Serotypes and susceptibilities of paediatric clinical isolates of Streptococcus pneumoniae in Crete, Greece, before and after the heptavalent pneumococcal conjugate vaccine

All Streptococcus pneumoniae strains isolated from paediatric clinical samples at Heraklion University General Hospital in the 10-year period 2000–2009 were tested for serotype and susceptibility to antimicrobials. Among a total of 258 strains, 159 were isolated in the 5-year period 2000–2004, before the introduction of the heptavalent pneumococcal conjugate vaccine (PCV7), and 99 in the post-PCV7 5-year period 2005–2009. The prevalence of PCV7-included serotypes decreased in the post-PCV7 period (p = 0.0002), but an increase was observed for serotypes 7F (p = 0.002) and 19A (p = 0.004). Pan-susceptibility rates and susceptibility to cotrimoxazole increased in the post-PCV7 period (p = 0.01 and p = 0.008, respectively), but serotype 19A emerged as a contributor to multi-resistance (p = 0.007). PCV7 was followed by decreased S. pneumoniae resistance and prevalence of vaccine-related serotypes but increased prevalence of serotypes 7F and 19A. Continuing surveillance is required after the recent introduction of PCV10 and PCV13.