Short communicationCharacterization of atypical Enteropathogenic Escherichia coli (aEPEC) isolated from dogs
Introduction
The EPEC pathotype comprises human pathogens that causes infantile diarrhea with two subgroups being recognized, typical (tEPEC) and atypical (aEPEC) EPEC. While both exhibit the major EPEC virulence trait, the ability to cause the attaching and effacing lesion (A/E), tEPEC strains carry the EPEC adherence factor (EAF) plasmid that encodes the bundle-forming pili (BFP), while aEPEC strains are negative for both EAF plasmid and BFP (Goffaux et al., 1997, Nataro and Kaper, 1998). Both are frequently isolated from humans (Afset et al., 2003, Beutin, 1991, Beutin et al., 2003, Gomes et al., 2004) and aEPEC is also frequently isolated from animals (Nakazato et al., 2004, Krause et al., 2005, Moura et al., 2009).
The LEE (locus for enterocyte effacement) region is a chromosomal pathogenicity island that encodes effectors’ proteins and a type III secretion apparatus involved in the formation of the A/E lesion. LEE also encodes the eae gene related to the protein intimin, which confers an intimate adherence to the host cell, and the tir gene expressing the Tir protein, that is translocated into the host cell membrane acting as the receptor of intimin (Finlay and Vallance, 2000). The eae gene shows higher polymorphism and 28 variants have been characterized (Lacher et al., 2006). The LEE of EPEC is generally inserted in two possible sites corresponding to DNA regions encoding the tRNA of selenocystein (selC) and phenylalanine (pheU) (Sperandio et al., 1998). In the same way, tir and the espA, espB and espD genes, encoded in LEE, have several subtypes (China et al., 1999).
EPEC has been isolated from dogs (Krause et al., 2005, Moura et al., 2009), with similar gene profile of strains recovered from humans, mainly children (Afset et al., 2003, Nunes et al., 2003, Gomes et al., 2004). Simultaneous tEPEC detection in a dog and a child living in the same house has been described in Brazil (Rodrigues et al., 2004), denoting the relevance of surveys of this agent as a potential zoonotic cause of human diarrhea (Afset et al., 2003). In this way, the present study describes the search and characterization of aEPEC strains from diarrheic and non-diarrheic dogs from Rio de Janeiro State, Brazil.
Section snippets
Fecal samples
Fecal samples from 101 dogs up to 3 months, diarrheic (n = 65) and non-diarrheic (n = 36), were collected during 2003 and 2004, from animals randomly chosen in five veterinary clinics in Rio de Janeiro and Niterói cities, in Rio de Janeiro State, Brazil. Each fecal sample was inoculated onto Cystine Lactose Electrolyte Deficient agar (Himedia Labs., Mumbai, India) and incubated for 24 h at 37 °C to obtain a confluent growth. Then, a thick bacterial suspension was prepared in phosphate buffered saline
Results
48% of the 101 fecal samples were positive for the eae gene, 33/65 (51%) belonging to the diarrheic animals and 15/36 (42%) to the non-diarrheic animals. Although eae-positive strains were more frequently found among diarrheic animals, the values did not differ significantly (data not shown). In one sample, from a diarrheic animal, was detected the simultaneous presence of stx1, stx2 and eae genes, and it was excluded from this study.
EPEC was recovered from 21 out of 48 eae-positive fecal
Discussion
EPEC strains have been implicated in diarrhea in several countries, including Brazil, in humans (Afset et al., 2003, Gomes et al., 2004) and animals (Nakazato et al., 2004, Krause et al., 2005). The involvement of aEPEC strains in infantile diarrhea is clearly increasing (Hernandes et al., 2009). Unlike tEPEC, aEPEC strains are frequently detected in animals and it is possible that some strains could be shared with humans.
This study screened the presence of the eae gene, a genetic marker of
Conclusion
In conclusion, the recovering of aEPEC strains from diarrheic and non-diarrheic dogs, whose genotypic and phenotypic profile are similar to those found in strains recovered from humans, reinforces the zoonotic potential of this EPEC category and emphasizes the importance of dogs like other animals as potential reservoirs for the transmission of these enteropathogens to humans, especially children.
Acknowledgements
This work was supported by Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ; grant 110.082/2008 to A.M.F.Cerqueira). We also thanks to FAPERJ and Conselho Nacional de Desenvolvimento Científico e tecnológico (CNPq) the fellowships for L.R. Araes and P.M.P. Almeida, respectivelly.
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