| Animal manures contain valuable nutrients which can be utilized for crop growth. Consequently, the wastes are often spread across field where produce is grown without treatment prior to land application. This practice is a potential threat to the environment and human health, as pathogens contained in the manures may have extended survival in soil, and could contaminate produce harvested for human consumption. Composting is a process that has been often implemented on-farm to inactivate pathogens resident in animal wastes. The objectives of this study were to: (1) perform a survey of South Carolina poultry farms to determine if the methods implemented resulted in the destruction of foodborne pathogens, and (2) determine the survival of E. coli O157:H7 in a dairy manure-based compost performed in uncontrolled environmental conditions.; In the survey of poultry farms, nine compost heaps at different stages in the composting process were analyzed on four poultry farms in upstate South Carolina. Both the materials used and composting methods differed among the farms surveyed. In the surveyed heaps, 71% of all internal samples contained moisture contents of less than 40%, which is considered as the minimum necessary for active composting. Ninety-one (91) of 141 compost samples analyzed were positive for coliform populations ranging from 1.00 to 6.00 log10 CFU/g. Approximately 94% of the surface samples analyzed were positive for coliforms, compared to less than 50% of the internal samples. Seventy-six percent of the surface samples were positive for presumptive Salmonella spp. Among all internal samples, ca. 26% and 19% were positive for presumptive Salmonella and Listeria spp, respectively. Both E. coli O157:H7 and L. monocytogenes was not detectedin any of the samples. Among finished compost samples (n=21), ca. 62%, 33%, and 14% were positive for coliforms, presumptive Salmonella, and presumptive Listeria, respectively.; In the investigation of the survival of E. coli O157:H7, two trials were performed involving duplicate compost heaps constructed on an outdoor, fenced site. The compost heaps were comprised of dairy manure, old hay, feed waste, a sawdust-calf feces mixture, and fresh hay. Samples of the composting mixture were inoculated with stx-negative E. coli O157:H7 B6914 at initial cell numbers of ca. 107 and 105 CFU/g for Trial 1 and Trial 2, respectively. Individual sample bags were placed on the surface and at three locations (top, center, and bottom) within each heap. In Trial 1, E. coli O157:H7 was detected by enrichment through 14 days within the heaps. When inoculated with 105 CFU/g in Trial 2, E. coli O157:H7 was detected only through days 2, 2, and 5 at the top, center, and bottom locations, respectively. For both trials, the pathogen survived at the heap's surface for up to 4 months. The indicator microorganism, E. coli, was inactivated at a rate similar to that of E. coli O157:H7.; Our studies demonstrated that foodborne pathogens may persist for extended periods of time in the compost surface. This is important because it suggests that improperly compost manures may serve as vectors in the dissemination of foodborne pathogens on food products intended for human consumption. |
