Dynamics of Escherichia coli Virulence Factors in Dairy Herds and Farm Environments in a Longitudinal Study in the United States.
Pathogenic Escherichia coli or its associated virulence factors have been frequently detected in dairy cow manure, milk, and dairy farm environments. However, it is unclear what the long-term dynamics of E. coli virulence factors are and which farm compartments act as reservoirs. This study assessed the occurrence and dynamics of four E. coli virulence factors (eae, stx1, stx2, and the gamma allele of the tir gene [γ-tir]) on three U.S. dairy farms. Fecal, manure, water, feed, milk, and milk filter samples were collected from 2004 to 2012. Virulence factors were measured by postenrichment quantitative PCR (qPCR). All factors were detected in most compartments on all farms. Fecal and manure samples showed the highest prevalence, up to 53% for stx and 21% for γ-tir in fecal samples and up to 84% for stx and 44% for γ-tir in manure. Prevalence was low in milk (up to 1.9% for stx and 0.7% for γ-tir). However, 35% of milk filters were positive for stx and 20% were positive for γ-tir. All factors were detected in feed and water. Factor prevalence and levels, expressed as qPCR cycle threshold categories, fluctuated significantly over time, with no clear seasonal signal independent from year-to-year variability. Levels were correlated between fecal and manure samples, and in some cases autocorrelated, but not between manure and milk filters. Shiga toxins 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 herds. E. coli virulence factors appear to persist in many areas of the farms and therefore contribute to transmission dynamics.
Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, USA Center for Food Safety and Security Systems, University of Maryland, College Park, Maryland, USA.
Elisabetta
E
Lambertini
Environmental Microbial and Food Safety Laboratory, USDA-ARS, Beltsville, Maryland, USA.
Jeffrey S
JS
Karns
Environmental Microbial and Food Safety Laboratory, USDA-ARS, Beltsville, Maryland, USA.
Jo Ann S
JA
Van Kessel
Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, USA.
Huilin
H
Cao
Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, USA GD Animal Health, Deventer, Netherlands.
Ynte H
YH
Schukken
Department of Veterinary and Biomedical Science, Pennsylvania State University, University Park, Pennsylvania, USA.
David R
DR
Wolfgang
Department of Animal Science, University of Vermont, Burlington, Vermont, USA.
Julia M
JM
Smith
Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, USA Center for Food Safety and Security Systems, University of Maryland, College Park, Maryland, USA akp@umd.edu.
Abani K
AK
Pradhan
D000818:Animals; D000829:Animals, Domestic / Q000382:microbiology*; D001419:Bacteria / Q000235:genetics / Q000472:pathogenicity*; D057138:Bacterial Shedding; D002417:Cattle / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D004783:Environmental Microbiology; D004926:Escherichia coli / Q000235:genetics* / Q000302:isolation & purification; D005516:Food Microbiology; D008137:Longitudinal Studies; D060888:Real-Time Polymerase Chain Reaction; D014481:United States; D037521:Virulence Factors / Q000032:analysis* / Q000235:genetics
D004269:DNA, Bacterial; D037521:Virulence Factors