Development of a multitarget real-time TaqMan PCR assay for enhanced detection of Francisella tularensis in complex specimens.
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ABSTRACT:
SUBMITTER: Versage JL
PROVIDER: S-EPMC309004 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Francisella tularensis, the etiologic agent of tularemia and a Class A Select Agent, is divided into three subspecies and multiple subpopulations that differ in virulence and geographic distribution. Given these differences, there is a need to rapidly and accurately determine if a strain is F. tularensis and, if it is, assign it to subspecies and subpopulation. We designed TaqMan real-time PCR genotyping assays using eleven single nucleotide polymorphisms (SNPs) that were potentially specific to closely related groups within the genus Francisella, including numerous subpopulations within F. tularensis species. We performed extensive validation studies to test the specificity of these SNPs to particular populations by screening the assays across a set of 565 genetically and geographically diverse F. tularensis isolates and an additional 21 genetic near-neighbor (outgroup) isolates. All eleven assays correctly determined the genetic groups of all 565 F. tularensis isolates. One assay differentiates F. tularensis, F. novicida, and F. hispaniensis from the more genetically distant F. philomiragia and Francisella-like endosymbionts. Another assay differentiates F. tularensis isolates from near neighbors. The remaining nine assays classify F. tularensis-confirmed isolates into F. tularensis subspecies and subpopulations. The genotyping accuracy of these nine assays diminished when tested on outgroup isolates (i.e. non F. tularensis), therefore a hierarchical approach of assay usage is recommended wherein the F. tularensis-specific assay is used before the nine downstream assays. Among F. tularensis isolates, all eleven assays were highly sensitive, consistently amplifying very low concentrations of DNA. Altogether, these eleven TaqMan real-time PCR assays represent a highly accurate, rapid, and sensitive means of identifying the species, subspecies, and subpopulation of any F. tularensis isolate if used in a step-wise hierarchical scheme. These assays would be very useful in clinical, epidemiological, and/or forensic investigations involving F. tularensis.
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Project description:A novel multitarget real-time PCR (RT-PCR) assay for the rapid identification of Bordetella pertussis, B. parapertussis, and B. holmesii was developed using multicopy insertion sequences (ISs) in combination with the pertussis toxin subunit S1 (ptxS1) singleplex assay. The RT-PCR targets for the multiplex assay include IS481, commonly found in B. pertussis and B. holmesii; IS1001 of B. parapertussis; and the IS1001-like sequence of B. holmesii. Overall, 402 Bordetella species and 66 non-Bordetella species isolates were tested in the multitarget assay. Cross-reactivity was found only with 5 B. bronchiseptica isolates, which were positive with IS1001 of B. parapertussis. The lower limit of detection (LLOD) of the multiplex assay was similar to the LLOD of each target in an individual assay format, which was approximately 1 genomic equivalent per reaction for all targets. A total of 197 human clinical specimens obtained during cough-illness outbreak investigations were used to evaluate the multitarget RT-PCR assay. The multiplex assay results from 87 clinical specimens were compared to the individual RT-PCR assay and culture results. The multitarget assay is useful as a diagnostic tool to confirm B. pertussis infections and to rapidly identify other Bordetella species. In conclusion, the use of this multitarget RT-PCR approach increases specificity, while it decreases the amount of time, reagents, and specimen necessary for RT-PCRs used for accurate diagnosis of pertussis-like illness.
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Project description:The objective of this study was to develop and validate a Taqman real-time PCR assay for the detection of Mycoplasma bovis (M. bovis). Unique primers targeting the highly conserved house-keeping gene (uvrC) were designed and the probe sequence was derived from a previously published microarray study. There was 100% agreement in the outcome between our assay and the other two published assays for M. bovis detection. The analytical limit of detection of our assay is 83 copies of the uvrC gene. This assay was validated on a total of 214 bovine clinical specimens that were submitted to the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL), Texas, USA. The specificity of the assay was assessed to be 100% since no cross-reactivity occurred with 22 other bacterial and other Mycoplasma species. We conclude that the uvrC gene serves as a good and reliable diagnostic marker for the accurate and rapid detection of M. bovis from a wider variety of specimen matrices.
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Project description:Tephritid fruit flies are ranked as one of the most damaging groups of insect pests. Morphological identification of fruit flies is mainly performed on adults due to the lack of adequate identification keys for immature stages. The peach fruit fly, Bactrocera zonata (Saunders), infests some of the principal commercial fruits and vegetables. It is, therefore important to avert its global dispersal, particularly by accurately identifying this species at ports of entry. In this study, a TaqMan real-time polymerase chain reaction (PCR) was developed for the accurate identification and sensitive detection of the peach fruit fly. A novel set of primers and probe were designed to specifically identify the mitochondrial cytochrome oxidase I (COI) gene. All specimens of peach fruit fly (including various life stages) were detected, and no cross reactivity with other tested tephritids were observed. Since this assay performed equally well with crushed insects and purified DNA, we note added efficiency by eliminating DNA extraction step. Considering the speed, specificity as well as sensitivity of the assay, Taqman real-time PCR can be used as a swift and specific method for pest species at ports of entry.
| S-EPMC6171934 | biostudies-literature
Project description:A real-time reverse transcriptase-polymerase chain reaction (RT-PCR) for the detection of bovine coronavirus (BCoV) RNA in clinical samples is described. The assay is based on TaqMan technology, consisting of two primers and one probe labeled with the reporter dye 6-carboxyfluorescein that binds selectively to the transmembrane-protein gene of BCoV. The BCoV real-time RT-PCR assay was able to detect the tested BCoV and BCoV-like viruses (canine respiratory coronavirus and bubaline coronavirus), whereas other common viral pathogens of cattle were not recognised by the established oligonucleotide set, thus showing that the test was specific for bovine-like CoVs. The detection limit of the assay was 20 BCoV RNA copies (1-log higher with respect to traditional gel-based RT-PCR) and the reproducibility was satisfactory, thus allowing for a sensitive and accurate measurement of the viral RNA load in clinical samples. Two hundred and twenty clinical specimens (92 rectal, 82 nasal and 46 ocular swabs) were subjected to gel-based and real-time RT-PCR. By conventional amplification, 43 rectal, 54 nasal and 34 ocular samples tested positive, whereas the TaqMan assay was able to detect the BCoV nucleic acid in 49 rectal, 60 nasal and 37 ocular swabs. The rapidity and high throughput of the BCoV TaqMan assay makes this method a powerful tool for a sensitive and specific diagnosis of BCoV infection in cattle.
| S-EPMC7112840 | biostudies-literature
Project description:Chlamydia pneumoniae, an important respiratory pathogen, is difficult to culture, and detection rates by conventional PCRs vary considerably. A new quantitative ompA-based real-time PCR assay based on TaqMan technology for detection of C. pneumoniae in respiratory samples is described, and its performance in terms of sensitivity and reproducibility is compared with those of four published conventional PCRs (one single-step PCR targeting a cloned PstI fragment; two nested PCRs, one targeting the 16S rRNA gene followed by hybridization and the other targeting the ompA gene; and a touchdown enzyme time-release [TETR] PCR also targeting the 16S rRNA gene). Both ompA-based PCRs showed the best analytical sensitivity. All five assays could detect even lower target levels from spiked sputum, with the 16S rRNA assays performing better than the ompA-based nested PCR (10(-6) inclusion-forming units [IFU] were detected in four of four and two of four replicates by the 16S rRNA TETR PCR and the 16S rRNA nested PCR, respectively). In general, the ompA-based real-time protocol produced the most consistent positive results for all replicates tested down to 10(-6) IFU. Eight of 45 patient sputum specimens (18%) were C. pneumoniae DNA positive in at least one of four replicates tested by at least one assay. Without taking into consideration the analytical sensitivity or the reproducibility of the test results, the numbers of C. pneumoniae DNA-positive sputum specimens (n = 8) were four, three, two, two, and one for the 16S rRNA TETR assay, the PstI-based single-step PCR, the ompA-based real-time PCR, the ompA-based nested touchdown PCR, and the 16S rRNA-based nested PCR, respectively. However, the overall rate of concordance of positive results was low. Only one cell culture-positive sputum specimen was positive by four of five assays (14 of 16 replicates; mean cycle threshold value, 25; 10(8) particles/ml of sputum). Thirty-seven specimens were C. pneumoniae negative by all five assays for all replicates tested, as were all negative controls (n = 65 to 100 per testing panel). No PCR inhibitors were detected by real-time PCR or by the 16S rRNA-based nested assay. We confirm that the analytical sensitivity of an assay for the detection of C. pneumoniae does not necessarily predict its ability to detect its target in sputum. A quantitative, fast, and easy-to-handle diagnostic approach such as the ompA-based real-time TaqMan PCR described here might improve the detection of C. pneumoniae in respiratory samples.
| S-EPMC149699 | biostudies-literature
Project description:BACKGROUND:Muscovy duck parvovirus (MDPV) causes high mortality and morbidity in Muscovy ducks, with the pathogenesis of the virus still unknown in many respects. Specific MDPV detection is often rife with false positive results because of high identity at the genomic nucleotide level and antigenic similarity with goose parvovirus (GPV). The objective of this study was to develop a sensitive, highly specific, and repeatable TaqMan-based real-time PCR (qPCR) assay for facilitating the molecular detection of MDPV. RESULTS:The specific primers and probe were designed based on the conserved regions within MDPVs, but there was a variation in GPVs of the nonstructural (NS) genes after genetic comparison. After the optimization of qPCR conditions, the detection limit of this qPCR assay was 29.7 copies/?l. The assay was highly specific for the detection of MDPV, and no cross-reactivity was observed with other non-targeted duck-derived pathogens. Intra- and inter-assay variability was less than 2.21%, means a high degree of repeatability. The diagnostic applicability of the qPCR assay was proven that MDPV-positive can be found in cloacal swabs samples, Muscovy duck embryos and newly hatched Muscovy ducklings. CONCLUSIONS:Our data provided incidents that MDPV could be possible vertically transmitted from breeder Muscovy ducks to Muscovy ducklings. The developed qPCR assay in the study could be a reliable and specific tool for epidemiological surveillance and pathogenesis studies of MDPV.
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Project description: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.
| S-EPMC3009662 | biostudies-literature
Project description:A real-time TaqMan PCR assay based on the gene encoding the protein p37 was developed to detect Mycoplasma hyorhinis. Its specificity was validated with 29 epidemiologically unrelated M. hyorhinis strains (28 field strains and one reference strain) and other mycoplasma species or with other microorganisms commonly found in pigs. The estimated detection limit of this qPCR assay was 125 microorganism equivalents/?l. The same 29 epidemiologically unrelated M. hyorhinis strains and four previously fully sequenced strains were typed by two portable typing methods, the sequencing of the p37 gene and a multilocus sequence typing (MLST) scheme. The first method revealed 18 distinct nucleotide sequences and insufficient discriminatory power (0.934). The MLST scheme was developed with the sequenced genomes of the M. hyorhinis strains HUB-1, GDL-1, MCLD, and SK76 and based on the genes dnaA, rpoB, gyrB, gltX, adk, and gmk. In total, 2,304 bp of sequence was analyzed for each strain. MLST was capable of subdividing the 33 strains into 29 distinct sequence types. The discriminatory power of the method was >0.95, which is the threshold value for interpreting typing results with confidence (D=0.989). Population analysis showed that recombination in M. hyorhinis occurs and that strains are diverse but with a certain clonality (one unique clonal complex was identified). The new qPCR assay and the robust MLST scheme are available for the acquisition of new knowledge on M. hyorhinis epidemiology. A web-accessible database has been set up for the M. hyorhinis MLST scheme at http://pubmlst.org/mhyorhinis/.
| S-EPMC3993664 | biostudies-literature
Project description:We compared an Aspergillus fumigatus-specific Taqman real-time PCR assay for the diagnosis of invasive aspergillosis (IA) with the enzyme-linked immunosorbent assay Platelia Aspergillus method. Patients with proven or probable IA had positive results with at least one of the two methods. The PCR method seems to be more specific, and a combination of the two should improve the diagnosis of IA.
| S-EPMC344496 | biostudies-literature