Purpose: The objective of this study was to evaluate a new triple buffered peptone (TBP) against LB and BP for the recovery of Salmonella from inoculated broiler feed.
Methods: In each of two replications, triplicate 5-g samples of non-medicated broiler feed was individually inoculated with approximately 70 cells/gram of one of four nalidixic acid resistant Salmonella serovars (Enteritidis, Heidelberg, Kentucky or Typhimurium, n=6 per serogroup). Samples were incubated (24h, 37°C) in 45 mL of broth (LB, BP or TBP). After incubation, the pH of the broth was measured and all broths were streaked on brilliant green sulfa agar containing 200 ppm nalidixic acid, incubated overnight at 37°C and evaluated for the presence of typical Salmonella colonies.
Results: The mean pH of TBP pre-enrichment media containing feed (6.6) was significantly (P<0.01) higher than BP (5.1) or LB (4.4). Salmonella was recovered from all (24+/24) samples pre-enriched in TBP. All samples (24+/24) pre-enriched in BP yielded positive Salmonella results. However, significantly fewer (P<0.01) samples pre-enriched in LB were found to be positive (2+/24). One positive sample was a Salmonella Typhimurium and one was a Salmonella Heidelberg.
Significance: Broiler feed pre-enriched in LB or BP suffers a significant decrease in pH during incubation compared to TBP. Pre-enrichment of feed in LB results in lower recover of inoculated Salmonella than either BP or TBP. TBP showed promise as a means to maintain near neutral pH in feed samples during pre-enrichment and may allow the accurate detection of Salmonella in feed and other similar samples.