Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 3, 2006
Publication Date: June 19, 2006
Citation: Ravva, S.V., Sarreal, C.Z., Duffy, B., Stanker, L.H. 2006. Survival of escherichia coli o157:h7 and salmonella enterica in manure waste water from dairy lagoons. Journal of Applied Microbiology. 101(2006):891-902 Interpretive Summary: Storing of manure waste water in lagoons is a common practice of dairies. Water conservation encourages the recycling of waste water for lane washing and for irrigation of crops ultimately used as silage on the dairy. In terms of the life-cycle analysis of foodborne pathogenic bacteria, a pressing question is whether holding lagoons are an on-site reservoir for long-term survival or proliferation of pathogens. If so, then understanding factors that influence pathogen competitiveness in this environment will facilitate development of intervention strategies to break the cycle. We monitored the survival of Escherichia coli O157:H7 and Salmonella enterica in manure waste water from on-site holding lagoons equipped with or without circulating aerators. We found that both pathogens failed to establish in manure waster water from both circulated and non-circulated lagoons. Both pathogens declined rapidly from dairy lagoon waste water, however, Salmonella declined with a lower decimal reduction rates from the circulated waters. These studies suggest that proper management of waste water before its use in irrigation or as fertilizer is essential to reduce pathogen transfer to food and fodder crops.
Technical Abstract: Aims: To determine the survival of Escherichia coli O157:H7 and Salmonella enterica in manure waste water from on-site holding lagoons equipped with or without circulating aerators. Methods and Results: Survival was monitored in microcosms of waste water with and without scale-size circulators. Laboratory strains used as inoculum had poor survival rates and none proliferated in water from lagoons with or without aerators. Water from manure lagoons equipped with circulators did not enhance the decline of E.coli O157:H7. In contrast, serovars of Salmonella declined significantly in circulated microcosms (D = 4.9 d) as compared to non-circulated microcosms (D = 7.8 d). Strain variation in survival was observed with both pathogens. A non-EHEC E. coli (MM260) isolated from the circulated lagoon was more competitive than any of the pathogens when reintroduced into the microcosms. The decline rate of E. coli O157:H7 Odwalla strain increased proportionately with the inoculum load. Introduced E. coli failed to establish itself in waste water even after four sequential inoculations simulating continuous fecal input to the lagoon. Conclusions: Escherichia coli O157:H7 and Salmonella enterica failed to establish and proliferate in waste water microcosms equipped with or without circulating aerators. Both pathogens declined rapidly from dairy lagoon waste water, however, Salmonella declined with a lower D value in the circulated waters. Significance and Impact of the study: This study furthers our knowledge of pathogen growth in manure waste water, and suggests that proper management of waste water before its use in irrigation or as fertilizer is essential to reduce pathogen transfer to crops.