Community-Acquired Pneumonia versus Health Care-Associated Pneumonia
In 2005, Kollef et al 9 published the first study to delineate and analyze a cohort of culture-positive health care-associated pneumonia patients.9 The most common pathogens in all pneumonia cohorts (community-acquired, health careassociated, hospital-acquired, and ventilator-associated pneumonia) were S. aureus and P. aeruginosa (Figure 2).
Mortality among health care-associated pneumonia patients was significantly greater than community-acquired pneumonia patients (19.8% vs 10.0%; P .0001), and health care- associated pneumonia etiology more closely resembled hospital-acquired and ventilator-associated pneumonia than community-acquired pneumonia. The authors concluded that health care-associated pneumonia should be a separate category of pneumonia and that its microbial etiol- ogy necessitates empiric coverage for resistant organisms. A major limitation of this study is the high incidence of resistant organisms among communityacquired pneumonia patients (17.1% Pseudomonas, 8.9% MRSA). This challenges current beliefs regarding communityacquired pneumonia etiology and would effectively make current community-acquired pneumonia treatment recommendations irrelevant if it were widely true.