Pathogenicity of attaching effacing enteropathogenic Escherichia coli isolated from diarrheic suckling and weanling rabbits for newborn rabbits

Abstract

The pathogenicity of six strains of Escherichia coli originating from different commercial rabbitries was tested in neonatal rabbits. Two strains isolated from healthy weaned rabbits (O7:H6 and O9:H?) did not induce any clinical sign or lesion. Two strains (O109:H2) isolated from diarrheic suckling rabbits caused yellow diarrhea 36 to 60 h after inoculation and high mortality between 60 and 72 h after infection. At 12 h after infection, light and electron microscopy showed attachment to epithelial cells and effacement of microvilli from proximal small intestine to colon. Bacteria were often present in the apical cytoplasm of epithelial cells. The two strains isolated from diarrheic weanling rabbits (O109:H2 and O15:H-) did not induce any clinical sign. Attachment to epithelial cells and effacement of microvilli was observed 48 h after inoculation in distal small intestine, cecum, and colon. These data are further evidence for the existence of two groups of attaching effacing enteropathogenic E. coli in rabbits, showing different preferences for age group and intestinal compartment.

Attaching-effacing Bacteria in Animals

“…Attaching-effacing Bacteria in Animals AE lesions have been reported in all regions of the gastrointestinal tract from the stomach to the rectum. In the small intestine, blunting, atrophy and fusion of villi accompany the changes described above (Moon et al, 1983;Peeters et al, 1984a;Moxley and Francis, 1986;Schoonderwoerd et al, 1988;Pearson et al, 1989Pearson et al, , 1999Iijima et al, 1990;Helie et al, 1991;Fagundes-Neto et al, 1995;Higgins et al, 1997;Gunning et al, 2001). Crypt hyperplasia is also reported in the small intestine (Ulshen and Rollo, 1980;Pospischil et al, 1987).…”

“…Intracytoplasmic bacteria (both in vacuoles and free within the cytoplasm) have been observed in AE lesions due to EPEC and EPEC-like organisms in human patients (Fagundes-Neto et al, 1995), rabbits (Takeuchi et al, 1978;Peeters et al, 1984a), pigs (Helie et al, 1991), dogs (Wada et al, 1996a) and cotton-top tamarins (Mansfield et al, 2001b). The numbers of such bacteria appear to be small relative to the surface population (Takeuchi et al, 1978;Peeters et al, 1984a;Helie et al, 1991). In some cases, bacteria were seen in the lamina propria (Helie et al, 1991;Wada et al, 1996a).…”

“…Descriptions of the histopathological appearance of intestines colonized by AE bacteria are consistent across species. These species include cattle (Hall et al, 1985;Moxley and Francis, 1986;Pospischil et al, 1987;Schoonderwoerd et al, 1988;Janke et al, 1989Janke et al, , 1990Pearson et al, 1989;Iijima et al, 1990), pigs (Helie et al, 1991;Neef et al, 1994;Higgins et al, 1997), rabbits (Polotsky et al, 1977;Peeters et al, 1984a), human beings (Ulshen and Rollo, 1980;Rothbaum et al, 1982), monkeys (Mansfield et al, 2001b) and poultry (Fukui et al, 1995). In general, bacteria adhere to enterocytes in an extensive or multifocal pattern and typically have a distinct, coccoid appearance (Janke et al, 1989).…”

“…By contrast, weanling rabbits are typically affected at 4-6 weeks of age (Peeters et al, 1984d) by strains belonging to a range of serotypes, the most common of which include O15:H-, O26:H11, O103:H2 and O109:H2 (Peeters et al, 1984d(Peeters et al, , 1988Blanco et al, 1996). Experimentally, strains produced diarrhoea of variable consistency in a proportion of inoculated rabbits (Peeters et al, 1984d;Heczko et al, 2000); they differed in virulence (Peeters et al, 1988) and appeared to be avirulent in suckling rabbits, despite forming AE lesions in vivo (Peeters et al, 1984a). Diarrhoea started typically at approximately 6 days postinoculation (Cantey and Blake, 1977;Peeters et al, 1984d) and the gross findings included liquid intestinal contents, thickening or oedema of the intestinal wall, and swollen mesenteric lymph nodes (Cantey and Blake, 1977;Peeters et al, 1984d).…”

Role of non-O157 VTEC

“…A case of bloody diarrhoea from the United Kingdom has been reported (Thomas et al 1996), and it has been isolated from healthy humans in Canada Rahn et al 1998). This serotype is well known as a rabbit EPEC (Peeters et al 1984).…”