Survival of Salmonella enterica in poultry feed is strain dependent

Abstract

Feed components have low water activity, making bacterial survival difficult. The mechanisms of Salmonella survival in feed and subsequent colonization of poultry are unknown. The purpose of this research was to compare the ability of Salmonella serovars and strains to survive in broiler feed and to evaluate molecular mechanisms associated with survival and colonization by measuring the expression of genes associated with colonization (hilA, invA) and survival via fatty acid synthesis (cfa, fabA, fabB, fabD). Feed was inoculated with 1 of 15 strains of Salmonella enterica consisting of 11 serovars (Typhimurium, Enteriditis, Kentucky, Seftenburg, Heidelberg, Mbandanka, Newport, Bairely, Javiana, Montevideo, and Infantis). To inoculate feed, cultures were suspended in PBS and survival was evaluated by plating samples onto XLT4 agar plates at specific time points (0 h, 4 h, 8 h, 24 h, 4 d, and 7 d). To evaluate gene expression, RNA was extracted from the samples at the specific time points (0, 4, 8, and 24 h) and gene expression measured with real-time PCR. The largest reduction in Salmonella occurred at the first and third sampling time points (4 h and 4 d) with the average reductions being 1.9 and 1.6 log cfu per g, respectively. For the remaining time points (8 h, 24 h, and 7 d), the average reduction was less than 1 log cfu per g (0.6, 0.4, and 0.6, respectively). Most strains upregulated cfa (cyclopropane fatty acid synthesis) within 8 h, which would modify the fluidity of the cell wall to aid in survival. There was a weak negative correlation between survival and virulence gene expression indicating downregulation to focus energy on other gene expression efforts such as survival-related genes. These data indicate the ability of strains to survive over time in poultry feed was strain dependent and that upregulation of cyclopropane fatty acid synthesis and downregulation of virulence genes were associated with a response to desiccation stress.

Preharvest Salmonella Risk Contamination and the Control Strategies

“…As we already mentioned above, Salmonella has the capability to survive in a vast variety of commodities and to resist desiccation among other adverse conditions. During our work and research in Salmonella surveillance in animal feed, we have seen that Salmonella has the ability to remain in different animal feedstuffs for long time periods; this has been also confirmed by other research groups [33,34].…”

Salmonella spp. in poultry: a constant challenge and new insights

“…In addition, the pCVM29188_146 plasmid measures are not effective in controlling Salmonella spp. In some Salmonella strains, including those of serovar Enteritidis, isolated from food products with low water activity, an increase in virulence and the reduction of the infective dose was found (Aviles et al, 2013;Andino et al, 2014). It is believed that the increasing virulence of Salmonella spp.…”

“…in products with low water activity is the result of rpoS activation (the main stress response regulator), which directly affects the activation of virulence genes such as the invA, hilA and sipC (Aviles et al, 2013). However, experimental studies show that genes invA and hilA in S. Enteritidis are down regulated in low water activity, but the exact reason for the increased virulence of this serovar remains unknown (Andino et al, 2014).…”

Presencia y Resistencia a los Antimicrobianos de serovariedades de Salmonella enterica aisladas en una empresa avícola integrada del Ecuador

“…La distribución de serotipos de Salmonella cambió al final de la cadena productiva, siendo S. Infantis la serovariedad predominante. Ello probablemente se deba a que la supervivencia de Salmonella enterica puede variar según el serotipo (Andino et al 2014). Igualmente, la exposición repetida de la bacteria a un determinado ambiente hostil puede dar como re-sultado el surgimiento de cepas altamente resistentes a ese entorno (Humphrey 2004).…”