Nasopharyngeal carriage of Streptococcus pneumoniae in children from day-care centers in Smolensk

Abstract

Objective. To investigate a nasopharyngeal carriage and serotypes of S. pneumoniae in children aged 3 to 6 years from day-care centers in Smolensk. Materials and Methods. A total of 245 isolates of S. pneumoniae from 1027 nasopharyngeal swabs from healthy children attending day-care centers was tested. Identification of S. pneumoniae was performed according morphological, cultural and antigenic characteristics (Slidex pneumo-Kit, bioMeriеux, France), susceptibility to optohin and bile. Extraction of S. pneumoniae DNA (338) from nasopharyngeal specimens and cultures was performed using nucleic acids extraction kit AmpliSens® DNA-sorb-В (Interlabservice, Russia). Molecular typing was performed using CDC-recommended PCR method with 22 pairs of primers. Results. Children without signs of infection diseases from 14 day-care centers were examined, whose parents have signed an informed consent. There were 245 (24.0%) isolates of S. pneumoniae from 1027 specimens of nasopharynx’s swabs. The partly vaccinated with PCV13 were children aged 3–4 years – 311 (30.3%), in 95 children were healthy carriage (38.2%) of S. pneumoniae. The majority of children under 4 years (716⁄69.7%) were non vaccinated, healthy carriage of S. pneumoniae were 216 (29.3%). The predominant serotypes of S. pneumoniae in partly vaccinated children were: 3 (9.8%), 6AB (17.9%), 19F (13.8%), 11AD (12.2%), 23F (5.3%), 19A (2%), 18ABCF (1.6%), 14 (2%), 9AV (1.2%), 6CD (0.8%). The coincidence of S. pneumoniae serotypes in vaccinated children and included in PCV13 were 54%. The most common serotypes of S. pneumoniae in non-vaccinated children were: 11AD (12.2%), 15A/F (2%), 23A (2%), 22AF (0.4%), 19A (1.3%), 33FA/37 (1.6%) and non-typeable serotypes (27.8%). Conclusions. The low coverage of pneumococcal vaccine in children under 6 years shows the initial process of its implementation in Health Care. We detect the reduction of vaccine serotypes in children with incomplete immunization (54%) and notable increase in non-typeable serotypes (27.8%) in nonvaccinated children.