ibeA, a virulence factor of avian pathogenic Escherichia coli

The presence of ibeA, a gene encoding a known virulence factor of Escherichia coli strains responsible for neonatal meningitis in humans, was investigated in the genome of 213 avian pathogenic E coli (APEC) strains and 55 non-pathogenic E coli strains of avian origin. Fifty-three strains were found to be ibeA(+), all of which belonged to the APEC group. The ibeA gene is therefore positively linked to the pathogenicity of strains (P < 0.0001). Analysis of the serogroup of strains revealed a positive association of ibeA with serogroups O18, O88 and O2. On the contrary, only 1/59 078 strains are ibeA(+), indicating a negative association of ibeA with this serogroup (P < 0.0001). The role of ibeA in the virulence of the APEC strain BEN 2908 was investigated by constructing an ibeA mutant. Challenge assays on 3-week-old chickens showed a reduced virulence for the ibeA mutant. Furthermore, the APEC strain BEN 2908 was able to invade brain microvascular epithelial cells, this invasion being significantly reduced upon inactivation of ibeA. Altogether, these results suggest a role of ibeA in the pathogenicity of some APEC strains and confirm the close relationship between APEC and other human extraintestinal pathogenic E. coli isolates.