Abstract
Community-acquired pneumonia (CAP) is a common and a serious illness. Streptococcus pneumoniae accounts for about half of all cases of CAP. Atypical pneumonia, ie, pneumonia due to Mycoplasma pneumoniae. Chlamydia pneumoniae. Legione species or viruses, is more common among patients treated on an ambulatory basis where these pathogens can collectively cause up to half of all cases of pneumonia. Changes in patient and microbe populations alter The epidemiology of pneumonia. Aspiration and Gram-negative rod pneumonia tend to be more common in nursing home populations. The emergence of macrolide- and beta-lactam-resistant S pneumoniae has major implications for the approach to patients with CAP.