Genotypic and phenotypic characterization of Escherichia coli isolates from dogs manifesting attaching and effacing lesions

Abstract

Thirteen Escherichia coli isolates from dogs manifesting attaching and effacing lesions were characterized genetically with respect to the presence of the following virulence determinants associated with human enteropathogenic E. coli (EPEC): eaeA, encoding the outer membrane protein intimin; eaeB, which is necessary for inducing signal transduction; bfpA, encoding the bundle-forming pilus; and the EAF (stands for EPEC adherence factor) plasmid. These isolates were also analyzed phenotypically with respect to adherence to mammalian cells in vivo and in vitro. Nine of these 13 isolates were found to be eaeA positive by PCR; four of these nine were eaeB positive. The 5 end, but not the 3 end, of the eaeA gene was amplified by PCR when primers derived from the eaeA gene of EPEC were used. Six and eight of these 13 isolates were found to be bfpA positive and EAF positive, respectively. The bfpA gene and EAF locus were found on high-molecular-weight plasmids, whereas the eaeA and eaeB genes were chromosomally located when present. Only one canine E. coli isolate, 4221, which was positive for eaeA, eaeB, bfpA, and EAF, adhered to HEp-2 cells in a localized manner and was positive in the fluorescence actin staining test. The nine eaeA-positive isolates adhered to the mucosal surface of piglet ileal explants and induced some microvillus effacement. However, when tested in experimentally inoculated gnotobiotic piglets, isolate 4221 did not induce attaching and effacing lesions at any level of the intestinal tract. Our results indicate that canine E. coli isolates associated with attaching and effacing lesions share some properties with human EPEC but form a heterogeneous group.

Attaching-effacing Bacteria in Animals

“…When putative canine strains of EPEC (Drolet et al, 1994a) were examined in vitro, it was found that all of nine eae-positive isolates adhered to piglet ileum and produced AE lesions, but only one adhered and formed FAS-positive lesions on HEp-2 cells (Beaudry et al, 1996). Putative AEEC isolated from dogs and cats encompassed a range of serogroups (Holland et al, 1999a).…”

Cloning and characterization of the esp region from a dog attaching and effacing Escherichia coli strain 4221 and detection of EspB protein-binding to HEp-2 cells

“…Dog EPEC (DEPEC) strain 4221 possesses sequences homologous to eae and espB [15]. When tested with HEp-2 cells, strain 4221 showed a localized adherence and is positive in the £uorescence actin staining test [15]. These ¢ndings indicate that DEPEC strain 4221 is more similar to human EPEC isolates than to AEEC isolates obtained from pigs [16], rabbits [17] or calves [13].…”

“…E. coli strain 4221 was isolated from the intestinal contents of a dog with diarrhea and demonstrating typical AE lesions [15]. This strain was stored on Dorset medium at 4³C and grown on blood agar or in trypticase soy broth (Difco Laboratories, Detroit Mich) at 37³C.…”

“…Natural infections with AEEC in dogs have also been described [3,14]. It was shown that canine AEECs carry nucleotide sequences related to the EPEC adherence factor (EAF) sequence, bfpA, eae and espB genes [14,15]. Dog EPEC (DEPEC) strain 4221 possesses sequences homologous to eae and espB [15].…”

“…It was shown that canine AEECs carry nucleotide sequences related to the EPEC adherence factor (EAF) sequence, bfpA, eae and espB genes [14,15]. Dog EPEC (DEPEC) strain 4221 possesses sequences homologous to eae and espB [15]. When tested with HEp-2 cells, strain 4221 showed a localized adherence and is positive in the £uorescence actin staining test [15].…”