A Variant of Mycobacterium ranae Requiring Streptomycin for Growth

Abstract

M. ranae is a fast-growing, acid-fast, nonpathogenic bacillus, which rapldly develops streptomycin resistance in vitro. When streptomycin resistant organisms were heavily plated on a deficient medium containing streptomycin, and incubated for 10-15 days, another variant was isolated which would grow only in the presence of streptomycin (100 [gamma]/ml.). Unlike the parent and the streptomycin-resistant strains, this variant was not inhibited by sulfathia-zole. The work is continuing in an attempt to isolate a similar variant from pathogenic tubercle bacilli.