Detection of Enterobacter sakazakii Strains by Real-Time PCR

2005 ◽  
Vol 68 (8) ◽  
pp. 1623-1627 ◽  
Author(s):  
BURKHARD MALORNY ◽  
MARTIN WAGNER
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Taqman Probe ◽  
Rrna Gene ◽  
Powdered Infant Formula ◽  
Enterobacter Sakazakii ◽  
Negative Results ◽  
False Negative Results ◽  
Diagnostic Detection

A precise 5′ nuclease (TaqMan) real-time PCR was developed and validated in house for the specific detection of Enterobacter sakazakii isolates. Specifically designed nonpatented primers and a hydrolysis (TaqMan) probe were used to target the 16S rRNA gene. All 27 E. sakazakii and 141 non–E. sakazakii strains tested with the real-time PCR were identified correctly. To monitor false-negative results, an internal amplification control was coamplified with the same primers used for the E. sakazakii DNA. The detection probability of the assay was 56% when an E. sakazakii cell suspension containing 102 CFU/ml was used as template in the PCR (0.5 CFU per reaction) and 100% with a 103 CFU/ml suspension. This PCR assay should be very useful for the diagnostic detection of E. sakazakii in foods, especially powdered infant formula, after cultural enrichment.

Detection of Streptococcus pneumoniae in Sputum Samples by Real- Time PCR.

2020 ◽  
Vol 18 ◽  
Author(s):  
Pegah Shakib ◽  
Mohammad Reza Zolfaghari
Keyword(s):  
Streptococcus Pneumoniae ◽  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Cross Sectional Study ◽  
Laboratory Culture ◽  
Cross Sectional ◽  
Negative Results ◽  
False Negative Results ◽  
Pcr Method

Background: Conventional laboratory culture-based methods for diagnosis of Streptococcus pneumoniae are time-consuming and yield false negative results. Molecular methods including real-time (RT)-PCR rapid methods and conventional PCR due to higher sensitivity and accuracy have been replaced instead traditional culture assay. The aim of the current study was to evaluate lytA gene for detection of Streptococcus pneumoniae in the cerebrospinal fluid of human patients with meningitis using real-time PCR assay. Material and Methods: In this cross-sectional study, a total of 30 clinical specimens were collected from patients in a period from September to December 2018. In order to evaluate the presence of lytA gene, conventional and real-time PCR methods were used without culture. Results: From 30 sputum samples five (16.66%) isolates were identified as S. pneumoniae by lytA PCR and sequencing. Discussion: In this research, an accurate and rapid real-time PCR method was used, which is based on lytA gene for diagnosis of bacteria so that it can be diagnosed. Based on the sequencing results, the sensitivity for detection of lytA gene was 100% (5/5).

scholarly journals False Negative Results in High Viremia Parvovirus B19-Samples Tested with Real-Time PCR

2010 ◽  
Vol 59 (2) ◽  
pp. 129-132 ◽  
Author(s):  
PIOTR GRABARCZYK ◽  
ALEKSANDRA KALIŃSKA ◽  
EWA SULKOWSKA ◽  
EWA BROJER
Keyword(s):  
Positive Result ◽  
Real Time ◽  
Real Time Pcr ◽  
Parvovirus B19 ◽  
False Negative ◽  
Immunocompromised Patients ◽  
Negative Results ◽  
False Negative Results ◽  
Parvovirus B 19 ◽  
The Way

Extremely high viremia is observed during some viruses infection, especialy in immunocompromised patients. False negative results of Parvovirus B 19 DNA tests performed with real-time PCR in high viremic samples are reported. The way of fluorescence diagrams analysis and algorithm of positive result confirmation to exclude such phenomenon are proposed.

scholarly journals False-Negative Results of a Validated Real-Time PCR Protocol for Diagnosis of Newcastle Disease Due to Genetic Variability of the Matrix Gene

2009 ◽  
Vol 47 (11) ◽  
pp. 3791-3792 ◽  
Author(s):  
G. Cattoli ◽  
C. De Battisti ◽  
S. Marciano ◽  
S. Ormelli ◽  
I. Monne ◽  
...  
Keyword(s):  
Genetic Variability ◽  
Real Time ◽  
Newcastle Disease ◽  
Real Time Pcr ◽  
False Negative ◽  
Negative Results ◽  
Matrix Gene ◽  
False Negative Results ◽  
The Matrix

scholarly journals Assessment of Commercial DNA Cleanup Kits for Elimination of Real-Time PCR Inhibitors in the Detection of Cyclospora cayetanensis in Cilantro

2020 ◽  
Vol 83 (11) ◽  
pp. 1863-1870
Author(s):  
ANGELA ASSURIAN ◽  
HELEN MURPHY ◽  
ALICIA SHIPLEY ◽  
HEDIYE NESE CINAR ◽  
ALEXANDRE DA SILVA ◽  
...  
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Threshold Values ◽  
Cyclospora Cayetanensis ◽  
Cycle Threshold ◽  
Negative Results ◽  
False Negative Results ◽  
Pcr Inhibitor ◽  
Zymo Research

ABSTRACT Inhibited reactions have occasionally been observed when cilantro samples were processed for the detection of Cyclospora cayetanensis using quantitative real-time PCR (qPCR). Partial or total inhibition of PCR reactions, including qPCR, can occur, leading to decreased sensitivity or false-negative results. If inhibition occurs, this implies the need for additional purification or cleanup treatments of the extracted DNA to remove inhibitors prior to molecular detection. Our objective was to evaluate the performance of five commercial DNA cleanup kits (QIAquick purification kit from Qiagen [kit 1], OneStep PCR inhibitor removal by Zymo Research [kit 2], NucleoSpin genomic DNA cleanup XS from Macherey-Nagel [kit 3], DNA IQ system by Promega [kit 4], and DNeasy PowerPlant pro kit from Qiagen [5]) to minimize qPCR inhibition using the U.S. Food and Drug Administration–validated Bacteriological Analytical Manual (BAM) Chapter 19b method for detection of C. cayetanensis in cilantro samples containing soil. Each of the five commercial DNA cleanup kits evaluated was able to reduce the qPCR internal amplification control cycle threshold values to those considered to be normal for noninhibited samples, allowing unambiguous interpretation of results in cilantro samples seeded at both a high oocyst level (200 oocysts) and a low oocyst level (10 oocysts). Of the five kits compared, kits 1, 2, and 3 did not show significant differences in the detection of C. cayetanensis, while significantly higher cycle threshold values, indicating lower recovery of the target DNA, were observed from kits 4 and/or 5 in samples seeded with 200 and 10 oocysts (P < 0.05). This comparative study provides recommendations on the use of commercial cleanup kits which could be implemented when inhibition is observed in the detection of C. cayetanensis in cilantro samples using the BAM Chapter 19b method. HIGHLIGHTS

scholarly journals A Multiplex Real-Time Polymerase Chain Reaction (TaqMan) Assay for the Simultaneous Detection of Meloidogyne chitwoodi and M. fallax

2006 ◽  
Vol 96 (11) ◽  
pp. 1255-1262 ◽  
Author(s):  
C. Zijlstra ◽  
R. A. Van Hoof
Keyword(s):  
Polymerase Chain Reaction ◽  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Simultaneous Detection ◽  
Chain Reaction ◽  
Meloidogyne Chitwoodi ◽  
Negative Results ◽  
False Negative Results ◽  
Polymerase Chain

This study describes a multiplex real-time polymerase chain reaction (PCR) approach for the simultaneous detection of Meloidogyne chitwoodi and M. fallax in a single assay. The approach uses three fluorogenic minor groove binding (MGB) TaqMan probes: one FAM-labeled to detect M. chitwoodi, one VIC-labeled to detect M. fallax, and one NED-labeled to detect the internal amplification control (IAC) to monitor false negative results. One common primer set is used for the amplification of part of the internal transcribed spacer (ITS) region of M. chitwoodi and M. fallax and one primer set for the amplification of the IAC. The test enabled detection of M. chitwoodi and/or M. fallax in DNA samples extracted from batches of juveniles, from single juveniles, and from infected plant material. Compared with current assays to detect M. chitwoodi and M. fallax, the multiplex real-time PCR offers the following advantages: it is faster because the test can simultaneously detect both quarantine species without the need for post-PCR processing; and it is at least 10 times more sensitive than a comparable regular PCR also targeting the ITS sequence. Inclusion of the IAC facilitates the interpretation of the FAM and VIC cycle threshold (Ct) values and can prevent the scoring of false negative results when FAM, VIC, and NED Ct values are high. The test allows precise quantification when only one of the two species is present in the sample. However, experiments with mixtures of genomic DNA of M. chitwoodi and M. fallax revealed that the ability of the multiplex real-time PCR assay to detect small quantities of DNA of one species is reduced when large quantities of DNA of the other species are present.

scholarly journals False-negative results in Real-Time PCR (RT-PCR) for meningococcal disease diagnosis

2013 ◽  
Author(s):  
Lucila Okuyama FUKASAWA ◽  
Maria Gisele GONÇALVES ◽  
Fabio Takenori HIGA ◽  
Maristela Marques SALGADO ◽  
Ana Paula Silva de LEMOS ◽  
...  
Keyword(s):  
Real Time ◽  
Meningococcal Disease ◽  
Real Time Pcr ◽  
False Negative ◽  
Disease Diagnosis ◽  
Rt Pcr ◽  
Negative Results ◽  
False Negative Results

scholarly journals Development and application of a canine endogenous internal positive control for use in real-time PCR assays

2018 ◽  
Vol 30 (5) ◽  
pp. 789-792 ◽  
Author(s):  
Joseph J. Modarelli ◽  
Pamela J. Ferro ◽  
Maria D. Esteve-Gasent
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
False Negative ◽  
Positive Control ◽  
Acid Extraction ◽  
Nucleic Acid Extraction ◽  
Negative Results ◽  
False Negative Results ◽  
Internal Positive Control ◽  
Pcr Assays

Real-time PCR (rtPCR) tests have become a method of choice in many diagnostic settings, both animal and human. A concern remains, however, regarding rtPCR assay inhibition during nucleic acid extraction and/or rtPCR reaction process that may result in false-negative results. The use of an internal positive control, either endogenous or exogenous, to mitigate this issue has become more commonplace. We identified and standardized an endogenous internal positive control that can be utilized in rtPCR assays targeting canine-specific pathogens in either a singleplex or multiplex format. The target chosen for the endogenous internal positive control (EIPC-K9) was a highly conserved region in canine mitochondrial DNA. Samples from 240 dogs and 11 other species were screened with EIPC-K9; all canine samples were detected, and no cross-amplification with other species tested was observed. Additionally, no inhibition was noted when comparing singleplex to multiplex rtPCR formats.

Evaluating real-time PCR for the quantification of distinct pathogens and indicator organisms in environmental samples

2004 ◽  
Vol 50 (1) ◽  
pp. 263-270 ◽  
Author(s):  
M. Lebuhn ◽  
M. Effenberger ◽  
G. Garcés ◽  
A. Gronauer ◽  
P.A. Wilderer
Keyword(s):  
Nucleic Acid ◽  
Real Time ◽  
Real Time Pcr ◽  
Environmental Samples ◽  
False Negative ◽  
Indicator Organisms ◽  
Negative Results ◽  
False Negative Results ◽  
Methodological Bias ◽  
Reliable Quantification

We evaluated quantitative real-time PCR (qPCR) and RTqPCR (for RNA species) for their ability to quantify microorganisms and viruses in problematic environmental samples such as cattle manure, digester material, wastewater and soil. Important developments included a standard spiking approach which compensated for methodological bias and allowed sample-to-sample comparison and reliable quantification. Programme CeTe was developed to calculate endogenous concentrations of target organisms (nucleic acid copies) for each sample separately from the generated standard curves. The approach also permitted assessment of the detection limit of the complete method, including extraction. It varied from sample to sample, due to different extraction efficiencies and variable co-extraction of PCR inhibitors. False negative results were thereby avoided. By using this approach we were able to optimise a DNA extraction protocol from the different tested sample types. Protocols for the extraction of RNA species from environmental samples were also optimised. DNA was (almost) not degraded after lethal shock (autoclaving) in the sterile environment. In contrast, the parallel selective cultivation and qPCR results for various microbial parameters from an anaerobic digester chain suggested that DNA from decaying organisms was readily recycled in metabolically active environments. It may, therefore, be used to determine viable organisms in samples exhibiting substantial metabolic turnover. It is proposed that our standard spiking approach, including data evaluation by the program CeTe, should be considered in future standardisation and norms for the quantification of nucleic acid containing organisms in environmental and product samples.

scholarly journals Performance Evaluation of a Commercial Real-Time PCR Assay and of an In-House Real-Time PCR for Trypanosoma cruzi DNA Detection in a Tropical Medicine Reference Center, Northern Italy

2020 ◽  
Vol 8 (11) ◽  
pp. 1692
Author(s):  
Silvia Stefania Longoni ◽  
Elena Pomari ◽  
Alberto Antonelli ◽  
Fabio Formenti ◽  
Ronaldo Silva ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Trypanosoma Cruzi ◽  
Real Time ◽  
Chagas Disease ◽  
Real Time Pcr ◽  
False Negative ◽  
Population Movements ◽  
Whole Process ◽  
Negative Results ◽  
False Negative Results

Chagas disease, a neglected protozoal disease endemic in Latin America, is also currently considered an emerging threat in nonendemic areas because of population movements. The detection of Trypanosoma cruzi DNA is increasingly being considered as important evidence to support Chagas disease diagnoses. However, further performance evaluation of molecular assays is useful for a standardization of strategy considering the whole process in routine diagnosis, especially for the different settings such as endemic and nonendemic countries. Seventy-five samples were collected from subjects screened for Chagas disease in Italy. The DNA was isolated from blood using automated extraction. We evaluated the performance of the commercial RealCycler® CHAG kit (pmPCR) based on satellite DNA (SatDNA) and of an in-house real-time PCR (ihPCR) targeting Sat and kinetoplast (k) DNAs, using the concordance of two serology assays as a reference standard. The sensitivity of kDNA and SatDNA tests by ihPCR and SatDNA by pmPCR were 14.29% (95% confidence interval (CI) 6.38 to 26.22), 7.14% (95% CI 1.98 to 17.29), and 7.14% (95% CI 1.98 to 17.29), respectively. Specificity was 100% for all PCR assays and targets. Overall, our results suggest that the preferred approach for clinical laboratories is to combine the kDNA and SatDNA as targets in order to minimize false-negative results increasing sensitivity.

scholarly journals Quantitation of Viral DNA by Real-Time PCR Applying Duplex Amplification, Internal Standardization, and Two-Color Fluorescence Detection

2001 ◽  
Vol 67 (6) ◽  
pp. 2837-2839 ◽  
Author(s):  
Franz Gruber ◽  
Falko G. Falkner ◽  
Friedrich Dorner ◽  
Thomas Hämmerle
Keyword(s):  
Real Time ◽  
Fluorescence Detection ◽  
Real Time Pcr ◽  
Parvovirus B19 ◽  
False Negative ◽  
Viral Dna ◽  
Negative Results ◽  
False Negative Results ◽  
Pcr Method ◽  
Internal Standardization

ABSTRACT A real-time PCR method was developed to quantitate viral DNA that includes duplex amplification, internal standardization, and two-color fluorescence detection without the need to generate an external standardization curve. Applied to human parvovirus B19 DNA, the linear range was from 102 to at least 5 × 106 copies per ml of sample. The coefficient of variation was 0.29 using a run control of 2,876 copies per ml. The method reduces the risk of false-negative results, yields high precision, and is applicable for other DNA targets.

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