Virulent and Avirulent Leptospires: Biochemical Activities and Survival in Blood

SUMMARY Three strains of virulent Leptospira pomona were compared with their avirulent progeny for differences in biochemical properties which might correlate with virulence. A loss of virulence for hamsters, cattle, and swine was not characterized by a loss of hemolytic, esterase, lipase, aminopeptidase, or phospholipase C activities. Phospholipase C activity was not neutralized by serum from rabbits immunized with L. pomona. The preferred substrate for leptospiral phospholipase C activity was lecithin, but glycero-phosphorocholine, phosphatidylserine, cephalin, cardiolipin, and lysolecithin were also hydrolyzed. Sphingomyelin was hydrolyzed by virulent L. pomona organisms; avirulent L. pomona, L. canicola, L. autumnalis, L. grippotyphosa, L. bataviae, L. icterohaemorrhagiae, and L. hardjo grown in protein-free medium were inactive. The crude lipids of rabbit hepatic tissue were hydrolyzed by both virulent and avirulent L. pomona leptospires; the end products of leptospiral lipolysis hemolyzed rabbit erythrocytes. Avirulent L. pomona organisms were more sensitive to lysis by fresh rabbit blood than were virulent leptospires. The leptospiricidal effect of blood was partially inhibited by the supernatant fluid of L. pomona cultures in synthetic medium.