Recovery of Salmonella enterica from Australian Layer and Processing Environments Following Outbreaks Linked to Eggs

Salmonella enterica are a significant cause of foodborne disease worldwide, with eggs being the mostimportant food vehicles for infection (Threlfall et al., 2014). In Australia, the most common serovar infecting humans is Typhimurium (Salmonella Typhimurium) with thousands of cases resulting from numerous outbreaks linked to eggs (Moffatt et al., 2016). To highlight Salmonella Typhimuriums capacity to navigate the farm to fork continuum we undertook an examination of the farm-derived microbiological and trace back evidence of Salmonella spp. gathered in response to outbreaks linked to eggs. Materials and Methods We reviewed investigation findings for Australian S. enterica outbreaks linked to eggs between 2001 and 2011, with our methods detailed elsewhere (Moffatt et al., 2016). Trace back data relating to outbreaks were obtained from records and correspondence with food safety regulators and investigators from state and territory primary industry departments (Moffatt et al., 2016). This included detail on the egg type and quality, extent of trace back, production systems, farm inspections, and Salmonella serovars recovered during sampling. Results Trace back and housing systems Commercially produced eggs were implicated in 159 (96%) of 166 outbreaks with the remainder involving backyard (noncommercial) eggs. For outbreaks involving commercial production, housing system detail was only available for 70 (44%) events. Of these 36 (52%) were cage, 33 (47%) free range, and 1 (1%) barn laid. Trace back was conducted for 106 (64%) outbreaks, identifying a specific farm on 72 (68%) occasions. From the available data, no difference between the proportion of outbreaks linked to eggs produced in cage and free range housing systems was found.