Utilization of carbonate and ammonia-based treatments to eliminate Escherichia coli O157:H7 and Salmonella Typhimurium DT104 from cattle manure

Aims: The objective of this study was to investigate alkaline treatments of cattle manure to kill coliforms, Escherichia coli O157:H7 and Salmonella Typhimurium DT104 based on their inhibition by carbonate ion and ammonia. Methods and Results: Pure cultures of S. Typhimurium DT104 and E. coli O157:H7 strains were treated with sodium carbonate and ammonia to determine threshold inhibitory concentrations. Fresh cattle manure samples were inoculated with the same strains and their survival was determined after addition of sodium hydroxide, ammonium sulphate, sodium carbonate and/or urea. Control of CO₃^-2 and NH₃ concentrations in manure by pH adjustment to 9.5 with sodium hydroxide to more than 5 and 30 mmol l^-1, respectively, killed more than 10⁶ cells g^-1 in 7 days. Addition of sodium carbonate enhanced the killing effect of NaOH by increasing the CO₃^-2 and NH₃ concentrations. Addition of 100 mmol l^-1 urea, produced high levels of CO₃^-2 and NH₃ and decreased all bacterial counts by at least 10⁶ cells g^-1 after 7 days. Conclusions: Reduction of food-borne pathogens in manure can be achieved by a combination of high concentrations of CO₃^-2 and NH₃ which are pH-dependent parameters. Significance and Impact of Study: Addition of urea could provide a simple manure treatment by combining both antimicrobial factors.