Characterization of sulfonamide resistance determinants and relatedness of Bordetella avium R plasmids.

Five plasmids, varying in size from 16 to 51.5 kb, were isolated from virulent strains of Bordetella avium and compared by restriction endonuclease digestion and DNA-DNA hybridization. These plasmids confer resistance to streptomycin and sulfonamides, and three of the five also confer resistance to tetracycline, but they are not closely related. Four of the plasmids, pRL100, p4093, pCW, and pWAM, carried determinants related to the heat-labile type I plasmid-mediated dihydropteroate synthase of the plasmid R388, while one plasmid, p4168, carried a determinant related to the heat-stable type II dihydropteroate synthase of pGS05.