Investigating the causes of diarrhoeal illness

Every year 2.4 billion cases of diarrhoeal illness occur globally with 4.6 million cases in New Zealand.

Yet of the faecal samples submitted for testing to New Zealand clinical laboratories, 70-80% do not have a pathogen detected.

ESR scientist Angela Cornelius has led a research project to develop a better tool to understand the role of some species and subspecies groups in human gastroenteritis and provide some answers as to what might be causing some of these “unsolved” cases.

The tool is a new assay - designed to detect 28 taxa (genera, species and sub-species groups) within Epsilonproteobacteria. This bacterial class includes Helicobacter pylori, which causes gastritis and stomach cancer, as well as Campylobacter jejuni and C. coli, which are collectively the most common cause of human bacterial gastroenteritis globally. This class also contains several species suspected of causing human gastroenteritis but where the causal role has not yet been established. Methods currently employed to detect pathogens from diarrhoeal samples in New Zealand, as well as many other countries, will recognise C. jejuni and C. coli but other species in this class are not detected.

Diarrhoeal illness affects children in greater numbers than adults. The Epsilonproteobacteria assay developed in this project was tested on faecal samples collected as part of a childhood gastroenteritis case control study undertaken in Brussels, Belgium. The species C. concisus was detected in 13% of cases (children with diarrhoea) and 8.5% of controls (children without diarrhoea) but this difference was not statistically different. In contrast, C. jejuni was detected in 9.8% of cases and <1% of controls, a difference that was statistically significant. These results confirm C. jejuni has an important role in childhood gastroenteritis but the role of C. concisus remains unsubstantiated.