Transmission and pathogenicity of Gallibacterium anatis and Escherichia coil in embryonated eggs

摘要

In laying hens, Escherichia colt (E. coil) and Gallibacterium anatis (G. anatis) are considered the two major pathogens causing reproductive tract disorders, either as single infections or as co-infections. Vertical transmission has been confirmed for E. con but remains to be clearly demonstrated for G. anatis. The aim of the present study was to investigate the ability of both G. anatis and E. coil at eggshell transmission using an embryonated egg dipping model, and to investigate the possible interaction between the two organisms in an embryonated egg injection model. Embryonated eggs were dipped into brain heart infusion broth containing 10(8) CFU/ml either of G. anatis 12656-12 liver, E. coil ST95 or E. coil ST141, respectively. E. colt ST95 and ST141 were re-isolated from the interior egg contents in 60% (12/20) and 85% (17/20) of the eggs, respectively, while G. anatis 12656-12 was only re-isolated from the interior egg contents in 6.7% (3/45) eggs. Eggs were injected with 10-1000 CFU of either G. anatis 12656-12, E. coli ST95 or ST141 into the allantoic cavity. As few as 10 CFU of G. anatis 12656-12 resulted in 100% mortality within 24 h post injection whereas the E. colt injected embryos all died at 48 h post injection. Significant difference in CFU counts were observed for G. anatis when compared G. anatis injection group with either of the two G. anatis E. coil co-injection groups. Sixteen hours post injection, a significant difference in embryo mortality could be observed when comparing co-injected embryonated eggs (G. anatis and E. coil) and single-injected (G. anatis or E. coil) embryonated eggs.