Evaluation of a Triple Buffered Peptone Broth for Detection of Salmonella in Broiler Feed

Abstract

The pH of pre-enrichment media containing feed/ingredients can become acidic during incubation due to bacterial utilization of feed carbohydrates. This decrease in pH can result in cell injury or death, negatively impacting the detection of Salmonella. Our objective was to evaluate a new triple buffered peptone (TBP) against buffered peptone water (BPW) and lactose broth (LB) for the recovery of Salmonella from feed. Liquid cultures of nalidixic acid resistant strains of Salmonella (Enteritidis, Heidelberg, Kentucky or Typhimurium) were added to the pre-enrichment media alone, to pre-enrichment media containing feed or to artificially inoculated feed stored 1 or 7 d to evaluate the effect of the medium on the recovery of Salmonella. Three replicates per treatment were conducted. After incubation at 37 °C for 24 h, the pH of the medium was measured prior to plating onto brilliant green sulfa agar plates supplemented with 200 ppm nalidixic acid (BGSNA). Plates were incubated and evaluated for presence of typical Salmonella colonies. The experiment was replicated. TBP was observed to exhibit significantly better buffering capacity than BPW or LB. Additionally, TBP was able to recover Salmonella 100% of the time compared to BPW (97.9%) and LB (61.5%). TBP shows promise to maintain neutral pH during pre-enrichment which may allow for a more accurate detection of Salmonella in feed.