Glycosylative inactivation of chalcomycin and tylosin by a clinically isolated Nocardia asteroides strain

Studies on the susceptibility of pathogenic Nocardia to macrolide antibioti cs, chalcomycin and tylosin, showed that most of the Nocardia species exami ned were highly resistant to both antibiotics, although N. nova was moderat ely susceptible. N. asteroides IFM 0339 converted these macrolides into ina ctive metabolites by glycosylation at 2'-OH or glycosylation and reduction of the 20-formyl group. The structures of the metabolites were determined f rom NMR and MS data to be 2'-[O-(beta -D-glucopyranosyl)]chalcomycin (2), 2 '-[O-(beta -D-glucopyranosyl)]tylosin (5) and 20-dihydro-2'-[O-(beta -D-glu copyranosyl)]tylosin (4).