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Projects for Specific Foodborne Pathogens

Listeria

Survey of ready-to-eat dairy products for quantitative levels of Listeria monocytogenes (ESR Food, 2003-2004)

While listeriosis is an infrequent disease in New Zealand, it rates highly for NZFSA risk management action as it has a high fatality rate. While ready-to-eat (RTE) meats have previously been associated with an outbreak (and other incidents) of listeriosis in New Zealand, other ready-to-eat foods are also likely to contribute to foodborne listeriosis. While surveys of RTE meats are currently taking place, the aim of this project is a comprehensive national survey over two years of the prevalence and levels of Listeria in retail RTE dairy foods in New Zealand. The objectives of the project are to more accurately estimate exposure to Listeria monocytogenes via RTE dairy products, to evaluate the effectiveness of HACCP based food safety programmes, and to direct risk management strategies. In addition, the relative proportionality of the disease burden imposed by RTE dairy products will be facilitated by PFGE sub-typing isolates for comparison with human case isolates through the National Typing Database. Lastly, this project will augment the pasteurization process review (refer microbiological risk profiling) by providing data against which to assess the effectiveness of non-pasteurisation antimicrobial treatments for dairy products (raw milk cheeses).

Exposure to Listeria monocytones via unpackaged ready-to-eat meats (ESR Food, 2004-2005)

The WHO Listeria risk assessment concluded that counts of less than 100cfu/g of L. monocytogenes on RTE products offers minimum risk to human health. Nevertheless, regulatory and commercial microbiological criteria continue to reflect zero-tolerance until quantitative data is available. Similarly, regulatory requirement for full separation between raw material and cooked product will remain in place until quantitative data shows that cross-contamination through incomplete separation does not exceed WHO recommended levels. The Listeria monocytogenes in ready-to-eat meats risk profile identified that data in New Zealand concerning the level of L. monocytogenes in RTE meats does not exist and that prevalence data were a decade old, hence unreliable. The current study is intended to provide information on the levels and prevalence of L. monocytogenes on unpackaged ready-to-eat meats RTE meats sold unpackaged at delicatessens, supermarket delicatessen counters, butchers etc, and to examine the growth of L. monocytogenes on naturally contaminated meats under different storage conditions. The data will enable this transmission route to be assessed in terms of relative risk to the population, to inform risk mitigation prioritization and to facilitate re-assessment of regulatory requirements.

National typing database (ESR Food, 2003-2005)

A standardised, national, pulsed-field gel electrophoresis (PFGE) microbial sub-typing database is being implemented to allow more effective detection of clonal linkages between human case isolates and food/environmental isolates of Campylobacter, Salmonella, Shiga-toxigenic E. coli (STEC) and Listeria. The National Typing Database will be an important tool facilitating the identification of factors that, if controlled, should reduce the burden of human gastroenteritis in New Zealand. In addition, subsequent research directions will be identified that will enable better management the risks of food-borne disease. All NZFSA sponsored projects that isolate the aforementioned zoonotic hazards will be required to subtype isolates and submit the data to the National Typing Database. The aim of this continuing project is to provide food-specific input into the development of the National Typing Database though completion of PulseNet certification, participation in testing the pilot system, and validation of results from historical NZFSA and MoH projects against the new procedures.