Elsevier

Veterinary Microbiology

Volume 196, 30 November 2016, Pages 72-77
Veterinary Microbiology

Short communication
Lambs are an important source of atypical enteropathogenic Escherichia coli in southern Brazil

https://doi.org/10.1016/j.vetmic.2016.10.009Get rights and content

Highlights

  • Food-producing animals are an important source of zoonotic pathogens.

  • aEPEC is more commonly detected in lambs than in adult sheep.

  • Lambs raised for meat harbor aEPEC strains with potential to cause diseases in humans.

  • A zoonotic potential of aEPEC is reinforced.

Abstract

Food-producing animals can harbor Escherichia coli strains with potential to cause diseases in humans. In this study, the presence of enteropathogenic E. coli (EPEC) was investigated in fecal samples from 130 healthy sheep (92 lambs and 38 adults) raised for meat in southern Brazil. EPEC was detected in 19.2% of the sheep examined, but only lambs were found to be positive. A total of 25 isolates was characterized and designated atypical EPEC (aEPEC) as tested negative for bfpA gene and BFP production. The presence of virulence markers linked to human disease as ehxA, paa, and lpfAO113 was observed in 60%, 24%, and 88% of the isolates, respectively. Of the 11 serotypes identified, eight were described among human pathogenic strains, while three (O1:H8, O11:H21 and O125:H19) were not previously detected in aEPEC. Associations between intimin subtypes and phylogroups were observed, including eae-θ2/A, eae-β1/B1, eae-α2/B2 and eae-γ1/D. Although PFGE typing of 16 aEPEC isolates resulted in 14 unique pulsetypes suggesting a genetic diversity, specific clones were found to be distributed in some flocks. In conclusion, potentially pathogenic aEPEC strains are present in sheep raised for meat, particularly in lambs, which can better contribute to dissemination of these bacteria than adult animals.

Introduction

Enteropathogenic Escherichia coli (EPEC) are one of the major causative agents of diarrhea worldwide, particularly among children under five years (Lanata et al., 2013). This important group of diarrheagenic E. coli is characterized by the ability to induce attaching and effacing (A/E) lesions on intestinal epithelium, and absence of Shiga toxin production (Kaper, 1996). A chromosomal pathogenicity island designated locus of enterocyte effacement (LEE) contains the genes responsible for the A/E phenotype, among them eae and tir, which encode an outer membrane protein called intimin and its translocated receptor Tir, respectively (Frankel and Phillips, 2008). More than 30 intimin types and subtypes have been described based on the polymorphism of eae (Blanco et al., 2006, Horcajo et al., 2011).

EPEC is divided into typical (tEPEC) and atypical (aEPEC) considering the presence or absence of the EPEC adherence factor (EAF) plasmid, which encodes a type-IV fimbriae named Bundle-Forming Pilus (BFP) (Kaper, 1996). aEPEC and tEPEC strains differ significantly regarding to genotypic and phenotypic features (Trabulsi et al., 2002). Epidemiological studies have indicated that aEPEC are more prevalent than tEPEC in many regions of the world, including Brazil (Hernandes et al., 2009, Hu and Torres, 2015).

Humans are the major natural reservoir for tEPEC strains, which are rarely recovered from animal hosts (Trabulsi et al., 2002). In contrast, there is mounting evidence that the diarrhea caused by aEPEC can be considered as a zoonosis because strains showing same serotypes and genetic profiles have been isolated from humans and different animal species (Moura et al., 2009, Horcajo et al., 2011). Therefore, the monitoring of aEPEC in farm animals as sheep becomes of particular interest, since pathogenic strains can be transmitted to humans by animal-derived food or by direct contact with animals and their environments (Brandal et al., 2012, Otero et al., 2013).

In this study, we describe for the first time the isolation and characterization of aEPEC from sheep raised for meat in southern Brazil.

Section snippets

Sample collection, culture and biochemical identification of E. coli

The study was conducted in ten slaughter sheep producing farms of the Paraná State, southern Brazil. The farms were located on four municipalities within a 3000 km2 area. Rectal swabs were collected from 130 animals without diarrhea (92 lambs aged up to six months, and 38 adult sheep) between April and September 2010. Lambs were preferentially sampled since they have better meat quality and a higher consumer preference than adult sheep (Hopkins and Mortirner, 2014). Each farm was visited once,

Results

EPEC was detected in 70% (7/10) of the flocks studied, and prevalence on farms ranged from 0% to 42.8%. Overall, 25 (19.2%) out of 130 fecal samples were positive for EPEC (Table 1), all of which were obtained from lambs (p < 0.0001).

Only one eae-positive colony was detected in each EPEC-positive sample. Thus, a total of 25 EPEC isolates were recovered, all of which produced intimin and were considered aEPEC, since they were negative for the bfpA gene and did not produce BFP (Table 2). aEPEC

Discussion

EPEC strains have been isolated from many animal species worldwide, particularly those served for food production as sheep. Prevalence rates up to 55% have been documented in ovine feces (Krause et al., 2005, Fröhlicher et al., 2008). In addition, EPEC has also been detected in milk (Otero et al., 2013) and carcass (Busia et al., 2014) from sheep. In Brazil, studies conducted in São Paulo State found EPEC in less than 10% of the ovine tested (Vettorato et al., 2009, Maluta et al., 2014), while

Conclusion

In conclusion, southern Brazilian sheep serve as reservoir for a great diversity of aEPEC strains, some of them showing virulence characteristics associated with human disease, reinforcing the zoonotic potential of this pathotype. Moreover, the animal age seems to influence the prevalence of aEPEC in ovine, with lambs showing a higher risk of shedding these bacteria than adult sheep. Since young sheep have better meat quality and, consequently, are more intended for human consumption than older

Acknowledgments

We gratefully acknowledge Dr. Agostinho Ludovico and Dr. Marilucia Ludovico for contribution on sample collection, and Evanilde Maria Gonçalves for technical assistance. This work was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Brazil), Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia, the European Regional Development Fund (ERDF) (CN2012/303) and the

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    Present address: Laboratório de Bacteriologia, Instituto Butantan, São Paulo, SP, Brazil.

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