. Although the QuantiFast™ kit is cheaper, the abTES™ kit demonstrated a lower LOD, supporting its use as a second-line referral-laboratory diagnostic tool in Sabah, Malaysia.

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Detection of Eight Respiratory Bacterial Pathogens Based on Multiplex Real-Time PCR with Fluorescence Melting Curve Analysis

Canadian Journal of Infectious Diseases and Medical Microbiology ◽

10.1155/2020/2697230 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Liuyang Hu ◽

Bing Han ◽

Qin Tong ◽

Hui xiao ◽

Donglin Cao

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Limit Of Detection ◽

Bacterial Pathogens ◽

Melting Curve ◽

Cost Effective ◽

Culture Method ◽

Curve Analysis ◽

Melting Curve Analysis ◽

Fluorescence Melting Curve Analysis

Background and Objective. Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Pseudomonas aeruginosa, and Mycobacterium tuberculosis are primary respiratory bacterial pathogens contributing to morbidity and mortality in developing countries. This study evaluated the diagnostic performance of multiplex real-time PCR with fluorescence melting curve analysis (MCA) assay, which was used to detect eight respiratory bacterial pathogens simultaneously. Methods. A total of 157 sputum specimens were examined by multiplex real-time with fluorescence MCA, and the results were compared with the conventional culture method. Results. Multiplex real-time PCR with fluorescence MCA specifically detected and differentiated eight respiratory bacterial pathogens by different melting curve peaks for each amplification product within 2 hours and exhibited high repeatability. The limit of detection ranged from 64 to 102 CFU/mL in the multiplex PCR system. Multiplex real-time PCR with fluorescence MCA showed a sensitivity greater than 80% and a 100% specificity for each pathogen. The kappa correlation of eight bacteria ranged from 0.89 to 1.00, and the coefficient of variation ranged from 0.05% to 0.80%. Conclusions. Multiplex real-time PCR with fluorescence MCA assay is a sensitive, specific, high-throughput, and cost-effective method to detect multiple bacterial pathogens simultaneously.

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Development of a DNA-Based Detection Method for Cocos Nucifera Using TaqMan™ Real-Time PCR

Foods ◽

10.3390/foods9030332 ◽

2020 ◽

Vol 9 (3) ◽

pp. 332

Author(s):

Jasmin Wrage ◽

Oxana Kleyner ◽

Sascha Rohn ◽

Jürgen Kuballa

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Detection Method ◽

Immunoglobulin E ◽

Limit Of Detection ◽

Cocos Nucifera ◽

Cross Reactivity ◽

Pcr Assay ◽

Probe System ◽

Ige Mediated

So far, only a few cases of immunoglobulin E (IgE)-mediated coconut allergies have been described in the literature. Due to a growing consumption of coconut-containing foods in occidental countries, the number of coconut allergies may also increase. As there is no causative immunotherapy in clinical routine, appropriate food labelling is particularly important, also with regard to cross-contamination, to prevent serious health consequences. The purpose of this study was to develop a DNA-based detection method for coconut (Cocos nucifera). Initially, three sets of coconut-specific primers were designed and tested. A TaqMan™ probe was then developed to identify and quantify coconut by real-time PCR assay. With 27 other plant and animal species, the specificity of the primer/probe system was tested and cross reactivity was excluded. In a dilution series, a limit of detection of 1 pg/µL was determined. Thus, the developed real-time PCR assay is a suitable method to detect coconut in food.

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Real-Time PCR Detection of Parapoxvirus DNA,

Clinical Chemistry ◽

10.1373/clinchem.2005.060335 ◽

2006 ◽

Vol 52 (2) ◽

pp. 316-319 ◽

Cited By ~ 53

Author(s):

Andreas Nitsche ◽

Mathias Büttner ◽

Sonja Wilhelm ◽

Georg Pauli ◽

Hermann Meyer

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Limit Of Detection ◽

Cross Reactivity ◽

Probit Analysis ◽

Animal Origin ◽

Pcr Assay ◽

Medical Practitioners ◽

B2l Gene ◽

Zoonotic Infections

Abstract Background: Detection of parapoxviruses is important in various animals as well as in humans as zoonotic infections. Reliable detection of parapoxviruses is fundamental for the exclusion of other rash-causing illnesses, for both veterinarians and medical practitioners. To date, however, no real-time PCR assay for the detection of parapoxviruses has been reported. Methods: A minor groove binder–based quantitative real-time PCR assay targeting the B2L gene of parapoxviruses was developed on the ABI Prism and the LightCycler platforms. Results: The real-time PCR assay successfully amplified DNA fragments from a total of 41 parapoxvirus strains and isolates representing the species orf virus, bovine papular stomatitis virus, pseudocowpoxvirus, and sealpoxvirus. Probit analysis gave a limit of detection of 4.7 copies per assay (95% confidence interval, 3.7–6.8 copies per reaction). Scabs contain a sufficient amount of parapoxvirus DNA and can therefore be used for PCR without any DNA preparation step. No cross-reactivity to human, bovine, or sheep genomic DNA or other DNA viruses, including orthopoxviruses, molluscum contagiosum viruses, and yaba-like disease viruses, was observed. Conclusion: The presented assay is suitable for the detection of parapoxvirus infections in clinical material of human and animal origin.

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Development and evaluation of duplex TaqMan real-time PCR assay for detection and differentiation of wide-type and MGF505-2R gene-deleted African swine fever viruses

BMC Veterinary Research ◽

10.1186/s12917-020-02639-2 ◽

2020 ◽

Vol 16 (1) ◽

Author(s):

Zhenhua Guo ◽

Kunpeng Li ◽

Songlin Qiao ◽

Xin-xin Chen ◽

Ruiguang Deng ◽

...

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Large Scale ◽

Limit Of Detection ◽

African Swine Fever ◽

Economic Losses ◽

Clinical Samples ◽

Diagnosis Method ◽

Pcr Method ◽

And Control

Abstract Background African swine fever (ASF) is the most important disease to the pigs and cause serious economic losses to the countries with large-scale swine production. Vaccines are recognized as the most useful tool to prevent and control ASF virus (ASFV) infection. Currently, the MGF505 and MGF360 gene-deleted ASFVs or combined with CD2v deletion were confirmed to be the most promising vaccine candidates. Thus, it is essential to develop a diagnosis method to discriminate wide-type strain from the vaccines used. Results In this study, we established a duplex TaqMan real-time PCR based on the B646L gene and MGF505-2R gene. The sequence alignment showed that the targeted regions of primers and probes are highly conserved in the genotype II ASFVs. The duplex real-time assay can specifically detect B646L and MGF505-2R gene single or simultaneously without cross-reaction with other porcine viruses tested. The limit of detection was 5.8 copies and 3.0 copies for the standard plasmids containing B646L and MGF505-2R genes, respectively. Clinical samples were tested in parallel by duplex real-time PCR and a commercial ASFV detection kit. The detection results of these two assays against B646L gene were well consistent. Conclusion We successfully developed and evaluated a duplex TaqMan real-time PCR method which can effectively distinguish the wide type and MGF505 gene-deleted ASFVs. It would be a useful tool for the clinical diagnosis and control of ASF.

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Development and Evaluation of Duplex TaqMan Real-Time PCR Assay for Detection and Differentiation of Wide-Type and MGF505 Gene-Deleted African Swine Fever Viruses

10.21203/rs.3.rs-59710/v1 ◽

2020 ◽

Author(s):

Zhenhua Guo ◽

Kunpeng Li ◽

Songlin Qiao ◽

Xinxin Chen ◽

Ruiguang Deng ◽

...

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Large Scale ◽

Limit Of Detection ◽

African Swine Fever ◽

Economic Losses ◽

Clinical Samples ◽

Diagnosis Method ◽

Pcr Method ◽

And Control

Abstract Background: African swine fever (ASF) is the most important disease to the pigs and cause serious economic losses to the countries with large-scale swine production. Vaccines are recognized as the most useful tool to prevent and control ASF virus (ASFV) infection. Currently, the MGF505 and MGF360 gene-deleted ASFVs or combined with CD2v deletion were confirmed to be the most promising vaccine candidates. Thus, it is essential to develop a diagnosis method to discriminate wide-type strain from the vaccines used. Results: In this study, we established a duplex TaqMan real-time PCR based on the B646L gene and MGF505-2R gene. The sequence alignment showed that the targeted regions of primers and probes are highly conserved in the genotype II ASFVs. The duplex real-time assay can specifically detect B646L and MGF505-2R gene single or simultaneously without cross-reaction with other porcine viruses tested. The limit of detection was 5.8 copies and 3.0 copies for the standard plasmids containing B646L and MGF505-2R genes, respectively. Clinical samples were tested in parallel by duplex real-time PCR and a commercial ASFV detection kit. The detection results of these two assays against B646L gene were well consistent. Conclusion: We successfully developed and evaluated a duplex TaqMan real-time PCR method which can effectively distinguish the wide type and MGF505 gene-deleted ASFVs. It would be a useful tool for the clinical diagnosis and control of ASF.

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