Growth of Pathogenic Leptospirae by Replacing Rabbit Serum with Mycobacterium Phlei or Mycobacterium Smegmatis.

This strain appeared to consist of a mixture of two variants: 4 of 20 subcultures from single colonies were coagulase-negative; the remaining 16 were coagulase-positive. The two variants differed also in respect to toxin production. The hemolytic zones produced on 5% rabbit blood agar by the coagulasenegative variant were smaller than the zones produced by the coagulase-positive one. This property was shown to be constant in five successive subcultures. In fluid medium, the coagulase-negative variant did not produce any alpha toxin, whereas the coagulase-positive one produced twice the amount produced by the strain from NCTC. Consequently, the coagulasepositive variant was chosen for further alpha toxin production. The new strain from NCTC as well as the isolated variants of the strain were found to be of the same phage type: 42D, at a routine test dilution of X 1000 (Rosendal et al., Acta Pathol. Microbiol. Scand. 58:72, 1963). The two variants have been taken into the NCTC under the following numbers: coagulasepositive variant, NCTC 10,344; coagulasenegative variant, NCTC 10,345.