A comparison of microbiology and demographics among patients with healthcare-associated, hospital-acquired, and ventilator-associated pneumonia: a retrospective analysis of 1184 patients from a large, international study.

BACKGROUND: Acceptance of healthcare-associated pneumonia (HCAP) as an entity and the associated risk of infection by potentially multidrug-resistant (MDR) organisms such as methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas and Acinetobacter have been debated. We therefore compared patients with HCAP, hospital-acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP) enrolled in a trial comparing linezolid with vancomycin for treatment of pneumonia.

METHODS: The analysis included all patients who received study drug. HCAP was defined as pneumonia occurring < 48 hours into hospitalization and acquired in a long-term care, subacute, or intermediate health care facility; following recent hospitalization; or after chronic dialysis.

RESULTS: Data from 1184 patients (HCAP = 199, HAP = 379, VAP = 606) were analyzed. Compared with HAP and VAP patients, those with HCAP were older, had slightly higher severity scores, and were more likely to have comorbidities. Pseudomonas aeruginosa was the most common gram-negative organism isolated in all pneumonia classes [HCAP, 22/199 (11.1%); HAP, 28/379 (7.4%); VAP, 57/606 (9.4%); p = 0.311]. Acinetobacter spp. were also found with similar frequencies across pneumonia groups. To address potential enrollment bias toward patients with MRSA pneumonia, we grouped patients by presence or absence of MRSA and found little difference in frequencies of Pseudomonas and Acinetobacter.

CONCLUSIONS: In this population of pneumonia patients, the frequencies of MDR gram-negative pathogens were similar among patients with HCAP, HAP, or VAP. Our data support inclusion of HCAP within nosocomial pneumonia guidelines and the recommendation that empiric antibiotic regimens for HCAP should be similar to those for HAP and VAP.