Detection of virulence genes in Salmonella Heidelberg isolated from chicken carcasses

Abstract

During the last years, Brazilian government control programs have detected an increase of Salmonella Heidelberg in poultry slaughterhouses a condition that poses a threat to human health However, the reasons remain unclear. Differences in genetic virulence profiles may be a possible justification. In addition, effective control of Salmonella is related to an efficient epidemiological surveillance system through genotyping techniques. In this context, the aim of this study was the detection of 24 virulence-associated genes in 126 S. Heidelberg isolates. We classified the isolates into 56 different genetic profiles. None of the isolates presented all the virulence genes. The prevalence of these genes was high in all tested samples as the lowest number of genes detected in one isolate was 10/24. The lpfA and csgA (fimbriae), invA and sivH (TTSS), and msgA and tolC (intracellular survival) genes were present in 100% of the isolates analyzed. Genes encoding effector proteins were detected in the majority of SH isolates. No single isolate had the sefA gene. The pefA gene was found in only four isolates. We have also performed a screening of genes associated with iron metabolism: 88.9% of isolates had the iroN gene and 79.4% the sitC gene. Although all the isolates belong to the same serotype, several genotypic profiles were observed. These findings suggest that there is a diversity of S. Heidelberg isolates in poultry products. The fact that a single predominant profile was not found in this study indicates the presence of variable sources of contamination caused by SH. The detection of genetic profiles of Salmonella strains can be used to determine the virulence patterns of SH isolates.