Antimicrobial susceptibilities and serotypes of Streptococcus pneumoniae isolates from elderly patients with pneumonia and acute exacerbation of chronic obstructive pulmonary disease.

In the elderly, Streptococcus pneumoniae is the most common cause of pneumonia and one of the most frequently isolated pathogens in cases of acute exacerbation of chronic obstructive pulmonary disease (AECOPD). This study was conducted to compare the pneumococcal isolates obtained during episodes of AECOPD and pneumonia in patients of ≥65 years old and to analyze whether in patients with AECOPD and pneumonia within a short interval, the same isolate caused both episodes. This laboratory-based study was performed between 2005 and 2008. Pneumococcal isolates from episodes of pneumonia (n = 401) and AECOPD (n = 398), matched one-to-one by date of isolation, were characterized. The serotypes and genotypes of other pneumococcal isolates causing pneumonia and AECOPD in the same patient were compared. In patients with pneumonia, COPD as an underlying disease was not associated with more-drug-resistant pneumococci. In contrast, isolates causing AECOPD showed higher rates of resistance than those causing pneumonia. Serotypes 1, 3, and 7F were more frequent in pneumonia. The same pneumococcus was involved in 25.7% (9/35 patients) of patients with two consecutive AECOPD episodes but in only 6.3% (2/32 patients) of COPD patients with pneumonia and exacerbation (Fisher's exact test; P = 0.047). Less invasive serotypes were isolated more often in AECOPD and were more resistant to antimicrobials. The presence of a specific pneumococcal serotype in AECOPD does not predict the etiology of subsequent pneumonia.