Accelerating the Deactivation of Salmonella enterica Serovar Newport and Escherichia coli O157:H7 in Dairy Manure by Modifying pH or Temperature

Abstract

To assess methods for control of disease-causing bacteria in animal manures prior to field application, we manipulated the temperature or adjusted pH of dairy manure to high (3.5 to 5) or low (10 to 12) values with aluminum sulfate or hydrated lime, and inoculated the manure with Salmonella enterica serovar Newport or Escherichia coli O157:H7, then incubated the manure at ambient temperature. At pH  4.2, S. Newport was eliminated within 6 days; however at pH >4.2 S. Newport was suppressed only temporarily and recovered to concentrations near the unamended controls. pH required to eliminate E. coli O157:H7 was  4.5. Both pathogens were killed by pH  11.0. The pathogens were eliminated within 2 weeks when inoculated manure was incubated at 37°C, whereas at 22°C and 4°C, the organisms persisted for much longer periods. S. Newport survived for over 300 days at 4°C, which has implications for manure spreading in colder seasons.