OBSERVATIONS ON THE PHYSICAL AND BIOLOGICAL CHARACTERISTICS OF LEPTOSPIRA

Abstract

Morphologically, Leptospiras are exceedingly variable, the form and size depending on medium, temp., and rate of growth. They carry a positive charge at ordinary reactions, but at p h 9.2, become negatively charged. The important distinctions between Leptospira and some of the true viruses are sedimentability and filter-ability. Leptospira may be sedimented by prolonged centrifugation at 3000 revolutions; 4-5 hrs. seem to suffice practically to free a suspension. Only a relatively small proportion of the organisms pass through a Berkefeld or Seitz filter. Leptospiras are readily cultivable on artificial media. The most satisfactory procedure for primary cultivation from infected animals is to cover the blood-free fibrin clot, or sedimented red cells, with a small amount of Noguchi''s Leptospira medium. Leptospiras are obligatory aerobes and the pathogenic forms die promptly when placed under anaerobic conditions.