Molecular mechanisms associated with survival of <i>Salmonella enterica</i> in broiler feed are serovar and strain dependent

Food animals including poultry are known as a major reservoir for Salmonella. Poultry and poultry products are the leading sources of non-Typhi serotypes of Salmonella enterica. Feed has been recognized as a source of Salmonella in chickens. However, considering the fact that feed components have very low water activity of 0.4 approximately. The mechanisms of Salmonella survival in the feed and subsequent colonization of poultry are unknown. Given the conditions of the source of the main ingredients, processing, transportation and storage, poultry feed has a higher potential than other sources to become contaminated with Salmonella. Data indicate that prevalence of Salmonella enterica in human foodborne illness is not related to their prevalence of isolation from feed. Thus, it appears that survival in poultry feed may be an independent factor unrelated to virulence of specific serovars of Salmonella.

In this research, we examine the survival rates and gene expression of Salmonella in poultry feed. Fifteen different serovars isolated from human infections or poultry inoculated in poultry feed were assayed to determine survival rates at 0, 4, 8, 24 hours, 4 and 7 days. In addition, genes associated with colonization (hilA, invA) and survival via fatty acids synthesis (cfa, fabA, fabB, fabD) were evaluated using real-time PCR at four different time points, 0, 2, 4, and 24 hours after inoculation. This study demonstrated that the ability of Salmonella enterica to survive over storage time in poultry feed was serovar and strain dependent. Furthermore, the data indicate that the upregulation of short chain fatty acid synthesis and down regulation of virulence genes may be associated with survival in poultry feed.