OBSERVATIONS ON THE SUSCEPTIBILITY OF PNEUMOCOCCI TO SULFAPYRIDINE, SULFATHIAZOLE AND SULFAMETHYLTHIAZOLE

Abstract

Strains of pneumococci initially susceptible to the bac-teriostatic action of either sulfapyridine, sulfathiazole or sulfamethylthiazole were made resistant by growth in media containing increasing concs. of each of these 3 drugs. Strains accommodated in this manner to growth in any one of these drugs acquired resistance of a high degree to the action of the homologous drug, and also became resistant to the other 2 chemicals to approx. the same extent. Strains varied in the ease with which fastness was acquired. Strains of pneumococci isolated from patients before treatment with drugs was started almost all showed a high degree of susceptibility to sulfapyridine, sulfathiazole and sulfamethylthiazole in vitro. Individual strains and types varied in this respect. The greatest resistance was found among Type XXXIII strains. Strains isolated from 3 patients after several days of drug therapy and during a relapse of pulmonary infection were found to be relatively resistant to the drugs. In 2 cases, pneumococci of the same type, isolated before the beginning of drug therapy, were found to be highly susceptible. In other patients who failed to respond to chemotherapy, however, no change in the susceptibility of the pneumococci could be demonstrated.