Enhancing Food Safety Through Control of Food-Borne Disease Agents

NON-TECHNICAL SUMMARY: Some agriculture practices are related to food borne disease. Meat and fresh produce can be contaminated by exposure to manure during slaughter and organic fertilization. Develop pre-harvest strategies to reduce the fecal shedding of food borne pathogens by livestock. <P>

APPROACH: The inter-laboratory studies will be conducted in Alabama, Arkansaw, Iowa, Kentucky, Michigan, Minnesota, Mississippi, Nebraska, New York, North Carolina, South Carolina, Tennessee and Virginia. It is anticipated that the first annual project meeting will be devoted to the review, and subsequently to a priorization of the factors to be evaluated. Annual plans of work (POWs) will consist of experiemtns to be carried out by the participants to collect essential data for each factor. Subsequently, data will be interpreted by the participants so that recommendations can be made. The annual meetings will serve as the primary means of exchanging and comparing data.
<P>

PROGRESS: 2000/10 TO 2006/09<BR>
During the lifetime of this project three major projects were undertaken: 1) Development of a mixture of colicinogenic Escherichia coli capable of inhibiting E. coli O157:H7; 2) Utilization of sodium carbonate to treat cattle manure against pathogenic bacteria; and 3) Development of a model to predict the growth of Listeria monocytogenes in frankfurters. For the first completed project, an initial stage was developed to screen more than 500 E. coli isolates to identify organisms capable of inhibiting enterohemorrhagic E. coli. A total of 25 potentially colicinogenic E. coli from different animal species were identified and selected for further characterization. From this initial selection, a final number of 14 strains that were capable of producing from 1 to 4 colicins and that had no pathogenic genes were selected for testing in an animal trial. The collection of colicinogenic strains could also inhibit other STEC strains such as (O26, O111 and O153), but most Salmonella strains were resistant to their colicins. When calves artificially inoculated with E. coli O157:H7 were fed with a mixture of 8 colicinogenic E. coli strains capable of producing colicin E7 type, the fecal shedding of serotype O157:H7 was reduced from 1 to 1.5 log CFU/g in comparison to the control group and the colonization of intestinal tissues was significantly reduced. The potential for resistance to colicins was also investigated, which stressed the importance of using multiple colicins. In laboratory experiments to treat cattle manure against Salmonella and E. coli O157:H7, we were able to observe significant reductions of viable counts when samples were treated with sodium carbonate. Addition of 40 mM sodium carbonate to manure or adjustment of pH to 9 reduced bacterial counts to less than 10 CFU/g after 7 days, and the final carbonate concentration was 250 mM. Addition of 80 mM sodium carbonate or urea to pH-9.5 manure eliminated Salmonella, E. coli O157:H7 and fecal coliforms in 4 days. Urea stimulated the carbonate production rate (40 mM/day). These results indicate that the carbonate treatment of cattle manure to kill food-borne pathogens can be achieved in a relatively short time, and urea can also be used as source of carbonate. In a third project, the growth of Listeria monocytogenes was modeled based on the Monod and Arrhenius model, first based on a single strain. In that study, the effect of temperature on growth was determined using a novel approach of time to detect in liquid media and frankfurters. Additional experiments were conducted to identify the fastest growing strains among a collection of 19 strains at temperatures in the range of refrigeration temperature abuse. The parameters of the best fitting model were used to select the fastest growing strains. On 57 growth curves (19 strains at 3 temperatures), the linear Monod equation fit well for 93% of the growth curves, followed by Gompertz (70.1%), Baranyi-Roberts (52.6%) and Logistic (42.1%) models. These results indicated that a simple linear model also could adequately describe bacterial growth and be used for selection of the fastest growing organisms.
<BR><BR>
IMPACT: 2000/10 TO 2006/09<BR>
The control of foodborne pathogens on the farm is critical for the prevention of gastrointestinal disease. E. coli O157:H7 could be controlled in its national reservoir with competing bacteria and with manure treatments. Colicinogenic E. coli could offer a novel alternative to displace pathogenic E. coli from the gastrointestinal tract of cattle. Safety-based growth models are a very useful tool for risk assessment of Listeria monocytogenes in deli meats.