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At least 163 records · Page 9Linked to original sources
PubMed2000

Direct detection of apoptotic cells in peripheral blood from highly pathogenic SHIV-inoculated monkey.

Apoptosis in peripheral blood leukocytes (PBL) has been estimated by the enhancement of spontaneous apoptosis after in vitro culture, because apoptotic cells have not been observed directly in freshly isolated PBL in the course of HIV/AIDS. In monkeys infected with a highly pathogenic simian/human immunodeficiency virus (SHIV), which corresponds to rapid progressors of HIV infection, a high frequency of apoptotic cells was directly detected in fresh PBL by electron-microscopic studies. Peripheral blood apoptosis transiently occurred after intense plasma viremia, and peaking at 3 weeks postinfection; occurrence was not limited specifically to lymphocytes, but also occurred in other types of leukocytes. Apoptosis in peripheral lymph nodes was also detected following intense plasma viremia. However, the in vivo apoptosis was not detected in nonpathogenic SHIV-infected monkeys that showed no cell loss. Thus, we directly showed the apoptosis of PBL, which might be associated with pathogenic SHIV produced during the time of plasma viremia.

Animals↗
PubMed1991

Comparison of conventional susceptibility tests with direct detection of penicillin-binding protein 2a in borderline oxacillin-resistant strains of Staphylococcus aureus.

Six selected strains of Staphylococcus aureus classified as borderline oxacillin-resistant, according to standard disk diffusion and microdilution susceptibility test methods, and seven methicillin-resistant and seven methicillin-susceptible control strains were examined for the presence of penicillin-binding protein 2a (PBP 2a) by fluorography and immunoblotting and for DNA hybridization with a mec-specific probe in a dot blot assay. Oxacillin agar screen tests with and without NaCl supplementation were also performed with all strains. PBP 2a was detected both by fluorography and by immunoblotting in all seven methicillin-resistant control strains and in none of the susceptible controls. PBP 2a was detected in two borderline strains. Results of agar screen tests performed without NaCl supplementation were completely concordant with susceptibility determined by PBP 2a and mec detection methods. Agar screening with NaCl supplementation was less accurate. These findings were confirmed with 20 additional borderline strains. Direct detection methods for the presence of PBP 2a or mec, the gene encoding it, allow accurate and definitive classification of borderline strains. Further efforts to develop a rapid, clinically useful, antibody detection system for PBP 2a are warranted.

Animals↗
PubMedDate not supplied

[Direct detection in diarrheal stools of Escherichia coli adhesion factors CFA/I, CFA/II and E8775 by the india ink immune reaction].

An India ink immune reaction was used for the direct detection, in diarrhoeal stools, of Escherichia coli possessing the CFA/I, CFA/II and E8775 fimbriae. With this method, a presumptive diagnosis of enterotoxigenic E. coli (ETEC) can rapidly be made. Staining required the bivalency of rabbit anti-fimbriae IgG; the F(ab')2 fragment was necessary. The reaction was impossible with purified Fab fragment. A comparative study of this technique and detection by culture of ETEC strains showed good correlation when the India ink immune reaction was performed at the beginning of infection.

Antigens, Bacterial↗
PubMed1991

Evaluation of the rapid CLEARVIEW Chlamydia test for direct detection of chlamydiae from cervical specimens.

The CLEARVIEW Chlamydia test (Unipath, Mountain View, Calif.), a 30-min immunoassay, was compared to a standard tissue culture technique for the direct detection of chlamydiae from 677 cervical specimens obtained from 667 patients. For data analysis, 15 specimens were eliminated because of toxicity in the culture and 14 were eliminated because of failure of the extracted specimen to migrate in the CLEARVIEW test, one of the latter group being culture positive. Of the remaining 648 specimens, 40 were culture positive, of which 38 were detected by the CLEARVIEW test, and 12 specimens were positive only by the CLEARVIEW test. Therefore, the CLEARVIEW in comparison with culture was easier to perform, more rapid, and in this low prevalence (6.2%) population had a 95.0% sensitivity, 98.0% specificity, and 76.0% positive and 99.7% negative predictive values.

Adolescent↗
PubMed1992

Evaluation of an automated immunodiagnostic assay system for direct detection of herpes simplex virus antigen in clinical specimens.

The Vitek ImmunoDiagnostic Assay System (VIDAS) is a 2 1/3-h automated qualitative enzyme-linked fluorescent immunoassay developed for the direct detection of herpes simplex virus (HSV) antigen in clinical specimens. A total of 356 clinical specimens submitted for HSV isolation were prospectively evaluated with the VIDAS, and the results of the technique were compared with those of both HSV isolation in cell culture and Herpchek, a nonautomated enzyme immunoassay. Compared to cell culture, VIDAS had a sensitivity of 91.6% and a specificity of 89.3%, with positive and negative predictive values of 82.6 and 95.0%, respectively. In comparison to Herpchek, VIDAS had a sensitivity of 93.7% and a specificity of 93.0%, with positive and negative predictive values of 89.4 and 95.9%, respectively. The results demonstrated that the VIDAS required minimal manipulation in order to produce results comparable to those of Herpchek and HSV isolation in cell culture.

Antigens, Viral↗
PubMed2004

Accurate sensitivity in optically preamplified direct detection.

We present a novel model for calculating the bit error rate in optical communication systems in the case of on-off keying intensity modulation and optically preamplified direct detection. The model accounts for the intersymbol interference and is based on the Laguerre photon-count probability distribution predicted by photodetection theory. For a non-return-to-zero modulation format an accurate value of the sensitivity for a quantum-limited receiver of 33.9 photons/bit is obtained.

Journal Article↗
PubMed2003

Evaluation of the BDProbeTec ET system for direct detection of Mycobacterium tuberculosis in pulmonary and extrapulmonary samples: a multicenter study.

We evaluated the BDProbeTec ET system (Becton Dickinson, Sparks, Md.), a strand displacement amplification-based technique, for direct detection of Mycobacterium tuberculosis in 867 clinical samples. Of 294 extrapulmonary specimens, 52 had positive results by both BDProbeTec ET and culture and 209 had negative results by both methods; sensitivity and specificity were 76.5 and 95.9%, respectively. After resolution of discrepancies, the sensitivity rose to 77.8%.

Body Fluids↗
PubMedDate not supplied

[Direct detection by ligase chain reaction of Mycobacterium tuberculosis complex in pleural fluid].

Our purpose was to investigate the utility of the DNA amplification by ligase chain reaction (LCR) for the direct detection of Mycobacterium tuberculosis complex (MTC) in pleural fluid specimens from patients suspected for tuberculous pleural effusion. We have used the LCx M. tuberculosis kit (Abbott) which uses the amplification of the gene that encodes for antigen b. We have examined 81 pleural fluid specimens by isolation (on Löwenstein-Jensen medium and MB/BacT system) and by LCR. Out of 10 positive specimens in culture, 4 were also positive by LCR; out of 71 negative specimens in culture, 8 were positive by LCR. We have re-evaluated the LCR results according to the clinical diagnosis, sustained by the successful therapy, and to the pathological diagnosis on the pleural biopsy. The sensitivity and specificity of LCR in the diagnosis of tuberculous pleural effusion were 31.5% and 100%. This commercial LCR kit is a rapid, specific, but less sensitive test for the routine diagnosis of the tuberculous pleural effusion.

Humans↗
PubMed2002

Amplification of RNA by NASBA allows direct detection of viable cells of Ralstonia solanacearum in potato.

AIMS: The objective of this study was to develop a Nucleic Acid Sequence Based Amplification (NASBA) assay, targeting 16S rRNA sequences, for direct detection of viable cells of Ralstonia solanacearum, the causal organism of bacterial wilt. The presence of intact 16S rRNA is considered to be a useful indicator for viability, as a rapid degradation of this target molecule is found upon cell death. METHODS AND RESULTS: It was demonstrated by RNase treatment of extracted nucleic acids from R. solanacearum cell suspensions that NASBA exclusively detected RNA and not DNA. The ability of NASBA to assess viability was demonstrated in two sets of experiments. In the first experiment, viable and chlorine-killed cells of R. solanacearum were added to a potato tuber extract and tested in NASBA and PCR. In NASBA, only extracts spiked with viable cells resulted in a specific signal after Northern blot analysis, whereas in PCR, targeting 16S rDNA sequences, both extracts with viable and killed cells resulted in specific signals. In the second experiment, the survival of R. solanacearum on metal strips was studied using NASBA, PCR-amplification and dilution plating on the semiselective medium SMSA. A positive correlation was found between NASBA and dilution plating detecting culturable cells, whereas PCR-amplification resulted in positive reactions also long after cells were dead. The detection level of NASBA for R. solanacearum added to potato tuber extracts was determined at 104 cfu per ml of extract, equivalent to 100 cfu per reaction. With purified RNA a detection level of 104 rRNA molecules was found. This corresponds with less than one bacterial cell, assuming that a metabolically active cell contains ca 105 copies of rRNA. Preliminary experiments demonstrated the potential of NASBA to detect R. solanacearum in naturally infected potato tuber extracts. CONCLUSIONS: NASBA specifically amplifies RNA from viable cells of R. solanacearum even present in complex substrates at a level of 100 cfu per reaction. SIGNIFICANCE AND IMPACT OF THE STUDY: The novel NASBA assay will be particularly valuable for detection of R. solanacearum in ecological studies in which specifically viable cells should be determined.

Base Sequence↗
PubMedDate not supplied

Direct detection of thermotolerant campylobacters in chicken products by PCR and in situ hybridization.

We have evaluated the use of PCR and fluorescent in situ hybridization (FISH) techniques for the detection of thermotolerant campylobacters in naturally contaminated chicken products. 16S rRNA sequence data was used to design two specific primers and an oligonucleotide probe for PCR and FISH analyses, respectively. The PCR protocol amplified a 439-bp fragment corresponding to a portion of specific 16S RNA gene from thermotolerant campylobacters. The detection range of the PCR assay varied between 10 cells (after enrichment) to 10(2) cells per mL (without enrichment). FISH probes were able to identify thermotolerant Campylobacter species in 'spiked' and 'unspiked' naturally contaminated samples. PCR and FISH were performed on naturally contaminated samples and compared with the isolation of cells on selective media. The in situ hybridization technique was less sensitive than PCR, although its sensitivity of detection was increased considerably after 22 h of enrichment. These results confirm the usefulness of 16S rRNA-based techniques for the direct detection of campylobacters in food samples.

Animals↗
PubMed1995

Development and testing of monoclonal antibody-based rapid immunodiagnostic test kits for direct detection of Vibrio cholerae O139 synonym Bengal.

We report on the development and testing of two monoclonal antibody-based rapid immunodiagnostic test kits, BengalScreen, a coagglutination test, and Bengal DFA, a direct fluorescent-antibody test, for direct detection of Vibrio cholerae O139 synonym Bengal in clinical and environmental specimens. The BengalScreen test requires less than 5 min to complete and can be used in the field. Bengal DFA, being more sensitive than BengalScreen, requires only one reagent and less than 20 min for detection and enumeration of V. cholerae O139 synonym Bengal. In tests for specificity, all 40 strains of V. cholerae O139 reacted with both test kits, whereas 157 strains of heterologous species examined did not, yielding 100% specificity in this study. A field trial was conducted in with both BengalScreen and Bengal DFA, and the results were compared with those obtained by conventional culture methods. BengalScreen demonstrated a sensitivity of 95%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 94%. Results obtained by Bengal DFA, on the other hand, were 100% sensitive and 100% specific and yielded 100% positive and negative predictive values compared with culture methods. In a second evaluation, 93 stool specimens from Mexico that were negative for V. cholerae O139 by culture were also tested with both the BengalScreen and Bengal DFA kits. None of the 93 specimens were positive for V. cholerae O139 by both tests. A concentration method was optimized for screening of environmental water samples for V. cholerae O139 synonym Bengal with rapid test kits. BengalScreen results were unequivocally positive when water samples contained at least 2.0 x 10(3) CFU/ml, whereas Bengal DFA demonstrated an unequivocally positive reaction when the water sample contained at least 1.5 x 10(2) CFU/ml. When Bengal DFA was compared with conventional culture methods for enumeration of V. cholerae O139 synonym Bengal organisms, no difference was observed.

Agglutination Tests↗
PubMed2002

Direct detection of yessotoxin and its analogues by liquid chromatography coupled with electrospray ion trap mass spectrometry.

A liquid chromatography mass spectrometry (LC-MS) method is proposed for the sensitive, specific and direct detection of yessotoxin and its analogues, marine biotoxins which are associated with diarrhetic shellfish poisoning (DSP) and which have been found in the North Adriatic sea since 1995. The LC-MS method provided a detection limit of 70 pg for yessotoxin in full scan mode and was applied to determine the toxic profiles of a number of extracts or partially purified fractions of toxic mussels collected along the Emilia Romagna coasts (Italy) in the period 1995-1999. Detection of a desulfo-yessotoxin derivative from Mytilus galloprovincialis collected in 1998 is also reported.

Animals↗
PubMedDate not supplied

Evaluation of the Gen-Probe PACE II assay for the direct detection of Neisseria gonorrhoeae in endocervical specimens.

Evaluation of a non-isotopic DNA-rRNA hybridization assay [Probe Assay-Chemiluminescence Enhanced System (PACE II, Gen-Probe, San Diego, CA)] for the direct detection of Neisseria gonorrhoeae from clinical specimens was compared with culture. Culture and probe tests were performed on 795 endocervical specimens. Results demonstrated that total positives by culture were 18 (2.3% of total); both culture and the DNA-rRNA assay agreed in all cases but four. The PACE II yielded four hybridization-positive results with negative companion cultures. The sensitivity, specificity, and positive and negative predictive values for PACE II were 100%, 99.5%, and 82%, and 100%, respectively. The four discrepant results were resolved using a competitive nucleic acid hybridization assay with recalculated sensitivity, specificity, and positive and negative predictive values of 100, 99.7, and 91.6 and 100%, respectively. Overall, the DNA-rRNA assay offered a number of advantages over culture. The assay was more rapid, able to be performed directly on clinical specimens, and provided superior transport stability.

Adolescent↗
PubMed2003

MRI detection of weak magnetic fields due to an extended current dipole in a conducting sphere: a model for direct detection of neuronal currents in the brain.

To investigate the feasibility of direct MR detection of neuronal activity in the brain, neuronal current flow was modeled as an extended current dipole located in a conducting sphere. The spatially varying magnetic field induced within the sphere by such a dipole was calculated, including its form close to and within the current source. The predicted field variation was experimentally verified by measurements of the variation in phase of the MR signal in a sphere containing a model dipole. The effects of the calculated magnetic field distributions on the phase and magnitude of the signal in MR images were explored. The minimum detectable dipole strength under normal experimental conditions was calculated to be about 4.5 nAm, which is similar in magnitude to dipole strengths from evoked neuronal activity, and is an order of magnitude smaller than dipole strengths expected from spontaneous activity. This minimum detectable dipole strength increases with increasing spatial extent of the primary current distribution. In the experimental work, the effects of a field of [1.1 +/- 0.5] x 10(-10) T strength were detected, corresponding to the maximum net field caused by a dipole of 6.3 nAm strength with a spatial extent of 3 x 3 x 2 mm(3).

Action Potentials↗
PubMed2005

Direct detection in clinical samples of multiple gene mutations causing resistance of Mycobacterium tuberculosis to isoniazid and rifampicin using fluorogenic probes.

BACKGROUND: This study evaluates a method based on real-time PCR for direct detection in clinical samples of the common mutations responsible for isoniazid and rifampicin resistance of Mycobacterium tuberculosis. METHODS: Six pairs of fluorogenic 5' exonuclease probes (Taqman), mutated and wild-type, were designed for six targets: codon 315 of katG, substitution C209T in the regulatory region of inhA, and codons 513, 516, 526 and 531 of rpoB. RESULTS: A total of 98 clinical samples harbouring resistant bacilli from 55 patients and 126 samples harbouring susceptible bacilli from 126 patients were processed. The isolates from samples were tested for drug susceptibility with the radiometric method and sequenced for the same genetic targets. Among the samples, 93 harboured isoniazid-resistant bacilli. According to the sequencing results, 30 had mutations in katG, 30 in inhA and 33 (35.4%) had no mutations in these targets. All 27 clinical specimens harbouring rifampicin-resistant bacilli showed mutations in rpoB. The detection threshold of this method in detecting target genes in serial dilutions of artificial samples was 1.5 x 10(3) cfu/mL. In clinical samples, the sensitivity ranged from 30.4 to 35.3% for smear-negative samples and from 95.1 to 99.2% for smear-positive samples, with a specificity of 100%. In this study, the overall sensitivity in detecting patients having the target mutations was 74.3%. CONCLUSIONS: The main advantage of the described method is the possibility of detecting rifampicin and isoniazid resistance within 48-72 h after sample collection, with a sensitivity of nearly 100% in smear-positive samples if the chosen target is responsible for the resistance.

Antitubercular Agents↗
PubMedDate not supplied

A solid-phase enzyme immunoassay (Gonozyme) test for direct detection of Neisseria gonorrhoeae antigen in urogenital specimens from patients at a sexually transmitted disease clinic.

The Gonozyme test (Abbott Laboratories; North Chicago, IL), a solid-phase enzyme immunoassay (EIA), was evaluated for direct detection of antigens from Neisseria gonorrhoeae in clinical specimens. Results of the EIA were compared with those of culture and gram stain. Separate swab specimens for each procedure were collected from cervical secretions of 119 females and urethral exudate of 198 males (total, 324 specimens) seen in a sexually transmitted disease clinic. Cultures from 132 specimens were positive for gonococci (27 women and 105 men), and gram stains of 119 specimens were positive (14 women and 105 men). The EIA test was positive for 145 specimens (34 women and 111 men). The sensitivities of EIA for females and males were 88.5% and 99.0%, respectively, as compared with 29.6% and 98.1% for gram stain. Specificities of EIA were 89.2% and 92.5%, while those of gram stain were 93.5% and 86.0%, respectively. Overall accuracy of the EIA was 89.1% for females and 95.9% for males. In veiw of the speed and independence from viable organisms of the EIA test, the lack of good gram stain sensitivity for females, and the inherent drawbacks of culture, the Gonozyme test, if used in conjunction with culture, can detect a higher percentage of patients with genital gonorrhea than can culture alone. However, EIA in its present form cannot be used as the sole criterion for a laboratory diagnosis of gonococcal disease because of the ethical and medicolegal consequences of an EIA-positive, culture-negative result.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Bacterial↗
PubMed2004

Direct detection of a phase change in PdO/CeO2 supported on chi-Al2O3 by means of in situ high-temperature measurements of XRD and FTIR.

Phase changes between PdO and Pd metal can be directly detected in PdO/CeO2 catalysts supported on chi-Al2O3 by means of in situ high-temperature measurements of X-ray diffraction and FT-IR in relation to the catalytic activity for the methane oxidation of microcrystalline PdO. Reversible changes in the solid phases are observed from PdO to Pd and Pd to PdO under O2-deficient and O2-excess atmospheres, respectively. Nanosizes of PdO and Pd crystallites, the distorted PdO crystal structure along the (110) plane, and also a distorted Pd metal crystal structure along the (200) plane as well as the large surface area elucidate the high catalytic activity for the methane oxidation of PdO/CeO2 catalysts prepared with an atomic ratio of Pd:Ce = 1:1.

Journal Article↗
PubMed2002

An evaluation of the BD ProbeTec ET system for the direct detection of Mycobacterium tuberculosis in respiratory samples.

In controlling the spread of tuberculosis, early detection of disease caused by organisms of the Mycobacterium tuberculosis complex (MTBC) is vital. The BD ProbeTec ET system provides a method for the direct detection of MTBC by strand displacement amplification. Two hundred and five respiratory samples from patients with a high probability of tuberculosis were assessed by ProbeTec and by microscopy and culture for mycobacteria. ProbeTec positive results were obtained with 101 of 109 samples from which MTBC organisms were isolated. ProbeTec correctly signalled 78 of 81 samples that gave growths of mycobacteria other than tubercle bacilli (MOTT) as negative. Three samples gave false-positive results, corrected on repeat testing. Positive and negative predictive values (PPV, NPV) were 0.97 and 0.90 and the system showed a sensitivity and specificity of 92.7% and 96.0%, respectively. These values rose to PPV 0.97, NPV 0.96, sensitivity 97.1% and specificity 96.0% when data from the small number of gastric lavage samples tested were removed from the analysis. The BD ProbeTec ET system offers a robust and reliable molecular biological approach to the detection of MTBC organisms in respiratory samples in a semi-automated format.

Bacteriological Techniques↗