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Comparative evaluation of identification systems for testing methicillin-resistant strains of Staphylococcus aureus.

Several commercial systems are available to distinguish between Staphylococcus aureus and the coagulase-negative species of the Micrococcaceae family. Four latex agglutination systems (Accu-Staph, SeroSTAT, Staphaurex, and Staphylatex) and two hemagglutination systems (Hemastaph and Staphyloslide) were compared for their performance in the rapid identification of 232 isolates of staphylococci, including 114 of methicillin-resistant S. aureus. Accu-Staph, Staphaurex, and Staphyloslide correctly identified 100% of the methicillin-resistant S. aureus isolates; Hemastaph and Staphylatex, 99.1%; and SeroSTAT, 94.7%. Most reactions were easy to interpret, although 15% of the SeroSTAT reactions were weak. Autoagglutination occurred only with isolates of coagulase-negative staphylococci. False-positive reactions were rare and occurred only with systems which did not detect autoagglutination. Five of these six systems appear to be adequate for the rapid identification of S. aureus, including methicillin-resistant isolates.

Coagulase↗

Receptor-specific agglutination tests for detection of bacteria that bind globoseries glycolipids.

Specific binding to the globoseries of glycolipid receptors explains the adherence of uropathogenic Escherichia coli to host cells. The minimal receptor disaccharide Gal alpha 1----4Gal beta [galactose alpha (1----4)galactose beta] is recognized by most attaching clinical isolates. However, wild-type isolates can express adhesins with several different receptor specificities. Bioassays do not permit separate analysis of each receptor specificity, since the target cells contain multiple potentially receptor-active molecules. In this study, bacterial adhesins were analyzed by using receptors immobilized into latex beads in one of two ways. In one way, di- and trisaccharides were covalently linked via a spacer arm to latex beads coupled with bovine serum albumin. In the other way, receptor-active glycolipids were coated onto the bovine serum albumin-latex beads. The latex beads were subsequently used for agglutination by using type strains with known receptor specificity. The composition was optimized regarding receptor structure and size of latex beads. Gal alpha 1----4Gal beta was as active as the trisaccharide derivative Gal alpha 1----4Gal beta 1----3glucose or Gal alpha 1----4Gal beta 1----3glucosamine. Among the natural glycolipids tested, globotetraosylceramide was the most active. Subsequently, the sensitivity and specificity of the Gal alpha 1----4Gal beta-latex and globotetraosylceramide-latex reagents were compared for 733 E. coli urinary isolates. Hemagglutination of human erythrocytes was used as the positive standard. No significant difference in the specificity or sensitivity of the latex reagents was found; the sensitivity ranged from 86%, when isolates agglutinating human erythrocytes of blood groups P1 and p were included, to 93%, when those isolates agglutinating erythrocytes of blood group p were excluded. These reagents provide tools for bacterial identification in patients with urinary tract infection.

Adhesins, Escherichia coli↗

Problems with rapid agglutination methods for identification of Staphylococcus aureus when Staphylococcus saprophyticus is being tested.

Six rapid agglutination tests for identification of Staphylococcus aureus were evaluated by using 62 strains of S. aureus, 63 strains of S. saprophyticus, and 67 strains of other coagulase-negative staphylococci. S. saprophyticus was responsible for 19 of 26 false-positive results and 20 uninterpretable reactions. Thus, urinary staphylococcal isolates that are positive by rapid agglutination tests may require other confirmatory tests for the identification of possible S. saprophyticus.

Hemagglutination Tests↗

Staphylococcus aureus strains which are not identified by rapid agglutination methods are of capsular serotype 5.

A total of 183 recent Staphylococcus aureus clinical isolates were tested with three commercially available rapid agglutination methods. The capsular polysaccharide type and resistance to oxacillin of these isolates were also determined. Seven isolates were not identified correctly by agglutination methods. All isolates not identified by the rapid methods were of capsular serotype 5, and of these isolates, six were resistant to oxacillin. The results suggest that these agglutination kits can be improved by the use of antibodies reactive with S. aureus capsular polysaccharide.

Agglutination Tests↗

Detection of IgG rheumatoid factor by concanavalin A treatment and complement fixation with IgG rheumatoid factor.

Concanavalin A (Con A) froms precipitates with carbohydrate-rich protein such as IgM, IgD, IgE, and IgA. Since IgG contains little carbohydrate and does not react with Con A, the activity of IgG-rheumatoid factor (RF) can be measured in the supernate of the Con A-treated serum. When the latex fixation test (LFT) and the sensitized sheep cell agglutination test (SSCA) were perfromed in the supernate for the detection of IgG-RF, LFT was positive in 32-1% of sera, out of 137 sera originally positive for LFT, and SSCA was positive in 18-5% of sera, out of 119 sera originally positive for SSCA. IgG-RF exhibited lower complement fixing ability than IgM-RF and correlated with agglutination titres of IgG-RF, while the CH50 of the original serum did not correlate with haemolytic activities of either IgM-RF or IgG-RF.

Arthritis, Rheumatoid↗

Clinical significance of rheumatoid factors in early rheumatoid arthritis: results of a follow up study.

Serum rheumatoid factors (RF) were measured yearly in 135 women with rheumatoid arthritis by the Waaler-Rose and latex fixation tests and IgM, IgA, and IgG RF were measured by enzyme linked immunosorbent assays (ELISAs). The patients were followed up from an early phase of the disease for a mean duration of six years. Patients with a persistently positive RF test, irrespective of the type of test used, had more radiological abnormalities, more disease activity, worse functional ability, more extra-articular manifestations, and needed more treatment with second line drugs than patients with persistently negative or variably positive and negative test results during the follow up. Increased RF levels, especially a high level of IgA RF within three years of the onset of symptoms, was prognostic for a more severe disease outcome six years after the onset of symptoms.

Adult↗

Familial congestive cardiomyopathy with positive rheumatoid factor. Report of one family.

Three members of one family had cardiomyopathy of the congestive type. Autopsies of 2 brothers revealed marked dilatation of the left ventricle with diffuse interstitial fibrosis of unknown origin. The father's diagnosis was based on clinical findings. In one brother, a positive latex fixation test for rheumatoid factor had been documented when he were healthy. Another brother had a positive test for rheumatoid factor almost simultaneously with the onset of the disease. It remained positive until both died. Thus, the positive rheumatoid factor presumably reflected primary or independent immunologic defects rather than a secondary immunologic mechanism in these cases of familial congestive cardiomyopathy.

Cardiomyopathy, Hypertrophic↗

An ELISA for IgA-IgG and IgM-RF measurement. II. RF in several disease and control groups and under gold therapy in RA.

The before introduced solid phase ELISA was employed for the RF determination in the sera of RA patients and controls. The threshold values for positive results (calculated as the 95% distribution percentile of healthy donors) were 8, 3, and 3 U/ml for IgA, IgG, and IgM-RF, respectively. The results confirm the validity of the assay with clear negative results in several negative control groups (healthy donors, patients of the oto-, rhino-, laryngeal ambulance, diabetes mellitus, degenerative arthropathies; n = 111, median IgA, IgG and IgM-RF values of less than or equal to 2, less than or equal to 2 and less than or equal to 1 U/ml, respectively; 25-75% distribution percentiles within the median value) and positive results in the positive control group (seropositive RA; n = 20, median IgA, IgG and IgM-RF values of 324, 479 and 170 U/ml, respectively). 16/24 patients with so-called seronegative RA (negative Latex Fixation Test or Waaler Rose Test) had positive results in the ELISA, two of them had rheumatoid nodules clinically. The IgG-RF activity in the ELISA appears to be a good parameter for the course control of RA under gold therapy. 10 RA patients with clinical improvement of disease (declining ESR, CRP, joint index) after six months of gold therapy (= 0.6 g total gold amount) had a decline of total RF activity of 70% in median, whereas 10 patients with no clear effect on disease activity had only a decline of 20% in median.

Arthritis, Rheumatoid↗

The role of HLA B27 in the diagnosis and management of low-back pain and sciatica.

Present diagnostic criteria for ankylosing spondylitis (AS) lean heavily on the x-ray examination, but there is much dispute as to its efficacy, especially in mild or early cases. Determinations of the HLA B27 histocompatibility antigen appear to define the population at risk far better than any other means. Of 31 patients who had the HLA B27 antigen, all had negative latex fixation tests and axial polyarthritic complaints (seronegative spondyloarthropathy or rheumatoid variant). Three had Reiter's syndrome and one had ulcerative colitis. Of the remaining 27 patients, nine had definite AS, 11 had probable AS, and seven had possible AS. Eleven of the 27 underwent at least one invasive spinal procedure (myelogram, laminectomy, fusion, facet denervation) before a diagnosis of AS was made.

Adult↗

Diagnostic performances of anti-cyclic citrullinated peptides antibody and antifilaggrin antibody in Korean patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease of unknown etiology. We studied the diagnostic performances of anti-cyclic citrullinated peptides antibody (anti-CCP) assay and recombinant anti-citrullinated filaggrin antibody (AFA) assay by enzyme linked immunosorbent assay (ELISA) in patients with RA in Korea. Diagnostic performances of the anti-CCP assay and AFA assay were compared with that of rheumatoid factor (RF) latex fixation test. RF, anti-CCP, and AFA assays were performed in 324 RA patients, 251 control patients, and 286 healthy subjects. The optimal cut off values of each assay were determined at the maximal point of area under the curve by receiver-operator characteristics (ROC) curve. Sensitivity (72.8%) and specificity (92.0%) of anti-CCP were better than those of AFA (70.3%, 70.5%), respectively. The diagnostic performance of RF showed a sensitivity of 80.6% and a specificity of 78.5%. Anti-CCP and AFA showed positivity in 23.8% and 17.3% of seronegative RA patients, respectively. In conclusion, we consider that anti-CCP could be very useful serological assay for the diagnosis of RA, because anti-CCP revealed higher diagnostic specificity than RF and AFA at the optimal cut off values and could be performed by easy, convenient ELISA method.

Adolescent↗

Immunodiagnosis of bacterial meningitis.

The quest for the search of rapid, cheap, easy to perform and highly sensitive and specific tests has resulted into the introduction and application of various new tests for the diagnosis of bacterial meningitis. Most of these tests are based on immunological principles, viz. counter-immunoelectrophoresis, latex agglutination test, co-agglutination, radio-immunoassay, haemagglutination inhibition as well as study of immune profile of cerebrospinal fluid. Apart from these certain non-immunological tests viz. Limulus amoebecyte lysate test, gas liquid chromatography, nitroblue tetrazolium dye reduction test have also been evaluated to make the laboratory diagnosis of this important clinical entity rapid and more reliable. These tests have been discussed and their current status presented.

Counterimmunoelectrophoresis↗

[Rapid laboratory detection of antigens of infective agents of infections and technical means for their realization].

A system of new accelerated and rapid methods for the detection of the antigens of the infective agents of plague, cholera, tularemia and brucellosis were developed on the basis of solid phase immunosuspension tests: the passive hemagglutination (PHA) test and the latex agglutination (LA) test. The immunological and physico-chemical properties of suspensions in the PHA and LA tests made it possible to use extraneous sources of energy (centrifugal acceleration and the electric field) to accelerate these tests. The results of the PHA and LA tests were registered with the use of a densitometer, model Ultrascan 2202, and a tester, model C 34014.2. To apply centrifugal acceleration and the electric field, a laboratory centrifuge and an electrophoretic microchamber were designed. Densitometry was carried out on modified plates and conductometry, with the use of modified electrodes. The time of obtaining the results of the PHA and LA tests was 15-30 minutes with the use of centrifugation and 2-5 minutes in the electric field, which made it possible to regard these tests as rapid.

Antigens, Bacterial↗