Penicillin-binding protein genotyping of penicillin-nonsusceptible Streptococcus pneumoniae isolates from the nasopharynx of healthy preschool children

Streptococcus pneumoniae is one of the most frequent bacterial identified causes of community-acquired pneumonia, otitis media and meningitis. It is, as well, a common cause of bacteraemia’s significant morbidity and mortality. Beta-lactam antibiotics (BLAs) are the first line of empirical treatment for pneumococcal infections. The targets of BLAs are penicillin-binding proteins (PBPs), the modifications of which are one of the reasons why pneumococci are non-susceptible to BLAs. In our work, a total of 39 Streptococcus pneumoniae isolates were obtained from 176 healthy children, both vaccinated and non-vaccinated. The isolates were tested for antimicrobial susceptibility, and their penicillin-binding proteins (PBPs) were typed by the restriction fragment length of the polymorphism analysis of their pbp genes. The most frequent serotypes among the penicillin non-susceptible Streptococcus pneumoniae (PNSSP) isolates were 23B, 35B and 19F. Restriction enzyme analyses of pbp1a, pbp2b, and pbp2x genes revealed 5, 3 and 3 different patterns, respectively, and a total of 4 different PBPs profiles of PNSSP isolates belonging to serotypes not included in pneumococcal conjugate vaccines were demonstrated. We conclude that the level of resistance should be monitored constantly to ascertain the effect of current pneumococcal conjugate vaccines, as well as to recognize new circumstances developing in Poland, as well as the possibility of multiple, independent imports of resistant strains from abroad.