Ventilator-associated pneumonia (VAP) is a commonplace complication of intensive care patients ventilated for longer than 48 hours. Methicillin-resistant Staphylococcus aureus (MRSA) is the cause of late onset VAP in up to about 30% of cases in US hospitals. Ineffective treatment of MRSA VAP clearly leads to prolonged mechanical ventilation and is probably associated with higher mortality. The purpose of this protocol is to directly compare linezolid and vancomycin specifically for MRSA VAP.

Inclusion Criteria:

• The patient must have or be suspected of having a ventilator-associated pneumonia (VAP) due to MRSA.
• Patient must be hospitalized for at least 5 days, must be ventilator-dependent ≥ 48 hours prior to screen/baseline, and anticipated to remain on the ventilator for 72 hours after enrollment so follow-up BAL can be performed.
• Clinical picture compatible with pneumonia (acquired during ventilation)
• Chest X Ray at baseline/screen or within 24 hours of initiation of therapy must be consistent with diagnosis of pneumonia

Exclusion Criteria:

• Hypersensitivity to linezolid, vancomycin, or one of the excipients in any of these drug formulations.
• Infections due to gram-positive organisms known to be resistant to either of the study drugs.
• Any antibiotic used in the treatment of MRSA, such as vancomycin, TMP/SMX, rifampin, or linezolid, for more than 48 hours prior to patient's enrollment into the study.
• Patients with neutropenia, AIDS, lymphoma or anticipated chemotherapy.
• Patients who have long-term tracheostomy (for more than 60 days). Acute tracheostomy patients are allowed.