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Viability of zoonotic pathogens Escherichia coli and Salmonella in swine manure slurries with and without a urease inhibitor and thymol.

Wells JE, Varel VH

USDA-ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933-0166, USA. jim.wells@ars.usda.gov

AIMS: To determine the effects of urine, a urease inhibitor and/or an odour-reducing antimicrobial compound, on zoonotic pathogens in swine manure slurries. METHODS AND RESULTS: Swine faeces were collected and blended with different amounts of urine. Marker strains of Salmonella enterica subsp. enterica serovar Typhimurium and Escherichia coli O157:H7 were inoculated into the manure slurries with or without the urease inhibitor, N-(n-butyl) thiophosphoric triamide, or the antimicrobial compound thymol. In slurries containing approximately 1 : 1 or 2 : 1 of urine and faeces, the decreases in colony forming units (CFU) of Salm. Typhimurium and E. coli were similar and few counts were observed after 14 days. When the urine content of the slurry was increased to 5 : 1, both strains died off rapidly. When NBPT was added to the slurries, pathogen CFU was not affected in the 1 : 1 slurry. The 2 : 1 and 5 : 1 slurries had higher urea content and NBPT increased CFU of both pathogens. Thymol addition rapidly killed the pathogens and few CFU of Salmonella or E. coli were observed after day 1. CONCLUSIONS: These experiments demonstrate that urea hydrolysis in swine manure affects pathogens. Inhibition of urea hydrolysis may promote pathogen viability. SIGNIFICANCE AND IMPACT OF THE STUDY: Manure amendments that prevent urea hydrolysis may promote pathogen persistence. Additional treatments with antimicrobials may be required to kill pathogens.

Published 20 March 2008 in Lett Appl Microbiol, 46(4): 477-82.
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