The spectrum of pneumococcal empyema in adults in the early 21st century.

Background: Increased rates of empyema have been reported in children after the introduction of the pneumococcal conjugate vaccine (PCV7). Our objective was to describe the risk factors for pneumococcal empyema in adults and to analyze the differences in the incidence, disease characteristics, and serotype distribution between the pre- and post-PCV7 eras.

Methods: An observational study of all adults hospitalized with invasive pneumococcal disease (IPD) who presented with empyema in 2 Spanish hospitals was conducted during the periods 1996-2001 (prevaccine period) and 2005-2009 (postvaccine period). Incidences of empyema were calculated. A multivariate analysis was performed to identify variables associated with pneumococcal empyema.

Results: Empyema was diagnosed in 128 of 1080 patients with invasive pneumococcal disease. Among patients aged 18-50 years, the rates of pneumococcal pneumonia with empyema increased from 7.6% to 14.9% (P = .04) and the incidence of pneumococcal empyema increased from 0.5 to 1.6 cases per 100,000 person-years (198% [95% confidence interval {CI}, 49%-494%]). The incidence of empyema due to serotype 1 increased significantly from 0.2 to 0.8 cases per 100,000 person-years (253% [95% CI, 67%-646%]). Serotype 1 caused 43.3% of cases of empyema during the postvaccine period. Serotypes 1 (odds ratio [OR], 5.88; [95% CI, 2.66-13]) and 3 (OR, 5.49 [95% CI, 1.93-15.62]) were independently associated with development of empyema.

Conclusions: The incidence of pneumococcal empyema in young adults has increased during the postvaccine period, mainly as a result of the emergence of serotype 1. Serotypes 1 and 3 are the main determinants of development of this suppurative complication.