Risk factors for drug-resistant bacterial pneumonia in older patients hospitalized with pneumonia in a Chinese population.

BACKGROUND The relationship between healthcare-associated pneumonia (HCAP) and resistant bacteria is unclear. The aim of this study was to identify the risk factors for pneumonia caused by drug-resistant bacteria (DRB). METHODS A prospective cohort study was conducted at a tertiary teaching hospital in Hong Kong. Consecutive older patients (aged ≥65 years) were hospitalized with pneumonia from January 2004 to June 2005. DRB comprised methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae and Acinetobacter baumannii. RESULTS The entire cohort consisted of 1176 older patients. Of 472 (40.1%) patients with etiological diagnosis established, bacterial pneumonia was found in 354 (30.1%) cases. DRB were isolated in 48 patients: P. aeruginosa (41), MRSA (5) and ESBL producing enteric bacilli (3). Co-infection with P. aeruginosa and MRSA was found in one patient. The prevalence of DRB in culture-positive pneumonia was 20.1% (48/239). Patients with DRB were more likely to have limitation in activities of daily living, bronchiectasis, dementia, severe pneumonia, recent hospitalization and recent antibiotic use. Logistic regression revealed that bronchiectasis [relative risk (RR) 14.12, P = 0.002], recent hospitalization (RR 4.89, P < 0.001) and severe pneumonia (RR 2.42, P = 0.010) were independent predictors of drug-resistant bacterial pneumonia. CONCLUSION Recent hospitalization is the only risk factor for HCAP which is shown to be associated with DRB. Nursing home residence is not a risk factor. The concept of HCAP may not be totally applicable in Hong Kong where the prevalence of drug-resistant pathogens in pneumonia is low.