ACTIVITIES OF THE GLYCYLCYCLINES N,N-DIMETHYLGLYCYLAMIDO-MINOCYCLINE AND DIMETHYLGLYCYLAMIDO-6-DEMETHYL-6-DEOXYTETRACYCLINE AGAINST NOCARDIA SPP AND TETRACYCLINE-RESISTANT ISOLATES OF RAPIDLY GROWING MYCOBACTERIA

Susceptibilities to the new semisynthetic tetracycline (Tet) compounds N,N-dimethylglycylamido-minocycline (DMG-MINO) and dimethylglycylamid o-6-demethyl-6-deoxytetracycline (DMG-DMDOT) were compared with those to doxycycline, minocycline, and Tet for 198 Tet-resistant (Tet(r)) an d 33 Tet-susceptible (Tet(s)) clinical isolates of rapidly growing myc obacteria (RGM) including the Mycobacterium fortuitum group, Mycobacte rium abscessus, Mycobacterium chelonae, and Mycobacterium mucogenicum and 68 isolates belonging to six taxa of Nocardia spp, All Tet(r) RGM were highly susceptible to the glycylcyclines. The MICs at which 50 an d 90% of isolates are inhibited were less than or equal to 0.125 and l ess than or equal to 0.25 mu g/ml, respectively, for DMG-DMDOT and les s than or equal to 0.25 and 1 mu g/ml, respectively, for DMG-MINO, The MIC of DMG-DMDOT at which 50% of Tet(r) strains are inhibited was the same as that for Tet(s) strains for each of the four taxa of RGM, The new agents were less active against Nocardia spp. MICs of DMG-DMDOT w ere comparable to those of minocycline except for the MICs for Nocardi a brasiliensis sensu stricto, the new taxon Nocardia pseudobrasiliensi s, and some isolates of Nocardia nova, against which they were four- t o eightfold more active, The MICs of DMG-DMDOT were consistently lower than those of DMG-MINO for RGM. This class of drugs offers exciting t herapeutic potential for RGM and for selected species of Nocardia.