Abstract
Enterohemorrhagic Escherichia coli (EHEC), enteropathogenic E. coli (EPEC), and Shigatoxigenic E. coli (STEC) are carried by healthy adult cattle and even more frequently by young calves in their intestinal tract, especially at the height of the recto-anal junction. The purpose of the present study was to assess the presence of ten EHEC, EPEC, and/or STEC O serotypes (O5, O26, O80, O103, O111, O118, O121, O145, O157, and O165) in calves sampled via recto-anal mucosal swabs (RAMS) at three dairy farms in Belgium. A total of 233 RAMS were collected on three consecutive occasions from healthy <6-month-old Holstein-Friesian calves and submitted to a PCR targeting the eae, stx1, and stx2 genes after non-selective overnight enrichment growth. The 148 RAMS testing positive were streaked on four (semi-)selective agar media; of the 2146 colonies tested, 294 from 69 RAMS were PCR-confirmed as EHEC, EPEC, or STEC. The most frequent virulotype was eae+ EPEC and the second one was stx1+ stx2+ STEC, while the eae+ stx1+ and eae+ stx1+ stx2+ virulotypes were the most frequent among EHEC. The majority of EHEC (73%) tested positive for one of the five O serotypes detected (O26, O103, O111, O145, or O157) vs. 23% of EPEC and 45% of STEC. Similarly, more RAMS (73%) harbored EHEC isolates positive for those five serotypes compared to EPEC (53%) or STEC (52%). This survey confirms that (i) healthy young dairy calves are asymptomatic carriers of EHEC and EPEC in Belgium; (ii) the carrier state rates, the virulotypes, and the identified O serotypes differ between farms and in time; and (iii) a majority of EPEC belong to so far unidentified O serotypes.
Highlights
Enterohemorrhagic Escherichia coli (EHEC) are important human pathogens responsible for hemorrhagic colitis (HC), the origin of their name, and the life-threatening hemolytic-uremic syndrome (HUS)
The purpose of the present study was to assess the presence of the “gang-of-seven” and of three other (O5, O80, and O118) (AE-)Shigatoxigenic E. coli (STEC) and enteropathogenic E. coli (EPEC) O serotypes in healthy
Eleven of the PCR-positive RAMS were sampled from calves with signs of diarrhea
Summary
Enterohemorrhagic Escherichia coli (EHEC) are important human pathogens responsible for hemorrhagic colitis (HC), the origin of their name, and the life-threatening hemolytic-uremic syndrome (HUS). Their most important virulence-associated properties are the Shiga toxins (Stx and/or Stx2), encoded by phage-located genes (stx and stx2), and the production of the histological attaching–effacing (AE) lesion, encoded by genes located on a pathogenicity island (the locus of enterocyte effacement or LEE), including the eae gene coding for the intimin adhesin. Not all Stx- and AE-producing E. coli cause HC in humans and, the acronym EHEC is not appropriate for them. Human infection most frequently occurs via the consumption of animal- or plant-derived foodstuffs contaminated with ruminant, mostly cattle, feces. Cattle can be asymptomatic carriers in their intestinal tract, more especially in the colon and at the height of the recto-anal junction [2,6,7,8]
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