Key Point

It has been established that health care–associated pneumonia is a unique disease entity with clear differences from community-acquired pneumonia.

ST. LOUIS—As medicine evolves, it must sometimes break with tradition. Such a break may again be necessary, this time in the way that pneumonia is classified.

In a large multi-institutional study, it was confirmed that pneumonia related to care in nursing homes and other nonhospital facilities is a distinct entity with its own unique microbiology, epidemiology, and outcomes. Thus, it should no longer be called community-acquired pneumonia (CAP) but health care–associated pneumonia (HCAP), said the study authors.¹ Lead author Marin H. Kollef, MD, is Associate Professor in the Division of Pulmonary and Critical Care Medicine at Washington University in St. Louis.

"HCAP, traditionally classified into the CAP category, is clinically more similar to HAP and should be treated as such until culture data become available," the authors asserted. "[T]he next generation of national treatment guidelines ... would benefit by differentiating HCAP from CAP."

Using a large database of US inpatients, the authors retrospectively analyzed the records of 4,543 patients hospitalized with culture-positive pneumonia during a two-year period. Of these patients, 48.9% had CAP, 21.7% had HCAP, 18.4% had hospital-acquired pneumonia (HAP), and 11% had ventilator-associated pneumonia (VAP).

The rate of infection with Staphylococcus aureus, the predominant pathogen in all pneumonia groups, was 25.5% in the CAP group, 46.7% in the HCAP group, 47.1% in the HAP group, and 42.5% in the VAP group.

"The rate of MRSA infection (56.8%) in HCAP patients with S aureus infection was significantly higher than in patients with all other pneumonia types," pointed out the authors. Among CAP, HAP, and VAP patients infected with S aureus, the MRSA rates were 34.8%, 48.6%, and 34.4%, respectively.

Of the gram-negative pathogens detected, Pseudomonas species predominated; the infection rates were 17.1% for CAP, 25.3% for HCAP, 18.4% for HAP, and 21.2% for VAP. Haemophilus, Klebsiella, Escherichia, Enterobacter, and Acinetobacter species were among the other gram-negative organisms that were found in the four pneumonia groups.

The mean length of hospital stay was 7.5 days for CAP, 8.8 days for HCAP, 15.2 days for HAP, and 23 days for VAP.

In an editorial that accompanied the study,² Hiramatsu and Niederman remarked that "the findings in this study establish very clearly that HCAP is a unique entity and one that differs from CAP, and in many ways is similar to nosocomial pneumonia, either HAP or VAP."

—Timothy Begany

References
1. Kollef MH, Shorr A, Tabak YP, et al. Epidemiology and outcomes of health-care–associated pneumonia: results from a large US database of culture-positive pneumonia. Chest.2005;128:3854-3862.
2. Hiramatsu K, Niederman MS. Health-care–associated pneumonia: a new therapeutic paradigm. Chest. 2005; 128:3784-3787.

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