Activation of complement by leptospires and its bactericidal activity.

Bactericidal activity of complement was found to be effective on saprophytic Leptospira biflexa strains and not on Leptospira interrogans strains, by means of viable counting; the killing effect on saprophytic strains was probably due to a direct activation of the complement system via the alternative pathway. On the contrary the pathogenic strains seemed to activate the complement at a lower extent and were, in any case, resistant to the lytic action of the activated complement.