Studies on Pathogenic Leptospirae

VI. Effect of Tween 80 on the Growth of Leptospira canicola and Leptospira icterohaemorrhagiae

Abstract

Effect of Tween 80 on the growth of Leptospira canicola strain Utrecht and L. icterohaemorrhagiae strain Mikawajima was examined. The suspension of washed leptospira was inoculated into modified Korthof's basal medium containing varied amounts of Tween 80 and cultured at 30 C. Cell numbers were counted by using Petroff-Hausser counting chamber every other day. Optimum Tween 80 concentrations for L. canicola were 0.0125 and 0.025%. Cell counts in the second sub-cultures reached 108 per ml the same as the primary cultures. Generation time of L. canicola in 0.025% Tween 80 medium was about 13 hours. Growth of L. icterohaemorrhagiae was inhibited at concentrations greater than 0.0125 per cent. Cell numbers increased about 4 times at concentration of 0.0000125% Tween 80. L. canicola utilizes Tween 80 as a nutrient while L. icterohaemorrhagiae appears sensitive to it. A difference of more than 1, 000 times in maximal growth-supporting concentration between L, canicola and L. icterohaemorrhagiae exists. This difference appears to be caused by difference in surface structure and metabolic requirements.