Research Article: Comparative study on the efficacy of sodium hypochlorite, aqueous ozone, and peracetic acid in the elimination of Salmonella from cattle manure contaminated various surfaces supported by Bayesian analysis

Date Published: May 23, 2019

Publisher: Public Library of Science

Author(s): Ameer Megahed, Brian Aldridge, James Lowe, George-John Nychas.


Providing the dairy industry with an effective and safe disinfectant is considered a key step in improving the farm hygiene and biosecurity. Salmonella infection via foodborne transmission remains a major public health threat. The main objective of this study was therefore to characterize and compare the decontamination power of NaOCl, aqueous-O3, and PAA against cattle manure based-Salmonella heavily contaminated various surfaces (plastic, nylon, rubber, and wood) using Bayesian analysis. In a crossover design, 14 strips of each material were randomly assigned between 3 groups, treatment (n = 6), positive-control (contaminated with feces-Salmonella mixture, but not exposed to disinfectants, n = 6), and negative control (laboratory blank, inoculated only with sterile water, n = 2). The strips were soaked in cattle manure inoculated with 107–108 of Salmonella Typhimurium-Choleraesuis (aSTC) and exposed to 50 mL of 200 ppm NaOCl, 9 ppm aqueous-O3, or 400 ppm PAA for 4 minutes. Bayesian methods were used for analysis. On plastic and nylon surfaces, NaOCl, aqueous-O3, or PAA reduce aSTC population to a safe level (>5.0-log10) within 4 minutes. On rubber surface, PAA and aqueous-O3 can produce a reduction in aSTC population 50% and 30% higher than NaOCl with posterior probabilities of 97% and 90%, respectively. However, PAA can produce reduction factor on wood surface 40% higher than aqueous-O3 and NaOCl with posterior probabilities of 97% and 73%, respectively. We conclude that smooth surfaces were most effectively decontaminated. Peracetic acid of 400 ppm can provide an effective means for controlling Salmonella population heavily contaminated various surfaces in dairy operations. However, the safe residues and strong reactivity makes aqueous-O3 and PAA attractive alternative disinfectants for improving farm hygiene and biosecurity.

Partial Text

Salmonellae are widespread among animals and considered one of the most reported zoonosis worldwide [1]. Approximately 94% of human Salmonellosis are foodborne via contact with infected animals or animal-related products. Salmonella contamination of the environment and food chain mostly comes from the infected fecal wastes of animals or humans [2]. Salmonella has a great impact on health and economic in both humans and animals. The annual economic costs from salmonellosis are approximately $3.7 billion [3]. In the dairy industry, the daily use of biocides is a common practice to minimize the introduction of these pathogens into food chains, environment, and consequently transmission to humans.

The first major finding of the study reported here was that PAA at a concentration of 400 ppm can provide an effective method for improving farm hygiene and biosecurity. The second major finding was that aqueous-O3 at a concentration of 9 ppm can provide an attractive alternative for NaOCl of 200 ppm for controlling manure-based Salmonella contaminated various surfaces in the dairy operations, even at high Salmonella population and in the presence of high organic matter. The third major finding was that using washing water can provide a practical sampling method for evaluating the decontamination power of biocides especially on contaminated simple surfaces. To the best of our knowledge, this is the first study used Bayesian analysis for describing and comparing the decontamination power of NaOCl, aqueous-O3, and PAA on heavily contaminated various surfaces with dairy cattle manure-based Salmonella in a worst case situation, such as may accidentally occur if cleaning were insufficient.

This study provides an accurate and practical guide for controlling Salmonella in the dairy operations, where the chlorine-based disinfectants, aqueous-O3, and PAA can provide an efficient method for controlling the heavy bioload of Salmonella contaminated smooth surfaces in dairy operations. However, achieving high levels of aSTC reduction on complex surfaces in the presence of high organic matter is considered a challenge for NaOCl and aqueous-O3, but the low production of harmful residues makes aqueous-O3 and PAA with high concentrations attractive alternative disinfectants for improving farm hygiene and biosecurity.




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