|Ravva, Subbarao - Subba|
Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2007
Publication Date: 4/1/2007
Citation: Ravva, S.V., Korn, A.M. 2007. Extractable Organic Components and Nutrients in Wastewater Influence the Growth of Escherichia coli 0157:H7 in Dairy Lagoons. Applied and Environmental Microbiology. 73(7):2191-2198. Interpretive Summary: Outbreaks of foodborne illnesses caused by pathogenic bacteria are increasingly being linked to fresh produce. Animal manure is a potential pathogen reservoir, and the close proximity of dairy operations and croplands in California cannot be ignored. We have worked on developing improved detection methods for pathogens, and on understanding how manure management systems affect the chemical environment on dairies. Our long-term goals are to develop integrated manure management systems that reduce pathogen numbers on dairies, thereby reducing chances for food contamination in the field. Data on survival and growth of a foodborne pathogen, Escherichia coli O157:H7, as influenced by the nutrients and other components of wastewater from manure lagoons are presented.
Technical Abstract: The influence of nutrients in wastewater from dairy lagoons on the survival of Escherichia. coli O157:H7 was monitored. Initially, the survival of E. coli in wastewater was compared with or without removing the competing native organisms by filter-sterilization or autoclaving. E. coli declined rapidly in filter-sterilized water and exhibited a slower decline in non-sterile water, while they proliferated in autoclaved water. Subsequently, the growth of E. coli O157:H7 strains was monitored in 300 MICRO volumes of filter-sterilized wastewater supplemented with incremental proportions of LB broth. E. coli strains grew incrementally with LB supplementation, but failed to grow in filter-sterilized wastewater. Consequently, the influence of organic extracts of wastewater on the growth of E. coli in LB media was monitored, followed by scale-up tests in wastewater from lagoons. Acidic and basic extracts of wastewater inhibited the growth of E. coli in LB, while the neutral aqueous extract improved growth. However, a scale-up with a 3-fold increase of acidic components supplemented to wastewater did not result in any additional decline of E. coli O157:H7 as compared with the unsupplemented wastewater. When protected inside a 300 kDa dialysis tube and exposed to diffusible components of wastewater, E. coli survived longer with a decimal reduction time of 18.1 days as compared to 3.5 days when inoculated directly to the wastewater. Although wastewater can potentially provide nutrients to naturally occurring human pathogens, components in wastewater and other interactions with native organisms in dairy lagoons can influence the growth of freshly introduced pathogens from manure.