The Susceptibility of Pleuropneumonia-Like Organisms to the in Vitro Action of Antibiotics: Aureomycin, Chloramphenicol, Dihydrostreptomycin, Streptomycin, and Sodium Penicillin G

Abstract

In view of the probable pathogenicity of pleuropneumonia-like organisms, their susceptibility to various antibiotics was detd. in a fluid thioglycollate medium containing 20% ascitic fluid. Streptomycin inhibited all of 12 strains of pleuropneumonia-like organisms at concns. obtainable in the blood stream. Dihydrostreptomycin affected only 6 of 12 strains and these at relatively high concns. Aureomycin and chloramphenicol likewise required high concns. to inhibit growth of susceptible strains, and enhanced the growth. Crystalline Na penicillin G did not affect the pleuropneumonia-like organism in a concn. as high as 1000 U./ml. The group of pleuropneumonia-like organisms appears to be very heterogeneous. The L forms may be bacterial variants resistant to the action of many antibiotics and chemotherapeutic agents.