Theses and Dissertations

Issuing Body

Mississippi State University


Wang, Chiling

Committee Member

Bailey, Richard H.

Committee Member

Hood, Anna

Committee Member

Huston, Carla

Committee Member

Wills, Robert W.

Date of Degree


Document Type

Dissertation - Open Access


Veterinary Medicine

Degree Name

Doctor of Philosophy


College of Veterinary Medicine


Veterinary Medical Science Program


Sampling in onarm production environments presents challenges that must be considered when doing hazard analysis. The sensitivity and specificity of the test used and the sample types chosen will have an impact on the food safety outcome and food safety decisions made during the interpretation of results. In this work, broiler houses were sampled for the presence of Salmonella spp. using two different sampling strategies and four different microbiological isolation procedures. The study was undertaken after complications arose during a field study evaluating the role darkling beetles play in the transmission of foodborne pathogens. It was determined that, based on this work, incorporating a secondary enrichment procedure into the isolation protocol significantly increased the isolation rate from the various sample types, including drag swabs and litter samples. It was also determined that when attempting to characterize the Salmonella-status of a particular broiler house, no one sampling strategy is superior. The results of this study demonstrate that both drag swabs and litter samples need to be utilized to accurately determine if the pathogen is present in a flock. Not only did the secondary enrichment procedure have a higher isolation frequency than the other three methods compared, it also highlighted the discrepancies of the other methods. Two commonly used isolation procedures, tetrathionate and Rappaport-Vassiliadis, were found to disagree on a significant number of samples analyzed. While the isolation frequencies for these procedures were not found to be statistically different, the analysis for agreement, kappa, did indicate that the procedures did not identify the same samples as positive. Overall, the secondary enrichment procedure identified all the samples positive that were also found to be positive by either of the other methods used. Since the secondary enrichment method is a modified version of the traditional delayed secondary enrichment procedure, which requires five additional day of incubation, this study also compared these two procedures. It was determined that the secondary enrichment protocol was as effective for isolating Salmonella from broiler house samples as the delayed secondary enrichment procedure. The secondary enrichment procedure, did however, provide for a quicker turn around for results.