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Predictive Model for Managing Vibrio parahaemolyticus Growth in Australian Oysters

Develops a predictive model using temperature data to manage V. parahaemolyticus growth in oysters, reducing health risks through optimized supply chains. This study aims to enhance food safety in the Australian oyster industry by understanding the influence of temperature on V. parahaemolyticus proliferation. The research provides insights into designing flexible cold chains, emphasizing the importance of storage conditions for raw seafood products. The mathematical model developed offers a tool for oyster growers to prevent microbial contamination and improve consumer health outcomes.

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Predictive Model for Managing Vibrio parahaemolyticus Growth in Australian Oysters

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  1. A Tool to Manage Vibrioparahaemolyticus growth in Australian Oysters Judith Fernandez-Piquer, Tom Ross, John Bowman, Mark Tamplin Food Safety Centre, Tasmanian Institute of Agricultural Research, University of Tasmania, Hobart, Tasmania 7005 Australia

  2. INTRODUCTION

  3. Actual situation www.usatoday.com (19th October ’09)

  4. Actual situation • Low numbers of food poisoning cases in Australia • Some countries already have action levels for Vp • Codex is considering action levels • Uncertainties: • Oyster species • Geographical locations

  5. Microbial Hazards • Filter-feeders: biological contamination in water accumulation • Pathogens likely to occur in Australian oysters are virus, Vibrio spp and toxins • Vibrios are salt tolerant and occur naturally in estuaries

  6. Vibrio spp. • Vibrio illnesses are mostly caused by V. cholerae, V. vulnificus and V. parahaemolyticus

  7. Vibrio parahaemolyticus (Vp) • Is a curved, rod-shaped, gram-negative bacterium • Pathogenic & non-pathogenic strains • Raw, undercooked or mishandled seafood 60oC 15min Post-harvest: outgrowth!

  8. Commercial supply chain • What is cold chain? • Primary production • Final consumption • Why cold chain? • Influence of water temperature • Salinity • Air temperature after harvest • Length of refrigeration until consumption (appropriate)

  9. Predictive microbiology • Knowledge of response of microorganisms to different environmental conditions: TEMPERATURE • Mathematical model is an algorithm describing the effects of different factors on microbial viability √SGR= 0.2016x(T-14.3339)x{1-exp[0.0113x(T-55.3482)]}

  10. Aim To develop a predictive model for V. parahaemolyticus growth in live Australian Oysters that can be used to design commercial supply chains and reduce consumer health risk.

  11. RESULTS

  12. Model development: data

  13. Model development: maths √SGR= 0.2016x(T-14.3339)x{1-exp[0.0113x(T-55.3482)]}

  14. Model evaluation

  15. Model comparison

  16. CONCLUSIONS

  17. CONCLUSIONS and BENEFITS • 1) This model demonstrates to industry the influence of • temperature on Vp growth • Allows oyster cold chain to be designed less prescriptive and more flexible • 2)Models should be developed for species and possibly a growing region. • Can show a distinction for Australian oyster industry • 3)Vp didn’t grow at 15oC (PO), 28oC (SRO) • May provide Australian oyster industry with more • cost-effective storage

  18. ACKNOWLEDGEMENTS • PhD scholarship (Seafood CRC, Oyster Consortium) • EIPRS scholarship (UTAS) • Supervisory team (Mark Tamplin, Tom Ross and John Bowman) • Project team (UTAS, SARDI, NSW DPI, ASQAP in Tas-SA-NSW) • Oyster growers (Tasmania, NSW, SA) • Colleagues from UTAS • My family

  19. Very tasty, very • nutritious!!!

  20. “ This work formed part of a project of the Australian Seafood Cooperative Research Centre, and received funds from the Australian Government’s CRCs Programme, the Fisheries R&D Corporation and other CRC Participants”.

  21. Oyster Industry in AUS Sydney Rock Oyster (Saccostrea glomerata) Pacific Oyster (Crassostrea gigas)

  22. Safety Management • Australian Shellfish Quality Assurance Program (ASQAP) Operation Manual, October 2006 (FSANZ standard 4.2.1) • Storage conditions for consumption as raw product

  23. Material & Methods • Tasmanian Pacific Oysters • Inoculation • Storage conditions (15-30oC) • Enumeration on TCBS • Growth curves using DMfit (SGR) • Secondary model (SGR at different T)

  24. Material & Methods • NSW Pacific Oysters (PO) and Sydney Rock Oysters (SRO) • Natural Vp • Enumeration using MPN+PCR • Storage conditions (15-30oC) • Growth curves using DMfit (SGR)

  25. trh • tdh • tlh 1 2 3 Strains: 39 40 57 58 59 60 Inoculation diagram 1) Drilling 2) Injection

  26. CONCLUSIONS BENEFITS • Growth model (15-30oC): how fast Vp grows at different temperatures • Tmin: 15oC (for PO: higher than the 10C recommended at the moment) • Slower Vp growth in oyster than in broth: necessity of a different model than the one in broth available • Vp viability is different in PO and SRO: this supports the idea that different oyster species show different behaviour

  27. TCBS • Counts: • 1) Selective media for Vibriospp CFU/g= [(70+75)/2]*dilution factor

  28. MPN+PCR • Counts: • 1) Enrichment step 2) Vp confirmation • (Most Probable Number) genetically MPN/g= MPN result*dilution factor

  29. Results: 4 parameters square-root Model

  30. Results: Growth Profiles

  31. FUTURE WORK • Real performance of the model (oyster shipment with temperature loggers) • Generating data for understanding of the differences between PO and SRO (bacterial profiles)

  32. Results: Growth Profiles

  33. Vibrio outbreaks in AUS • V. cholerae: • 2006: 1 incident (imported whitebait), OzFoodNet • V. vulnificus: • 1988-90: 4 incidents in NSW, 2 deaths (raw oysters) Kraa, 1995 • 1989-90: 3 cases in NSW septicaemia wound infection • 1991: 1 case in Victoria specticaemia Maxwell, 1991 • V. parahaemolyticus; • 1977-84: incident in NSW (seafood at a restaurant), Davey 85 • 1990: incident in Sydney (prawns from Indonesia), Kraa 95 • 1992: 2 incidents (prawns), Kraa 95 • 1992: 1 death (raw oyster), kraa 95 • 2002: 1 incident (seafood), OzFoodNet • 2005: 1 incident (oysters), Anon 05 • 4 cases in 1992 nacrozis • 1995-02: no outbreaks related to Vibrio but noroviurs, HepA and Salmonella. • Oysters: • 2001-07: unknown, norovirus and Salmonella. Data source: OzFoodNet

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