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Biomedical subjects

J P Harford

Publications and source records attributed to J P Harford.

7 recordsLinked to original sources
PubMed2001

The use of Lenticules for the process control of enumeration techniques in food and environmental microbiology.

AIMS: Lenticules consist of control-dried plano convex discs in which biologically-active materials are contained within a water-soluble matrix. They can be produced to contain stable numbers of bacteria from 10 cfu lenticule-1 to 108 cfu lenticule-1 with a wide variety of organisms. These experiments were carried out to validate their use as a tool for internal quality control in quantitative microbiology. METHODS AND RESULTS: The Lenticules were used routinely in standard quantitative microbiological procedures across five laboratories. Results showed the materials to be stable, homogeneous and capable of identifying systematic errors. CONCLUSIONS: The Lenticules provide suitable, stable control materials. SIGNIFICANCE AND IMPACT OF THE STUDY: Routine internal quality control of quantitative measurements is greatly improved; the materials are easy to use and enable comparisons between laboratories to be made.

Bacteria↗
PubMed1987

An evaluation of a commercially available enzyme immunoassay test for the rapid detection of salmonellae in food and environmental samples.

A total of 91 food and environmental samples were examined for the presence of salmonellae using a commercially available enzyme immunoassay kit (EIA) and a conventional culture technique. A 78% agreement was obtained, but reexamination of culture-negative, EIA-positive samples gave agreement of 86%. The problem of comparing EIA and culture results is discussed. A partially selective pre-enrichment broth was tested in 37 samples and gave better EIA ratios. Artificially contaminated cooked foods gave 100% agreement.

Culture Media↗
PubMed1987

Public Health Laboratory Service enzyme linked immunosorbent assay for detecting Toxoplasma specific IgM antibody.

An enzyme linked immunosorbent assay (ELISA) based on the antibody class capture method for the detection of specific IgM against Toxoplasma gondii, using the microtitre plate format, was developed. Antigen binding was detected using a monoclonal antibody, CIE3, conjugated to horseradish peroxidase. Prior mixing of the conjugate and antigen improved the stability of these reagents as well as removing an incubation stage from the assay. The incubation time of less than four hours permits a rapid throughput of specimens. Using the assay, a total of 163 sera were examined in a three centre study and good agreement was found. Results were expressed as arbitrary enzyme immunoassay units (EIUs) against a freeze dried standard. Throughout the study the standard serum showed a coefficient of variation less than 10% across the microtitre plate. By measuring IgM titres in patients having toxoplasmic lymphadenopathy with a known date of onset, IgM class antibodies were shown to peak at two months, persisting for about six months. In addition, a case of laboratory acquired toxoplasmosis was monitored. Sera shown to contain rheumatoid factor and antinuclear factor did not give false positive results. This rapid, robust, and simplified assay is used by the Public Health Laboratory Service Toxoplasma Reference Units and will provide a standard with which other assays can be compared.

Animals↗
PubMed1987

Use of monoclonal antibodies in an ELISA to detect IgM class antibodies specific for Toxoplasma gondii.

Two monoclonal antibodies CH6 and C1E3 were used in an antibody class capture assay for the detection of IgM antibodies specific for Toxoplasma gondii. CH6 was used on the solid phase to capture human IgM. After a Toxoplasma gondii antigen had been added, specifically bound material was detected using C1E3 coupled to horseradish peroxidase. The assay was compared with an established system using polyclonal antisera at both the capture and antigen detection stages. A good correlation was found, with 97.3% (125 of 128) of sera giving the same classification in both assays. Three sera were positive only in the polyclonal system. No false positive results were found when 118 negative sera were examined. The two monoclonal antibodies provide a viable alternative to the use of polyclonal sera at the capture and antigen detection stages in the antibody class capture assay for the measurement of specific IgM against T gondii.

Animals↗
PubMed1985

Detection of specific IgG and IgM antibodies to Toxoplasma gondii with a commercially available enzyme immunoassay kit system.

A total of 138 serum samples submitted for toxoplasma serology have been examined by enzyme immunoassay using kits produced by Labsystems Oy for the detection of specific antibodies of the IgG and IgM class. Results were compared with the dye test, an indirect haemagglutination test, and an indirect immunofluorescence test for specific IgM. The enzyme immunoassay was less sensitive than the dye test, but by running both IgG and IgM enzyme immunoassays, 92.4% sensitivity was achieved. The specificity of the enzyme immunoassay was good, with only one dye test negative serum giving a positive (but weak) IgG enzyme immunoassay reaction. Thirty serum samples from patients with no evidence of exposure to Toxoplasma gondii gave negative results in the IgM enzyme immunoassay. Enzyme immunoassay results were expressed in enzyme immunoassay units, as a percentage value of a standard serum. This convention will be of value in the direct comparison of assay systems and in the application of quality control procedures.

Fluorescent Antibody Technique↗
PubMed1980

An evaluation of the ToxHA test for the detection of antibodies to Toxoplasma gondii in human serum.

The titre of antibodies to Toxoplasma gondii was compared in 1985 sera by use of an indirect haemagglutination test (ToxHA test--Wellcome Reagents Ltd) and the dye test. Sera from 42 patients with clinical or serological indications of recent toxoplasmosis were also examined to determine if the ToxHA test would be of value in detecting early stages of the disease. Nine recent cases of lymphadenopathy and four cases of eye infection were not detected by the test. In addition, a large number of sera found negative in the dye test gave a positive result in the haemagglutination test.

Antibodies↗