Salmonella enterica subsp. salamae serovar Sofia, a prevalent serovar in Australian broiler chickens, is also capable of transient colonisation in layers

ABSTRACT 1. Salmonella enterica subsp. salamae serovar sofia (S. sofia) is a prevalent strain of Salmonella in Australian broilers and has been isolated from broiler chickens, litter, dust, as well as pre- and post-processing carcasses, and retail chicken portions but has never been reported in commercial Australian layers or eggs. 2. To investigate whether a S. sofia isolate from a broiler could colonise layers, one-month-old Hyline brown layers were orally inoculated with S. sofia and colonisation was monitored for 2–4 weeks. 3. Overall, 30–40% of the chickens shed S. sofia from the cloaca between 6 and 14 d post-inoculation which then declined to 10% by d 21. Necropsy at 2 weeks post-inoculation revealed 80% of birds harboured S. sofia in the caecum, whilst, by 4 weeks post-infection, no chickens were colonised with S. sofia in the gastrointestinal tract, liver or spleen. Additionally, no aerosol ‘bird to bird’ transfer was evident. 4. This study demonstrated that laying hens can be colonised by broiler-derived S. sofia; however, this colonisation was transient, reaching a peak at 14 d post-inoculation, and was completely cleared by 28 d post-inoculation. The transience of colonisation of S. sofia in layers could be a factor explaining why S. sofia has never been detected when screening for Salmonella serotypes found in Australian laying hens or eggs.