Development of Resistance to and Dependence on Streptomycin in Mycoplasma pneumoniae In Vitro

ABSTRACT Mycoplasma pneumoniae developed high degrees of resistance to streptomycin and dependence on streptomycin after serial subculture in broth media containing streptomycin. The streptomycin‐dependent organisms failed to grow, as indicated by a color change of the medium, in the absence of streptomycin but grew in limited concentrations of streptomycin in broth media. The minimum growth‐inhibitory concentration of streptomycin for the parent sensitive strain was very close to the minimum concentration of streptomycin which permitted the growth of the streptomycin‐dependent organism. The broth cultures showing streptomycin dependence were shown to consist of streptomycin‐dependent organisms or a mixture of streptomycin‐dependent and ‐resistant organisms, as tested on agar media containing varying concentrations of streptomycin.