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Microtiter latex antiglobulin test for the detection of antibodies to DNP, digoxin, HCG and similar antigens.

A microtiter latex antiglobulin test (LAGT) with heavy-and-stable latex particles was developed. Antibodies of weak avidity, such as rabbit antisera to DNP or digoxin were much enhanced by the LAGT, whereas the method only slightly promoted strong avidity antibody, such as that found in rabbit antisera to human chorionic gonadotrophin. A microtiter latex agglutination-inhibition test (LAGIT) proved to be an effective tool for detection of weak antigenic substances such as digoxin and DNP.

Animals↗

Comparison of costs for testing a wide variety of drugs of abuse per urine specimen in a drug abuse urine screening program and frequent urine collections.

Existing urine testing techniques in a drug abuse urine screening program with their capacity to analyze urine specimens per day are discussed. The start-up cost using each technique and cost per specimen are presented. A single step extraction technique using ion-exchange paper to absorb drugs prior to thin-layer chromatography (TLC) as reported by these laboratories will cost $0.58 per specimen, for testing the entire aray of drugs of abuse (at least 9-14 tests per specimen). Sensitivity reported using TLC technique for the morphine base is 0.15 mug/ml (minimum volume of urine needed 20 ml), 0.10 mug/ml if the volume of urine available is 30-35 ml, and 0.07 mug/ml if the volume of urine available is 43-50 ml.

Chromatography, Gas↗

Comparison of three major antigen detection methods for the diagnosis of Group B streptococcal sepsis in neonates.

Because of the difficulty encountered in diagnosing early onset Group B streptococcal disease (GBS) in neonates and because of the proliferation of tests to detect the antigen in urine, we made qualitative and quantitative comparisons among the three major, commercially available, antigen detection systems. The methods compared were Wellcogen latex agglutination, Phadebact coagglutination, and counterimmunoelectrophoresis (CIE). We tested urine, with or without serum, and tracheal or gastric aspirates from 176 neonates admitted to Columbus Children's Hospital, with suspected GBS disease. Wellcogen and Phadebact were equally sensitive indicators of neonatal GBS sepsis (100%) as compared to CIE which was only 30% sensitive. CIE, however, did not produce any false-positives (100% specificity) while Phadebact coagglutination and Wellcogen latex agglutination were approximately 98% specific. As a side bar to the main study, we also set out to determine whether tracheal or gastric aspirates would be consistent and convenient sources of antigen as compared to urine. Consequently we determined that neither aspirate is a good source of antigen as performed by our method.

Antigens, Bacterial↗

Comparison of a reversed passive latex agglutination and a polymerase chain reaction for identification of cholera toxin producing Vibrio cholerae O1.

Production of cholera toxin (CT) in AKI medium and conservation of CT gene (ctx) of 49 strains of Vibrio cholerae O1 were compared by reversed passive latex agglutination (RPLA) and polymerase chain reaction (PCR). The production of CT agreed with conservation of the ctx in 48 out of the 49 strains. Ten strains were positive, and 38 strains were negative by both methods. Only one strain was negative in RPLA and positive in PCR. This suggested that the combination of AKI-SW and RPLA is comparable to PCR to identify CT-producing V. cholerae O1.

Agglutination Tests↗

Prospective evaluation of Candida antigen and antibody assays for detection of Candida infections in children with malignant disease.

The clinical efficacy of assays for Candida albicans antigens by latex agglutination and for antibodies by indirect haemagglutination were prospectively evaluated in the diagnosis of invasive Candida infections in 38 children suffering from acute leukaemia or other malignant disease. The controls were 74 other patients without any malignancy; 72 of these had no signs or symptoms of fungal infections, but 2 had an invasive C. albicans infection. During a period of 21 months, 302 serum samples were tested by both assays, and the results were compared with clinical and other microbiological data. Invasive fungal infection was diagnosed on clinical grounds in 2 of the immunocompromised children, and periodic gut colonization was demonstrated in 11 of 36 (31%) children in this group. Positive Candida antigen was detected in 14 patients (37%) and a positive antibody titre in 7 patients (18%). Colonization was not correlated with antigen or antibody titre. Compared with the presence of invasive fungal infection, the antibody assay detected all four infections, whereas the antigen assay detected one of the two C. albicans septicaemias. Although the Candida antibody assay performed well, a detectable change in antibody titres appeared only slowly. Thus it was of no clinical help when antifungal treatment was to be considered. Follow-up of antibody titres, however, gave confirmation of the presence of fungal infection as well as the response to antifungal treatment.

Adolescent↗

Comparison of latex agglutination, indirect hemagglutination, and ELISA techniques for the detection of Toxoplasma gondii-specific antibodies in the serum of cats.

The primary purpose of this study was to determine whether commercially available latex agglutination and indirect hemagglutination kits for the detection of Toxoplasma gondii-specific antibodies were capable of detecting T. gondii-specific immunoglobulin M (IgM) in the serum of cats. Serum samples from 35 cats containing either T. gondii-specific IgM, T. gondii-specific immunoglobulin G (IgG), or both were collected. Each serum sample was assayed using a latex agglutination kit, an indirect hemagglutination kit, an enzyme-linked immunosorbent assay (ELISA) for the detection of T. gondii-specific IgG, and an ELISA for the detection of T. gondii-specific IgM. When serum samples containing only T. gondii-specific IgM as determined by ELISA were assayed, the latex agglutination kit and the indirect hemagglutination kit detected antibodies in 33.3% and 13.3%, respectively. When T. gondii-specific IgG was present in a serum sample, the results from the latex agglutination kit, the indirect hemagglutination kit, and the IgG-ELISA were similar; however, there was a wide variation in titer magnitude results between the three assays. It was concluded that the latex agglutination kit and the indirect hemagglutination kit did not adequately detect T. gondii-specific IgM in feline serum.

Animals↗

Alpha-hemolysin contributes to the pathogenicity of piliated digalactoside-binding Escherichia coli in the kidney: efficacy of an alpha-hemolysin vaccine in preventing renal injury in the BALB/c mouse model of pyelonephritis.

Digalactoside-binding (Gal-Gal) pili and alpha-hemolysin of Escherichia coli have been implicated as important virulence determinants in the pathogenesis of human ascending, nonobstructive pyelonephritis. The pathogenic significance of these determinants was evaluated in vitro and in the BALB/c mouse pyelonephritis model by employing wild-type, avirulent laboratory, and genetically defined cosmids, transformants, and recombinant strains. In vitro data suggest that the cytolytic activity of hemolysin is significantly (P less than 0.05) enhanced among digalactoside-binding strains which agglutinate erythrocytes. The basis of increased hemolysis is related presumably to more efficient delivery of the toxin to target lipid substrate in the host plasma membrane. Intravesicular administration of bacteria that express both digalactoside binding and hemolysin generally resulted in greater mortality and renal parenchymal injury in mice than strains that expressed none or only one of these determinants. Analyses convincingly demonstrate that digalactoside-binding pili are correlated with upper urinary tract colonization and that hemolysin is correlated with septicemia and renal parenchymal damage. These determinants collectively constitute the minimal virulence factors to produce disease in this model. Their efficacy as vaccines for the prevention of pyelonephritis was also assessed. A purified Gal-Gal pilus vaccine prevented (P less than 0.05) subsequent colonization by a challenge wild-type strain that exhibited homologous pili. The hemolysin vaccine did not abrogate subsequent bacterial renal colonization on challenge, but it did protect (P less than 0.05) mice which survived challenge from subsequent renal injury compared with those in the saline control group. The combination of these determinants was also protective. The combination of Gal-Gal pili and hemolysin in a vaccine preparation represents a potentially worthwhile strategy for human immunoprophylaxis against pyelonephritis by interdicting several steps in the pathogenesis of a bacterial mucosal infection.

Animals↗

Comparison of methods for serotyping isolates of Haemophilus influenzae.

This study compared four methods for serotyping isolates of Haemophilus influenzae. Slide agglutination with commercial antisera (Difco Laboratories and Wellcome Diagnostics), coagglutination (Phadebact Haemophilus Test [Pharmacia Fine Chemicals]), latex agglutination with affinity-purified anticapsular antibody, and counterimmunoelectrophoresis with multiple antisera were used to serotype 80 isolates of H. influenzae. Coagglutination and counterimmunoelectrophoresis correctly identified all 80 isolates as either type b or not type b. Slide agglutination and latex agglutination each successfully identified 76 of the 80 isolates; however, each of these two methods failed to type four isolates because of agglutination of controls. We recommend slide agglutination or coagglutination as the serotyping methods of choice in most laboratories because they are simple, accurate, and rapid. Slide agglutination with Difco antiserum can be performed at the lowest cost.

Agglutination Tests↗

Comparison of a yellow latex reagent with other agglutination methods for the identification of Staphylococcus aureus.

A new commercial yellow latex agglutination reagent (Bacto-Staph) was compared with the slide and tube coagulase tests and three other commercial reagents for the identification of 283 Staphylococcus aureus and 54 non-S. aureus staphylococcal strains. Test sensitivities for the identification of S. aureus were as follows: tube coagulase, 99.6%; slide coagulase, 98.6%; Bacto-Staph, 99.6%; Staphylatex, 98.6%; Sero STAT Staph, 98.2%; and Staphyloslide, 97.5%. No false-positive reactions were observed with any of the commercial reagents.

Agglutination Tests↗

Diagnosis of invasive candidiasis in patients with and without signs of immune deficiency: a comparison of six detection methods in human serum.

Visceral candidiasis in 56 patients, 39 of whom were thought to be immune deficient, was investigated using three serological detection methods--whole cell agglutination, haemagglutination, and counterimmunoelectrophoresis for antibodies; two determinations of circulating antigens--haemagglutination inhibition and latex agglutination; and determination of the arabinitol:creatinine ratio. Of the 39 patients with suspected immune deficiency, 13 had confirmed invasive candidiasis and 26 were colonised; of those without signs of immune deficiency, 10 patients also had invasive candidiasis and seven were colonised. Twenty three patients with invasive candidiasis were analysed in total. For suspected immune deficient patients the best discrimination between visceral candidiasis and colonisation was obtained by combining the results of haemagglutination inhibition and arabinitol:creatinine ratio. For patients without signs of immune deficiency the best discrimination between invasive candidiasis and colonisation was achieved with counterimmunoelectrophoresis. The results of the serological tests confirmed the classification on clinical grounds of those with and without immune deficiency.

Agglutination Tests↗

Comparison of fluorescent antibody, bacitracin susceptibility, latex agglutination, coagglutination, and API 20S for identifying group A streptococci.

A total of 200 beta-hemolytic streptococci, isolated from clinical specimens submitted to our laboratory, were identified as group A versus non-A using the fluorescent antibody technique (FA), bacitracin susceptibility (BBL, Difco, and Raven disks), SeroSTAT, Streptex, Phadebact, and the API 20S system. Of the 122 group A isolates, all methods except SeroSTAT and Phadebact yielded 92-99% agreement when compared with the Lancefield precipitin test. Phadebact yielded an 84% agreement and SeroSTAT changed from 83 to 98% after trypsinization. Numerous false positives were obtained and only FA (91%) and API 20S (96%) yielded better than 90% agreement on non-A identification when compared with the Lancefield test. The most false positives were obtained (45%) using the SeroSTAT reagents. Considering accuracy, our data suggests the FA technique to be the method of choice for identifying group A streptococci.

Agglutination Tests↗