Strain Specificity and Production of Antibiotic Substances

Abstract
Different strains of the same bacterial sp. may vary greatly in their sensitivity to streptomycin. The ratio of sensitivity to a given prepn. varied for Escherichia coli from 100 to 10 units with an av. of 35; for Proteus vulgaris 75 to 10 units (av. 35); for Staphylococcus aureus, 20 to 75 units (av. 34); and for Bacillus subtilis, 30 to 250 units (av. 109). A streptomycin-resistant strain of P. vulgaris showed also a certain degree of resistance to streptothricin but none at all to clavacin. A strain of S. aureus that was made only slightly resistant to streptomycin showed no resistance to streptothricin. Several highly resistant strains of S. aureus showed no increase in resistance to clavacin and to an antibiotic substance isolated from a spore-forming soil bacterium, and only a trace of increased resistance to streptothricin.

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