scholarly journals PCR and Blood Culture for Detection ofEscherichia coli Bacteremia in Rats

1999 ◽  
Vol 37 (8) ◽  
pp. 2479-2482 ◽  
Author(s):  
Alexandra Heininger ◽  
Marlies Binder ◽  
Sibylle Schmidt ◽  
Klaus Unertl ◽  
Konrad Botzenhart ◽  
...  
Keyword(s):  
Blood Culture ◽  
Detection Rate ◽  
False Negative ◽  
Diagnostic Procedures ◽  
Microbial Pathogens ◽  
Gene Encoding ◽  
E Coli ◽  
Negative Results ◽  
False Negative Results ◽  
Male Wistar Rats

Critically ill patients often develop symptoms of sepsis and therefore require microbiological tests for bacteremia that use conventional blood culture (BC) techniques. However, since these patients frequently receive early empirical antibiotic therapy before diagnostic procedures are completed, examination by BC can return false-negative results. We therefore hypothesized that PCR could improve the rate of detection of microbial pathogens over that of BC. To test this hypothesis, male Wistar rats were challenged intravenously with 106 CFU of Escherichia coli. Blood was then taken at several time points for detection of E. coliby BC and by PCR with E. coli-specific primers derived from the uidA gene, encoding β-glucuronidase. In further experiments, cefotaxime (100 or 50 mg/kg of body weight) was administered intravenously to rats 10 min after E. colichallenge. Without this chemotherapy, the E. coli detection rate decreased at 15 min and at 210 min after challenge from 100% to 62% of the animals with PCR and from 100% to 54% of the animals with BC (P, >0.05). Chemotherapy decreased the E. coli detection rate at 25 min and at 55 min after challenge from 100% to 50% with PCR and from 100% to 0% with BC (P, <0.05). Thus, at clinically relevant serum antibiotic levels, PCR affords a significantly higher detection rate than BC in this rat model. The results suggest that PCR could be a useful adjunct tool supplementing conventional BC techniques in diagnosing bacteremia.

scholarly journals Inequality in the Frequency of the Open States Occurrence Depends on Single 2H/1H Replacement in DNA

Molecules ◽  
2020 ◽  
Vol 25 (16) ◽  
pp. 3753 ◽  
Author(s):  
Alexander Basov ◽  
Mikhail Drobotenko ◽  
Alexandr Svidlov ◽  
Eugeny Gerasimenko ◽  
Vadim Malyshko ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
False Negative ◽  
Deuterium Atom ◽  
Base Pairs ◽  
Gene Encoding ◽  
Negative Results ◽  
False Negative Results ◽  
Nitrogenous Base ◽  
Open States ◽  
Different Parts

In the present study, the effect of 2H/1H isotopic exchange in hydrogen bonds between nitrogenous base pairs on occurrence and open states zones dynamics is investigated. These processes are studied using mathematical modeling, taking into account the number of open states between base pairs. The calculations of the probability of occurrence of open states in different parts of the gene were done depending on the localization of the deuterium atom. The mathematical modeling study demonstrated significant inequality (dependent on single 2H/1H replacement in DNA) among three parts of the gene similar in length of the frequency of occurrence of the open states. In this paper, the new convenient approach of the analysis of the abnormal frequency of open states in different parts of the gene encoding interferon alpha 17 was presented, which took into account both rising and decreasing of them that allowed to make a prediction of the functional instability of the specific DNA regions. One advantage of the new algorithm is diminishing the number of both false positive and false negative results in data filtered by this approach compared to the pure fractile methods, such as deciles or quartiles.

scholarly journals Contrast of Real-Time Fluorescent PCR Methods for Detection of Escherichia coli O157:H7 and of Introducing an Internal Amplification Control

2019 ◽  
Vol 7 (8) ◽  
pp. 230 ◽  
Author(s):  
Zhao ◽  
Xia ◽  
Liu
Keyword(s):  
Real Time ◽  
Water Samples ◽  
False Negative ◽  
Internal Amplification Control ◽  
Pcr Assay ◽  
The Real ◽  
E Coli ◽  
Negative Results ◽  
False Negative Results ◽  
Fluorescent Pcr

Various constituents in food specimens can inhibit the PCR assay and lead to false-negative results. An internal amplification control was employed to monitor the presence of false-negative results in PCR amplification. In this study, the objectives were to compare the real-time PCR-based method by introducing a competitive internal amplification control (IAC) for the detection of Escherichia O157:H7 with respect to the specificity of the primers and probes, analytical sensitivity, and detection limits of contamination-simulated drinking water. Additionally, we optimized the real-time fluorescent PCR detection system for E. coli O157:H7. The specificity of primers and probes designed for the rfbE gene was evaluated using four kinds of bacterial strains, including E. coli O157:H7, Staphylococcus aureus, Salmonella and Listeria monocytogenes strains. The real time PCR assay unambiguously distinguished the E. coli O157:H7 strains after 16 cycles. Simultaneously, the lowest detection limit for E. coli O157:H7 in water samples introducing the IAC was 104 CFU/mL. The analytical sensitivity in water samples had no influence on the detection limit compared with that of pure cultures. The inclusion of an internal amplification control in the real-time PCR assay presented a positive IAC amplification signal in artificially simulated water samples. These results indicated that real-time fluorescent PCR combined with the IAC possessed good characteristics of stability, sensitivity, and specificity. Consequently, the adjusted methods have the potential to support the fast and sensitive detection of E. coli O157:H7, enabling accurate quantification and preventing false negative results in E. coli O157:H7 contaminated samples.

scholarly journals Accuracy of SARS-CoV-2 molecular laboratory testing: insight on recurrence infection and the new emergent strains

2021 ◽  
Vol 2 (1) ◽  
pp. 5-13
Author(s):  
Huda Hassan Al-Griw
Keyword(s):  
Genetic Variability ◽  
False Negative ◽  
Diagnostic Procedures ◽  
Test Results ◽  
Prevention Measures ◽  
Laboratory Methods ◽  
Negative Results ◽  
Virus Rna ◽  
False Negative Results ◽  
Rapid Spread

The rapid spread of the SARS-CoV-2 virus and increased number of deaths urged the world to provide accurate diagnostic procedures and apply the correct prevention measures to eradicate the disease. Molecular assays are designed to test the presence of virus RNA. The assays have wanting accuracy represented by false positive and false negative results, in particularly with continuous emerging of SARS-CoV-2 genetic variability. Miss interpretation of the test results can lead to bad outcomes for both individuals and the surrounding community when assuming the test is perfect. This review provides an update of the currently available molecular laboratory methods and address the effect of ongoing SARS-CoV-2 genetic variability on the performance of RT-PCR, the problem of re-positive test result in recovered patients and provides elements to be considered for performing SARS-CoV-2 test and interpreting the test results.

scholarly journals Assessment of a Multiplex LAMP Assay (Eazyplex® CSF Direct M) for Rapid Molecular Diagnosis of Bacterial Meningitis: Accuracy and Pitfalls

2021 ◽  
Vol 9 (9) ◽  
pp. 1859
Author(s):  
Anne-Gaëlle Leroy ◽  
Elise Persyn ◽  
Sophie-Anne Gibaud ◽  
Lise Crémet ◽  
Paul Le Turnier ◽  
...  
Keyword(s):  
Antibiotic Therapy ◽  
Lumbar Puncture ◽  
False Negative ◽  
Lamp Assay ◽  
Predictive Values ◽  
Amplification Curve ◽  
E Coli ◽  
Negative Results ◽  
False Negative Results ◽  
Automated Software

Background: Automated molecular panels are attractive tools for improving early meningitis diagnosis. This study assessed the Eazyplex® CSF direct M panel (EP), a multiplex real-time Loop-Mediated Isothermal Amplification assay. Methods: From December 2016 to December 2019, cerebrospinal fluid (CSF) samples were routinely tested with the EP V1.0. CSF parameters and microbiological and clinical data were retrospectively collected. Results: Out of 230 CSF samples, the EP yielded positive, negative, and invalid results for 32 (13.9%) (16 N. meningitidis, nine S. pneumoniae, two S. agalactiae, two E. coli, two H. influenzae, one L. monocytogenes), 182 (79.1%), and 16 (7%) samples, respectively. Among the positive samples, 14 (44%) remained negative in culture (antibiotic therapy before lumbar puncture (n = 11), meningococcal meningitis (n = 3)). High CSF protein concentrations and cellularity were associated with LAMP inhibition, counteracted by centrifugation. The automated software yielded 13 false positive and five false negative results. Amplification curve analysis was necessary and enabled the attainment of positive (PPA) and negative percentage agreement and positive and negative predictive values of 91.4%, 100%, 100%, and 98.3%. Three false negative results remained (two E. coli and one N. meningitidis). E. coli presented the poorest PPA (50%). Conclusion: This work confirms the strong performance of the EP, of particular interest in cases of antibiotic therapy before lumbar puncture.

New Diagnostic Possibilities for Neonatal Sepsis

2018 ◽  
Vol 35 (06) ◽  
pp. 575-577 ◽  
Author(s):  
Chryssoula Tzialla ◽  
Cristian Achille ◽  
Lina Bollani ◽  
Mauro Stronati ◽  
Alessandro Borghesi ◽  
...  
Keyword(s):  
Blood Culture ◽  
Early Diagnosis ◽  
Neonatal Sepsis ◽  
False Negative ◽  
Clinical Applications ◽  
Morbidity And Mortality ◽  
Negative Results ◽  
False Negative Results ◽  
Novel Biomarkers ◽  
Diagnostic Approaches

AbstractProgress in neonatal care has decrease morbidity and mortality due to neonatal sepsis (NS). Although diagnosis of sepsis continues to rely on blood culture, this method is too slow and limited by false-negative results. There are numerous sepsis biomarkers that have been evaluated for the early diagnosis of NS, but, to date, there is no single ideal biomarker, though novel biomarkers are becoming more sophisticated and specific in their clinical applications. This review provides an overview of the current diagnostic approaches available or under development for diagnosing NS.

Critical Evaluation of Impedance Phlebography for the Diagnosis of Deep Vein Thrombosis

1974 ◽  
Vol 31 (02) ◽  
pp. 273-278
Author(s):  
Kenneth K Wu ◽  
John C Hoak ◽  
Robert W Barnes ◽  
Stuart L Frankel
Keyword(s):  
Deep Vein Thrombosis ◽  
False Positive ◽  
False Negative ◽  
Critical Evaluation ◽  
Original Method ◽  
Vein Thrombosis ◽  
Negative Results ◽  
False Negative Results ◽  
Deep Vein ◽  
Positive Results

SummaryIn order to evaluate its daily variability and reliability, impedance phlebography was performed daily or on alternate days on 61 patients with deep vein thrombosis, of whom 47 also had 125I-fibrinogen uptake tests and 22 had radiographic venography. The results showed that impedance phlebography was highly variable and poorly reliable. False positive results were noted in 8 limbs (18%) and false negative results in 3 limbs (7%). Despite its being simple, rapid and noninvasive, its clinical usefulness is doubtful when performed according to the original method.

Scoring System for the Diagnosis of COVID-19

2020 ◽  
Vol 13 (1) ◽  
pp. 413-414 ◽  
Author(s):  
Mohamed Farouk Allam
Keyword(s):  
Scoring System ◽  
Clinical Symptoms ◽  
False Negative ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Negative Results ◽  
False Negative Results ◽  
Symptoms And Signs

Due to the international spread of COVID-19, the difficulty of collecting nasopharyngeal swab specimen from all suspected patients, the costs of RT-PCR and CT, and the false negative results of RT-PCR assay in 41% of COVID-19 patients, a scoring system is needed to classify the suspected patients in order to determine the need for follow-up, home isolation, quarantine or the conduction of further investigations. A scoring system is proposed as a diagnostic tool for suspected patients. It includes Epidemiological Evidence of Exposure, Clinical Symptoms and Signs, and Investigations (if available). This scoring system is simple, could be calculated in a few minutes, and incorporates the main possible data/findings of any patient.

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).

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