Differences in the outer membrane-related properties of the six classical Brucella species.

Outer membrane-related properties (such as auto-agglutination and susceptibility to various compounds) of strains representative of the six classical species of the genus Brucella were assessed. The differences identified could not be fully explained based on the smooth or rough phenotype of the strain. Smooth strains of the closely related species Brucella melitensis and B. abortus exhibited different susceptibility patterns and the rough, virulent B. ovis and B. canis strains were equally or more resistant to conditions such as pH, non-immune serum, hydrogen peroxide and bactericidal cationic peptides than smooth strains. Such heterogeneity in outer membrane characteristics could account for differences in pathogenicity and host tropism.