Molecular analysis of virulence genes of Salmonella Infantis isolated from chickens and turkeys

Abstract

In this study, virulence genes of S. Infantis strains, which are commonly isolated from chickens and turkeys in Turkey, were analyzed, and the virulence genes of S. Infantis and other common serovars aside from S. Infantis were compared. In this study, 200 S. Infantis strains isolated from litter, powder, environmental sources, rodent samples and broiler chicken carcasses from a chicken slaughterhouse obtained from chickens (broiler chickens, breeders, laying hens) and 24 S. Infantis strains isolated and identified from litter, powder, environmental and rodent samples obtained from turkeys were analyzed. A total of 40 strains, comprising 10 strains from each Salmonella serovar (S. Typhimurium, S. Enteritidis, S. Kentucky and S. Hadar) (chicken-origin) were also selected from the collection of strains for comparison with S. Infantis strains. The virulence genes of 264, comprising 224 S. Infantis strains and 40 strains from common serovars other than S. Infantis were analyzed. A conventional polymerase chain reaction (PCR) was used to analyze the 11 genes associated with the virulence (sipA, sipD, sopD, sopB, sopE, sopE2, sitC, ssaR, sifA, spvC and pefA) in these strains. SipA, ssaR and sopE genes were found in the 209 S. Infantis strains (93.3%), sipD in 208 (92.85%), sopB in 207 (92.41%), sitC in 206 (91.96%), sifA in 203 (90.62%), sopD in 198 (88.39%), sopE2 in 166 (74.1%), spvC in 20 (8.92%) and the pefA virulence gene in one strain (0.44%). It was found that 74.55% of S. Infantis strains were distributed in gene patterns 1 and 2. In this study, the sopE2 virulence gene in S. Infantis strains was analyzed for the first time. The involvement of the dominant gene patterns of the S. Infantis strains isolated from broiler chicken and broiler chicken carcasses, and the fact that none of S. Infantis strains belonging to the breeders and laying hens were included in these patterns, indicated that S. Infantis entered the broilers not through the breeders, but through environmental factors. The presence of sipA, sipD, sopD, ssaR, sopB, sopE, sifA and sitC virulence genes in S. Infantis strains were found to be similar, but remarkable differences were found compared to the S. Typhimurium and S. Enteritidis strains in the presence of sopE2, spvC and pefA virulence genes. This study examining the virulence genes of S. Infantis strains provides detailed information aimed at providing an understanding of the pathogenesis and epidemiology of Salmonella in poultry.

Keywords: Broiler; Foodborne pathogen; PCR; Pathogenesis; Turkey.