Emergence of invasive pneumococcal disease caused by multidrug-resistant serotype 19A among children in Barcelona

SummaryObjectiveTo describe the epidemiology of invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae serotype 19A.MethodsWe studied all children and adolescents with IPD caused by serotype 19A who were admitted to a Children's Hospital in Barcelona (1997–2007). Serotyping, antibiotic susceptibility and clonal analysis were performed.ResultsComparing the pre-vaccine period (1997–2001) with the early vaccine period (2002–2004) and the late vaccine period (2005–2007) there was an increase of IPD caused by serotype 19A: 1 of 58 episodes (1.7%) vs. 8 of 54 episodes (14.8%) vs. 27 of 123 episodes (21.9%), respectively (P = 0.002). All S. pneumoniae serotype 19A isolated in the pre-vaccine and early vaccine periods (n = 9) were penicillin susceptible, while in the late vaccine period, 12 of 27 (44%) were penicillin nonsusceptible (P = 0.01).A clonal analysis revealed 15 different sequence types (STs) expressing serotype 19A. 10 of them were preexisting STs associated with serotype 19A including the multidrug-resistant ST320 and ST276.ConclusionThere was an increase of IPD caused by S. pneumoniae serotype 19A which was mainly related with the emergence of preexisting clones several of them closely related with international multidrug-resistant clones. These results should be considered when selecting the new conjugate pneumococcal vaccines.