Food safety

It starts down on the farm

 The pathogen cycle: E. coli 0157:H7 is shed from ruminants to the environment

Healthy ruminant animals are an important reservoir of faecal-derived human pathogens such as Campylobacter and shiga-toxin producing Escherichia coli (STEC). As such, these animals are the primary sources of bacterial contamination of meat and vegetables. Our research aims to address the current gap in knowledge on the routes of transmission of these pathogens so that we can determine the risk to food safety and consequently market access.

Bacterial survival, resistance and adaptation

 Diagram showing how bacteria quickly develop resistance to antimicrobial agents (e.g. antibiotics)

Understanding the effect of stress and physiological status of the microflora associated with different foods and their production is paramount if we are to determine the true risk to human health and develop mitigation strategies to reduce the incidence of food-borne illness. We have a number of FRST funded collaborative programmes and PhD studentships looking into the effect of sanitizers on resistance and adaptation, the effect of stress on the survival of E. coli O157:H7 and the potential of naturally occurring bacteria in raw milk to lower the risk of toddlers developing asthma.

Mitigation - biocontrol technologies for safer foods

By understanding the physiological status and routes of transmission of bacteria from the farm to the food processing plant, we can start to develop strategies that mitigate the risk of food-borne illness.

IMPACT

 

IMproved PAthogen Control Technologies for New Zealand Meat is a collaborative FRST programme (AgResearch, Massey University and ESR) that serves as a platform for the development of biocontrol technologies for pathogens.

Biocontrol technologies have the potential to reduce or eliminate current chemical interventions used by the food industry to prolong shelf-life and improve food assurance. Working in collaboration with Stephen On at ESR (Christchurch Science Centre) and Professor Nigel French at Massey University (mEpiLab, Hopkirk Institute), AgResearch (Hopkirk Institute) is looking at quorum sensing, a signalling system that bacteria use to communicate with each other using chemical messages.

 Possible signalling pathways: chemical signals influence bacterial behaviour

If these messages can be controlled, it may be possible to manipulate the message so that pathogenic bacteria would not be able to grow or survive, and thereby improve the safety of meat products. Researchers at ESR are investigating the potential of specific phages of E. coli O157:H7 and Campylobacter as a novel mitigation technology for use in food. To determine the most effective point in the food-processing chain to apply these new technologies, Massey University is putting data gathered by the two CRIs into computer-based models.

Long-term cross sectional study for the isolation of zoonotic pathogens from cattle

Before meaningful intervention strategies can be adopted, the scale of excretion and the spatial distribution of animals shedding pathogens must be understood. In conjunction with our collaborators at Massey University (mEpiLab), we are undertaking a MAF-funded multi-year study to determine whether animals from particular areas in New Zealand are associated with higher levels of pathogen excretion. Molecular typing methods are used to establish the potential virulence of isolated bacteria and whether particular transport practices or processing methods may influence excretion. Identification of particular factors associated with increased risk of excretion will then be targeted for intervention strategies.

Molecular epidemiology, phylogeny and genealogy of zoonotic pathogens

New Zealand food products are sometimes contaminated with pathogens, some of which are unique to New Zealand. Certain Campylobacter jejuni strains associated with human disease may reflect the emergence of a specific New Zealand lineage. In a Marsden-funded study with our collaborators at Massey University (mEpiLab) we will be able to determine the ancestry of the unique New Zealand isolates and their importance in human infection, using DNA sequence typing methods, complete genome sequencing and modelling their mutation and recombination events.

Risk assessment – evaluating the possible harm of food contaminants

Human food may become contaminated with harmful substances, most often from natural sources. Examples are the contamination of honey with tutin, a neurotoxin from the New Zealand native bush, tutu, and the contamination of seafood with toxins derived from marine microalgae. By use of animal models, an assessment can be made of the levels of such contaminants in food that are unlikely to have adverse effects on human health. In this way, regulatory authorities can establish maximum permitted levels of contaminants in food, thereby safeguarding human health and wellbeing.

Some of our “industry good” projects funded through MPI-NZFSA, MIA, Beef and Lamb NZ and MIRINZ Inc:

• Evaluation of regulatory approved methods for detection of E. coli 0157:H7 and determination of the cause of false positives
• Evaluating processes for reducing E. coli O157:H7 on bobby carcasses through chilling and freezing
• Impact of intensified farm practices on incidence of E. coli O157:H7 on adult dairy cows and bobby veal
• E. coli O157:H7 and Salmonella Brandenburg longitudinal studies and Quantitative Risk Assessment
• Influence of sample freezing on the efficiency of detection of E. coli O157:H7 using the Assurance GDS E. coli O157:H7 screen method
• Risk assessment of tutin, a poison that may contaminate honey
• Risk assessment of cyclic imines, toxins derived from various species of marine dinoflagellates.

To deliver the best outcomes and solutions for New Zealand primary industries AgResearch works collaboratively on a number of MSI funded projects

• MSI – IMPACT; ESR and Massey University (C03X0701 IMproved PAthogen Control Technologies for New Zealand Meat, ESR)
• MSI – Clean Water Productive Land (AgResearch)
• MSI – Safe New Zealand Seafood (CAWX0703 Cawthron Institute).