Growth of V. parahaemolyticus in Tropical Blacklip Rock Oysters

The opportunistic pathogen poses a significant food safety risk worldwide, and understanding its growth in commercially cultivated oysters, especially at temperatures likely to be encountered post-harvest, provides essential information to provide the safe supply of oysters. The Blacklip Rock Oyster (BRO) is an emerging commercial species in tropical northern Australia and as a warm water species, it is potentially exposed to spp. In order to determine the growth characteristics of in BRO post-harvest, four strains isolated from oysters were injected into BROs and the level of was measured at different time points in oysters stored at four temperatures. Estimated growth rates were -0.001, 0.003, 0.032, and 0.047 log CFU/h at 4 °C, 13 °C, 18 °C, and 25 °C, respectively. The highest maximum population density of 5.31 log CFU/g was achieved at 18 °C after 116 h. There was no growth of at 4 °C, slow growth at 13 °C, but notably, growth occurred at 18 °C and 25 °C. growth at 18 °C and 25 °C was not significantly different from each other but were significantly higher than at 13 °C (polynomial GLM model, interaction terms between time and temperature groups < 0.05). Results support the safe storage of BROs at both 4 °C and 13 °C. This growth data will inform regulators and assist the Australian oyster industry to develop guidelines for BRO storage and transport to maximise product quality and safety.