Salmonella enterica serovar Enteritidis infection is a common concern in poultry production for its negative effects on growth as well as food safety for humans. Identification of molecular markers that are linked to resistance to Salmonella Enteritidis may lead to appropriate solutions to control Salmonella infection in chickens. This study investigated the association of candidate genes with resistance to Salmonella Enteritidis in young chickens. Two native breeds of Malaysian chickens, namely, Village Chickens and Red Junglefowl, were evaluated for bacterial colonization after Salmonella Enteritidis inoculation. Seven candidate genes were selected on the basis of their physiological role in immune response, as determined by prior studies in other genetic lines: natural resistance-associated protein 1 (NRAMP1), transforming growth factor β3 (TGFβ3), transforming growth factor β4 (TGFβ4), inhibitor of apoptosis protein 1 (IAP1), caspase 1 (CASP1), lipopolysaccharide-induced tumor necrosis factor (TNF) α factor (LITAF), and TNF-related apoptosis-inducing ligand (TRAIL). Polymerase chain reaction-RFLP was used to identify polymorphisms in the candidate genes; all genes exhibited polymorphisms in at least one breed. The NRAMP1-SacI polymorphism correlated with the differences in Salmonella Enteritidis load in the cecum (P = 0.002) and spleen (P = 0.01) of Village Chickens. Polymorphisms in the restriction sites of TGFβ3-BsrI, TGFβ4-MboII, and TRAIL-StyI were associated with Salmonella Enteritidis burden in the cecum, spleen, and liver of Village Chickens and Red Junglefowl (P< 0.05). These results indicate that the NRAMP1, TGFβ3, TGFβ4, and TRAIL genes are potential candidates for use in selection programs for increasing genetic resistance against Salmonella Enteritidis in native Malaysian chickens.
Salmonella infection is an important risk to public health, as newly hatched chicks are very sensitive to Salmonella and the infection transfers to humans through contaminated meat and eggs. Vaccination and antibiotic treatment are common strategies to control salmonellosis. However, it is doubtful whether these strategies succeed, because immune functions depend on the activity of several genes. Genetic improvement of the immune system is an effective method to control salmonellosis. There is genetic variation among breeds and individuals inside breeds in terms of resistance to infection. Genes responsible for resistance to disease can be identified through quantitative trait loci and gene expression analysis. High-throughput technologies assist us to detect single nucleotide polymorphisms (SNPs) and to analyse the regulation of several genes simultaneously. By now, several SNPs have been detected in the chicken genome that influence the function of immune genes. Additionally, the expression level of genes varies during infection depending on the breed and age of chicken and environmental conditions. This review summarizes the results of previous studies on the identification of genes and gene regulation during Salmonella infection in chickens.
Salmonella enteritidis (SE) is a common cause of food-borne disease in humans and loss of growth in poultry. An effective method to inhibit salmonellosis is to increase the genetic resistance of poultry to Salmonella through genetic selection programmes that may be performed using phenotypic or genotypic data. A better understanding of the effects of Salmonella infection on the expression of inflammatory and anti-infectious cytokines and antimicrobial molecules is essential for choosing potential markers in selection programmes. The aim of this study was to investigate the expression of NRAMP1, TLR4, IL8 and IFNg genes in the caecum and spleen of Malaysian village chickens and red jungle fowl 48 h after inoculation with SE. Real-time reverse transcription PCR was used to quantify the fold-change in mRNA expression. The results showed that all the genes were highly expressed 48 h post-infection in the caecum of the village chickens. Overall, these results showed that Malaysian indigenous chickens have appropriate innate immune responses to SE infection.
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