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Evaluation of the Decontamination Power of Aqueous and Gaseous Ozone on Various Contaminated Surfaces with Cattle Manure containing Salmonella

Ameer Megahed, Brian A and James Lowe

Despite using ozone (O3) as an attractive alternative disinfectant for more than a century, little is known about the killing capacity of O3 against Salmonella contaminated different surfaces in dairy operations. Accordingly, our objective was to characterize the killing capacity of aqueous and gaseous O3 at different operational conditions on Salmonella Typhimurium and Salmonella Choleraesuis (aSTC) contaminated plastic, metal, nylon, rubber, and wood surfaces. In a crossover design, 14 strips of each material were randomly assigned between 3 groups, treatment (n=6), positive-control (n=6), and negative-control (n=2). The strips were loaded with aSTC (107-108) and exposed to aqueous O3 of 2, 4, and 9 ppm for 4 minutes, and gaseous O3 of 1 and 9 ppm for 30, 60, and 120 minutes. Plastic and metal surfaces were most effectively decontaminated, an aqueous O3 of 4 ppm reduced aSTC by 6.7 and 5.2- log10, respectively, and 9 ppm resulted in no detectable aSTC. On nylon and rubber, aqueous O3 of 9 ppm reduced aSTC population to a safe level (5.8 and 5.1-log10). On wood, both aqueous and gaseous O3 at up to 9 ppm were unable to reduce aSTC to undetectable limit. Interestingly, aSTC load and sequential washing showed same impacts on the reduction rate of aSTC on complex surfaces. Our findings strongly indicate that aqueous O3 of 9 ppm for 4 minutes exposure is an effective means to clear smooth surfaces of a high Salmonella load. However, sequential washing or decrease the bacterial load is needed to effectively decontaminate complex surfaces.