Surveillance of invasive diseases caused by Streptococcus pneumoniae in Italy: evolution of serotypes and antibiotic resistance in different age groups before and after implementation of PCV7

Background: PCV7 has been available in Italy since 2001, however only in 2005 national recommendations were issued and vaccination was implemented with different modalities by the Regions. Objectives: Aim of this study was to describe changes in serotype distribution and antibiotic susceptibility of S. pneumoniae from invasive pneumococcal diseases (IPD) in the last decade. Study Design: S. pneumoniae isolates from IPD, collected through a national surveillance system, were serotyped and antibiotic susceptibility was determined by E-test. Data were analyzed according to age groups (5 years, >5-64 years, 65 years) and to 3 time periods: prior, during and after PCV7 implementation (2001- 2003, 2006-2008 and 2009-2011). Results: The percentage of PCV7 serotypes (vaccine serotypes, VS) decreased over the years not only in children (from 60% to 26%) but also in the other age groups. Penicillin resistance was rather low in 2001-2003 (7-12%), but peaked in children in 2006-2008 (24%), and decreased in 2009-2011, while erythromycin resistance slightly decreased over the 3 periods. Conclusions: PCV7 use has largely impacted the epidemiology of S. pneumoniae in Italy, with a decrease in VS in all age groups.The impact of PCV 13, available in Italy since the end of 2010, requires future evaluations.