Abstract
Conclusions
It was possible to increase the resistance of Gram-negative bacilli to over 50,000 units per ml, in all cases studied, by passage through increasing concentrations of streptomycin in broth and on agar plates.
In most instances resistance increased gradually, the change being more rapid on surface plates than in broth.
In the course of transfers on streptomycin agar, 4 instances of sudden increase in resistance of isolated colonies from relatively low values to over 50,000 units per ml were noted.
The organisms made resistant by exposure to streptomycin in broth showed marked pleomorphism and in some instances suffered changes in their biochemical reactions. When resistance developed as a result of exposure to the agent on surface plates, however, there was less pleomorphism, and no changes in biochemical reactions were noted. Resistant organisms obtained from the patient during or after treatment showed no morphological or cultural differences from the original sensitive strains isolated from the same patient.
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