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E. coli Salmonella Max Teplitski2 1. This document is SL-239, a fact sheet of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date March 2006. Reviewed March 2009. Visit the EDIS Web site at http://edis.ifas.ufl.edu. 2. Max Teplitski, assistant professor, Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611-0290. Despite impressive gains in modern biology and medicine, diseases are not disappearing. On the contrary, humans and farm animals are constantly exposed to new pathogens and antibiotic-resistant strains of 'old bugs'. In the last two decades, Salmonella strain DT104 that is resistant to multiple antibiotics, and highly virulent E. coli strain O157:H7 were identified. While the majority of E.coli strains are non-pathogenic and normally reside in healthy human intestine, strain O157:H7 is estimated to cost the U.S. economy millions of dollars each year (ERS/USDA 2001a). Similarly, Salmonella is estimated to infect over 1.4 million Americans, and to cost the U.S. economy ~ $3 billion annually (ERS/USDA 2001b). Fairly or not, farming operations are often blamed for these disease outbreaks, as they have been associated with meat, poultry, produce and farm waste runoff. Significant effort has been made by universities and research agencies to help eliminate Salmonella and pathogenic E. coli from animal and dairy farms. This article highlights findings from these recent studies. Most Salmonella and pathogenic E. coli can infect humans, domestic animals, and many wild animals. Flies caught around farms often carry Salmonella, and shed up to ten million bacteria per dropping (enough to cause disease in a healthy adult male). On average, ten percent of pets, feral animals, and rodents carry Salmonella. Random samples from farms indicated that a similar percentage of farm animals may be infected. Infected animals (including horses, cattle and poultry) are not always visibly sick. However these 'asymptomatic' carrier animals shed billions of virulent organisms in each ounce of their feces. Virulent E. coli strains can survive for a few months in animal waste, and Salmonella can persist in untreated farm waste for up to two years (Winfield and Groisman 2003). Proper utilization and composting of animal wastes are important steps for reducing Salmonella and E. coli contamination, and breaking the cycle of reinfection. Contaminated animal and human wastes are important reservoirs of these pathogens. Farm run-off, contaminated with the E.coli O157:H7 strain along with other bacteria, was blamed for the
E. coli and Salmonella on animal farms: sources, survival and management 2 deadliest waterborne outbreak in North America (Holme 2003). Therefore, it is crucial to develop strategies for reducing or eliminating pathogens in farm wastes. Maintaining the temperature of composting animal waste at 160-170F for 2-3 weeks seems to effectively kill these pathogens. Forced aeration or manual turning of compost and the associated increased alkaline reaction also seem to reduce the Salmonella and E. coli bacteria numbers. Research also suggested that vermicomposting (composting using earthworms) eliminates Salmonella and E. coli from wastes (Kumar and Sukaran 2005), although the mechanism of this selective elimination is unknown. Kumar and Sukaran (2005) indicated that these pathogens were not detectable after passage through the guts of earthworms. Regardless of the composting method, during the first 2-5 weeks of composting, wastes and liquid runoff should be contained to prevent seepage of bacteria into ground water, where Salmonella can survive for months. The role of different bedding materials in survival of Salmonella and E. coli is unclear. On-farm studies at the Ohio State University indicated that there were fewer E. coli bacteria in cattle raised on sand bedding compared to those raised on wood shavings, while a German study reported that there was no difference in the number of Salmonella isolated from broilers raised on wood shaving bedding or on plastic trampoline floors. Other factors, like moisture content of different bedding materials, their temperature, processing, aeration, etc., may make interpretation of these results difficult. Salmonella and E.coli can contaminate healthy herds by several routes: 1) introduction of infected animals (pathogens then spread rapidly by mutual grooming or through infected water and feed); 2) contaminated drinking water; 3) flies and other insects; and 4) feeding improperly composted poultry litter. Poultry litter is commonly used as a cattle feed supplement, although some consumers may find this practice unappetizing. Most researchers agree that proper ensiling of broiler or turkey litter eliminates Salmonella and E. coli, and may increase digestibility of the feed (Davis, et al. 2002; Hopkins and Poore 2001). The use of deeply ensiled broiler or poultry litter, therefore, can be both economical and safe (Bucklin, et al. 2004, Butcher and Miles 2003.). On farms, harmful bacteria are often isolated from animal drinking water and water vessels. Once pathogens contaminate water vessels, they become established and form biofilms (bacterial communities encased in a protective slime layer). Frequent and thorough mechanical removal of microbial biofilms with brushes, hot water with soap, or diluted bleach solutions, is also effective in reducing the microbial loads in animal drinking water. To prevent survival of bacteria in drinking water, scientists suggest supplementation with sodium chlorate (Anderson, et al. 2000). Sodium chlorate targets a specific enzyme, respiratory nitrate reductase, found in Salmonella, E. coli and related bacteria. The reductase enzyme then processes sodium chlorate to the chlorite form, which is lethal to Salmonella and E. coli. Most representatives of normal microflora do not have the same enzyme, and therefore are insensitive to the chlorate treatment. This specificity is a major advantage of sodium chlorate over broad-spectrum non-selective antibiotics. Under laboratory conditions, sodium chlorate is effective at low concentrations (1.25 mM, which would correspond to a concentration of 0.13 g/L). Sodium chlorate has to be used and handled with caution, because it has known toxic effects at higher concentrations (1,200-1,700 mg/kg of body weight; EXTOXNET 1995). Because antibiotic resistance arises in bacteria at an alarming rate, much research has focused on finding alternative treatments that do not involve the use of antibiotics. For example, the promotion of beneficial gut bacteria can increase resistance of animals to possible Salmonella infections. Sources of beneficial gut bacteria may vary. Free-range chicks usually acquire such bacteria normally. Feed of pen-raised chicks may be supplemented with various commercial probiotic formulations. Probiotic or competitive exclusion bacterial mixes in the form of spray for eggs were also shown to be
E. coli and Salmonella on animal farms: sources, survival and management 3 moderately effective in inoculating hatchlings with beneficial gut organisms (Nisbet, et al. 1998; Nisbet 2002; Hume, et al. 1998). Alternatively, used poultry litter from healthy flocks could be used. Several studies demonstrated that raising newly hatched leghorn chicks on Salmonella-free littered bedding, or supplementation of their feed with litter, actually makes chicks more resistant to Salmonella infection. Supplementation of animal rations with corn or sorghum silage also increases animal resistance to infection, perhaps in part due to the beneficial lactic bacteria found in silage. This protective effect of beneficial bacteria in used litter and silage is probably similar to the commercial probiotics: beneficial bacteria colonizing animal guts outcompete and prevent Salmonella colonization and infection. These methods may help control Salmonella and pathogenic E. coli on the farm. Proper hygiene, (Simonne, et al. 2005)quarantining of new animals and certified testing, however, remain the most important and least expensive means to prevent the spread of harmful bacteria. Education of the farm personnel on microbiological safety is also important. To help meet these education demands, the Soil and Water Science Department (UF/IFAS) has developed a short course on the Ecology of Bacterial Pathogens Keeping E. coli and Salmonella out of Water Supplies, Recreation Areas, Pet Shops and Agricultural Produce. A course description is available online at: http://conference.ifas.ufl.edu/soils/pathogens. Always wash your hands with very warm water and soap before and after tending to animals (be it pets, cattle, poultry, wildlife or their products). Wash and disinfect soiled clothes, tools and work surfaces with hot soapy water and freshly prepared solutions of bleach (prepared according to the manufacturers instructions). Wearing bioprotective plastic footwear over shoes usually functions to minimize or prevent transfer of pathogens onto or off the farm. Anderson, R. C., S. A. Buckley, L. F. Kubena, L. H. Stanker, R. B. Harvey, and D. J. Nisbet. 2000. Bactericidal effect of sodium chlorate on Escherichia coli O157:H7 and Salmonella typhimurium DT104 in rumen contents in vitro. J Food Prot 63:1038-42. Bucklin, R. A., J.P. Jacob, R.A. Nordstedt, D.R. Sloan, R. S. Tervola, and F.B. Mather. 2004. Storage of Broiler Litter. UF/IFAS EDIS Fact Sheet PS-15. http://edis.ifas.ufl.edu/ps003. Butcher, G. D., and R. D. Miles. 2003. Minimizing Microbial Contamination in Feed Mills Producing Poultry Feed. UF/IFAS EDIS Fact Sheet VM93. http://edis.ifas.ufl.edu/vm054. Carver, K., M. J. Mahovic, R. M. Goodrich, and K. R. Schneider. 2005. Dealing with Foodborne Illness: Typhoid Fever, Salmonella Typhi. UF/IFAS EDIS Fact Sheet FSHN0514. http://edis.ifas.ufl.edu/fs125. Davis, J. R., J. K. Apple, D. H. Hellwig, E. B. Kegley, and F. W. Pohlman. 2002. The effect of feeding broiler litter on microbial contamination of beef carcasses. Bioresour. Technol. 84:191-196. ERS/USDA. 2001a. Briefing Room--economics of foodborne disease: E. coli. http://www.ers.usda.gov/briefing/FoodborneDisease/ ecoli/. ERS/USDA. 2001b. Briefing Room--economics of foodborne disease: Salmonella. http://www.ers.usda.gov/briefing/FoodborneDisease/ salmonella/. Extension Toxicology Network (EXTOXNET). 1995. Pesticide Information Profiles: Sodium Chlorate. http://extoxnet.orst.edu/pips/sodiumch.html. Holme, R. 2003. Drinking water contamination in Walkerton, Ontario: positive resolutions from a tragic event. Water Sci Technol 47(3):1-6. Hopkins, B. A., and M. H. Poore. 2001. Deep-stacked broiler litter as a protein supplement for dairy replacement heifers. J Dairy Sci 84, no. 2:299-305. Hume M. E., D. E. Corrier, D. J. Nisbet, J. R. DeLoach. 1998. Early Salmonella challenge time and reduction in chick cecal colonization following treatment with a characterized competitive exclusion culture. J Food Prot. 61(6):673-6.
E. coli and Salmonella on animal farms: sources, survival and management 4 Kumar, A. G., and G. Sekaran. 2005. Enteric pathogen modification by anaecic earthworm, Lampito mauritii. Journal of Applied Sciences and Environmental Management. 9:15-17 Nisbet, D. J. 2002. Defined competitive exclusion cultures in the prevention of enteropathogen colonisation in poultry and swine. Antonie Van Leeuwenhoek. 81(1-4):481-6. Nisbet, D. J., G. I. Tellez, V. K. Lowry, R. C. Anderson, G. Garcia, G. Nava, M. H. Kogut, D. E. Corrier, and L. H. Stanker. 1998. Effect of a commercial competitive exclusion culture (Preempt) on mortality and horizontal transmission of Salmonella gallinarum in broiler chickens. Avian Dis. 42(4):651-6. Petridis, H., G. Kidder, and A. Ogram. 2002. E. coli O157:H7 A Potential Health Concern. UF/IFAS EDIS Fact Sheet SL146. http://edis.ifas.ufl.edu/ss197. Schneider, K. R., R. M. Goodrich, and M. A. Kirby. 2003. Preventing Foodborne Illness: E. coli O157:H7. UF/IFAS EDIS Fact Sheet FSHN031. http://edis.ifas.ufl.edu/fs097. Schneider, K. R., R. M. Goodrich, and S. Z. Waithe. 2003. Preventing Foodborne Illness: Salmonellosis. UF/IFAS EDIS Fact Sheet FSHN0214. http://edis.ifas.ufl.edu/fs096. Simonne A., J. Brecht, S. Sargent, M. Ritenour, and K. R. Schneider. 2005. Good Worker Health and Hygiene Practices: Training Manual for Produce Handlers. UF/IFAS EDIS Fact Sheet FCS8769. http://edis.ifas.ufl.edu/fy743. Winfield, M. D., and E. A. Groisman. 2003. Role of non-host environments in the lifestyles of Salmonella and Escherichia coli. Appl Environ Microbiol 69:3687-3694.