Growth temperatures, virulence, survival, and nutrition of leptospires.

Abstract

SUMMARY Some virulent and avirulent pathogenic leptospires and saprophytic leptospires grew continuously at 37°C, while others did not; variations amongst strains of the same serotype occurred and there was no correlation with virulence. Each of 21 strains survived 24 months’ storage in semisolid polysorbate medium (P-80 medium) without intervening subculture and one strain tested after 52 months was still viable and fully virulent. Semisolid and liquid P-80 media had a shelf-life of at least 36 and 12 months respectively at 23–25°C. One per cent. albumin was shown to favour the survival of leptospires. In experiments with modified or incomplete semisolid P-80 medium, various leptospiral strains grew and survived when polysorbate, 60,40, or 20 were substituted for polysorbate 80, and when polysorbate, NH4Cl, thiamine, or vitamin B12 were omitted. However, the omission of any polysorbate orof vitamin B12 had a strikingly adverse effect on growth. These modified media were used to culture blood infected withpomona (HCE). Continuous subculture eventually failed to produce readily-detectable macroscopic growth in the absence of either polysorbate, NH4Cl or thiamine, but continuous subculture in the absence of vitamin B12 was successful. Nutrient-depleted P-80 media were still capable of maintaining viability and a low level of growth, probably because of the micro-nutrients in the one per cent. albumin component. Continuous subculture of pomona (MU) from hamster liver was successful regardless of the presence of vitamin B12 in the medium, but vitamin B12 was essential for similar subculture of the same organism isolated from kidney.