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Role of dust in Salmonella transmission on chicken farms is not well characterised. Salmonella Typhimurium (ST) infection of commercial layer chickens was investigated using a novel sprinkling method of chicken dust spiked with ST and the uptake compared to a conventional oral infection. While both inoculation methods resulted in colonisation of the intestines, the Salmonella load in liver samples was significantly higher at 7 dpi after exposing chicks to sprinkled dust compared to the oral infection group. Infection of chickens using the sprinkling method at a range of doses showed a threshold for colonisation of the gut and organs as low as 1000 CFU/g of dust. Caecal content microbiota analysis post‐challenge showed that the profiles of chickens infected by the sprinkling and oral routes were not significantly different; however, both challenges induced differences when compared to the uninfected negative controls. Overall, the study showed that dust sprinkling was an effective way to experimentally colonise chickens with Salmonella and alter the gut microbiota than oral gavage at levels as low as 1000 CFU/g dust. This infection model mimics the field scenario of Salmonella infection in poultry sheds. The model can be used for future challenge studies for effective Salmonella control. [ABSTRACT FROM AUTHOR]

Reptiles are carriers of Salmonella and can intermittently shed bacteria in their faeces. Contact with snakes and lizards is a source of human salmonellosis. Here, two populations of reptiles, wild and captive were surveyed for Salmonella. One hundred thirty wild‐caught reptiles were sampled for Salmonella including 2 turtle, 9 snake and 31 lizard species. Fifty‐two of 130 (40%) animals were Salmonella positive: one of 5 (20%) turtles, 7 of 14 (50%) snakes and 44 of 111 (39.6%) lizards. One hundred twenty‐two reptiles were sampled from a zoo collection including 1 turtle, 6 tortoise, 9 lizard, 14 snake and 1 crocodile species. Forty‐two of 122 (34.4%) captive reptiles sampled were Salmonella positive. Salmonella was most commonly isolated from lizards and snakes. Fifteen serotypes were identified from zoo and 19 from wild‐caught reptiles and most were members of subspecies enterica (I), salamae (II), arizonae (IIIa) or diarizonae (IIIb). Antimicrobial susceptibility testing was conducted on all Salmonella isolates; only two exhibited resistance, a Salmonella subsp. (II) ser. 21:z10:z6 (Wandsbek) isolate cultured from a wild‐caught reptile and a Salmonella Typhimurium DT120 isolated from a captive snake. The invasive capacity of reptile‐associated Salmonella strains into cultured human intestinal epithelial (Caco2) and mouse macrophages cell lines (J774A.1) was also investigated. All isolates were invasive into both cell lines. Significant (P ≤ 0.001) variability in invasiveness into polarized Caco2 cells was observed. Salmonella Eastbourne exhibited the highest invasiveness into Caco2 cells and Salmonella Chester the lowest, with mean per cent recoveries of 19.99 ± 0.32 and 1.23 ± 0.30, respectively. Invasion into J774A.1 macrophages was also variable but was not significant. Salmonella subsp. II ser. 17:g,t:‐ (Bleadon) exhibited the highest invasiveness into J774A.1 with a mean per cent recovery of 10.19 ± 0.19. Thus, reptile‐associated Salmonellae are likely to have different capacities to cause disease in humans. [ABSTRACT FROM AUTHOR]

Abstract: Vaccination of chicks with Salmonella (S.) Typhimurium aroA deletion mutants has previously been shown to inhibit intestinal colonization of wild‐type S. Typhimurium strains. In Australia, Bioproperties VaxSafe™ STM1 strain is the only licensed and commercially available S. Typhimurium vaccine. This vaccine is a live attenuated aroA deletion mutant. Currently, it is recommended that the first dose of the STM1 vaccine is administered through coarse spray. It is unclear whether this mode of administration effectively permits intestinal colonization. Furthermore, it is not known whether the STM1 strain prevents or inhibits Salmonella colonization of chicks following this first dose. This study investigated both in vitro and in vivo colonization parameters. Invasiveness was assessed using an in vitro invasion assay into sections of ileum and caecum collected from day‐old chicks. The S. Typhimurium definitive types (DT) 9 and 44 exhibited the greatest invasion into both intestinal segments. STM1 was invasive but was significantly less so than both isolates of S. Typhimurium. In dual and triple infections, no competitive microbial interactions between STM1 and wild‐type Salmonella were observed. In vivo colonization inhibition was also tested. Vaccinated and nonvaccinated day‐old chicks were challenged with S. Typhimurium DT9. Both STM1 and S. Typhimurium DT9 were found in spleen, liver, ileum, caecum and caecal contents from day 2 postinfection. No significant exclusion effect was observed in vaccinated and challenged chicks. [ABSTRACT FROM AUTHOR]