Newer antibiotics for MRSA and other Gram - positive cocci infections

NEWER ANTIBIOTICS FOR MRSA AND OTHER GRAM - POSITIVE COCCI INFECTIONS

It is not only MRSA that has become a major problem organism in recent years; VRE and penicillin-resistant Strep. pneumoniae (pneumococci) have also become much more prevalent, prompting fears of serious treatment problems due to the small number of antibiotics that remained effective. The emergence of Staph. aureus strains which showed intermediate sensitivity to vancomycin or to glycopeptides in general (designated VISA or GISA respectively) caused particular concern, and accelerated the introduction of three new antibiotics intended primarily for the treatment of Gram-positive cocci infections.

The first of these, approved in 1999, is a fixed-ratio combination of the two streptogramin antibiotics, dalfopristin and quinupristin (30 : 70). This bactericidal intravenous product is recommended for the treatment of serious infections with vancomycin-resistant Ent. faecium and multiresistant strains of staphylococci and pneumococci. The second, linezolid (2001), is an orally active, synthetic antimicrobial possessing an essentially bacteristatic action against Gram-positive organisms, with no useful activity against Gram-negatives. It is used for the treatment of MRSA, VRE and pneumococcal infections, and although isolated early reports of resistance did arise, the development of resistance during treatment has been rare. Daptomycin (2003) is a lipopeptide with a novel mode of bactericidal action destabilizing the bacterial cell membrane, which means that cross-resistance with existing drugs is unlikely to arise. It is administered intravenously and used for skin and soft tissue infections by Gram-positive organisms and for Staph. aureus endocarditis; it is particularly useful for infections by VISA and GISA strains of this species.