Susceptibility of Organisms of the Order Mycoplasmatales to Optochin

Fifty-two Mycoplasma and Acholeplasma strains, including eight T-mycoplasmas, were tested for their susceptibility to optochin to determine the value of the test for differentiating between these organisms. Taxo-P discs showed a marked variation in their inhibitory effect from lot to lot and within each lot. They were found unsuitable, and wells withoptochin solution were used instead. Some difference in susceptibility to optochin was found not only between but also within the tested Mycoplasma and Acholeplasma species. The T-mycoplasmas appeared to be more resistant to optochin than the other mycoplasmas and the acholeplasmas. From the results of this study it is concluded that the optochin test isof very limited value in the characterization and identification of mycoplasmas and acholeplasmas.