New research from PHF Science is helping scientists better understand how a common foodborne bacterium causes illness, with findings that could help strengthen food safety surveillance and risk assessment in Aotearoa New Zealand.
The study, published in the journal Pathogens, investigated Yersinia enterocolitica, a bacterium responsible for yersiniosis, an infection that typically causes gastrointestinal symptoms such as diarrhoea, abdominal pain and fever.
Yersiniosis is the second most commonly notified foodborne disease in New Zealand, making it an important focus for public health research and food safety monitoring.
While some types of Yersinia enterocolitica are well established as causes of human illness, scientists have long debated whether others are capable of causing disease.
The new research provides important insights into one of these less-understood types, known as Biotype 1A, and suggests it may cause illness in ways that differ from other strains of the bacterium.
Challenging existing understanding
Biotype 1A accounts for approximately 20 to 30 percent of notified yersiniosis cases in New Zealand each year. However, its role in causing illness has been the subject of international scientific debate. Unlike other types of Y. enterocolitica known to cause disease, Biotype 1A lacks many of the genetic features traditionally associated with the bacterium's ability to infect humans.
To investigate this further, PHF Science researchers combined genetic analysis with laboratory experiments using a model of the human intestine. They found the Biotype 1A isolate tested was less capable of attaching to and invading single-layer intestinal cells than types already recognised as disease-causing.
However, despite these differences, the Biotype 1A isolate still triggered a strong inflammatory response in the intestinal organ-chip model. This finding is significant because inflammation is one of the ways the body responds to infection and can contribute to the symptoms experienced during gastrointestinal illness, particularly in people with underlying health conditions.
The results suggest Biotype 1A may have the potential to cause illness through a different biological mechanism than previously recognised, even without many of the genetic characteristics normally associated with disease-causing Yersinia.
Although further research is needed to establish exactly how this occurs in people, the findings challenge some existing assumptions about what makes a particular type of Y. enterocolitica capable of causing illness.
Different patterns of infection in New Zealand
The study also highlighted differences in the populations affected by different types of Y. enterocolitica. Evidence indicates Biotype 1A is more frequently identified among adults of European ethnicity and on the South Island, while Biotype 2/3, the most frequently notified type in New Zealand, was more commonly observed among children of Asian ethnicity and more so in the North Island. These differences suggest the various types of Y. enterocolitica may have distinct epidemiological patterns, including differences in the groups most frequently affected.
Understanding these patterns is important for public health surveillance. It can help researchers identify where further investigation is needed and better understand the factors that may influence infection and illness. The findings do not establish why these differences occur, but they provide valuable information to guide future research into the relationship between bacterial characteristics, existing health conditions and disease.
Bringing together different areas of scientific expertise
A key strength of the study was its combination of several scientific approaches to build a more complete picture of the bacterium. Genomic analysis enabled researchers to examine the genetic characteristics of different Y. enterocolitica types, while public health surveillance information provided insights into patterns of infection in the New Zealand population.
Emerging intestinal cell technologies (Emulate organ-on-a-chip) also allowed the team to investigate how the bacteria interact with human cells, including their ability to attach, invade and trigger inflammation. Bringing these approaches together is particularly valuable when investigating bacteria whose ability to cause disease is not yet fully understood.
Supporting food safety in Aotearoa
The research builds on PHF Science's extensive contribution to understanding Yersinia infections in New Zealand, an area that remains a priority for New Zealand Food Safety.
Foodborne illness continues to place a burden on individuals, communities and the health system. Understanding the bacteria responsible, how they cause illness and which populations may be most affected is essential to supporting effective prevention and public health responses.
The findings also demonstrate the value of combining established expertise in genomic surveillance and public health intelligence with newer laboratory technologies.
As scientists continue to investigate the role of Biotype 1A, this research provides an important foundation for future studies and may help inform surveillance approaches and food safety risk assessments in Aotearoa.