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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #318526
Title: Dynamics of Escherichia coli virulence factors in dairy herds and farm environments in a longitudinal study in the United States

Author
item LAMBERTINI, ELIZABETH - University Of Maryland
item Karns, Jeffrey
item Van Kessel, Jo Ann
item CAO, HUILIN - University Of Maryland
item SCHUKKEN, YNTE - Cornell University
item WOLFGANG, DAVID - Pennsylvania State University
item SMITH, JULIA - University Of Vermont
item PRADHAN, ABANI - University Of Maryland

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2015
Publication Date: 4/24/2015
Citation: Lambertini, E., Karns, J.S., Van Kessel, J.S., Cao, H., Schukken, Y.H., Wolfgang, D.R., Smith, J.M., Pradhan, A.K. 2015. Dynamics of Escherichia coli virulence factors in dairy herds and farm environments in a longitudinal study in the United States. Applied and Environmental Microbiology. 81:4477-4488.

Interpretive Summary: Although most Escherichia coli (E. coli) are non-pathogenic, some E. coli, such as enteropathogenic E. coli (EPEC) and shiga-toxigenic E. coli (STEC), cause disease in humans and have been associated with foodborne illness. Dairy farms are known reservoirs of pathogenic E. coli although generally they do not cause disease in the animals. Pathogenic E. coli or the virulence factors (genetic elements) associated with pathogenicity have been detected in manure, milk, and the farm environment. It is unclear which farm compartments are reservoirs for EPECs and STECs, and their long-term dynamics have not not described. This study assessed occurrence and dynamics of four major E. coli virulence factors (eaeA, stx1, stx2, and '-tir) on three U.S. dairy farms. Fecal, manure, water, feed, milk, and milk filter samples were collected from 2004 to 2012. All virulence factors were detected in most compartments on all three farms. Fecal and manure samples showed the highest prevalence, up to 53% stx and 21% '-tir in feces, and up to 84% stx and 44% '-tir in manure. Prevalence was low in milk (up to 1.9% stx and 0.7% '-tir); however, milk filter prevalence was up to 35% stx and 20% '-tir. All factors were frequently detected in feed and water. Prevalence and levels of the virulence factors fluctuated significantly over time. Levels were correlated between fecal and manure samples, and in some cases autocorrelated. No clear seasonality effect distinct from year-to-year variability was observed. Based on observations, no single farm compartment contributed to persistence or transmission of E. coli virulence factors. Shigatoxins (the toxins released by shigatoxigenic E. coli) were nearly ubiquitous and 10 to 18% of the lactating cows were potential shedders of the STEC, E. coli O157, at least once during their time in the herd. This information will be useful to other scientists and regulatory agencies.

Technical Abstract: Dairy farms are known reservoirs of enteropathogenic E. coli (EPEC). EPEC, or the virulence factors associated with pathogenicity, have been detected in manure, milk, and the farm environment. It is unclear which farm compartments are reservoirs for EPEC and their long-term dynamics are not described. This study assessed occurrence and dynamics of four major E. coli virulence factors (eaeA, stx1, stx2, and '-tir) on three U.S. dairy farms. Virulence factors were measured by post-enrichment quantitative PCR. Fecal, manure, water, feed, milk, and milk filter samples were collected from 2004 to 2012. All virulence factors were detected in most compartments on all three farms. Fecal and manure samples showed the highest prevalence, up to 53% stx and 21% '-tir in feces, and up to 84% stx and 44% '-tir in manure. Prevalence was low in milk (up to 1.9% stx and 0.7% '-tir); however, milk filter prevalence was up to 35% stx and 20% '-tir. All factors were frequently detected in feed and water. Prevalence and levels of the virulence factors, expressed as qPCR cycle threshold categories, fluctuated significantly over time. Levels were correlated between fecal and manure samples, and in some cases autocorrelated. No clear seasonality effect distinct from year-to-year variability was observed. Based on observations, no single farm compartment contributes to persistence or transmission of E. coli virulence factors. Shigatoxins were nearly ubiquitous and 10 to 18% of the lactating cows were potential shedders of E. coli O157 at least once during their time in the herd.