Growth, cultural characteristics, and antibacterial sensitivity of Leptospira interrogans serovar hardjo

Nutrient requirements of Leptospira interrogans serovar hardjo were investigated using a 1% bovine serum albumin (BSA) medium, supplemented separately with polysorbates (Tweens) 80, 60, 40, 20, NH4Cl, and vitamins thiamine and cyanocobalamin (vitamin B12). L. hardjo was tested in vitro against 30 antibacterial compounds incorporated into semisolid medium (0.2% agar) at 3 compound concentrations. Growth was superior in polysorbate 80 (oleic acid rich) and polysorbate 40 (palmitic rich) media. A linear growth response to vitamin B12 could be shown. Hamster isolates all required thiamine and vitamin B12 for growth. The antibacterial compounds could be classed as: 100% bacteriocidal, bacteriocidal at the 2 highest concentrations, bacteriocidal at only 1 concentration, and completely noninhibitory. The tetracyclines were strongly bacteriocidal. The comparative growth rates of hamster isolates were much reduced when compared to the type strain hardjoprajitno. These studies were performed acknowledging that the polysorbates were mixtures of fatty acids. Nephelometry was used as an accepted method to monitor the synthesis of leptospiral cell mass.