When Leptospira canicola was grown in a synthetic medium in the presence of 14C‐labeled acetate, the acetate was readily oxidized and incorporated into non‐lipid components of the cells. Only very small amounts of 14C‐acetate were incorporated into long chain fatty acids. The effect of the addition, to the growth medium, of different long chain fatty acids, on the fatty acid composition of phosphatidylethanolamine and triglycerides of L. canicola was studied. When grown on palmitate, palmitic acid, cis‐Δ9‐ and cis‐Δ11‐hexadecenoic acid were isolated. When grown on stearate, stearic, palmitic, oleic and cis‐Δ11‐hexadecenoic acid were found. When grown on oleate the later was the major component of the cell's lipids. Phosphatidylethanolamine isolated from L. canicola which was grown on Tween, contained oleic acid at the α position and palmitic, stearic and 11‐hexadecenoic acid at the β position. When L. canicola was grown in the presence of [1‐14C]palmitate or [1‐14C]stearate the corresponding monounsaturated acids were also labeled. Oxidative decarboxylation of 14C‐labeled 11‐hexadecenoic acid isolated from L. canicola which was grown on Tween plus [1‐14C]‐palmitate indicated that the monoenoic acid was labeled exclusively at the carboxy‐carbon.

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A protein-free chemically defined medium for cultivation of pathogenic Leptospira was developed. The medium permitted continued serial subculturing of 9 serogroups (52 strains) of the 12 serogroups (61 strains) tested. Growth was initiated from small inocula, and the growth rate and maximal cell yields were similar to those on serum-containing media. The nutritional requirements of serogroups L. canicola, L. pomona, and L. grippotyphosa were studied in a basal medium composed of inorganic salts, a fatty acid, vitamin B12, and thiamine. AU strains tested utilized ammonium chloride as the sole nitrogen source. A fatty acid, vitamin B12, and ferrous ions were essential. Growth and calcium ions. was stimulated by thiamine, potassium,

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In 1970-1979, the incidence of human leptospirosis in Israel was 0.7 per 100,000 population. The majority of the cases (62%) occurred in northeastern Israel (Upper Galilee). Prior to 1973 the main infecting serotypes were grippotyphosa (41%) and Hebdomadis szwajizak (31%). Following the first outbreak of Hebdomadis hardjo infection in 1973, a change occurred in the epidemiologic pattern of human leptospirosis, with hardjo becoming the most common serotype (59%). Hardjo infection outbreaks were sporadic and localized to dairy farms. The peak of incidence was during the summer months, June-September. All the patients with hardjo were dairy workers. The illness was relatively mild and mostly unicteric. Cattle seemed to be the principal source of hardjo infection for man.