Dynamics of Escherichia coli Virulence Factors in Dairy Herds and Farm Environments in a Longitudinal Study in the United States

Abstract

g 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, stx 1 , stx 2 , and the gamma allele of the tir gene [␥-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 ␥-tir in fecal samples and up to 84% for stx and 44% for ␥-tir in manure. Prevalence was low in milk (up to 1.9% for stx and 0.7% for ␥-tir). However, 35% of milk filters were positive for stx and 20% were positive for ␥-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. Diarrheagenic Escherichia coli isolates of several pathovars of public health importance, such as enteropathogenic E. coli (EPEC), Shiga-toxigenic E. coli (STEC), and enterohemorrhagic E. coli (EHEC), have been observed in dairy herds (1-3) as well as in milk (4-10) and other dairy products (4-8, 11, 12). Beef cattle are also known to harbor pathogenic E. coli (13-16). Dairy animals also enter the meat production chain, contributing to meatborne infections (17). Infection by these classes of pathogenic E. coli can have serious health impacts in humans (8). The cost of human health losses in the United States due to E. coli O157 alone was estimated to amount to $405 million per year (18). Numerous E. coli outbreaks have been linked to the consumption of milk and dairy products (19)(20)(21)(22) and to direct contact with dairy farm animals and environments (23, 24). Milk contamination is usually due to fecal contamination. Intestinal colonization by STEC serogroups such as E. coli O157 is usually subclinical in cows and calves and therefore is often undetected. STEC and EHEC have almost never been associated with nonenteric infections in cows, such as mastitis, although other classes of pathogenic E. coli have been known to cause mastitis (25).A virulence factor is a phenotypic trait, usually a large molecule or complex, which determines the ability of E. coli and other bacterial pathogens to infect a h...

Molecular Identification of Virulence Genes of Escherichia coli Isolated from Cow Milk and Its Products in Abuja, Nigeria

“…In this study, the intimin eae gene was detected in 8(28.6%) of the E. coli isolates recovered from the milk samples. The finding is consistent with the reports [13,17,31,38,43] with prevalence (100%, 36%, 44.19%, 4.05-13.4%, 18.0%-24.3%) in these locations (Iran, South Africa, USA, Saudi Arabia) respectively. Al-zogibi et al [31] reported eae gene of 10(58.82%) in E. coli isolates from raw beef, E. coli isolates from milk and dairy products in Iran were positive for eae genes [4], E. coli isolates from faecal samples of diarrheic calves [2] and chicken meat [44] were positive for eae gene in Iran.…”

Prevalence, antimicrobial resistance, and genotyping of Shiga toxin-producing Escherichia coli in foods of cattle origin, diarrheic cattle, and diarrheic humans in Egypt

“…STEC was detected in 6.5%, 6%, and 7% of all food, milk, and meat samples, respectively. These findings were higher than those in previous reports (1.9-4.1%) in the USA [31] but lower than reports (10.7-29.7%) from other countries [32][33][34]. STEC isolates were found in 12% of diarrheic cattle samples; higher rates (18.7-53.2%) were reported from another location in Egypt [18] and elsewhere [31,35].…”

Prevalence of Escherichia coli O157 and Salmonella spp. in solid bovine manure in California using real‐time quantitative PCR

“…in bovine manure in various regions in the US. (Hancock et al 1997;Dargatz et al 2000;Alam and Zurek 2006;LeJeune et al 2006;Lambertini et al 2015;Rodriguez-Rivera et al 2016). Jay et al (2007) reported that 26 of 77 (33Á8%) cattle faecal samples collected at a ranch on the central California coast were positive for E. coli O157:H7.…”