Secreted Proteins of Avibacterium paragallinarum Are Lethal for Chicken Embryo
Avibacterium paragallinarum causes infectious coryza in chickens. This bacterium secretes proteins of 110 kDa (a putative RTX protein) and 120 kDa. Expression of these proteins increases by the addition of CaCl2, MgSO4, MnSO4, or ferric ammonium citrate and diminishes with CuSO4 or ZnCl2. Protein expression is optimal at 37C and pH 7.5. Mortality (90100%) of chicken embryos was observed when secreted proteins (SPs) from A. paragallinarum reference or field isolates (serogroup A or C) were inoculated via yolk sac and was not observed when SPs from A. avium, a chicken respiratory tract indigenous bacterium, were inoculated. A. paragallinarum SPs could contain toxins responsible for the embryo deaths. Indeed, presence of the putative RTX protein of 110 kDa was confirmed by Western blotting with antibodies against the Actinobacillus pleuropneumoniae RTX ApxI, a closely related RTX protein.
avibacterium paragallinarum infectious coryza rtx protein