AF/R2 Adhesin and Cytopathic Effect as Virulence Traits of Diarrhea-Inducing Escherichia coli O103 in European Rabbit

Abstract

Escherichia coli strains belonging to 0103:K-:H2 serovar and rhamnose negative biovars are responsible for frequent life-threatening diarrheas in weaned rabbits from national breeding units in western Europe (Blanco et al., 1994; Camguilhem and A. Milon, 1989). According to their mechanisms of pathogenesis, these strains may be considered as enteropathogenic E. coli (EPEC)-like. They adhere to intestinal brush border and to HeLa cells by mean of an adhesin called AF/R2 (Adhesive Factor/Rabbit 2) (Milon et al., 1990). They do not produce known toxins (i.e. ST, LT, SLT, CNF, CLDT) (Blanco et al., 1994; Mariani-Kurkdjian et al., 1993) and bear sequences homologous to EPEC eaeA (Leroy et al., 1994). Recently, a new phenotype has been identified based on an in vitro test that includes a short contact between bacterias and HeLa cells, followed by washes and incubation of cells in presence of gentamicin. After several days, cells treated by 0103 strains develop a cytopathic effect (CPE): apparition of giant cells with a heavy stress fibers cytoplasmic network.