Determination of Listeria in Dairy and Environmental Samples: Comparison of a Cultural Method and a Colorimetric Nucleic Acid Hybridization Assay

1993 ◽  
Vol 56 (7) ◽  
pp. 581-584 ◽  
Author(s):  
BERNHARD URL ◽  
ALI HEITZER ◽  
ERNST BRANDL
Keyword(s):  
Nucleic Acid ◽  
Environmental Samples ◽  
False Negative ◽  
False Negative Rate ◽  
Nucleic Acid Hybridization ◽  
Hybridization Assay ◽  
Sample Enrichment ◽  
Density Values ◽  
The Mean

The efficiency of the International Dairy Federation (IDF) Listeria detection method (IDF Standard 143:1990) was compared to that of a colorimetric nucleic acid hybridization assay. Out of 250 naturally contaminated cheese and environmental samples tested, the IDF method revealed 153 and the Gene-Trak assay 144 positive samples, respectively. Hence, the Gene-Trak assay gave a false-negative rate of 5.9%. False-positive samples could not be detected. When Oxford and LPM agar were compared for suitability as the streaking medium for the Gene-Trak assay, more satisfactory results were obtained with the Oxford agar. Both the overall number of positive samples and the mean optical density values of the Gene-Trak-positive samples were higher with Oxford than with LPM agar. The extension of sample enrichment time from 1 d (Gene-Trak-assay), and 2 d (IDF method), respectively, to 7 d resulted in a small increase in the number IDF method-positive samples but led to a drastic decrease in the number of Gene-Trak-positive samples.

Comparative Studies of Nucleic Acid Hybridization Assay for Listeria in Foods

1988 ◽  
Vol 71 (3) ◽  
pp. 669-673 ◽  
Author(s):  
Jeffrey D Klinger ◽  
Andrew Johnson ◽  
Daniel Croan ◽  
Pauline Flynn ◽  
Kevan Whippie ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Environmental Samples ◽  
False Negative ◽  
False Negative Rate ◽  
Nucleic Acid Hybridization ◽  
Hybridization Assay ◽  
Rapid Screening ◽  
Bacterial Strains ◽  
Synthetic Dna ◽  
Conventional Culture

Abstract A nucleic acid hybridization assay has been developed for Listeria spp. in dairy foods and environmental samples. The assay is based on detection of unique Listeria 16S rRNA sequences by using a 32Plabeled synthetic DNA probe. Inclusivity and exclusivity of the probe were confirmed with 139 Listeria isolates representing all known species, and 73 non-Listeria bacterial strains. In this paper, we present results from our preliminary studies comparing the hybridization assay with conventional culture on a total of 575 specimens that represent a variety of inoculated and uninoculated foods and environmental samples. The assay, which is done in a filter manifold format after 2 days of cultural enrichment, requires a total assay time of less than 2.5 days. The false-negative rate for all sample groups tested using the GENE-TRAK hybridization assay was less than the rate for culture. Thus, the new assay allows rapid screening of the indicated product groups and provides reliable numerical results

The application of viral nucleic acid detection and lung CT in COVID-19 diagnosis

2020 ◽  
Author(s):  
Rui Hu
Keyword(s):  
Nucleic Acid ◽  
Clinical Symptoms ◽  
Virus Disease ◽  
False Negative ◽  
False Negative Rate ◽  
Diagnostic Methods ◽  
Nucleic Acid Detection ◽  
Viral Nucleic Acid ◽  
Early Medical Intervention ◽  
Lung Ct

The Corona Virus Disease 2019 (COVID-19) has the characteristics of fast propagation speed and strong pathogenicity and has attracted wide attention of people, medical workers, and researchers around the world. Accurate, rapid, and timely screening and diagnosis of COVID-19 is of great significance to control the development of the epidemic situation and save the lives of patients. Currently, the detection of viral nucleic acid and lung CT is the main screening and diagnostic methods of COVID-19. Nucleic acid detection has the advantages of fast, strong specificity and high sensitivity, but there is a certain false-negative rate. CT result of lung examination is visual, but it is not typical due to the uncertain time of clinical symptoms and the early medical intervention. Therefore, the diagnosis of COVID-19 should include a combination of epidemiological history, clinical symptoms, imaging, and laboratory tests.

Detection and identification of poliovirus in environmental samples using nucleic acid hybridization

1990 ◽  
Vol 36 (9) ◽  
pp. 664-669 ◽  
Author(s):  
David R. Preston ◽  
G. Rasul Chaudhry ◽  
Samuel R. Farrah
Keyword(s):  
Tissue Culture ◽  
Nucleic Acid ◽  
Environmental Samples ◽  
Nucleic Acid Hybridization ◽  
Dot Blot ◽  
Polio Virus ◽  
Detection And Identification ◽  
Specificity And Sensitivity ◽  
Hybridization Procedure ◽  
Great Specificity

A procedure was developed to effectively extract viral RNA from poliovirus tissue-culture lysates while eliminating the hybridization background associated with tissue cultures uninfected with poliovirus. Poliovirus cDNA cloned into a pUC vector was used as probe. Both the recombinant plasmids and the cDNA showed great specificity towards poliovirus. However, both probes hybridized with the single-stranded DNA coliphage [Formula: see text]. Tissue culture was found to be an effective method to increase the number of viruses found in environmental samples to a level detectable by hybridization procedures, whereas direct hybridization of RNA from unamplified and highly concentrated raw wastewater showed poor hybridization signals. The specificity and sensitivity of the hybridization procedure developed during these studies indicate that this method may be best suited for the identification rather than the detection of viruses isolated from environmental samples. Key words: nucleic acid hybridization, polio virus, water, dot blot.

scholarly journals Computed tomography parameters for atlantooccipital dislocation in adult patients: the occipital condyle–C1 interval

2016 ◽  
Vol 24 (4) ◽  
pp. 535-545 ◽  
Author(s):  
Eduardo Martinez-del-Campo ◽  
Samuel Kalb ◽  
Hector Soriano-Baron ◽  
Jay D. Turner ◽  
Matthew T. Neal ◽  
...  
Keyword(s):  
Adult Population ◽  
False Negative ◽  
False Negative Rate ◽  
Adult Patients ◽  
Radiographic Measurement ◽  
Occipital Condyle ◽  
Cutoff Values ◽  
Specificity And Sensitivity ◽  
The Mean ◽  
Atlantooccipital Dislocation

OBJECT Atlantooccipital dislocation (AOD) in adults cannot be diagnosed with adequate specificity and sensitivity using only CT or plain radiography, and the spine literature offers no guidelines. In children, the most sensitive and specific radiographic measurement for the diagnosis of AOD is the CT-based occipital condyle–C1 interval (CCI). The goal of the current study was to identify the normal CCI in healthy adults and compare it with the CCI in adults with AOD to establish a highly sensitive and specific cutoff value for the neuroimaging diagnosis of AOD. METHODS A total of 81 patients, 59 without AOD and 22 with AOD, were included in this study. Measurements obtained from thin-slice CT scans of the craniovertebral joint to assess atlantooccipital dislocation included the CCI, condylar sum, the Wholey and Harris intervals, Powers and Sun ratios, Wackenheim line, and Lee X-lines. RESULTS The group of patients without AOD included 30 men (50.8%) and 29 women (49.2%) with a mean age of 42.4 ± 16 years (range 19–87 years). The group of patients with AOD included 10 men (45.5%) and 12 women (54.5%) with a mean age of 38.2 ± 9.7 years (range 20–56 years). Interrater reliabilities within a 95% CI were all greater than 0.98 for CCI measurements. A total of 1296 measurements of the CCI were made in 81 patients. The mean CCI for non-AOD patients was 0.89 ± 0.12 mm, the single largest CCI measurement was 1.4 mm, and the largest mean for either right or left CCI was 1.2 mm. The mean condylar sum was 1.8 ± 0.2 mm, and the largest condylar sum value was 2.2 mm. Linear regression with age predicted an increase in CCI of 0.001 mm/year (p < 0.05). The mean CCI in AOD patients was 3.35 ± 0.18 mm (range 1.5 mm–6.4 mm). The shortest single CCI measurements in the AOD patients were 1.1 mm and 1.2 mm. The mean condylar sum for all 22 AOD patients was 6.7 ± 2.7 mm and the shortest condylar sums were 3.0 mm. Cutoff values for AOD were set at 1.5 mm for the CCI and 3.0 mm for the condylar sum, both with a sensitivity of 1 and false-negative rate of 0. Sensitivity for the Powers, Wholey, Harris, Sun, Wackenheim, and Lee criteria were determined to be 0.55, 0.46, 0.27, 0.23, 0.41, and 0.41, respectively. CONCLUSIONS The CCI is shorter in adult patients as opposed to the pediatric population. The revised CCI (1.5 mm) and condylar sum (3.0 mm) cutoff values have the highest sensitivity and specificity for the diagnosis of AOD in the adult population.

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