The Distribution of in Pasture-Raised Broiler Farm Soils Is Potentially Related to University of Vermont Medium Enrichment Bias toward over .

The occurrence of has been widely investigated in the poultry production chain from the processing plant to the final product. However, limited data are available on species, including , in the poultry farm environment. Therefore, fecal and soil samples from 37 pastured poultry flocks from 10 all-natural farms over 3 years were assessed to determine the prevalence and diversity of within these alternative poultry farm environments using standard cultural and molecular methods. species were isolated in 15% of poultry farm samples and included (65.7%), (17.4%), and (15.1%). Additional multiplex PCR serotyping showed group 1/2a-3a to be the most dominant serovar group. Based on these results, monoculture growth experiments were conducted on four soil isolates (three isolates representing the three recovered serovar groups and one isolate) to determine if culture medium [tripticase soy broth (TSB) and University of Vermont modified enrichment broth (UVM)], inoculum concentration (10 or 10 CFU/ml), or incubation temperature (20, 30, and 42°C) differentially affected these species. Overall, very few significant growth differences were observed between the behavior of the three isolates (representing the three recovered serovar groups) under the growth conditions tested. Alternatively, at 30°C in UVM with the lower inoculum concentration, the isolate had a significantly shorter lag phase than the isolates. In coculture growth studies under these same incubation conditions, the lag phase of and was similar, but the final concentration of was significantly higher than . However, cocultures in UVM for high inoculum concentration did not show preferential growth of over . These results indicate that the use of UVM as an enrichment medium may preferentially allow to outcompete at low concentrations, biasing the prevalence from these farm samples toward and potentially underreporting the presence of in these environments.