Methicillin-resistant staphylococci and their treatment in the intensive care unit.

Methicillin resistance in Staphylococcus aureus (MRSA) and the coagulase-negative staphylococci (MRCNS) is widespread and continues to increase in prevalence, particularly in the health care setting. The clinical significance of methicillin resistance for patients with staphylococcal infections is not clear: studies in patients with bacteremia, pneumonia, and mediastinitis show a higher mortality with MRSA infection compared to methicillin-sensitive Staphylococcus aureus (MSSA) infection, though this may be due to underlying patient, pharmacodynamic, or microbiological differences. For serious methicillin-resistant staphylococcal infections, vancomycin-based regimens are preferred. Treatment alternatives for patients with severe methicillin-resistant infections who are unable to tolerate vancomycin include linezolid and quinupristin/dalfopristin; these agents should be considered second-line options, given the relative lack of clinical experience and the nonsignificant but consistent trends toward worse outcomes in bacteremia and pneumonia with these agents compared to vancomycin. For less severe infections, treatment options also include trimethoprim-sulfamethoxazole, or fluoroquinolones in combination with rifampin.