Predictive Factors for Invasive Disease Due to Penicillin-Resistant Streptococcus pneumoniae: A Population-Based Study

A prospective population-based study was carried out to determine predictive factors associated with penicillin-resistant pneumococcal invasive disease. A total of 374 patients (250 males and 124 females; mean age, 50.3 +/- 27 years) with invasive pneumococcal infection were admitted to one of the five hospitals in El Vallés County (an industrial area with 800,000 inhabitants in the province of Barcelona, Spain) over a period of 5 years. Of the 374 episodes, 21 (5.6%) were due to highly penicillin-resistant pneumococci and 67 (17.9%) to intermediately penicillin-resistant pneumococci. Multivariate analysis showed a statistically significant association between infection with intermediately penicillin-resistant pneumococci and an age of 0-4 years (odds ratio [OR] = 5.3; 95% confidence interval [CI] = 2.2-12.6), the presence of an immunosuppressive underlying disease (OR = 3.0; 95% CI = 1.5-6.0), and the previous use of beta-lactam antibiotics (OR = 2.1; 95% CI = 1.0-4.5). Infection with highly penicillin-resistant pneumococci was associated only with the previous use of beta-lactam antibiotics (OR = 5.9; 95% 95% CI = 2.2-15.8). Highly resistant strains were of serotypes 6, 9, 14, 15, 19, and 23, of which all but serotypes 9 and 15 are included in the newly formulated conjugated vaccine.