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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Research Project #430681

Research Project: Antimicrobial Resistance and Ecology of Zoonotic Foodborne Pathogens in Dairy Cattle

Location: Environmental Microbial & Food Safety Laboratory

Project Number: 8042-32000-110-00-D
Project Type: In-House Appropriated

Start Date: Mar 17, 2017
End Date: Mar 16, 2021

Objective:
Objective 1: Examine the relationship between gut bacteria and the bovine host to determine factors that contribute to observed age-related differences in colonization by AMR bacteria. 1A: Determine the capacity of resistant E. coli strains to bind or attach to intestinal epithelial cells. 1B: Evaluate and compare the growth rates of resistant E. coli strains in media that is supplemented with bovine colostrum or milk replacer. 1C: Examine the developing microbial community structure in the young calf intestine and the ability of resistant E. coli strains to outcompete other strains/species in these communities. Objective 2: Examine and determine if resistance determinants in bacteria are linked to specific genomic characteristics that influence bacterial colonization capacity in the young dairy calf. 2A: Identify non-resistance conferring genomic features in calf-associated MDR E. coli that facilitate the colonization of the gut of newborn calves. 2B: Examine the ability of generic, susceptible E. coli strains to outcompete MDR E. coli strains in the gut of newborn calves. Objective 3: Compare and contrast interactions between bovine host cells and Salmonella enterica to identify factors that contribute to differences between Salmonella serotypes that behave as commensal inhabitants of the dairy cow gut and serotypes that are transient in the cow or cause systemic infections.

Approach:
Although the products of American dairy farms are overwhelmingly safe, food producing animals are known reservoirs for bacteria that are detrimental to human health and outbreaks have been attributed to consumption of contaminated raw milk, raw milk products, or meat. Additionally, the impact of animal production on the burden of antibiotic resistant bacteria affecting humans has become a major issue although the contribution of dairy farming to this burden is currently unknown. This project is composed of three major objectives relating to bacteria of public health importance that are associated with dairy animals. Resistant bacteria are more prevalent in dairy calves than in cows and multi-drug resistant bacteria are often found in pre-weaned calves. We will take a three-pronged approach to study resistance in dairy calves. We will investigate interactions between resistant E. coli and intestinal epithelial cells, relationships between resistant E. coli and the developing gut community, and associations between resistance determinants and genomic characteristics that influence bacterial colonization capacity in the calf. This project also builds on previous work characterizing the ecology of bacterial pathogens in dairy animals by determining factors associated with the establishment and maintenance of infections in cows. We will analyze the ability of Salmonella strains to bind to bovine epithelial cells and relate observed differences in binding and gene expression to factors responsible for the persistence of commensal-type Salmonella serotypes in dairy cows. We will compare the interactions of these serotypes with host intestinal cells with the interactions of serotypes that are transient in the cow or cause systemic infections in dairy cows. The project will improve our understanding of antibiotic resistance in dairy calves and commensal Salmonella infections in dairy cows so that new approaches for mitigation can be developed.