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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Characterization and Interventions for Foodborne Pathogens » Research » Research Project #441489

Research Project: Molecular Analysis of Foodborne Pathogen Responses to Stressors

Location: Characterization and Interventions for Foodborne Pathogens

Project Number: 8072-42000-094-000-D
Project Type: In-House Appropriated

Start Date: Jan 12, 2022
End Date: Jan 11, 2027

Objective 1: Characterization of environmental and food-related stress responses of Shiga-toxin producing Escherichia coli (STEC). Sub-objective 1.1: Analysis of STEC O157:H7 responses to acid, heat and biocides with emphasis on the role of RpoS and Rcs regulons. Sub-objective 1.2: Genomic adaptation of environmentally-adapted STEC O157:H7 upon exposure to synthetic gastric fluid. Sub-objective 1.3: Genomic adaptation of environmentally-adapted STEC O157:H7 upon exposure to SOS-inducing stress. Objective 2: Molecular analysis of Campylobacter’s responses to biotic and abiotic stresses encountered in host- and food-environments. Sub-objective 2.1: Consequences of Campylobacter exposure to short-chain fatty acids. The molecular level effects on motility, attachment/invasion of eukaryotic cell lines, and biofilm formation. Sub-objective 2.2: Campylobacter molecular responses during co-incubation with bacteria isolated from poultry environments. The effects the other bacteria have on Campylobacter survival, aggregation (auto-aggregation and co-aggregation), attachment and biofilm development on poultry skin. Objective 3: Molecular analysis of Listeria monocytogenes’ responses to biotic and abiotic stresses encountered in food and food-processing environments. Sub-objective 3.1: Studies of sanitizer- and stress-induced viable-but-nonculturable (VBNC) state in L. monocytogenes. Sub-objective 3.2: Investigation of molecular responses of L. monocytogenes exposed to modiffied atmosphere packaging (MAP) in chicken meats using transcriptomics. Sub-objective 3.3: Investigation of genome evolution of L. monocytogenes exposed to long-term nutrient-limiting, non-selective stress condition. Objective 4: Phenotypic and genetic characterization of extra-intestinal pathogenic Escherichia coli (ExPEC) isolated from poultry and produce. Sub-objective 4.1: Analysis of ExPEC isolated from chickens and humans: biofilm assays, virulence gene profiles, antimicrobial resistance profiles, whole genome comparison of ExPEC strains isolated from chicken and human infections. Sub-objective 4.2: Transcriptomics of ExPEC strains in chicken meat.

The goal of this project is to use omic technologies (proteomic, genomic, and transcriptomics methods) and bioinformatics in a systems approach to understand how pathogens become resistant to food-related stresses, to determine their pathogenicity, and to identify markers for detection and typing. Pathogens that will be investigated include: Shiga toxin-producing Escherichia coli (STEC) and extraintestinal pathogenic E. coli (ExPEC), Campylobacter species, and Listeria monocytogenes. We will use omic technologies to analyze a large variety of strains of each of the pathogens to identify genes and proteins necessary for pathogens to survive stresses encountered in food environments and cause human illness. Research on pathogenic E. coli will focus on examining the association between acid tolerance in STEC and virulence potential, curli expression, biofilm formation, and persistence. This work will provide information to understand the virulence characteristics of STEC and how food environment-related conditions may impact the virulence and persistence in the food environment. We will examine poultry and swine as reservoirs for food-borne infections linked to ExPEC and STEC, respectively, and characterize isolated strains to determine their virulence. The omic data will also reveal genetic markers for identification, molecular typing, and detection of these pathogens. In previous work, we found that the use of certain polyphosphates commonly used during poultry processing increased the survival of Campylobacter by causing subtle changes in pH. Building on our previous research, we will investigate strain diversity and mechanisms of tolerance to stresses, including acid and exposure to antimicrobial compounds, as well as investigate factors affecting attachment and biofilm formation of Campylobacter. In addition, there has been limited effort to identify the microbial makeup of poultry and the processing environment and how these may provide a survival advantage for Campylobacter. Thus, we will investigate environmental stresses that affect the survival and persistence of Campylobacter during poultry processing and the role that the microbial ecology of this environment plays in this process. Finally, we will examine stress responses in L. monocytogenes and explore novel approaches to control this pathogen and determine the genes and proteins that help the pathogen overcome stresses. Genes that are essential for the survival and growth of L. monocytogenes under weak organic acid conditions in RTE meat will be determined. We will also investigate the effect of olive leaf extracts on inactivation of L. monocytogenes, and using transcriptomics, we will determine the molecular responses of this pathogen when exposed to the olive leaf extracts. The research will expand the knowledge on the survival mechanisms of important food-borne pathogens, provide insight into the evolution of pathogens, as well as tools to detect, identify, and type food-borne pathogens, and will assist in the development of practical preservation systems that minimize health risks and assist regulators in making science-based food safety decisions.