Prevalence and characteristics of Shiga toxin-producing Escherichia coli in finishing pigs: Implications on public health

Wonhee Cha; Pina M Fratamico; Leah E Ruth; Andrew S Bowman; Jacqueline M Nolting; Shannon D Manning; Julie A Funk

doi:10.1016/j.ijfoodmicro.2017.10.017

Prevalence and characteristics of Shiga toxin-producing Escherichia coli in finishing pigs: Implications on public health

Int J Food Microbiol. 2018 Jan 2:264:8-15. doi: 10.1016/j.ijfoodmicro.2017.10.017. Epub 2017 Oct 21.

Authors

Wonhee Cha¹, Pina M Fratamico², Leah E Ruth², Andrew S Bowman³, Jacqueline M Nolting³, Shannon D Manning¹, Julie A Funk⁴

Affiliations

¹ Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
² Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA 19038, USA.
³ Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, OH 43210, USA.
⁴ Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USA. Electronic address: funkj@cvm.msu.edu.

PMID: 29080423
DOI: 10.1016/j.ijfoodmicro.2017.10.017

Abstract

Shiga toxin-producing Escherichia coli (STEC) are important food-borne pathogens, which can cause serious illnesses, including hemorrhagic colitis and hemolytic uremic syndrome. To study the epidemiology of STEC in finishing pigs and examine the potential risks they pose for human STEC infections, we conducted a longitudinal cohort study in three finishing sites. Six cohorts of pigs (2 cohorts/site, 20 pigs/cohort) were randomly selected, and fecal samples (n=898) were collected every two weeks through their finishing period. Eighty-two pigs (68.3%) shed STEC at least once, and the proportion of STEC-positive pigs varied across sites (50-97.5%) and cohorts (15-100%). Clinically important serotypes, O157:H7 (stx_2c, eae) and O26:H11 (stx_1a, eae), were recovered from two pigs at sites C and A, respectively. The most common serotype isolated was O59:H21 (stx_2e), which was particularly prevalent in site B as it was recovered from all STEC positive pigs (n=39). Each cohort showed different patterns of STEC shedding, which were associated with the prevalent serotype. The median shedding duration of STEC in pigs was 28days, consistent with our prior study. However, among pigs shedding O59:H21 at least once, pigs in cohort B2 had a significantly longer shedding duration of 42days (P<0.05) compared to other cohorts. Stx2e was the most commonly observed stx variant in finishing pigs (93.9%), in accordance with the previous studies. Stx2e has been reported to be significantly associated with edema disease in pigs, however, the pathogenicity in humans warrants further investigations. Nonetheless, our findings affirm that pigs are an important reservoir for human STEC infections, and that the circulating serotypes in a cohort and site management factors may significantly affect the prevalence of STEC. Molecular characterization of STEC isolates and epidemiological studies to identify risk factors for shedding in pigs are strongly warranted to further address the significance to public health and to develop mitigation strategies.

Keywords: Cohort; Finishing pigs; Prevalence; Shedding duration; Shiga toxin-producing Escherichia coli.

MeSH terms

Adhesins, Bacterial / genetics*
Animals
Escherichia coli Infections
Escherichia coli Proteins / genetics*
Feces / microbiology
Foodborne Diseases / microbiology*
Humans
Longitudinal Studies
Prevalence
Public Health
Serogroup
Shiga-Toxigenic Escherichia coli / classification*
Shiga-Toxigenic Escherichia coli / genetics*
Shiga-Toxigenic Escherichia coli / isolation & purification
Shiga-Toxigenic Escherichia coli / pathogenicity
Sus scrofa / microbiology*
Swine

Substances

Adhesins, Bacterial
Escherichia coli Proteins