Detection of Salmonella spp. survival and virulence in poultry feed by targeting the hilA gene

Aims: The objectives of this work were to evaluate immunomagnetic beads and a reverse transcriptase (RT)-PCR method for the detection of Salmonella inoculated into feed. In addition, a reverse transcriptase (RT)-PCR method was evaluated for quantifying virulence gene hilA expression of Salmonella ssp. in poultry feed matrices and utilized to determine the influence of poultry feed environmental factors on Salmonella hilA expression. Methods and Results: An immunomagnetic separation technique was evaluated for increased recovery of Salmonella from feed. Salmonella cultures were inoculated into feed samples and exposed to heat treatments of 70 degrees C and sampled periodically. From these samples, RNA was collected and hilA gene expression was measured relative to the housekeeping 16S rRNA gene. The immunomagnetic bead protocol increased recovery by 1 log. The up-regulation of hilA was demonstrated after 5 and 10 min of inoculated feed samples being exposed to heat treatment. Conclusions: From this work, the data indicate that the ability to detect live Salmonella cells in feed samples may be increased by targeting the hilA gene. Significance and Impact of the Study: Foodborne salmonellosis originating from poultry is a major problem, and feed is a leading source of contamination in poultry, but detection in feed is complicated by low concentrations. The assays and experiments in this study examine possible improvements to recovery and detection of Salmonella in feed.