DIFFERENTIATION OF PATHOGENIC AND SAPROPHYTIC LEPTOSPIRES WITH 8-AZAGUANINE.

Johnson, Russell C. (University of Minnesota, Minneapolis), and Palmer Rogers. Differentiation of pathogenic and saprophytic leptospires with 8-azaguanine. J. Bacteriol. 88:1618-1623. 1964.-The use of the purine analogue, 8-azaguanine, as a differential agent for the separation of pathogenic and saprophytic leptospires was investigated. Growth of strains of the saprophyte Leptospira biflexa was almost insensitive to the bacteriostatic action of 8-azaguanine at concentrations varying from 25 to 600 mug/ml; these saprophytic leptospires were serially transferred five times in media containing 225 mug without any change in growth rate or cell yield. In contrast, decreased growth rate and cell yield of the pathogenic serotypes were observed with 25 to 50 mug/ml of 8-azaguanine. Complete inhibition of growth occurred at concentrations of 100 mug/ml and above. A medium containing 225 mug/ml of 8-azaguanine was successfully used to differentiate 20 serotypes of pathogenic leptospires and 10 saprophytic strains. L. andaman CH11, L. semarang Veldrat S1 73, and L. andaman Correa, were classified with the L. biflexa strains on the basis of their growth response to 8-azaguanine.