Comparative in Vitro Response of Tubercle Bacillus (H37RV) to Dihydrostreptomycin,Para-aminosalicylic Acid,and Dihydrostreptomycin-para-aminosalicylate. ∗

Abstract

Summary

1. The in vitro growth of the H37Rv strain of tubercle bacilli was inhibited by 0.82 νg DHSM/cc, by a concentration of DHSM-PAS containing 0.41 νg DHSM/cc and by 0.205 νg DHSM/cc when PAS was added in a 3:1 molecular ratio of PAS: DHSM. 2. The fifth serial transfer of H37Rv into increasing concentrations of DHSM resulted in a stain growing readily in over 2000 νg DHSM/cc while the tenth such transfer of the organisms into increasing concentrations of DHSM-PAS resulted in a strain growing readily in over 1000 νg DHSM-PAS/cc. No increase in resistance on the part of organisms transferred into increasing concentrations of DHSM with PAS present in a 1:3 molecular ratio has so far been found. 3. Organisms resistant to the compound (DHSM-PAS) were found to be also resistant to DHSM alone, to PAS alone, and to the mixture of DHSM and PAS.