Multi-drug resistant (MDR) Salmonella serovars are among the most important fooodborne pathogens worldwide. Previously, our research group reported the common occurrence of MDR Salmonella serovars in swine production environment regardless of antimicrobials use status in the production units.
These findings imply that selective pressure, other than antimicrobial use could be an important risk factor for the emergence and persistence of MDR Salmonella in the swine and potentially in other food animal production environments. Various chemical interventions such as biocides in the production environment and heavy metal micronutrients including copper and zinc in feed are commonly applied in commercial swine production systems. The role of these interventions, their epidemiological relationship and impact on the food safety important pathogens such as MDR Salmonella has not been understood. Preliminary investigations suggest the use of biocides and heavy metal micronutrients may be associated with antimicrobial resistance with some evidence that these interventions could have variable impact on occurrence and persistence of multi-drug resistant Salmonella. Our hypothesis is that the use of specific classes of biocides (disinfectants) and heavy metal micronutrients (copper and zinc) is associated with the occurrence and persistence of biocide, heavy metal resistant Salmonella and associated with multiple antimicrobial resistant Salmonella in the swine production environment.
To address this hypothesis, we use a longitudinal group (barn) randomized controlled study. In three different production systems, three farms per system, and four barns per farm have been selected. Fecal and feed samples will be collected to measure covariates (copper and zinc concentrations) and outcome variables (Salmonella prevalence and antimicrobial susceptibility). In addition assigned barn floor swabs are collected before and after disinfection of each barn and before placement of pigs in barns. During the study period six different batches of finisher pigs will be sampled in each barn. Resistance to biocides (three classes of disinfectants) and heavy metal micronutrients (copper and zinc) will be tested and their association with multi-drug resistance determined. We believe that the findings of this work could enable us to identify important risk factors for the occurrence and persistence of MDR Salmonella in swine production and the results could also have significant implications in other food animal production systems.
Bayleyegn Molla (Project Manager)
Wondwossen Gebreyes (Principle Investigator)
W.E. Morgan Morrow (Co-PI, North Carolina State University)
Paivi Rajala-Schultz (Associate Professor, The Ohio State University)
Elizabeth Dayton (Research Scientist, The Ohio State University)
USDA NRI 2007-01778 Project
Molla B, Sterman A, Mathews J, Artuso-Ponte V, Abley M, Farmer W, Rajala-Schultz P, Morrow WE, Gebreyes WA. Salmonella enterica in commercial swine feed and subsequent isolation of phenotypically and genotypically related strains from fecal samples. Appl Environ Microbiol. 2010 Nov;76(21):7188-93.
Zewde BM, Robbins R, Abley MJ, House B, Morrow WE, Gebreyes WA. Comparison of Swiffer wipes and conventional drag swab methods for the recovery of Salmonella in swine production systems. J Food Prot. 2009 Jan;72(1):142-6.