Role of Streptococcus pneumoniae infection in chronic obstructive pulmonary disease patients in Italy

Background: The aim of this study was to determine the incidence of exacerbations due to Streptococcus pneumoniae in chronic obstructive pulmonary disease (COPD) patients during stable state. Methods: We conducted a prospective, observational, cohort study including stable COPD patients, who were evaluated at least every 4 months over a 24-month period at the Respiratory Unit of the IRCCS Policlinico Hospital in Milan, Italy, from 2012 to 2015. Sputum samples were collected at enrollment during stable state to evaluate the frequency of S. pneumoniae colonization and in case of an acute exacerbation to evaluate the incidence of pneumococcal infection. Results: A total of 79 stable patients with moderate to very severe COPD were enrolled. A total of 217 samples were collected, and 27% (n = 59) of those were positive for S. pneumoniae. A total of four exacerbations due to S. pneumoniae occurred during follow up (0.31 per 100 person/month). Among positive samples of S. pneumoniae, 109 serotypes were identified. The most frequent serotypes in moderate-to-severe COPD patients during both stable state and exacerbation were 19F (12%), 18 (10%), 19A and 9V (9%) and 35 F (7%). Only 32% of COPD patients were effectively vaccinated for S. pneumoniae with PPV23 vaccine. Conclusion: The most frequent S. pneumoniae serotypes in COPD patients are 19F, 18, 19A, 9V and 35 F, and that almost 50% of S. pneumoniae strains could be covered by PCV13 in adult COPD patients.