Effects of Salmonella enteritidis Infection on TLR Genes Expression and Microbial Diversity in Laying Hens

Abstract

Background: Salmonella enteritidis (SE) is one of the critical foodborne pathogens, and mainly causes human diseases through contaminated water and food. In the current study, serological tests, histopathological observation and quantitative real-time PCR were used to assess the effect of Salmonella enteritidis infection on the immune system in chickens. To understand the influence of SE infection on the microflora profile of the cecum and oviduct, microbial community composition of the cecal contents and oviducal contents wereanalyzed through 16S rRNA sequencing. Results: Results showed that SEinfection caused damage to the digestive organs, reproductive organs, and immune organs in laying hens. The expression of TLR1a, TLR1b, TLR2, TLR4, TLR5, TLR7 and TLR15 in the cecum were induced, and the content of IFN-γ, TNF-α, IL-2 and IL-18 in serum were increased after SE infection. The composition of the microbial community significantly changed in cecal content, the dominant bacteria of Firmicutes increased, and Bacteroidetes decreased significantly. In the oviduct, the microbial diversity became complicated, the dominant bacteria Faecalibacterium was significantly increased, and Bacteroides was significantly decreased. Conclusions: Salmonella enteritidis infection triggered the host’s innate and adaptive response, increased the expression of TLRs and contents of cytokines and changed the microbial diversity in the cecum and oviduct. These findings willlay the foundation for further study on reducing the vertical transmission of Salmonella enteritidis, ensuring the production of clean eggs.

Expression of Toll‐like receptors and host defence peptides in the cecum of chicken challenged with Eimeria tenella

“…Furthermore, TLR2 and TLR4 appeared to be associated with host resistance to Toxoplasma gondii , Cryptosporidium parvum and Schistosoma japonicum in humans, cattle and mice 41–43 . In our study, increased expression in TLR2 and TLR4 transcriptional levels was observed in chickens infected with E. tenella , which were also reported in the cecum and spleen of S. enterica‐ infected chickens 44 . Previous studies reported that TLR4 signalling upregulates while TLR2 signalling downregulates macrophage antileishmanial activity during Leishmania donovani infection, suggesting that the contrasting roles of TLR2 and TLR4 could provide potential therapeutic targets for the control of Leishmaniasis 45 .…”

“…[41][42][43] In our study, increased expression in TLR2 and TLR4 transcriptional levels was observed in chickens infected with E. tenella, which were also reported in the cecum and spleen of S. enterica-infected chickens. 44 Previous studies reported that TLR4 signalling upregulates while TLR2 signalling downregulates macrophage antileishmanial activity during Leishmania donovani infection, suggesting that the contrasting roles of TLR2 and TLR4 could provide potential therapeutic targets for the control of Leishmaniasis. 45 Although these results partly explain the high correlation between TLR2 and TLR4, the molecular mechanism underlying this correlation might be complex, resulting in the initiation of multiple signalling cascades.…”