Activity of linezolid against Gram-positive cocci possessing genes conferring resistance to protein synthesis inhibitors

Linezolid belongs to a new class of antimicrobials, the oxazolidinones, tha t act by inhibiting protein synthesis. To detect cross-resistance with othe r inhibitors of protein synthesis (chloramphenicol, macrolides, lincosamide s, streptogramins, aminoglycosides and tetracyclines), the in vitro activit y of linezolid was determined against isolates harbouring known genes confe rring resistance to these antimicrobials. Neither the presence of modifying enzymes (LinA, LinA', LinB, Vgb, Vat, SatA, ANT(4') (4")-I, AAC(6')-APH(2" ), APHA-3 and Cat), nor the presence of an efflux mechanism (MsrA, MefE, Me fA, MreA, Vga, TetK and TeL), nor the modification or protection of antimic robial target (because of ribosomal methylases or TetM and TetO) affected l inezolid activity as demonstrated by similar in vitro activity against resi stant isolates and sensitive control isolates.