Description d’un sérogroupe (0103) d’Escherichia coli entéropathogène chez le lapin au sevrage

Protection of weaned rabbits against experimental Escherichia coli O103 intestinal infection by oral formalin-killed vaccine

In an attempt to vaccinate young weaned rabbits against life-threatening enterocolitis caused by Escherichia coli of the O103 serogroup, 32 New Zealand male rabbits were divided into three groups. One group remained unvaccinated as a control (Group C), and each of the other groups received one of two types of vaccine prepared with E. coli strain O103/10 cultured either in trypticase-soy broth (Group A) or in Minca agar (Group B). Bacteria were killed by formalin and administered per os for 10 consecutive days after weaning at a daily dose of 4 X 10(9) organisms. Six days after the last administration, all the animals were challenged with 1 X 10(4) virulent E. coli O103/10 and the experimental infection was monitored for 26 days. All rabbits in Group A were protected from symptoms of disease and remained alive, whereas two rabbits in Group B developed clinical signs and one died. Protection did not correlate with local or general responses to lipopolysaccharide (LPS) O103, as judged by measurement of anti-LPS O103 IgA in faeces or serum, or by serum agglutinating antibodies. Numbers of E. coli and E. coli O103 were significantly lower in vaccinated animals of Group A as compared with animals of the control group. The differences between both vaccine regimens may be partially explained by a different expression of the adhesins of strain O103/10, depending on the medium used to prepare the vaccine.

Enteric infections caused by non-enterotoxigenic Escherichia coli in animals: occurrence and pathogenicity mechanisms. A review

Not all E. coli that cause diarrhoea in farm animals act by elaborating the classical heat-labile or heat-stable enterotoxins. These newly recognised animal enteropathogenic E. coli (EPEC) attach to and efface the microvilli of the gut epithelium and resemble the well known human EPEC. In rabbits, only this type of E. coli enteritis is known to be important and a similar disease has been shown to occur in cattle also. There is no doubt that adherence factors are important in the pathogenesis of animal EPEC, but they are not well understood when compared with the adhesion of human EPEC, or to the adhesion of animal ETEC. The enteropathogenic effect is probably due to Shiga-like toxin, a cytotoxin that is active on Vero cells and has also been called Verotoxin. A different type of Verotoxin is produced by most serotypes that are associated with post-weaning diarrhoea and oedema disease in pigs. This toxin is suspected to play a role in the pathogenesis of the latter.

Biotypes of enteropathogenic Escherichia coli strains from rabbits

Forty-five enteropathogenic (enteropathogenic Escherichia coli-like) strains isolated in commercial rabbit farms were subdivided into four biotypes with the help of six carbohydrate fermentation tests, ornithine decarboxylase tests, and motility tests. E. coli strains which caused neonatal diarrhea in baby rabbits belonged to a single biotype, biotype 1, and displayed the same serotype antigens. Biotype 2 strains provoked diarrhea of variable severity in weaned rabbits and were also pathogenic for baby rabbits under laboratory conditions. Biotype 1 and biotype 2 strains resembled each other in many respects. Biotype 3 and biotype 4 (represented by a single strain) were highly pathogenic for weaned rabbits, but they provoked no symptoms or lesions in baby rabbits. Biotype 3 formed a homogeneous group of nonmotile strains which possessed the O15 antigen. Forty-two strains from nondiarrheic rabbits constituted a very heterogeneous collection of biotypes, most of which could easily be differentiated from the pathogenic types. Biotyping can be used to recognize rabbit pathogenic strains.