Disinfectant and Antimicrobial Susceptibility Profiles of Salmonella Strains from Feedlot Water-Sprinkled Cattle: Hides and Feces

The disinfectant and antimicrobial susceptibility profiles of 145 Salmonella strains obtained from feedlot water-sprinkled cattle were determined. A low prevalence of antimicrobial resistance (AMR) was observed, resistance was primarily observed to streptomycin (29.7%) and sulfamethoxazole (8.3%). All strains were susceptible to the 8 fluoroquinolones tested. The most common AMR traits were streptomycin resistance in serovar Kentucky, sulfamethoxazole resistance in Muenster and Cerro and amoxicillin/clavulanic acid-ceftiofur resistance in Meleagridis. Salmonella were more resistant to the disinfectants P-I, DC&R and Tek-Trol and disinfectant component THN than to other disinfectants. All strains were susceptible to triclosan, and all strains were resistant to chlorhexidine. Nearly 1/3 of the strains had low level resistance to benzalkonium chloride. The benzyl ammonium chlorides (BACs) C12, C14 and C16 were the most active ingredient in the disinfectant DC&R. C14BAC and C16BAC were shown to be more active as a disinfectant than was C12BAC. Didecyldimethyl ammonium chloride (C10AC) was the most active ingredient in the disinfectant P-128, and the most active ammonium chloride in this work and in all of our previous studies. No cross-resistance was observed. All manufacturer recommended application levels were above the observed MICs. However, observed MICs for DC&R and Tek-Trol were close to the suggested application rates and a small error in the disinfectant dilution could easily render these disinfects non-functional. The continued use of THN and formaldehyde in DC&R is questionable because these components are not effective, and their inclusion results only in additional unwanted chemicals in the environment.