Susceptibilities of Pleuropneumonia-like Organisms to Some Selective Bacteriostatic Agents

Abstract

Eight strains of pleuropneumonia-like organisms (PPLO), 4 strains of Gram-positive bacteria and 4 strains of Gram-negative bacteria were tested against selective bacteriostatic agents. Strikingly, the PPLO do not behave either as Gram-positive or Gram-negative micro-organisms in that they are not inhibited on solid medium by a 1:250,000 dilution of crystal violet, which normally inhibits Gram-positive organisms, nor by a 1:50,000 dilution of K tellurite, which normally inhibits Gram-negative organisms. Other substances tested were basic fuchsin, brilliant green, Nile Blue A, Na azide, and thionin. By using both crystal violet and K tellurite in the culture medium, the isolation of PPLO from specimens containing large numbers of bacteria is greatly facilitated.