Prolonged life expectancy has currently increased the proportion of the very elderly among patients with community-acquired pneumonia (CAP). The aim of this study was to determine the influence of age and comorbidity on microbial patterns in CAP patients over 65 years of age.
Prospective observational study of adult CAP patients (excluding nursing home) over a 12-year period. We compared patients aged 65-74 years, 75-84 years and >85 years for potential differences in clinical presentation, comorbidities, severity on admission, microbial investigations, etiologies, antimicrobial treatment, and outcomes.
We studied a total of 2149 patients: 759 (35.3%) patients aged 65-74 years, 941 (43.7%) aged 75-84 years, and 449 (20.8%) patients aged >85 years. At least one comorbidity was present in 1710 (79.6%) patients. Streptococcus pneumoniae was the most frequent pathogen in all age groups, regardless of comorbidity. Staphylococcus aureus, Enterobacteriaceae, and Pseudomonas aeruginosa accounted for 9.1% of isolates and Haemophilus influenzae, 6.4%. All these pathogens were isolated only in patients with ≥1 comorbidity. Mortality increased with age (65-74 y, 6.9%; 75-84 y, 8.9%; >85 y, 17.1%; p<0.001) and was associated with increased comorbidities (neurological, OR: 2.1, 95% CI: 1.5-2.1), PSI IV-V (OR: 3.2, 95% CI: 1.8-6.0), bacteremia (OR: 1.7, 95% CI: 1.1-2.7), the presence of a potential MDR pathogen (S. aureus, P. aeruginosa, Enterobacteriaceae; OR: 2.4, 95% CI: 1.3-4.3) and ICU admission (OR: 4.2, 95% CI: 2.9-6.1) on multivariate analysis.
Age does not influence microbial etiology itself, while comorbidities are associated with specific etiologies such as H. influenzae and potential MDR pathogens. Mortality in the elderly is mainly driven by the presence of comorbidities and potential MDR.