Study of immune response, colonization and invasion of chickens (Gallus gallus domesticus) by strains of Salmonella Enteritidis and Salmonella Typhimurium containing delections in the clpp and flid genes

Author(s)

Fernanda de Oliveira Barbosa

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2020-04-13.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2020-03-02
• Advisor: Angelo Berchieri Junior; Oliveiro Caetano de Freitas Neto

Abstract

Salmonella Enteritidis and Salmonella Typhimurium cause infections in humans and animals that are often associated with extensive intestinal colonization and faecal shedding. The presence of flagellar structure in the pathogen is related to the induction of intestinal inflammation and attenuation of systemic infection in the host. On the other hand, the absence of flagellin results in severe systemic infection as a result of mild inflammatory intestinal responses provoked by aflagellated strains. The hypothesis that higher flagellin production by Salmonella strains could induce immunogenic response during infection in chickens was evaluated in the present study. To investigate the consequences of flagellin overproduction, strains of Salmonella Enteritidis and Typhimurium containing clpP and fliD deletions (which lead to flagellin overexpression) were constructed, and pathogenicity and immunogenicity were compared with their respective wild-type strains in infected chickens. The results suggested that the increase in flagellin synthesis by SE ΔclpPΔfliD and STM ΔclpPΔfliD culminates in a deficit in the bacterial multiplication rate. However, that changes did not interfere with the capacity for caecal colonization and faecal excretion of mutant strains. The same was observed in the liver and spleen, but after 14 dpi, mutant strains tend to be eliminated from these organs. Even with higher flagellin synthesis, the mutant strains recruited similar amounts of lymphocytes and macrophages in the caecal tonsil, spleen and liver than wild-type strains. and high IL22 production at 7 dpi. While SE ΔclpPΔfliD triggered clinical signs similar to those induced by SE, but with higher levels of IL22 and IL18, but with repression of CCl4, CXCLi2 and IL17 in the intestine at the beginning of the infection. Apparently, the higher production of flagellin by both mutant strains altered the pathogenicity, possibly by altering the activation and modulation of the chicken's immune system. (AU)

• FAPESP's process: 16/18340-0 - Study of the immune response, colonization and invasion in poultry (Gallus gallus domesticus) by strains of Salmonella Enteritidis and Salmonella typhimurium containing deletions in genes ClpP and FliD
• Grantee: Fernanda de Oliveira Barbosa
• Support Opportunities: Scholarships in Brazil - Doctorate