Resistance to spiramycin in Streptomyces ambofaciens, the producer organism, involves at least two different mechanisms

Spiramycin resistance in antibiotic-producing Streptomyces ambofaciens was studied. Analysis of the development of spiramycin resistance revealed at least two distinct mechanisms. A spiramycin-inducible mechanism involving ribosomal modification conferred resistance to spiramycin and other macrolide antibiotics. The second resistance mechanism, observed in non-producing mutants, might be temporally regulated and could involve decreased permeability to the antibiotic.