A new type of inactivation of streptomycin by E. coli

Previously described cases of streptomycin inactivation by R-factor carrying strains of E. coli have not lead to any measurable decrease in antimicrobial potency in the bulk substrate toward the culture. In these cases each cell inactivates only a few molecules. Out of 1,800 strains of E. coli we have isolated five strains which inactivate streptomycin in large amounts giving a final concentration of the inactivation product of 0.25 mg/ml in 36 hours. Unlike all other streptomycin-resistant strains in investigated these five strains were sensitive to butyl-streptomycylamine, a streptomycin derivative acting in the same way as streptomycin. The crude inactivation product has been isolated. Inorganic phosphate is liberated by treatment with alkaline phosphatase resulting in a streptomycin-like compound without any antimicrobial activity.