Cloning of Bordetella bronchiseptica urease genes and analysis of colonization by a urease-negative mutant strain in a guinea-pig model.

The genes encoding urease were cloned from Bordetella bronchiseptica and the 5.2 kb of DNA essential for expression analysed in a T7 RNA polymerase transcription-translation system. At least four polypeptides with predicted molecular weights of 69,000, 26,000, 12,200 and 11,000 were found. Partial DNA sequence of the gene encoding the 69,000 Da polypeptide revealed high amino acid identity to the alpha-subunit of Proteus mirabilis urease, UreC and jack bean urease. A stable, unmarked deletion was constructed in this gene to create a urease-negative mutant of B. bronchiseptica. To assess colonization in a guinea-pig model, the urease-negative strain was inoculated with the urease-positive parental strain in a mixed infection. The urease-negative strain out competed the urease-positive strain in the trachea, lungs and caecum. We demonstrate that urease is not essential for B. bronchiseptica colonization of the guinea-pig respiratory and digestive tracts.