Detection of Escherichia albertii in retail oysters

Escherichia albertii is an emerging foodborne pathogen. Owing to its distribution in river water, it is important to determine the presence of E. albertii in aquaculture-related foods. In this study, we investigated the distribution of E. albertii in retail oyster samples. A total of 427 raw oyster samples (385 Pacific oysters, and 42 Japanese rock oysters) were enriched in modified Escherichia coli broth (mEC) or mEC supplemented with novobiocin (NmEC) at 42 °C. The cultures were used for E. albertii -specific nested PCR assay, as well as for E. albertii isolation using deoxycholate hydrogen sulfide lactose agar (DHL), DHL supplemented with rhamnose and xylose (RX-DHL), and MacConkey agar supplemented with rhamnose and xylose (RX-MAC). The population of E. albertii in nested PCR-positive samples was determined using the most probable number (MPN) method. E. albertii isolates were subjected to biochemical and genetic characterization. E. albertii was detected in 5 of 315 (1.6%) Pacific oyster samples (one piece each), 2 of 70 (2.9 %) Pacific oyster samples (25 g each), and 2 of 42 (4.8 %) Japanese rock oyster samples procured from four geographically distant regions. A total of 64 E. albertii strains were isolated from eight of the nine nested PCR assay-positive oyster samples, and the MPN value was under the detection limit (< 3 MPN/10 g). A specific season or month for detecting E. albertii was not observed in this study, suggesting that the pathogen is present in seawater. All the E. albertii isolates, except one, were positive for the virulence factor eae, indicating that these isolates have the potential to infect humans.

I Know Where Oysters Lie

This research honours the Baludarri (Sydney Rock Oyster). It is interdisciplinary in its approach and showcases the work of Australian born artist, Sarah Jane Moore. It presents key findings from an artistic residency at UNSW in Sydney, Australia, through the modalities of image, song and text. It highlights the importance of the humble oyster and maps an art-meets-science approach where Moore’s creative thinking seeks inspiration from her relationship with the work of an Indigenous scientist, Laura Parker. The oyster is Moore’s living data and the work maps the deep listenings necessary to foster communities that value reefs, hold oceans as sacred and regard the oyster as a precious entity to be celebrated, protected and nourished.

Larval energetics of the Sydney rock oyster Saccostrea glomerata and Pacific oyster Magallana gigas

Larvae are a critical dispersal stage of marine invertebrates, and their survival depends on nutrition and energetics. This study compared the size, survival, metabolic rate and egg and larval lipid class profiles of larvae of the endemic Sydney rock oyster Saccostrea glomerata and the invasive Pacific oyster Magallana gigas through a period of starvation for 5 and 9 d after fertilisation. Starved larvae grew without food until 5 d of age, at which point they stopped developing, but resumed growth when fed. Egg lipids profiles comprised 78.1 and 74.5% triacylglycerol for M. gigas and S. glomerata respectively. When fed, larvae of M. gigas were significantly larger in size and had faster growth and similar survival compared to S. glomerata. When starved, larvae of M. gigas and S. glomerata grew at similar rates, and there was a trend for lower survival of M. gigas. Larval endogenous lipid reserves were deleted in the first 24 h. Larvae of M. gigas had more total lipids and comparatively more diacylglycerols, monoacylglycerols, phospholipids and cholesterol, whereas S. glomerata had more diacylglycerols and produced sterol esters. Starvation altered the patterns of lipid assimilation, and metabolic rates of larvae of M. gigas and S. glomerata differed over time. When starved, S. glomerata larvae had greater capacity to cope with starvation compared to M. gigas, perhaps due to an evolutionary history in oligotrophic estuaries. As the climate rapidly changes in this global climate-change hotspot, S. glomerata is likely to be negatively affected.

Sydney rock oyster farming in Australia.

The 120-year-old Sydney rock oyster industry in New South Wales (NSW) and southern Queensland is one of the oldest aquaculture industries in Australia. The industry has been forced to adapt to competition from other species, tighter harvesting and oyster storage and handling requirements as well as eroding profit margins. Recent changes in farming practices include the move away from stick culture to single seed culture, as the half-shell market demands a more uniformly shaped oyster. When selective breeding demonstrated that it could reduce time to market (50 g whole weight) by nearly a year out of an industry average of 3.5 years, the industry wanted to try hatchery technology. Although the industry had never used hatchery technology before, it purchased 10 million spat or 8% of its annual spat requirement from hatcheries in 2003-2004, the first year that they were made available to farmers. The industry also embraced the Australian Shellfish Quality Assurance Program, which requires that shellfish harvest areas be classified on the basis of a sanitary survey and the results of an ongoing strategic water-sampling programme. This programme ensures product safety for the consumers and helps to provide the industry with a long-term future.