N,N-DIMETHYLGLYCYL-AMIDO DERIVATIVE OF MINOCYCLINE AND 6-DIMETHYL-6-DESOXYTETRACYCLINE, 2 NEW GLYCYLCYCLINES HIGHLY EFFECTIVE AGAINST TETRACYCLINE-RESISTANT GRAM-POSITIVE COCCI

The in vitro activities of the N,N-dimethylglycyl-amido derivative of minocycline (DMG-MINO) and 6-dimethyl-6-dexoxytetracycline (DMG-DMDOT) , members of a new generation of tetracyclines, were evaluated by an a gar dilution method and were compared with those of tetracycline and m inocycline against 224 tetracycline-resistant and 73 tetracycline-susc eptible recent clinical isolates of gram-positive cocci, including mul tiple-antibiotic-resistant methicillin-resistant Staphylococcus aureus and penicillin-resistant Streptococcus pneumoniae. The MICs of DMG-MI NO and DMG-DMDOT were up to 500- to 2,000-fold lower than those of tet racycline against methicillin-resistant S. aureus and Streptococcus pn eumoniae (MIC for 50% of strains tested [MIC(50)], <0.06 mu g/ml). Aga inst Streptococcus groups A, B, C, and G and Enterococcus faecalis, th e MIC,, was 0.5 mu g/ml. MIC(50)s were greater only for coagulase-nega tive staphylococci (2 mu g/ml). These data indicate that DMG-MINO; and DMG-DMDOT are very potent drugs, and further in vitro and in vivo stu dies are warranted.