Salmonella Reading (S. Reading) recently emerged as a major foodborne pathogen causing large multistate outbreaks in North America by consuming contaminated poultry products, mostly from turkeys. Understanding this newly emerged pathogen’s transmission and tissue colonization potential in poultry is crucial for mitigating future outbreaks.

A study was done aimed at understanding the ability of S. Reading to colonize reproductive tissues and contaminate the eggs of broiler breeder hens by Abubakar Isah, a graduate student at Mississippi State University and collaborators, and presented as a poster session during the 2024 International Poultry Scientific Forum.

Two S. Reading strains previously tagged with bioluminescence marker gene were used; a recent outbreak strain RS330 and a reference non-outbreak strain RS326.

Thirty-two commercial broiler breeder hens of 34 weeks of age were tested to ensure they were negative for Salmonella. The Salmonella-negative hens were randomly placed in individual cages and assigned to one of the two treatments (16 hens/strain) within an animal biosafety level-2 facility. Each hen was intravaginally challenged with 10⁸ CFU of the respective strain on day 1 and rechallenged on day 4.

Post challenge, eggs were collected daily to recover bioluminescent S. Reading strains from external eggshell surface and internal egg contents. On day 7 post-challenge, ten hens from each treatment were euthanized and ovaries, oviduct, and ceca were aseptically collected to identify bioluminescent S. Reading colonization.

Results showed that 70.5% and 34.5% of external eggshell surfaces and 4% and 1.8% of the internal egg contents tested positive for the outbreak and non-outbreak strains respectively. A chi-square test revealed that these differences in contamination rates were statistically insignificant (p>0.05).

Furthermore, 40% of ovaries, 70% of oviduct, and 70% of ceca samples from the hens challenged with the outbreak strain and 20% of ovaries, 70% of oviduct, and 80% of ceca from the non-outbreak strains tested positive.

Overall, the results demonstrate that S. Reading has the capability to colonize the reproductive tissue of hens, leading to egg contamination and cecal translocation. Future investigations are essential to determine whether S. Reading can remain viable within the egg throughout the incubation period until hatching, the researchers concluded.