No abstract

Serology is the principal laboratory method used to diagnose Mycoplasma pneumoniae infection. Meridian Diagnostics has developed the ImmunoCard Mycoplasma kit, a 10-min card-based enzyme-linked immunosorbent assay (ELISA) designed to detect immunoglobulin M (IgM) antibodies to M. pneumoniae. We compared the ImmunoCard with two M. pneumoniae IgM-specific assays (immunofluorescence assay [IFA] and ELISA) and a standard complement fixation (CF) procedure using 896 specimens submitted to clinical laboratories for M. pneumoniae serology. Equivocal results obtained by CF, IFA, or ELISA were resolved by testing with an additional method or by reviewing patient chart information. The ImmunoCard had sensitivities ranging from 74% compared with the ELISA to 96% compared with CF results resolved with IFA. ImmunoCard specificities ranged from 85% compared with the IgM-specific ELISA to 98% compared with IgM-specific IFA results resolved with clinical chart review. We also compared the ImmunoCard results with consensus results of 694 specimens tested on at least two non-ImmunoCard methods because of the lack of a ''gold standard'' for M. pneumoniae serology. Overall, the ImmunoCard Mycoplasma IgM assay had 90% sensitivity, 93% specificity, and 92% agreement with the consensus results. The ImmunoCard is technically less complex and requires less equipment than the three other assays. Our results indicate that the ImmunoCard Mycoplasma IgM assay is a valid and simple procedure which can reduce technologist time (and, thus, labor cost) and turnaround time for laboratories analyzing small numbers of specimens (<10 per batch) submitted for IgM anti-M. pneumoniae testing.

A rapid (2.5 h) direct enzyme immunoassay (EIA) for Clostridium difficile toxin A was developed for clinical use. Specimen centrifugation and filtration were not required. The EIA detected toxin A levels in patient stool as low as 20 pg (2 ng/ml of stool). The test was 5,000 times more sensitive for toxin A than it was for toxin B and did not react with a panel of other bacterial species with the exception of one highly toxigenic strain of Clostridium sordellii. The EIA was compared with the cytotoxin assay, culture of toxigenic C. difficile (toxigenic culture), and latex agglutination by using 313 fresh stool specimens submitted from patients with suspected C. difficile-associated disease. Results read visually and with a plate reader were similar. Sixty-two specimens were positive by one or more tests, but only 22 (35%) were positive by all four laboratory methods. The EIA was 84.1% sensitive and 98.9% specific when it was compared with the cytotoxin assay. The use of toxigenic culture to referee discrepant results (EIA versus cytotoxin assay) showed the EIA sensitivity and specificity to be 95.1 and 99.3%, respectively, with respect to other laboratory methods. Patient charts were reviewed for antibiotic-associated diarrhea on 108 specimens, including all those that were positive by at least one test method. Of 34 patients determined to have C. difficile-associated disease, 29 (85.3%) were positive by EIA, 32 (94.1%) were positive by the cytotoxin assay, 27 (79.4%) were positive by toxigenic culture, and 20 (58.8%) were positive by latex agglutination. Seven patients with antibiotic-associated diarrhea had a positive latex result, but results were negative by EIA, the cytotoxin assay, and toxigenic culture. The EIA demonstrated high specificity and good sensitivity for C. difficile-associated disease cases. The test can be used alone or in combination with the cytotoxin assay or toxigenic culture to provide rapid and sensitive results.

A three-center study was undertaken to compare several test methods for the detection of Clostridium difficile, associated toxin, or related markers by using 927 stool specimens. Methods included direct assay of cytotoxin in stool by tissue culture, C. difficile bacterial culture followed by cytotoxin assay, bacterial culture alone, latex agglutination assay, and the ImmunoCard C. difficile test (Meridian Diagnostics, Inc.). The sensitivities, as determined against direct cytotoxin assay results, of the ImmunoCard C. difficile and latex agglutination assays were 84 and 67%, respectively (92 and 77%, respectively, when adjusted for bacterial culture outcomes). Evaluation for C. difficile-associated disease (CDAD) among 864 patients was based on clinical criteria for antibiotic-associated diarrhea combined with laboratory evidence of toxin or toxin-producing C. difficile in stool specimens. The sensitivity of each test method for screening of CDAD was as follows: bacterial culture, 95%; culture with cytotoxin assay of isolates, 90%; ImmunoCard C. difficile test, 83%; cytotoxin assay 82%; and latex agglutination assay, 67% (P < 0.05 versus all other methods). The standard deviations of the test sensitivity statistics between study sites were ranked as follows: cytotoxin assay (؎3.1%) < ImmunoCard C. difficile test (؎5.7%) < latex agglutination assay (؎12.3%) < culture (؎24.7%) < culture with cytotoxin assay (؎28.0%). The data support the use of the ImmunoCard C. difficile test as an adjunct for the diagnosis of CDAD.

No abstract

The antiproliferative effect of 2',5' A3 core and 2',5'-3'dA3 (cordycepin trimer) core was measured in 8 human tumor cell lines. Cells were treated in a dose-response manner for 72 hr and the concentration of drug necessary to inhibit cell growth 50% (GI50) was determined. A wide range of sensitivities to these drugs was found, even among tumors of the same histological type. The cell lines showed different sensitivities and dose-response curves to the 2',5'A3 and 2',5'-3'dA3 cores. Uptake studies of the 2',5'A3 and 2',5'-3'dA3 cores, using high-pressure liquid chromatography, demonstrated that both cores were rapidly degraded in the tissue culture medium and taken up as adenosine or cordycepin, respectively. There was a direct correlation between the uptake of cordycepin and the antiproliferative effect. In contrast, there was no correlation between cell sensitivity and the uptake of the 2',5'A3 core degradation products. Analysis of intracellular nucleosides and nucleotides indicated that differences in intracellular metabolism of adenosine might explain the different sensitivities of the various cell lines to 2',5'A3 core. Molar equivalent concentrations of adenosine and cordycepin inhibited cell growth; however, equimolar concentrations of these nucleosides were not effective. In addition, the antiproliferative effect of both core compounds and their corresponding nucleosides could be potentiated by the addition of the adenosine deaminase inhibitor, deoxycoformycin. The results indicate that these cores act as prodrugs and that the active metabolites are their corresponding nucleosides.

Techniques available to practicing civil engineers for numerically modelling cohesive mud in rivers and estuaries are reviewed. Coupled models, treating water and sediment as a single process, remain research tools but are usually not three-dimensional. The decoupled approach, which separates water and sediment computations at each model time step, allows the three-dimensional representation of at least the bed and the use of well-proven, commercial, numerical, hydrodynamic models. Most hydrodynamic models compute sediment transport in suspension but may require modification of the dispersion coefficients to account for the presence of sediment. The sediment model deals with the sediment exchange between the water column and the bed using existing equations for erosion and deposition. Both equations relate the sediment exchange rates to the shear stress in the bottom boundary layer. In real rivers and estuaries, a depositional bed layer is associated with a period of low flow and shear, at slack tide for example, whereas in numerical models a layer is defined by the model time step. The sediment model keeps track of the uppermost layers at each model grid point, including consolidation and strengthening. Although numerical hydrodynamic models are based strongly on physics, sediment models are only numerical frameworks for interpolating and extrapolating full-scale field or laboratory measurements of "hydraulic sediment parameters," such as threshold shear stresses. Calibration and verification of models against measurement are therefore of prime importance.Key words: cohesive sediment, mathematical modelling, settling velocity, erosion, resuspension, deposition, fluid mud, bed layers.

The diagnosis of an acute episode of infections mononucleosis (IM) is made on the basis of clinical symptoms and serological evidence for development of heterophile antibodies. In an effort to obtain a very sensitive and specific assay for diagnosis of IM, we have developed MERISTAR:IM. The MERISTAR assay uses latex beads coated with purified bovine heterophile antigen. We compared the sensitivity and specificity and performance characteristics of the latex-based test to those of the commercially available erythrocyte-based Monospot test with serum samples from 363 suspected-IM patients and controls. A total of 28 samples from patients with confirmed IM were positive with the MERISTAR assay, while only 23 of the samples were positive with the Monospot assay. The two assays had equal specificity, as each test gave two false-positive results. In the technical performance of the assay, the MERISTAR assay was simpler and faster to perform than the Monospot assay.