Radical serotype rearrangement of carried pneumococci in the first 3 years after intensive vaccination started in Hungary

Streptococcus pneumoniae is responsible for a significant amount of morbidity and mortality worldwide. Healthy carriers, mainly young children, are the most important sources of infections. In the current study, we aimed to determine the changes that have occurred since the introduction of PCV-7 in Hungary. Nasal specimens were collected from 1,022 healthy children aged 3-6 years attending day-care centres. After thorough identification, pneumococcal isolates were serotyped, and their antibiotic sensitivity was determined. The carriage rate was found to be 34.9 %. A huge serotype rearrangement was detected compared to earlier results, with the previously leading serotype 14 having completely disappeared. Serotypes 11A, 35F, 19A, 6B, 15B, 3 and 38 were most prevalent, and 29 different types were identified in total. The PCV-7 types were responsible for 16.5 % of all serotypes, and 36.0 % are not covered by any pneumococcal vaccines. The isolates were sensitive to most tested antibiotics, except erythromycin (resistance was 21.6 %). Only one penicillin-resistant strain was found. The newly and rapidly emerging non-vaccine serotypes are much more sensitive, except serotype 19A. Conclusion: Due to PCV vaccination, a complete serotype arrangement occurred also in Hungary. The old paediatric serotypes were replaced by serotypes 11A, 35F, 19A, 6B, 15B, 3 and 38.