Low dose infection of hens in lay with Salmonella enterica serovar Enteritidis from different genomic clades

Authors: Guard, Jean; Rothrock, Michael; Jones, Deana; Gast, Richard

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2019
Publication Date: 4/9/2020
Citation: Guard, J.Y., Rothrock Jr, M.J., Jones, D.R., Gast, R.K. 2020. Low dose infection of hens in lay with Salmonella enterica serovar Enteritidis from different genomic clades. Avian Diseases. 64(1):7-15. https://doi.org/10.1637/0005-2086-64.1.7.
DOI: https://doi.org/10.1637/0005-2086-64.1.7

Interpretive Summary: A review of the literature on experimental models that infected chickens with the poultry-associated foodborne pathogen Salmonella enterica serovar Enteritidis (SE) revealed that few had been conducted at a low dose of cells in hens that were at the peak of production. Results showed that chickens might react differently to low dosages than high dosages and that selection of strain for conducting experiments impacted results. Results also suggested that i) sulfur in the environment of chickens might be a unique feature contributing to persistence of pathogenic Salmonella, and that ii) developing combination vaccines for poultry to protect against both organ invasion and cecal colonization are possible areas for interventions intended to reduce the level of SE causing foodborne illness. These studies complete objectives 3 and 4 of the OSQR cycle beginning Feb 1, 2016.

Technical Abstract: Salmonella enterica serovar Enteritidis is the leading cause of salmonellosis in people and modeling of infections in chickens is used to identify intervention strategies. Review of 80 manuscripts encompassing 119 experiments indicated that the mean dose of infection was 10exp8 CFU per bird. Experiments less than 10exp6 CFU were conducted mostly in immature birds. To address a lack of information on the impact of low dosages on the hen at lay, two experiments were conducted in triplicate. In Experiment A, hens were infected intramuscularly at 10exp3, 10exp5, and 10exp7 CFU. For Experiment B, hens were infected orally with 5 x 10exp3 CFU with 4 strains from different genomic clades. Samples cultured were liver, spleen, ovarian pedicle and paired ceca in both experiments. Eggshell microbiome taxa were assessed in Experiment B. Results indicated that dosages of 10exp3 CFU in both experiments produced enough positive samples to be used within models. The intramuscular route resulted in approximately twice as many positive samples as the oral route. The kinetics of infection appeared to differ between low and high dosages suggestive of a J- curve response. These resultscould impact risk assessments if the hen at lay has a non-linear response 52 to infectious dose.