Evaluation of Animal Genetic and Physiological Factors That Affect the Prevalence of Escherichia coli O157 in Cattle

Abstract

Controlling the prevalence of Escherichia coli O157 in cattle at the pre-harvest level is critical to reduce outbreaks of this pathogen in humans. Multilayers of factors including the environmental and bacterial factors modulate the colonization and persistence of E. coli O157 in cattle that serve as a reservoir of this pathogen. Here, we report animal factors contributing to the prevalence of E. coli O157 in cattle. We observe the lowest number of E. coli O157 in Brahman breed when compared with other crosses in an Angus-Brahman multibreed herd, and bulls excrete more E. coli O157 than steers in the pens where cattle were housed together. The presence of super-shedders, cattle excreting >105 CFU/rectal anal swab, increases the concentration of E. coli O157 in the pens; thereby super-shedders enhance transmission of this pathogen among cattle. Molecular subtyping analysis reveal only one subtype of E. coli O157 in the multibreed herd, indicating the variance in the levels of E. coli O157 in cattle is influenced by animal factors. Furthermore, strain tracking after relocation of the cattle to a commercial feedlot reveals farm-to-farm transmission of E. coli O157, likely via super-shedders. Our results reveal high risk factors in the prevalence of E. coli O157 in cattle whereby animal genetic and physiological factors influence whether this pathogen can persist in cattle at high concentration, providing insights to intervene this pathogen at the pre-harvest level.

Differing Populations of Endemic Bacteriophages in Cattle Shedding High and Low Numbers of Escherichia coli O157:H7 Bacteria in Feces

“…The majority (75.6%) of E. coli O157:H7 isolated from both SS and LS cattle was from one dominant PFGE subtype as has been previously reported (10,31) and suggests that certain dominant subtypes persist or readily disseminate among cattle. Some studies indicate that SS cattle may carry unique subtypes of E. coli O157:H7 (4, 32), whereas other studies do not identify common subtypes exclusive to high-shedding animals (6,33,34). In the current study, distinct PFGE subtypes were found exclusively in SS or LS cattle, suggesting that a relationship exists between subtypes of E. coli O157:H7 and the number of E. coli O157:H7 shed by cattle.…”

“…Shedding of E. coli O157:H7 is inconsistent, with some cattle shedding the organism for a few days while others may shed E. coli O157:H7 for weeks or months (4), suggesting that the nature of the host plays a role in the etiology of this bacterium. Supershedders are cattle that excrete the pathogen at concentrations of Ն10 4 CFU · g Ϫ1 of feces (5); they are thought to account for a small proportion of the cattle population and yet may contribute 80 to 96% of the total load of E. coli O157:H7 in the herd (5)(6)(7). Multiple factors contribute to shedding of E. coli O157:H7 in cattle, including diet (8), housing (9), season (10), stress (11), and age (12).…”

Rapid and Specific Detection of Escherichia coli O157:H7 in Ground Beef Using Immunomagnetic Separation Combined with Loop-Mediated Isothermal Amplification

“…The minimum infectious dose (MID) of EHEC O157:H7 is estimated to be around 10 to 100 CFU compared to more than one million CFU for other pathogenic strains of E. coli, mainly due to their increased virulence and toxicity [Greig et al, 2010]. EHEC O157:H7 can naturally be found in the intestinal contents of some cattle [Jeon et al, 2013] and due to the lack of receptors, they mainly act as asymptomatic carriers of the bacterium serving as an important source of infection to human [Pruimboom-Brees et al, 2000]. Cattle is regarded as 'super-shedders' of these bacteria as they colonize the recto-anal junction and excrete more than 10 3 to 10 4 CFU per gram of feces and may account for more than 90% of all E. coli O157:H7 excreted [Chase- Topping et al, 2008].…”

A Perspective on the Global Pandemic of Waterborne Disease

“…This should not be surprising, given that cattle are the primary reservoir of these bacteria and that high prevalence rates of EHEC in cattle herds have been frequently documented [48][49][50]. These and similar findings of environmental reservoirs for a variety of virulence genes in other bacterial species [51,52] are worrisome.…”