Characteristics of Streptococcus pneumoniae strains serotype 19A isolated from children in Moscow during the post-vaccination period (2015–2022)

Abstract

Introduction. Community-acquired pneumonia (CAP) is a leading cause of children mortality and morbidity worldwide. The introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) had a very good effect on the CAP prevalence. However, serotype 19A remains the leading cause of severe pneumococcal disease in both vaccinated and unvaccinated children. 
 The purpose of the work. To analyze the clonal epidemiology and sensitivity to antibacterial drugs of pneumococcus serotype 19A strains in the post-vaccination period for monitoring and control of vaccination.
 Materials and methods. The study included twenty six isolates of pneumococci serotype 19A isolated in children in Moscow between 2015 and 2022. Serotyping was carried out using the Neufeld capsule swelling test. Sensitivity was determined using the microdilution method. Resistance genes and multilocus sequence typing was performed using the PCR method.
 Results. By 2019–2022 the detection rate of serotype 19A decreased from 61.5% to 38.5%. A total of 12 different sequence types were identified. Most isolates belonged to 2 clonal complexes: CC230 (n = 15), CC320 (n = 6). Sixteen isolates exhibited a multidrug resistance phenotype (MDR). The dominant phenotype was extremely drug-resistant in the combination of β/Eri/Cli/TMP/Tet (43.8%). The most of MDR isolates belonged to clonal complexes: CC230 (8/16), CC320 (6/16) and Singleton 16988 (12.5%).
 Conclusion. After the introduction of PCV13, the prevalence of serotype 19A decreased, but MDR isolates of this serotype continued to increase. These results highlight the need for continued monitoring of the pneumococcal population exhibiting high resistance to reduce the risk of severe disease caused by this organism.