Showing papers on "Multiplex polymerase chain reaction published in 2009"

Multiplexed Real-Time PCR Assay for Discrimination of Plasmodium Species with Improved Sensitivity for Mixed Infections

Abstract: The implementation of real-time PCR for the diagnosis of malaria has been hampered by poor sensitivity for the detection of mixed infections. We have optimized a method that enhances the sensitivity of detection of minor species in mixed infections within a single multiplex reaction. Our assay uses species-specific forward primers in combination with a conserved reverse primer and largely overcomes primer competition for the minor species DNA. With a blind panel of clinical samples, we successfully identified the species in 13/16 mixed infections. This assay was further validated with 91 blood samples and demonstrated a specificity and sensitivity for single infections of 100% compared with nested PCR as the "gold standard." This test has been implemented for routine confirmation of malaria species in Alberta, Canada. In comparison with species identification by microscopy, the real-time PCR test demonstrated greater sensitivity for the identification of species causing low-level and mixed infections and for the discrimination of Plasmodium species other than Plasmodium falciparum. Our experience supports a role for real-time PCR in the identification of malarial species in conjunction with microscopy.

Large scale multiplex PCR improves pathogen detection by DNA microarrays

Abstract: Medium density DNA microchips that carry a collection of probes for a broad spectrum of pathogens, have the potential to be powerful tools for simultaneous species identification, detection of virulence factors and antimicrobial resistance determinants. However, their widespread use in microbiological diagnostics is limited by the problem of low pathogen numbers in clinical specimens revealing relatively low amounts of pathogen DNA. To increase the detection power of a fluorescence-based prototype-microarray designed to identify pathogenic microorganisms involved in sepsis, we propose a large scale multiplex PCR (LSplex PCR) for amplification of several dozens of gene-segments of 9 pathogenic species. This protocol employs a large set of primer pairs, potentially able to amplify 800 different gene segments that correspond to the capture probes spotted on the microarray. The LSplex protocol is shown to selectively amplify only the gene segments corresponding to the specific pathogen present in the analyte. Application of LSplex increases the microarray detection of target templates by a factor of 100 to 1000. Our data provide a proof of principle for the improvement of detection of pathogen DNA by microarray hybridization by using LSplex PCR.

Two-step multiplex polymerase chain reaction improves the speed and accuracy of genotyping using DNA from noninvasive and museum samples.

Abstract: Many studies in molecular ecology rely upon the genotyping of large numbers of low-quantity DNA extracts derived from noninvasive or museum specimens. To overcome low amplification success rates and avoid genotyping errors such as allelic dropout and false alleles, multiple polymerase chain reaction (PCR) replicates for each sample are typically used. Recently, two-step multiplex procedures have been introduced which drastically increase the success rate and efficiency of genotyping. However, controversy still exists concerning the amount of replication needed for suitable control of error. Here we describe the use of a two-step multiplex PCR procedure that allows rapid genotyping using at least 19 different microsatellite loci. We applied this approach to quantified amounts of noninvasive DNAs from western chimpanzee, western gorilla, mountain gorilla and black and white colobus faecal samples, as well as to DNA from ~100-year-old gorilla teeth from museums. Analysis of over 45 000 PCRs revealed average success rates of > 90% using faecal DNAs and 74% using museum specimen DNAs. Average allelic dropout rates were substantially reduced compared to those obtained using conventional singleplex PCR protocols, and reliable genotyping using low (< 25 pg) amounts of template DNA was possible. However, four to five replicates of apparently homozygous results are needed to avoid allelic dropout when using the lowest concentration DNAs (< 50 pg/reaction), suggesting that use of protocols allowing routine acceptance of homozygous genotypes after as few as three replicates may lead to unanticipated errors when applied to low-concentration DNAs.

High-throughput detection and multiplex identification of cell contaminations

Abstract: Unnoticed cell culture contamination by viruses, Mycoplasma, or other cell lines is not uncommon and a threat to laboratory safety and the quality of scientific results. We developed and validated a novel high-throughput Multiplex cell Contamination Test (McCT), which is currently able to detect 37 contamination markers in a single reaction. The assay is based on multiplex PCR with target-specific primers and subsequent hybridization of amplimers to specific oligonucleotide probes. McCT proved to be highly specific, sensitive and robust, and allows to analyze more than 1000 cell lysates per week. In conclusion, the novel McCT assay is a powerful high-throughput tool in assessing cell line purity.

Detection, Distribution, and Genetic Variability of 'Candidatus Liberibacter' Species Associated with Zebra Complex Disease of Potato in North America.

Abstract: The specificity and sensitivity of polymerase chain reaction (PCR) primers developed for ‘Candidatus Liberibacter solanacearum’ and ‘Candidatus Liberibacter psyllaurous’ were evaluated in conventional and real-time PCR assays. All PCR primers were specific for ‘Ca. L. psyllaurous’ and ‘Ca. L. solanacearum’ insomuch as they did not detect other prokaryotic plant pathogens that affect potato except for the putative pathogens associated with psyllid-yellows and haywire. Conventional PCR assays were capable of detecting 0.19 to 1.56 ng of total DNA per reaction, and real-time PCR was found capable of detecting 1.56 to 6.25 ng of total DNA per reaction, depending on the specific PCR primer set used. ‘Ca. Liberibacter’ species associated with zebra complex disease (ZC) was confirmed in plants affected by this disease throughout Texas from 2005 to 2008, in seed tubers produced in Wyoming in 2007, and in Colorado, Kansas, Nebraska, and Mexico in 2008. A multiplex PCR assay using ‘Ca. L. solanacearum’–spe...

A SNaPshot assay for the rapid and simple detection of four common hotspot codon mutations in the PIK3CA gene

Abstract: Activating mutations in the PIK3CA gene have been identified in a variety of human malignancies and are commonly detected in hotspot codons located in the helical and kinase domains in exons 9 and 20. Existing methodologies for the detection of PIK3CA mutations are time-consuming and/or expensive. In the present study we describe the first application of a PIK3CA SNaPshot assay to the screening of frequent mutations in these exons. A SNaPshot assay for the simultaneous detection of four frequent PIK3CA hotspot mutations (E542K, E545G, E545K and H1047R) has been developed and evaluated. The assay combines multiplex PCR amplification with a multiplex primer extension assay to allow targeted detection of all four mutations in one reaction. The method was tested using samples that had previously been analysed for mutations by high-resolution melting analysis and sequencing. All mutations detected were concordant and no false positive results were obtained. Sensitivity tests showed that the SNaPshot assay could detect mutant DNA when it represents 5–10% of the total DNA present. The application of the method to the analysis of DNAs extracted from formalin-fixed paraffin-embedded samples was also demonstrated. The SNaPshot assay described here offers a fast, sensitive, inexpensive and specific approach to the analysis of frequent PIK3CA mutations in both fresh and archival patient samples.

Two slow-step polymerase enzyme systems and methods

Abstract: Compositions, kits, methods and systems for nucleotide sequencing comprising producing polymerase reactions that exhibit two kinetically observable steps within an observable phase of the polymerase reaction. Two slow step systems can be produced, for example, by selecting the appropriate polymerase enzyme, polymerase reaction conditions including cofactors, and polymerase reaction substrates including the primed template and nucleotides.

Multiplex PCR assay for simultaneous detection and differentiation of Mycobacterium tuberculosis, Mycobacterium avium complexes and other Mycobacterial species directly from clinical specimens.

Abstract: Aims: Polymerase chain reaction (PCR) is the most rapid and sensitive method for diagnosing mycobacterial infections and identifying the aetiological Mycobacterial species in order to administer the appropriate therapy and for better patient management Methods and Results: Two hundred and thirty-five samples from 145 clinically suspected cases of tuberculosis were processed for the detection of Mycobacterial infections by ZN (Ziehl Neelsen) smear examination, L-J & BACTECTM MGIT-960 culture and multiplex PCR tests The multiplex PCR comprised of genus-specific primers targeting hsp65 gene, Mycobacterium tuberculosis complex-specific primer targeting cfp10 (Rv3875, esxB) region and Mycobacterium avium complex-specific primer pairs targeting 16S–23S Internal Transcribed Spacer sequences The multiplex PCR developed had an analytical sensitivity of 10 fg (3–4 cells) of mycobacterial DNA The multiplex PCR test showed the highest (77·24%) detection rate, while ZN smear examination had the lowest (20%) detection rate, which was bettered by L-J culture (34·4%) and BACTECTM MGIT-960 culture (50·34%) methods The mean isolation time for M tuberculosis was 19·03 days in L-J culture and 8·7 days in BACTECTM MGIT-960 culture Using the multiplex PCR, we could establish M tuberculosis + M avium co-infection in 1·3% HIV-negative and 2·9% HIV-positive patients The multiplex PCR was also highly useful in diagnosing mycobacteraemia in 38·09% HIV-positive and 15·38% HIV-negative cases Conclusions: The developed in-house multiplex PCR could identify and differentiate the M tuberculosis and M avium complexes from other Mycobacterial species directly from clinical specimens Significance and Impact of the Study: The triplex PCR developed by us could be used to detect and differentiate M tuberculosis, M avium and other mycobacteria in a single reaction tube

Multiplex PCR for Detection of Botulinum Neurotoxin-Producing Clostridia in Clinical, Food, and Environmental Samples

Abstract: Botulinum neurotoxin (BoNT), the most toxic substance known, is produced by the spore-forming bacterium Clostridium botulinum and, in rare cases, also by some strains of Clostridium butyricum and Clostridium baratii. The standard procedure for definitive detection of BoNT-producing clostridia is a culture method combined with neurotoxin detection using a standard mouse bioassay (SMB). The SMB is highly sensitive and specific, but it is expensive and time-consuming and there are ethical concerns due to use of laboratory animals. PCR provides a rapid alternative for initial screening for BoNT-producing clostridia. In this study, a previously described multiplex PCR assay was modified to detect all type A, B, E, and F neurotoxin genes in isolated strains and in clinical, food, environmental samples. This assay includes an internal amplification control. The effectiveness of the multiplex PCR method for detecting clostridia possessing type A, B, E, and F neurotoxin genes was evaluated by direct comparison with the SMB. This method showed 100% inclusivity and 100% exclusivity when 182 BoNT-producing clostridia and 21 other bacterial strains were used. The relative accuracy of the multiplex PCR and SMB was evaluated using 532 clinical, food, and environmental samples and was estimated to be 99.2%. The multiplex PCR was also used to investigate 110 freshly collected food and environmental samples, and 4 of the 110 samples (3.6%) were positive for BoNT-encoding genes.

Rapid Identification of Mycobacterium tuberculosis and Nontuberculous Mycobacteria by Multiplex, Real-Time PCR

Abstract: The rapid identification of mycobacteria from culture is of primary importance for the administration of empirical antibiotic therapy and for the implementation of public health measures, yet there are few commercially available assays that can easily and accurately identify the mycobacteria in culture in a timely manner. Here we report on the development of a multiplex, real-time PCR assay that can identify 93% of the pathogenic mycobacteria in our laboratory in two parallel reactions. The mycobacteria identified by this assay include the Mycobacterium tuberculosis complex (MTC), the M. avium complex (MAC), the M. chelonae-M. abscessus group (MCAG), the M. fortuitum group (MFG), and M. mucogenicum. The primer targets included the 16S rRNA gene and the internal transcribed spacer. The assay was initially validated with a repository of reference strains and was subsequently tested with 314 clinical cultures identified by the AccuProbe assay or high-performance liquid chromatography. Of the 314 cultures tested, multiplex, real-time PCR produced congruent results for 99.8% of the 1,559 targets evaluated. The sensitivity and the specificity were each 99% or greater for MTC (n = 96), MAC (n = 97), MCAG (n = 68), and M. mucogenicum (n = 9) and 95% and 100%, respectively, for MFG (n = 19). We conclude that this multiplex, real-time PCR assay is a useful diagnostic tool for the rapid and accurate identification of MTC and clinically relevant nontuberculous mycobacteria.

Development of Multiplex PCR Assays for Detection of Enterotoxigenic Escherichia coli Colonization Factors and Toxins

Abstract: Four multiplex PCR assays for detection of 19 enterotoxigenic Escherichia coli (ETEC) colonization factors and an improved ETEC toxin multiplex PCR were developed and tested on Bangladeshi and Bolivian ETEC strain collections. The assays will be useful for surveillance of ETEC infections in diagnostic laboratories that have access to PCR.

Conserved DNA-Derived Polymorphism (CDDP): A Simple and Novel Method for Generating DNA Markers in Plants

Abstract: A novel method for generating plant DNA markers was developed based on data mining for short conserved amino acid sequences in proteins and designing polymerase chain reaction (PCR) primers based on the corresponding DNA sequence. This method uses single 15- to 19-mer primers for PCR and an annealing temperature of 50°C. PCR amplicons are resolved using standard agarose gel electrophoresis. Using a reference set of rice genotypes, reproducible polymorphisms were generated. Since primers were designed using highly conserved regions of genes, markers should be generated in other plant species. We propose that this method could be used in conjunction with or as a substitute to other technically simple dominant marker methods for applications such as targeted quantitative trait loci mapping, especially in laboratories with a preference for agarose gel electrophoresis.

Evaluation of a multiplex PCR system for simultaneous detection of Salmonella spp., Listeria monocytogenes, and Escherichia coli O157:H7 in foods and in food subjected to freezing.

Abstract: Conventional culture methods were compared to a multiplex polymerase chain reaction (PCR) assay for simultaneous detection of Salmonella spp., Listeria monocytogenes, and Escherichia coli O157:H7 from enrichment cultures of various types of artificially inoculated and naturally contaminated foods. The multiplex PCR assay was evaluated in 44 types of spiked food samples, including meat, produce, fish, and dairy products targeting genes specific for each pathogen for simultaneous detection. The sensitivity of the assay was

Dual-priming oligonucleotide-based multiplex PCR for the detection of Helicobacter pylori and determination of clarithromycin resistance with gastric biopsy specimens.

Abstract: Background: Assessment of Helicobacter pylori (H. pylori) clarithromycin resistance has rarely been performed routinely despite an increasing resistance rate. Our aim was to develop and evaluate the use of dual-priming oligonucleotide (DPO)-based multiplex polymerase chain reaction (PCR) to detect point mutations in the 23S rRNA gene responsible for clarithromycin resistance of H. pylori. Materials and Methods: Gastric biopsy specimens from 212 untreated patients with dyspepsia were examined by culture, histology, and DPO-based multiplex PCR. A disk diffusion test and E-test were used for performing phenotypic antibiotic susceptibility tests. Results: Among the biopsy specimens tested, 22.2% (47/212), 42.5% (90/212), and 41.5% (88/212) of the specimens were classified as H. pylori positive by culture, histology, and DPO-based multiplex PCR, respectively. Among 96 strains identified by either culture or DPO-based multiplex PCR, 80 strains were clarithromycin-susceptible and 16 strains (16.7%) were clarithromycin-resistant. There was 94.1% (32/34) concordance between phenotypic susceptibility tests and DPO-based multiplex PCR. In two patients with discrepant results, only DPO-based multiplex PCR detected clarithromycin-resistant strains. DPO-based multiplex PCR identified additional 49 clarithromycin-resistant or clarithromycin-susceptible H. pylori among 165 culture-negative specimens. Conclusions: DPO-based multiplex PCR can be used as a practical method for the detection of H. pylori infection and the determination of clarithromycin susceptibility in addition to phenotypic antimicrobial susceptibility tests.

Rapid Detection of Extended Spectrum β-Lactamase (ESBL) for Enterobacteriaceae by use of a Multiplex PCR-based Method

Abstract: A multiplex PCR method has been developed to classify extended spectrum β-lactamase (ESBL) and plasmidmediated AmpC β-lactamase (PABL). This method consists of the use of two four-multiplex PCRs for the detection of TEM, OXA, SHV, CTX-M, CMY, and DHA type β-lactamases. We have compared findings from the use of conventional detection methods with that of this newly developed typing method. In testing for 73 ESBLproducing and PABL-producing isolates, 100% of the isolates were correctly identified as previously characterized types and, 44 types of β-lactamases were additionally identified from 33 isolates. This assay not only reduces the time for classification but also increases the accuracy for detection.

Simultaneous mutation and copy number variation (CNV) detection by multiplex PCR-based GS-FLX sequencing.

Abstract: We evaluated multiplex PCR amplification as a front-end for high-throughput sequencing, to widen the applicability of massive parallel sequencers for the detailed analysis of complex genomes. Using multiplex PCR reactions, we sequenced the complete coding regions of seven genes implicated in peripheral neuropathies in 40 individuals on a GS-FLX genome sequencer (Roche). The resulting dataset showed highly specific and uniform amplification. Comparison of the GS-FLX sequencing data with the dataset generated by Sanger sequencing confirmed the detection of all variants present and proved the sensitivity of the method for mutation detection. In addition, we showed that we could exploit the multiplexed PCR amplicons to determine individual copy number variation (CNV), increasing the spectrum of detected variations to both genetic and genomic variants. We conclude that our straightforward procedure substantially expands the applicability of the massive parallel sequencers for sequencing projects of a moderate number of amplicons (50-500) with typical applications in resequencing exons in positional or functional candidate regions and molecular genetic diagnostics.

Identification of Salmonella enterica subspecies I, Salmonella enterica serovars Typhimurium, Enteritidis and Typhi using multiplex PCR

Abstract: This study was designed to develop a multiplex PCR method with five specific primer pairs for the detection of Salmonella spp., Salmonella subspecies I, Salmonella enterica serovars Typhimurium, Typhi and Enteritidis. A multiplex PCR was constructed with five primer pairs for the detection of Salmonella and pathogenic Salmonella serovars, including a specific primer pair for Salmonella Typhi, based on the sequence comparison between genomic DNA sequences of 12 Salmonella strains. Each primer pair was specifically targeted to Salmonella spp., Salmonella subspecies I, Salmonella Typhimurium, Typhi and Enteritidis. This multiplex PCR was evaluated with various DNAs of Salmonella serovars that yielded high specificity for amplifying the expected PCR products of Salmonella serovars. Using this primer pair, a set of multiplex PCR was performed for the rapid identification of salmonellae and major pathogenic Salmonella serovars. Although this multiplex PCR method will need to be evaluated for a wide range of Salmonella serovars among multilaboratories, it should be useful for identifying clinically significant strains of Salmonella serovars rapidly and accurately without the need for serological testing.

High-Throughput Molecular Determination of Salmonella enterica Serovars by Use of Multiplex PCR and Capillary Electrophoresis Analysis

Abstract: Salmonella enterica is a leading cause of food-borne illness worldwide and is also a major cause of morbidity and mortality in domestic and wild animals. In the current study, a high-throughput molecular assay was developed to determine the most common clinical and nonhuman serovars of S. enterica in the United States. Sixteen genomic targets were identified based on their differential distribution among common serovars. Primers were designed to amplify regions of each of these targets in a single multiplex PCR while incorporating a 6-carboxyfluorescein-labeled universal primer to fluorescently label all amplicons. The fluorescently labeled PCR products were separated using capillary electrophoresis, and a Salmonella multiplex assay for rapid typing (SMART) code was generated for each isolate, based upon the presence or absence of PCR products generated from each target gene. Seven hundred fifty-one blind clinical isolates of Salmonella from Washington State, collected in 2007 and previously serotyped via antisera, were screened with the assay. A total of 89.6% of the isolates were correctly identified based on comparison to a panel of representative SMART codes previously determined for the top 50 most common serovars in the United States. Of the remaining isolates, 6.2% represented isolates that produced a new SMART code for a previously determined serotype, while the final 8.8% were from serotypes not screened in the original panel used to score isolates in the blinded study. This high-throughput multiplex PCR assay allowed simple and accurate typing of the most prevalent clinical serovars of Salmonella enterica at a level comparable to that of conventional serotyping, but at a fraction of both the cost and time required per test.

Simultaneous Identification of 14 Genital Microorganisms in Urine by Use of a Multiplex PCR-Based Reverse Line Blot Assay

Abstract: Received 21 January 2009/Returned for modification 27 February 2009/Accepted 31 March 2009 The aim of this study was to develop and evaluate a sensitive method for the simultaneous identification of 14 urogenital potential pathogens. A multiplex PCR-based reverse line blot (mPCR/RLB) assay was developed to detect 14 urogenital pathogens or putative pathogens, namely Trichomonas vaginalis, Streptococcus pneumoniae, Neisseria gonorrhoeae, Chlamydia trachomatis, Ureaplasma parvum, U. urealyticum, Gardnerella vaginalis, Haemophilus influenzae, herpes simplex virus type 1 (HSV1) and HSV2, N. meningitidis, Mycoplasma hominis, M. genitalium, and adenovirus, using two species-specific primer pairs and probes for each. The method was validated using a reference strain or a well-characterized clinical isolate of each target organism and was found to be both sensitive and specific. The limits of detection for the mPCR/RLB assay varied among the 14 target organisms from 4.2 10 1 to 7.0 10 11 ng/l of genomic DNA. There were no cross-reactions among any of the probes. This method was used to test 529 first-voided urine specimens from male patients with and without urethritis attending two Sydney sexual health clinics. One or more target species were detected in 193 (36%) subjects. Of 233 positive results, overall 216 (93%) were concordant between mPCR/RLB and a comparator method (culture and/or species-specific PCR), 9 were positive only by mPCR/RLB, and 8 were positive only by the comparator method. The mPCR/RLB method was an accurate, convenient, and inexpensive method for the detection of multiple potential pathogens in first-voided urine specimens from men.

Fast multiplexed polymerase chain reaction for conventional and microfluidic short tandem repeat analysis.

Abstract: The time required for short tandem repeat (STR) amplification is determined by the temperature ramp rates of the thermal cycler,the components of the reaction mix, and the properties of the reaction vessel. Multiplex amplifications in microfluidic biochip-based and conventionaltube-based thermal cyclers have been demonstrated in 17.3 and 19 min, respectively. Optimized 28-cycle amplification protocols generated alleleswith signal strengths above calling thresholds, heterozygous peak height ratios of greater than 0.65, and incomplete nontemplate nucleotide additionand stutter of less than 15%. Full CODIS-compatible profiles were generated using the Profiler Plus ID, COfiler and Identifiler primer sets. PCR per-formance over a wide range of DNA template levels from 0.006 to 4 ng was characterized by separation and detection on a microfluidic electropho-resis system, Genebench-FXTM. The fast multiplex PCR approach has the potential to reduce process time and cost for STR analysis and enablesdevelopment of a fully integrated microfluidic forensic DNA analysis system

Dual priming oligonucleotide-based multiplex PCR analysis for detection of BRAFV600E mutation in FNAB samples of thyroid nodules in BRAFV600E mutation-prevalent area

Abstract: Background. To evaluate the diagnostic value of dual priming oligonucleotide (DPO)-based multiplex polymer- ase chain reaction (PCR) for the detection of BRAF V600E muta- tions in ultrasound-guided fine-needle aspiration biopsy (US- FNAB) of thyroid nodules. Methods. Our institutional review board approved this ret- rospective study, and informed consent was not required from patients. The 130 patients underwent US-FNAB to evaluate BRAF status in thyroid nodules. In FNAB washouts, DPO- based multiplex PCR, direct DNA sequencing, and PCR- restriction fragment length polymorphism (RFLP) were used to detect BRAF V600E. The diagnostic performance of these meth- ods was calculated. We compared cytologic results by BRAF status.

PCR detection of enterohemorrhagic Escherichia coli O145 in food by targeting genes in the E. coli O145 O-antigen gene cluster and the shiga toxin 1 and shiga toxin 2 genes.

Abstract: Shiga toxin–producing Escherichia coli (STEC) strains belonging to serogroup O145 are an important cause of hemorrhagic colitis and hemolytic uremic syndrome worldwide. Cattle and other animals are potential reservoirs for this pathogen. To develop PCR assays for detection and identification of E. coli O145, the wzx (O-antigen flippase) and wzy (O-antigen polymerase) genes in the O145 O-antigen gene cluster that are specific for this serogroup were selected as targets. Oligonucleotide primers complementary to regions in the E. coli O145 wzx and wzy genes were designed to perform PCR assays with DNA from strains of E. coli O145, non–O145 E. coli serogroups, and other bacterial genera. The assays were highly specific for E. coli O145. A multiplex PCR assay targeting the E. coli O145 wzx and wzy genes and the Shiga toxin 1 (stx1) and Shiga toxin 2 (stx2) genes and a real-time multiplex PCR assay targeting the O145 wzy, stx1, and stx2 genes were developed for detection of STEC O145. The assays were u...