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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Research Project #440225

Research Project: Evaluation of Genetic and Management Factors to Reduce Foodborne Pathogens and Antimicrobial Resistance in Dairy Cattle

Location: Environmental Microbial & Food Safety Laboratory

Project Number: 8042-32420-008-000-D
Project Type: In-House Appropriated

Start Date: Mar 17, 2021
End Date: Mar 16, 2026

Objective 1: Elucidate the role of accessory genetic elements including siderophores, metabolism genes and transport factors on the persistence of multi-drug resistant bacteria in dairy animals and their environments. Sub-objective 1.A: Compare the growth of MDR and susceptible E. coli and S. enterica strains encoding accessory siderophores and iron transport mechanisms in bovine feces with and without iron supplementation. Sub-objective 1.B: Evaluate the role of dietary iron supplementation in the first two weeks after birth on MDR E. coli abundance in the calf gut. Sub-objective 1.C: Identify the effects of accessory myo-inositol transport and metabolism genes on the growth of MDR E. coli and susceptible E. coli strains. Objective 2: Evaluate the feasibility of commensal bacteria as modulators of pathogenic Salmonella enterica and antibiotic resistant E. coli carriage. Sub-objective 2.A: Examine the ability of commensal bovine gut bacteria and non-pathogenic S. enterica to outcompete pathogenic S. enterica strains in the bovine gut environment. Sub-objective 2.B: Examine the ability of susceptible E. coli strains to outcompete MDR E. coli strains in the gut of newborn calves. Objective 3: Identify the management factors involved in persistence of multi-drug resistant bacteria in milk-fed dairy calves.

Dairy animals, including milk-fed veal, and their farm environments are reservoirs for zoonotic pathogens and antimicrobial resistance and the impetus for this project is to develop solutions for reducing the prevalence of resistant and human pathogenic bacteria harbored by these animals. Our previous work identified preweaned calves as an important reservoir for antibiotic resistance; resistant bacteria appear to outcompete sensitive bacteria in the very young calf gut. We identified accessory genetic elements associated with the acquisition, transport, and metabolism of iron and myo-inositol, two essential nutrients for calf development, that may enhance the ability of resistant Enterobacteriaceae to outcompete sensitive strains in the neonatal calf gut. We will investigate the impact of these accessory genes on the ability of resistant strains to outcompete sensitive bacteria in iron-replete growth conditions using in vitro and in vivo approaches, as well as the impact of myo-inositol on resistant strain selection in vitro. We will also explore the ability of bovine commensal bacteria that are hypothesized antagonists of Salmonella to modulate the abundance of pathogenic S. enterica via competitive in vitro growth assays and by evaluating the ability of these commensals to prevent pathogenic S. enterica from attaching to and invading bovine epithelial cells. Similarly, animal studies will be conducted to evaluate the ability of antibiotic-susceptible E. coli to outcompete resistant E. coli in newborn calves with the aim of reducing the carriage of resistance in preweaned calves. Finally, we will conduct on-farm studies to identify management factors that influence the abundance and types of resistance harbored by veal calves. The ultimate goal of the project is to develop novel and practical mitigation approaches that can be employed by the dairy industry.