@article{payne_li_santos_williams_sheldon_2011, title={Survey of Salmonella populations from swine waste-treatment technologies}, volume={19}, number={2}, journal={Journal of Swine Health and Production}, author={Payne, J. B. and Li, X. and Santos, F. B. O. and Williams, M. and Sheldon, B. W.}, year={2011}, pages={100–106} }
 @article{payne_osborne_jenkins_sheldon_2007, title={Modeling the growth and death kinetics of Salmonella in poultry litter as a function of pH and water activity}, volume={86}, ISSN={["1525-3171"]}, DOI={10.1093/ps/86.1.191}, abstractNote={Contaminated poultry litter, serving as a reservoir for Salmonella, can be linked to both food safety concerns when contaminated birds enter processing plants and environmental concerns when used as a fertilizer. Predictive modeling allows for the estimation of microbial growth or inactivation as a function of controlling environmental growth factors. A study was conducted to observe the combined effects of pH and water activity (A(w)) at a constant temperature on Salmonella populations in used turkey litter to predict microbial response over time. Litter, first pH-adjusted and then inoculated with a 3-strain Salmonella serovar cocktail to an initial concentration of approximately 10(7) cfu/g, was placed into individual sealed plastic containers with saturated salt solutions for controlling A(w). A balanced design including 3 A(w) values (0.84, 0.91, 0.96), 3 pH values (4, 7, 9), and a constant temperature of 30 degrees C was used, with litter samples periodically removed and analyzed for Salmonella populations, pH, and A(w). At each combination of environmental factors, the Churchill or exponential inactivation mathematical models were used to describe the growth and death of Salmonella over time. Salmonella populations exhibited growth (approximately 2 log) with little decline up to 42 d in litter environments of pH 7 and 9 and a A(w) of 0.96. As litter A(w) and pH levels were reduced, populations declined, with the most drastic reductions (approximately 5 log in 9 h) occurring in low-pH (4) and low-A(w) (0.84) environments. Generalized models for bacterial growth and death under grouped pH environments were successfully developed to predict Salmonella behavior in litter over time. These findings suggest that the best management practices and litter treatments that lower litter A(w) to < or =0.84 and pH to < or =4 are effective in reducing Salmonella populations. The use of a single equation to predict the growth and decline of Salmonella populations as a function of pH and A(w) has potential application for use in the development of effective pathogen control strategies at the farm level.}, number={1}, journal={POULTRY SCIENCE}, author={Payne, J. B. and Osborne, J. A. and Jenkins, P. K. and Sheldon, B. W.}, year={2007}, month={Jan}, pages={191–201} }
 @article{li_payne_santos_levine_anderson_sheldon_2007, title={Salmonella Populations and Prevalence in Layer Feces from Commercial High-Rise Houses and Characterization of the Salmonella Isolates by Serotyping, Antibiotic Resistance Analysis, and Pulsed Field Gel Electrophoresis}, volume={86}, ISSN={0032-5791}, url={http://dx.doi.org/10.1093/ps/86.3.591}, DOI={10.1093/ps/86.3.591}, abstractNote={Salmonella species are recognized as a major cause of foodborne illnesses that are closely associated with the consumption of contaminated poultry and egg products. The objectives of this study were to evaluate the Salmonella populations and prevalence in layer feces during the laying cycle and molting of the hen and to characterize the layer fecal Salmonella isolates by serotyping, antibiotic resistance analysis, and pulsed field gel electrophoresis. Fecal samples were collected from a commercial layer complex consisting of 12 houses. Composite fecal samples across each row were collected as a function of bird age [18 wk (at placement), 25 to 28 wk (first peak of production cycle), 66 to 74 wk (molting), and 75 to 78 wk (second peak of production cycle)]. Bird ages and molting practice did not significantly affect (P > 0.05) Salmonella populations with an average of 1.25, 1.27, 1.20, and 1.14 log most probable number/g for the 18-, 25- to 28-, 66- to 74-, and 75- to 7-wk birds, respectively. However, the 18-wk birds had the highest prevalence of Salmonella (55.6%), followed by the 25- to 28-wk birds (41.7%), 75- to 78-wk birds (16.7%), and 66- to 74-wk birds (5.5%). Of the 45 Salmonella isolates characterized, the most predominant serovar was Salmonella Kentucky (62%). Thirty-five percent of the Salmonella isolates were resistant to at least 1 antibiotic. As expected, considerable genetic diversity was observed within and across the different serovars.}, number={3}, journal={Poultry Science}, publisher={Elsevier BV}, author={Li, X. and Payne, J.B. and Santos, F.B. and Levine, J.F. and Anderson, K.E. and Sheldon, B.W.}, year={2007}, month={Mar}, pages={591–597} }
 @article{santos_li_payne_sheldon_2005, title={Estimation of most probable number Salmonella populations on commercial North Carolina turkey farms}, volume={14}, ISSN={["1537-0437"]}, DOI={10.1093/japr/14.4.700}, abstractNote={Abstract Salmonellae are one of the primary causes of human gastroenteritis in the United States. Although there are many foods that may be contaminated with Salmonella, poultry products are one of the major vehicles for transmitting this organism to humans. However, the national incidence of poultry product contamination with Salmonella has declined since adoption of the Hazard Analysis and Critical Control Point (HACCP) food safety program. Further reductions in carcass contamination may require other approaches such as the adoption of on-farm pathogen reduction strategies. In this study Salmonella prevalence and populations from fresh excreta and litter composite samples taken from 12 commercial turkey farms were enumerated using the most probable number (MPN) method and compared as a function of farm, season (summer and winter), and bird age (3 vs. 19 wk). Moreover, litter pH, temperature, moisture content, water activity, and ammonia levels were monitored. All farms were Salmonella positive for at least one season, and populations ranged from 5.3 log MPN/g. Of the 48 separate fecal and litter composite samples analyzed, 70 and 79% were Salmonella-positive, respectively. Although the MPN enumeration method is much more labor intensive and costly than the prevalence method, it yields estimates of Salmonella populations instead of merely indications of presence or absence of the organism. Moreover, our findings demonstrated that the MPN method is significantly more sensitive compared with the prevalence procedure (for fecal samples). This study also demonstrated that Salmonella can be present at high populations during turkey production and that their populations and prevalence were significantly impacted by flock age (litter) and season by farm interactions (fecal). Furthermore, litter Salmonella populations appear to be associated with the interrelated parameters of litter pH, ammonia and moisture content.}, number={4}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Santos, FBO and Li, X and Payne, JB and Sheldon, BW}, year={2005}, pages={700–708} }
 @article{payne_kroger_watkins_2005, title={Evaluation of disinfectant efficacy when applied to the floor of poultry grow-out facilities}, volume={14}, ISSN={["1537-0437"]}, DOI={10.1093/japr/14.2.322}, abstractNote={Abstract A common practice is to wash and disinfect poultry grow-out barns after used litter has been removed. Because the floor of poultry barns includes the presence of soil and organic matter, a study was conducted to determine if disinfectants are effective in reducing bacterial and fungal populations. Commercial broiler houses were chosen as the test sites for the field trials. After the litter was removed from the facility, the floor was swept clean in the middle of the barn and between feed and water lines. Floor plots (1 ft2) were randomly assigned to 1 of 4 disinfectant treatments. The disinfectants evaluated were a phenolic compound, a quaternary ammonium compound, a nascent oxygen compound, and a compound that contains potassium peroxymonosulfate and sodium chloride as the active ingredients. Laboratory trials were also conducted to test the same 4 disinfectants. Nalidixic acid-resistant Salmonella Typhimurium (NAL-SAL) was inoculated onto sterile topsoil in metal pans. Each disinfectant was applied as a coarse spray (field trials) or via pipette (laboratory trials), and surface samples were taken over time. Samples were cultured to determine total aerobic bacterial plate counts, yeast and mold counts, and the prevalence of Campylobacter spp., and Salmonella spp., for the field trials, whereas the laboratory trial samples were cultured for populations of NAL-SAL. There was no significant difference in the prevalence of Campylobacter for any of the treated plots compared with the control plots for the field trials. Significant microbial population reductions were observed for most of the disinfectants tested in both field and laboratory trials. Results indicate that disinfectant type, application rate, time of exposure, and organic matter can impact total aerobic bacterial, yeast and mold, and Salmonella populations on the surface of soil.}, number={2}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Payne, JB and Kroger, EC and Watkins, SE}, year={2005}, pages={322–329} }