To pursue functional genetic characterization of Listeria monocytogenes, with focus on epidemic-associated clones implicated in the majority of foodborne listeriosis, and to apply genomic data-based subtyping for Listeria. To better elucidate the molecular ecology of Listeria in nature and in the processing plant environment, including the role of plasmids, phages, and genes involved in heavy metal and disinfectant resistance. To identify and characterize genetic attributes associated with the ability of Campylobacter to colonize food animals (poultry, swine, cattle) in vconventional and organic production systems and to identify potential host-associated genetic markers. To further investigate resistance of Campylobacter to antimicrobials. To further elucidate mechanisms for dissemination of resistance genes among campylobacters from food animals. To characterize potential associations between production system, hosts, population structure, and antimicrobial susceptibility profiles in Campylobacter from food animal production systems.
NON-TECHNICAL SUMMARY: Listeria monocytogenes and Campylobacter are leading bacterial foodborne pathogens in the United states and other industrialized nations. Listeria is implicated in foodborne disease with high mortality, and has resulted in serious economic damages to the food industry. Campylobacter is the leading bacteria agent of human diarrheal disease, and has become highly problematic due to its propensity to acquire resistance to antimicrobial agents, including those typically used for treatment of human infections. This project pursues the characterization of genetic, ecologic, and virulence attributes of Listeria strains which have been responsible for major outbreaks of foodborne disease. The purpose of the Listeria study is to contribute to science-based approaches to effectively monitor these problematic strains, and to design intervention strategies for foods and the processing plant environment. The project also investigates population structure and host associations of Campylobacter colonizing different food animals (poultry, swine, cattle), and pursues the elucidation of emergence and dissemination of antimicrobial resistance in this pathogen. The purpose of the Campylobacter study is to promote the molecular epidemiologic characterization of this pathogen, to identify and characterize molecular tools with potential for source-tracking applications, and to contribute to design of science-based strategies for eventual reduction of prevalence and antimicrobial resistance in this important zoonotic pathogen.
APPROACH: Molecular and genetic approaches utilizing genome sequence data for Listeria and Campylobacter will be employed in combination with bacteriological assays evaluating growth, biofilm formation, and stress tolerance. Hybridizations utilizing array formats will be employed for genome-level syubtyping (genomotyping), and transcriptional arrays will be used to investigate the impact of gene deletion on transcriptional profile of the organisms. When needed, subtyping will be supplemented with other tools, such as pulsed field gel electrophoresis and multiple locus sequence typing. Virulence involvement of relevant determinants will be pursued in collaboration with investigators employing animal and cell culture models. Classical bacteriologic and genetic procedures will be employed to determine the contribution of transformation and conjugation to dissemination of antimicrobial and heavy metal resistance determinants.