Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/2013
Publication Date: 5/10/2013
Citation: Kich, J.D., Uthe, J.J., Benavides, M.V., Cantao, M.E., Zanella, R., Tuggle, C.K., Bearson, S.M. 2013. TLR4 single nucleotide polymorphisms (SNPs) associated with Salmonella shedding in pigs [abstract]. Paper No. 2164. Interpretive Summary:
Technical Abstract: Background: Toll-like receptor 4 (TLR4) is a key receptor in the innate immune recognition of lipopolysaccharide (LPS) from Gram-negative bacteria; genetic variation in this specific gene has been linked with the host’s response to bacterial infections and disease resistance. Since colonization and transmission of Salmonella in asymptomatic pigs during the production period is a public health issue, the current study investigated the relationship between host genotype (TLR4 single nucleotide polymorphisms) and a phenotype important to pathogen transmission (Salmonella shedding). Material and Methods: Single nucleotide polymorphisms (SNPs) in the TLR4 gene were screened in forty crossbred pigs that were phenotypically chosen from 117 Salmonella enterica serovar Typhimurium-challenged animals based on their Salmonella shedding status (classified as low (20) or high (20) shedders), determined using bacteriological quantification data from day 2 to 21 post inoculation. Following DNA extraction, the TLR4 gene was amplified using nine primer sets designed to cover all exons of the TLR4 gene, ~600 bp of upstream DNA, ~500 bp of downstream DNA, and portions of introns 1 and 2. The fragments were sequenced and analyzed for genetic variation using Phred/Phrad/Consed/PolyPhred software. A minor allele frequency above 10% was the criteria to consider a SNP. Linkage disequilibrium and individual SNP association (Chisq and Fisher test) were analyzed using Plink software. Results: Sequence analysis revealed 18 SNPs; 12 have been previously described in the literature and six SNPs are novel. Eight of the 18 SNPs were located in the coding region of exon 3 and three of these were non-synonymous. Four SNPs were associated with Salmonella shedding (p less than or greater than 0.01), revealing a relationship between Salmonella shedding status and genetic variation in the TLR4 gene in swine. Conclusion: Identification of four SNPs associated with colonization and transmission of Salmonella during swine production will facilitate genetic selection for swine breeds that enhance food safety.