STUDIES ON LEPTOSPIRA ICTEROHAEMORRHAGIAE. II. A CRITICAL STUDY OF THE EFFECT OF PENICILLIN ON LEPTOSPIRA ICTEROHAEMORRHAGIAE IN VITRO AND IN LEPTOSPIROSIS IN GUINEA PIGS

Abstract

Penicillin [image] 0.4 U./ml. exerted a leptospirostatic effect in vitro, but showed no leptospirocidal effect even at 5000 U./ml. The leptospirae survived a limited no. of days only, longer at low temps. The leptospirostatic effect was . also evidenced in guinea pigs by disappearance of leptospirae from the blood 3-5 days after inoculation, when a daily dosage of about 800 U. and a serum level of > 0.2 U. were maintained. This did not clear the liver of leptospirae. No advantage was obtained by increasing the dose to 3000 U. daily. Some guinea pigs in which the development of lepto-spirosis was suppressed by early admn. of penicillin relapsed several days after the last dose of penicillin, but usually recovered spontaneously due to partial immunity developed in response to the large inoculum. Agglutination tests showed that fair amts. of antibodies were produced although development of leptospirosis was suppressed. Penicillin was effective only if given before the appearance of jaundice. It is estimated that a daily dose of 250,000 to 300,000 U. should be administered to human cases for leptospirostatic effect.