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The distribution of Neisseria meningitidis serogroup B and C polysaccharide antigen in blood and the prognostic significance of antigen concentration was examined by ultrasound-enhanced immunoagglutination of coated microparticles. Specimens (169 sera/plasma from 145 patients with confirmed meningococcal disease) were tested retrospectively. The ultrasonic immunoassay detected serum antigen in 136 samples from 112 patients. Titration of antigen-positive specimens allowed estimation of blood antigen concentration. The modal blood antigen titre was 1/16, corresponding to an estimated polysaccharide concentration of 0.85 microg/ml. The lowest mean blood antigen concentration found ultrasonically was 0.05 microg/ml; compared to the 1.98 microg/ml found by conventional latex agglutination, this represents an approximately 30-fold improvement in sensitivity. Three grades of outcome were correlated with the presenting antigen titre in 83 patients: (i)2 weeks hospitalisation, (ii)or =2 weeks hospitalisation and (iii) mortality. High polysaccharide concentrations correlated with mortality. Nine of 15 patients with a serum antigen titre of 1/64 or greater (or =3.4 microg/ml polysaccharide) died, whereas no patient with titres equal to or less than 1/4 (or = 0.21 microg/ml) died, including those patients in whom antigen was undetectable by ultrasonic immunoassay. Increasing antigen concentration significantly correlated with severity of outcome (P0.001). Ultrasound-enhanced agglutination provides a rapid prognostic indicator by sensitive measurement of serum antigen level.

A non-invasive serological assay devised in this laboratory had a sensitivity and specificity of 100% as determined by culture and confirmed by histology in a group of 47 patients who had undergone endoscopy. The correlation between serology and the non-invasive [14C] breath test was very good. Only one of 24 culture positive patients was, while all 23 culture negative patients were, breath test negative. In a group of 46 healthy elderly persons, however, significant anomalies between serology and breath test were observed. Only 83% of the breath test negative persons were seronegative, while only 68% of the breath test positive persons were seropositive. These results can be explained in terms of age related atrophic gastritis and immune incompetence, causing reduced colonisation and decreased antibody production, respectively. These investigations suggest that non-invasive tests for H pylori infection may not be reliable in the elderly.

Increasing constraints with escalating demands on endoscopy resources have prompted interest in evaluating ways of predicting clinically non-significant endoscopies. Previous systems have attempted to identify high-risk patients by collating known predisposing factors to ulcer disease. These have largely proved unsatisfactory due to their poor specificity and sensitivity. The main potential for reducing endoscopic workload lies in serodiagnosis of Helicobacter pylori. Screening by serology is now possible with a high sensitivity and specificity and has been suggested as an alternative. However, for serology to be adopted routinely further prospective studies are needed to establish the role of such a screening protocol. A prospective study was therefore undertaken with the following aims: (a) to validate an enzyme-linked immunosorbent assay (ELISA) against antral biopsy culture and histology and (b), to evaluate the predictive values of an ELISA result against endocopic findings.

The majority of patients with a Helicobacter pylori infection mount a systemic antibody response which is easily detectable by serological assays such as the enzyme-linked immunosorbent assay (ELISA) [1]. Positive results in bacterial agglutination and complement fixation tests [2] suggest that these antibodies possess some anti-bacterial activity. However, the infection persists suggesting an underlying ineffectiveness in the ability of the systemic antibody response to eradicate the infection.

Fast protein liquid chromatography and SDS-PAGE have been used to isolate and purify Helicobacter pylori urease. A nickel component of the urease was detected in the purified proteins by atomic absorption spectroscopy. The nickel was present only in the 61 kDa polypeptide and in the ratio of between five and six atoms to one molecule of urease, suggesting a hexameric structure. These results are discussed in relation to other bacterial ureases and urease activity at low pH.

The antigenicity ofHelicobacter pylori protein fractions separated by fast protein liquid chromatography size exclusion was investigated by EIA with sera from patients of well definedHelicobacter pylori status. The antigenic material ofHelicobacter pylori was confined to fractions 8 and 14 to 21. Urease containing fractions (14/15) and flagella containing fractions (17/18) were identified. Fraction 8 non-specifically bound human immunoglobulin as demonstrated by the binding ofHelicobacter pylori negative sera. The remaining fractions 14 to 21 when used individually as EIA antigens were 91–100 % specific, however fractions 16 to 19 showed a reduced sensitivity (78 %) compared with the acid extract (95 %). The urease fractions were 91 % sensitive. Purified urease antigen captured by antiurease monoclonal antibodies was 83 % sensitive and 93.3 % specific.

It is widely accepted that the majority of people with H. pylori infections amount a large circulating antibody response against that organism [1]. This response has proved to be so predictable that it forms the basis of serodiagnostic tests such as ELISA [2, 3]. The sensitivity and specificity of such tests depends largely on the antigen preparations used, although ELISAs using a variety of crude and more purified antigens are reported to be greater than 90 % sensitive and specific for detecting H. pylori infection [4, 5].

The urease is a prominent differential characteristic of Helicobacter pylori which is employed in diagnostic tests such as the C13/C14 breath test, serodiagnosis and the rapid CLO tests. The role of the enzyme is, as yet, unclear. The number of different ureolytic bacteria being found on the gastric mucosa of various hosts is increasing, raising the question of whether the ureases of these organisms are related.

A monoclonal antibody, CP11, has been produced which is directed against the ureas of Campylobacter pylori. This antibody has been used to look for antigenic cross-reactivity, in other ureolytic and non-ureolytic campylobacters, by immunohistological techniques. It has also been used to investigate the helical-shaped organisms found in the stomach of the human, monkey and cat (CS1) and the ileum of the rat (ST1). Interestingly the antibody cross-reacted with the gastric helical organisms from the human, monkey and cat but not with the rat helical organism. No cross-reactivity was observed with C. mustelae or the other ureolytic campylobacters, C. nitrofigilis and the urease positive thermophilic campylobacters. These results are discussed in relation to the phylotaxonomy of these organisms.