Reduction of Shiga Toxin-Producing E. coli and Salmonella Typhimurium on Cattle Hides by Spray Treatment with “Fit-L” (Levulinic Acid plus Sodium Dodecyl Sulfate)

Abstract

The efficacy of levulinic acid plus sodium dodecyl sulfate (SDS) at different concentration to inactivate STEC and Salmonella Typhimurium on cattle hides in vitro and in vivo as a surface spray treatment was determined. A mixture of six isolates of STEC, including serovars O26, O45, O103, O111, O121, and O157 (10 8 CFU/ml) and a mixture of 5 strains of S. 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 21˚C for 72 h or held 4˚C for 24 h. The hides were treated by surface spray with a commercial microbicide (Fit-L) at different concentrations at 45 psi for 15 s. Water only applied at 45 psi for 15 sec 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. For STEC-contaminated hides, treatment of Fit-L diluted at 1:11 (v/v) in tap water (4% levulinic acid plus 0.4% SDS for 5 min reduced STEC populations by 3.7 log CFU/cm 2 , when compared with the water only treatment. For S. Typhimurium-contaminated hides, treatment of Fit-L reduced the Salmonella population by 4.6 log CFU/cm2. Scrubbing hides with a brush for 30 s followed by Fit-L spray treatment further reduced Salmonella contamination by 0.5 log/cm2. Fit-L product diluted in tap water at 1:22 (v/v, 2% levulinic acid plus 0.2% SDS) was used as a surface wash for live beef cattle. Results revealed that surface spray of cattle with Fit-L reduced the E. coli population by 3.4 log CFU/cm2 at 5 min when compared with the tap water wash only control. No adverse effects for the cattle were observed after the spray treatment.