A Tool to Manage Vibrio parahaemolyticus 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

INTRODUCTION

Actual situation (19 th October ’09)

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

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

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

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

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

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

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.

RESULTS

Model development: data

Model development: maths √SGR= x(T )x{1-exp[0.0113x(T )]}

Model evaluation

Model comparison

CONCLUSIONS

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 15 o C (PO), 28 o C (SRO) May provide Australian oyster industry with more cost-effective storage

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

Very tasty, very nutritious!!!

“ 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”.

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

Safety Management Australian Shellfish Quality Assurance Program (ASQAP) Operation Manual, October 2006 (FSANZ standard 4.2.1) – Storage conditions for consumption as raw product SpeciesMaximum daysT ( o C) Pacific Oyster6-7≤10 (24h) Sydney Rock Oyster9-10Max 25 then ≤15 (72h)

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

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

Inoculation diagram 1.trh 2.tdh 3.tlh Strains: ) Drilling2) Injection

CONCLUSIONS BENEFITS Growth model (15-30 o C): how fast Vp grows at different temperatures T min : 15 o C (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

TCBS Counts: 1) Selective media for Vibrio spp CFU/g= [(70+75)/2]*dilution factor

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

Results: 4 parameters square-root Model

Results: Growth Profiles

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)

Results: Growth Profiles

Vibrio outbreaks in AUS V. cholerae: –2006: 1 incident (imported whitebait), OzFoodNet V. vulnificus: – : 4 incidents in NSW, 2 deaths (raw oysters) Kraa, 1995 – : 3 cases in NSW septicaemia wound infection – 1991: 1 case in Victoria specticaemia Maxwell, 1991 V. parahaemolyticus; – : 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 : no outbreaks related to Vibrio but noroviurs, HepA and Salmonella. Oysters: – : unknown, norovirus and Salmonella. Data source: OzFoodNet