Pseudomonas aeruginosa and Staphylococcus aureus are the two most common pathogens associated with HAP, VAP, and HCAP. All available evidence suggests that these organisms have become more resistant to antimicrobials over the past 10-15 years (63). MRSA is currently > 50% and fluoroquinolone resistance in Pseudomonas aeruginosa is at a similar rate. The key decision in initial empiric therapy is determining if the patient has risk factors for MDR organisms. The time of onset of HAP is used to classify patients as either “early-onset” or “late-onset” (5). However, many patients are admitted after a recent hospitalization or from a healthcare-associated facility (nursing home, dialysis center, etc.). These patients should be classified as at risk for MDR pathogens, regardless of when the pneumonia begins in the course of the current hospitalization. Healthcare-associated infections are bacteriologically similar to hospital-acquired infections (4,6,71-73). Most patients with HCAP are at risk for infection with MDR organisms, but in studies of HAP and VAP, hospitalization for at least 5 days is required to increase the risk of infection with these organisms (51).