Prevalence and risk factors for nasopharyngeal carriage of Streptococcus pneumoniae among adolescents

Data on the prevalence of pneumococcal nasopharyngeal carriage and its risk factors among adolescents are scarce. The aim of this study was to provide such information. A cross-sectional, population-based prospective study was conducted. Participants were 1013 adolescents (age range 10-19 years) randomly recruited in 22 public schools. Those schools were randomly chosen among 307 public schools from 11 Sanitary Districts of Salvador, Brazil. Nasopharyngeal samples were assessed by standard procedures to recover and identify Streptococcus pneumoniae. Data on potential risk factors were gathered by confidential interview based on a standardized questionnaire. Pneumococci were recovered from 8.2 % [83/1013, 95 % confidence interval (CI) 6.6-10.0]. By stepwise logistic regression, pneumococcal colonization was independently associated with younger age [odds ratio (OR) 0.85, 95 % CI 0.77-0.94, P=0.001], being male (OR 1.78, 95 % CI 1.11-2.85, P=0.02), exposure to passive smoke in the household (OR 1.76, 95 % CI 1.10-2.79, P=0.02), having an upper respiratory infection during recruitment (OR 2.67, 95 % CI 1.67-4.28, P<0.001) and having a history involving an episode of acute asthma during the last year (OR 2.89, 95 % CI 1.18-7.08, P=0.03). The estimated probability of pneumococcal colonization decreased with age (chi(2) for trend=8.52, P=0.003). These findings provide tools for increasing the use of prevention strategies for pneumococcal diseases, such as pneumococcal vaccination among asthmatic patients and public health measures to stop smoking.