Cross‐reactivity of the Axial Filament Antigen as a Criterion for Classification of Leptospira

Summary The relationship aniong 36 strains of leptospires belonging to 15 serogroups was established, using the cross‐reactivity of the axial filament antigen in the immunodiffusion reaction as a criterion. The pattern of cross‐reactions obtained was analysed by a hierarchical method, using agglomerative‐polythetic strategy. Eight groups were formed, comprising two complexes. These new groups showed limited correlation with the current classification based on agglutinin‐absorption reactions, but showed some correlation with classifications based on other data, such as genetic homology, resistance to purine analogues and lipase activity.