Abstract
Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen. Cattle are suggested to be an important reservoir for STEC; however, these pathogens have also been isolated from other livestock and wildlife. In this study we sought to investigate transmission of STEC, enterohemorrhagic E. coli (EHEC) and enteropathogenic E. coli (EPEC) between cattle and white-tailed deer in a shared agroecosystem. Cattle feces were collected from 100 animals in a Michigan dairy farm in July 2012, while 163 deer fecal samples were collected during two sampling periods (March and June). The locations of deer fecal pellets were recorded via geographic information system mapping and microsatellite multi-locus genotyping was used to link the fecal samples to individual deer at both time points. Following subculture to sorbitol MacConkey agar and STEC CHROMagar, the pathogens were characterized by serotyping, stx profiling, and PCR-based fingerprinting; multilocus sequence typing (MLST) was performed on a subset. STEC and EHEC were cultured from 12 to 16% of cattle, respectively, and EPEC was found in 36%. Deer were significantly less likely to have a pathogen in March vs. June where the frequency of STEC, EHEC, and EPEC was 1, 6, and 22%, respectively. PCR fingerprinting and MLST clustered the cattle- and deer-derived strains together in a phylogenetic tree. Two STEC strains recovered from both animal species shared MLST and fingerprinting profiles, thereby providing evidence of interspecies transmission and highlighting the importance of wildlife species in pathogen shedding dynamics and persistence in the environment and cattle herds.
Highlights
Shiga toxin-producing Escherichia coli (STEC) is a leading cause of foodborne infections in the U.S and represents a major public health concern These pathogens are characterized by their ability to produce Shiga toxin (Stx), which contributes to hemorrhagic colitis and hemolytic uremic syndrome (HUS) in some individuals
STEC, enterohemorrhagic E. coli (EHEC), and enteropathogenic E. coli (EPEC) Frequencies in Dairy Cattle and Deer Among the 100 cattle sampled in July, 2029 suspect colonies were characterized by PCR for a combination of stx and eae genes useful for initially classifying the pathogens
Cattle were significantly more likely to possess any of the three pathogens (OR: 2.7; 95% confidence intervals (95% CI): 1.48, 5.13) as well as EHEC or STEC combined (OR: 3.7; 95% CI: 1.52, 9.09) relative to deer during the June sampling
Summary
Shiga toxin-producing Escherichia coli (STEC) is a leading cause of foodborne infections in the U.S and represents a major public health concern These pathogens are characterized by their ability to produce Shiga toxin (Stx), which contributes to hemorrhagic colitis and hemolytic uremic syndrome (HUS) in some individuals. A subset of STEC strains known as enterohemorrhagic E. coli (EHEC), possess the locus of enterocyte effacement (LEE) with genes such as eae (intimin) that are important for the development of attaching and effacing lesions on intestinal epithelial cells (McDaniel et al, 1995). EHEC O157 was suggested to have evolved from LEE-positive enteropathogenic E. coli (EPEC) (Reid et al, 2000), a common cause of infantile diarrhea in developing countries (Kotloff et al, 2013), via the acquisition of Stx-converting bacteriophages. EPEC strains have been classified into typical EPEC based on the presence of the EPEC adherence factor (EAF) plasmid This plasmid harbors the bfp gene cluster encoding the bundle-forming pilus, which is essential for the initial attachment of EPEC to intestinal epithelial cells (Nataro and Kaper, 1998). Atypical EPEC strains lack bfp, though the prevalence of both types may be underestimated in developed countries without routine screening practices in place
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