Drug-Resistant Pneumonia Common

PHILADELPHIA — Drug-resistant pathogens are common among patients with severe, community-acquired pneumonia who present to the emergency department and require mechanical ventilation, based on a retrospective study with 266 patients.

“One-fifth of the patients who came through the emergency department [with pneumonia requiring mechanical ventilation support] and could not be confirmed to meet the criteria for health care-associated pneumonia had a resistant organism,” Dr. Matthew P. Schreiber said at the annual meeting of the American College of Chest Physicians.

This prevalence of drug-resistant pathogens among patients presumed to have community-acquired pneumonia was surprisingly high. The finding suggests that a severity-based guideline may work better than reliance on epidemiology to decide what empiric antibiotic regimen to use, said Dr. Schreiber, an internal medicine resident at the Washington (D.C.) Hospital Center.

For ICU patients with pneumonia who require mechanical ventilation, “antibiotic treatment to cover methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa would be appropriate,” he said.

The study examined records for patients who were admitted to the Washington Hospital Center during 2005–2007 who had a diagnosis of pneumonia and who required mechanical ventilation within 24 hours of hospitalization. Patients in the study also had microbiologic evidence of infection in a deep bronchial-brush specimen, blood culture, or urinary antigen, as well as clinical indication of infection from a primary source in their lungs. Isolates considered drug-resistant were methicillin-resistant S. aureus, P. aeruginosa, Acinetobacter, and pathogens producing an extended-spectrum β-lactamase.

Of the roughly 1,100 patients with pneumonia seen in the intensive care unit during each year studied at the hospital center, nearly 60% needed mechanical ventilation, and slightly more than 25% of these patients died during initial hospitalization. Microbiologic specimens were available for 147 patients identified with health care-associated pneumonia and for 119 patients with community-acquired pneumonia. In-hospital mortality was about 40% in both of these subgroups.

The prevalence of resistant isolates was 45% among the patients with a health care-associated infection and 21% among those who appeared to have community-acquired pneumonia. This high level of resistance in the patients with community-acquired pneumonia “was eye-opening to us,” Dr. Schreiber said.

“The concept of health care-acquired pneumonia does not fully account for the amount of resistant infections in the community. We feel that current American Thoracic Society criteria for health care-acquired pneumonia may not be readily usable in the emergency department” to identify patients at risk of infection with drug-resistant strains, Dr. Schreiber said.

In settings in which drug-resistant pneumonia is relatively common, the empiric antibiotic regimen should include a drug active against many resistant strains, such as linezolid (Zyvox) or vancomycin, and imipenem, or a combination of piperacillin and tazobactam (Zosyn) and a second agent with Pseudomonas coverage, he said.

Dr. Schreiber said that he had no financial disclosures.

The high level of resistance in the patients with community-acquired pneumonia 'was eye-opening.' DR. SCHREIBER