Molecular Characterization and Predictive Modeling of Salmonella spp. Recovered from Processed Poultry

NON-TECHNICAL SUMMARY: Salmonella spp. are recognized as major food-borne pathogens in the United States, causing an estimated 1.4 million cases of salmonellosis and over 500 death annually. Food of animal origin, especially poultry and poultry products, has been implicated in outbreak of human salmonellosis. A number of investigators have suggested that processing conditions may play a significant role in promoting/influencing the selection of pathogens during processing. Consequently, we investigated the prevalence and antimicrobial resistance of Salmonella spp. recovered from pre- and post-chill poultry carcasses. Our laboratory is analyzing the Salmonella spp. isolated from processed poultry by DNA fingerprinting to determine the genetic relationship. However, little information is available about the association between the presence of virulence factors in Salmonella spp. and their potential for causing human illness. In addition, there is lack of knowledge about the distribution of Salmonella contamination on the chicken carcass; especially for young chickens in the Cornish game hen class. Moreover, adequate information is not available about the development of predictive models for the growth of Salmonella in processed poultry as a function of strain variation under various environmental conditions. The purpose of this study is molecular characterization and predictive modeling of Salmonella spp. recovered from processed poultry. <P>APPROACH: Four hundred fourteen isolates of Salmonella recovered from processed poultry will be tested for three virulence genes by polymerase chain reaction to understand the association between the presence of virulence genes and their potential for causing human illness. In addition to three virulence genes, two bioassays will be used to evaluate pathogenic potential of the Salmonella isolates. Moreover, a total of 125 Samlonella spp. isolated from Cornish game hens will be analyzed by antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) to determine the clonal distribution of contamination on the chicken carcasses. Fifteen to twenty five isolates from PFGE clusters will be selected to develop predictive models for the growth of Salmonella on processed poultry as a function of strain variation under different environmental conditions such as different pH, temperature and chlorine concentrations. To develop primary models, growth of Samlonella spp. will be determined in pure broth cultures and on processed chicken at different combinations of temperature, pH and chlorine by standard methods. The experimental data will then be fit to an appropriate primary model to estimate values for growth/death parameters, such as lag phase duration, specific growth/death rate and maximum population density using Graph Pad Prism curve-fitting software. Secondary models (response surfaces) will be produced using SAS (SAS Institute, Cary, NC) software to select candidate models for bacterial behavior parameters as a function of strain variation under various environmental conditions. Secondary models will be validated by using model independent data under various environmental conditions. Model performance will also be measured by the established methods.