Purpose: The purposes of this study was to determine the efficacy of levulinic acid plus sodium dodecyl sulfate (SDS) to inactivate STEC and Salmonella Typhimurium on cattle hides as a surface spray treatment at different concentrations in vitro.
Methods: A mixture of six isolates of STEC, including serovars O26, O45, O103, O111, O121, and O157 (108 CFU/ml) and a mixture of 5 strains of Salmonella Typhimurium (108 CFU/ml) were sprayed on the surface of 10 x 10-cm sections of cattle hide. The inoculated hides were dried under a hood at either 21oC or 4oC for 72 h. The hides were treated by surface spray with a microbicide comprised of levulinic acid plus SDS at different concentrations at 45 psi for 15 s. Water only was used as the negative control. Sponge samples of the hides were collected at 1, 3, and 5 min after treatment and enumerated for STEC and Salmonella.
Results: For STEC-contaminated hides, 3% levulinic acid plus 0.5% SDS for 5 min reduced STEC populations by 2.3 log/cm2, compared to the water only treatment. For Salmonella Typhimurium-contaminated hides, treatment with 2% levulinic acid plus 0.2% SDS reduced the Salmonella population by 3.2 log/cm2. Scrubbing hides with a brush processing for 30 s followed by the microbicide spray treatment further reduced Salmonella contamination by 0.5 log CFU/cm2. However, for wet hides, a spray treatment with 4% levulinic acid plus 2% SDS for 5 min reduced Salmonella by only 1.3 log CFU/cm2.
Significance: These in vitro studies provide needed for designing validation studies for this live cattle hide intervention treatment to reduce STEC and Salmonella contamination.