This is a study on the effect of streptomycin, paraaminosalicylic acid, and sulfathiazole on tubercle bacilli. The findings of the author are essentially similar to those of other investigators:
Streptomycin-resistant strains of the tubercle bacillus are morphologically identical with corresponding streptomycin-sensitive strains.
Different strains develop resistance in vitro at a varying rate and in different degrees. Strains that have not been exposed to streptomycin may include highly streptomycin-resistant variants.
The growth of streptomycin-resistant strains on streptomycin-containing medium proceeds morphologically just as on normal medium. Such strains do not consist exclusively of organisms with the same degree of resistance but include also more sensitive cells.
Streptomycin resistance is specific, and streptomycin-resistant strains form no streptomycin-inactivating substance.
Streptomycin-resistant strains are affected morphologically by paraaminosalicylic acid as normal strains are, and their sensitivity to the drug is identical with that of corresponding sensitive strains.
Acquired resistance to paraaminosalicylic acid appears to occur frequently,