Inhibition of Salmonella in Feces and Soil from the Feedlot Environment Treated with Lactobacillus acidophilus NP51

Introduction: Salmonella is ubiquitous in the cattle feeding environment and can survive long term in soil and fecal matter creating a source of contamination to the hide and gastrointestinal track of cattle during the feeding phase. When fed, Lactobacillus acidophilus (NP51) reduced the presence of pathogens in the digestive track of cattle. This warrants investigation on NP51 as an environmental treatment to reduce Salmonella in the feedlot.  

Purpose: The objective of this study is to observe the effects of NP51 on fecal and soil samples inoculated with Salmonella.  

Methods: A 1000-g of fecal and soil were collected separately from a feedlot and inoculated with a cocktail containing three strains of Salmonella at 10³ CFU/g. Each sample type was divided into two 500-g aliquots.  One 500-g portion was treated with NP51 at 10⁹ CFU/g.  The other 500-g portion for both soil and fecal material remained untreated to serve as a control. All samples were stored at 37°C and were taken at 0, 24, and 48 hours. Ten grams were diluted in 90 ml of buffer peptone water and further serially diluted and spread plated in duplicate onto XLT4 agar. This process was replicated three separate times (n = 36). Data was log₁₀-transformed and analyzed using repeated measures ANOVA.

Results: There was a significant treatment effect (P ≤ 0.05) for the fecal samples treated with NP51 with 0.4 log CFU/g less Salmonella detected overall compared to the untreated sample. There were no significant differences observed for soil inoculated with Salmonella and treated with NP51 when compared to controls.

Significance: These data indicate reductions in the presence of Salmonella in inoculated fecal samples treated with NP51.  Decreasing Salmonella in the cattle feces is an important step in reducing overall prevalence in feedlot environment to help minimize the transfer of pathogens into food products.