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SUMMARYWe sought to explain seasonality and other aspects ofCampylobacter jejuniepidemiology by integrating population genetic and epidemiological analysis in a large 3-year longitudinal, two-centre, population-based study. Epidemiological information was collected for 1505 isolates, which were multilocus sequence-typed. Analyses compared pathogen population structure between areas, over time, and between clinical presentations. Pooled analysis was performed with published international datasets. Subtype association with virulence was not observed. UK sites had nearly identicalC. jejunipopulations. A clade formed by ST45 and ST283 clonal complexes showed a summer peak. This clade was common in a Finnish dataset but not in New Zealand and Australian collections, countries with less marked seasonality. The UK, New Zealand and Australian collections were otherwise similar. These findings map to knownin-vitrodifferences of this clade. This identifies a target for studies to elucidate the drivers of the summer peak in humanC. jejuniinfection.

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 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.

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.