Publication

Abstract : Approximately 10% of S. aureus isolates in the United States are susceptible to penicillin. However, many S. aureus strains, while resistant to penicillin, remain susceptible to penicillinase-stable penicillins, such as oxacillin and methicillin. Strains that are oxacillin and methicillin resistant, historically termed methicillin-resistant S. aureus (MRSA), are resistant to all ß-lactam agents, including cephalosporins and carbapenems, although they may be susceptible to the newest class of MRSA-active cephalosporins (e.g, ceftaroline). Strains of MRSA causing healthcare-associated infections are often resistant to other commonly used antimicrobial agents, including erythromycin, clindamycin and fluoroquinolones, while strains causing community-associated infections are often resistant only to ß-lactam agents, erythromycin and occasionally to fluoroquinolones. Since 1996, MRSA strains with decreased susceptibility to vancomycin (minimum inhibitory concentration [MIC], 4 – 8 μg/ml) and strains fully resistant to vancomycin (MIC ≥ 16 μg/ml) have been reported.