Streptococcus pneumoniae, a common human pathogen, colonizes the nasopharynx and causes diseases including acute otitis media (AOM). Herein, pneumococcal serotype distributions in children before and after PCV7 vaccination and in patients with pneumococcal disease in Siberian Russia (Krasnoyarsk) are reported. Analyses included antimicrobial susceptibility testing, sequence typing (ST), pulsed field gel electrophoresis, virulence‐related surface protein gene (VSG) typing with novel primers and structural analysis by scanning electron microscopy. In healthy children (HC) prior to administration of PCV7, drug‐susceptible serotype23F/ST1500 was a major pneumococcal genotype. In the PCV7 trial, multidrug‐resistant serotype19A/ST320 emerged in vaccinees after PCV7, exhibiting a PCV7‐induced serotype replacement. Multidrug‐resistant serotype19A/ST320 was evident in patients with AOM. Community‐acquired pneumonia (CAP) isolates showed genetic similarities to the AOM (ST320) genotype, constituting a common non‐invasive AOM–CAP group. In contrast, meningitis isolates were more divergent. Overall, 25 ST types were identified; five (20%) of which were Krasnoyarsk‐native. Regarding VSGs, PI‐1 (rlrA/rrgB), PI‐2 (pitA/B), psrP and cbpA were present at 54.3%, 38.6%, 48.6%, and 95.7%, respectively, with two major VSG content types, PI‐1−/PI‐2−/psrP +/cbpA + and PI‐1+/PI‐2+/psrP ‐/cbpA +, being found for HC and non‐invasive diseases, respectively. A major clone of serotype19A/ST320 (PI‐1+/PI‐2+) produced the longest pneumococcal wire (pilus) structures in colonies. ST1016 (PI‐1−/PI‐2−) in HC had HEp‐2 cell‐adherent pili. These results suggest that serotype19A/ST320 and related genotypes, with the VSG content type PI‐1+/PI‐2+/psrP −/cbpA +, emerged in vaccinees after PCV7 in Siberia, accompanying diseases in non‐vaccinated children, and that some genotypes (serotypes19A/ST320 and 18/ST1016) produced novel pneumococcal structures, predicting their roles in colony formation and adherence.
Aim. To investigate how the pneumococcal vaccination affects the distribution of Streptococcus pneumoniae serotypes.Materials and Methods. In 2011-2019, 1,852 healthy children (1,354 aged ≤ 5 years and 480 aged from 6 to 17 years) were examined for the nasopharyngeal pneumococcal carriage. Of them, 539 children were tested before the start of pneumococcal vaccination (2011-2014), while 1,313 were tested during the vaccine campaign (2015-2019). Pneumococcal strains were serotyped using multiplex polymerase chain reaction.Results. Streptococcus pneumoniae serotype distribution considerably differed between children ≤ 5 and 6-17 years of age. Serotypes 23F, 19F, 19A, 6AB, and 15BC were prevalent in children ≤ 5 years of age while the older children were characterised by a high prevalence of capsular serotypes (3 and 33AF/37), serogroup 9 (9AV and 9LN), non-typeable streptococci, as well as 19F, 6AB and 6CD serotypes. Vaccination was associated with a significantly decreased prevalence of Streptococcus pneumoniae carriage (from 41.5% to 19.2%) among children ≤ 5 years of age, while this reduction was less pronounced (from 13.5 to 9.0%) in older children. Vaccination led to the shift in the distribution of pneumococcal serotypes towards an increased prevalence of non-vaccine serotypes that was particularly prominent in children ≤ 5 years of age. In particular, vaccination reduced the prevalence of 23F and 19A pneumococcal serotypes but heightened prevalence of 11AD serotype and to the appearance of previously undetected serotypes such as 8, 10A, 17F, 22F, 24ABF, 34, and 39.Conclusion. Pneumococcal vaccination decreased prevalence of pneumococcal carriage, yet causing a serotype replacement effect requiring improved microbiological monitoring in children of all age groups.
Relevance. Pneumococcal disease remains an urgent public health problem, despite mass immunization of infants and young children. The impact of children’s universal vaccination on the morbidity and etiological structure in various clinical forms of infection remains unclear in children and adults. Аim. Тo evaluate the herd effect of children’s mass immunization with a 13-valent conjugated pneumococcal vaccine. Materials and Methods. The prophylactic efficacy of mass vaccination is studied within comparative retrospective epidemiological analysis of incidence rates and etiological structure of bacterial meningitis, ear diseases and mastoiditis, and community-acquired pneumonia in children and adults of Krasnoyarsk region in the pre- and post-vaccination periods, according to the official statistics and microbiological monitoring. Results. The changes in decrease of incidence rates with all clinical forms of pneumococcal infection except community-acquired pneumonia are revealed both in children and adults during mass immunization. Etiological structure changes and also changes of S. pneumoniae serotype distribution are detected in major clinical forms of infection. Conclusion. Reducing the incidence rates in children is determined predominantly by vaccinal prevention. The observed decrease of incidence rates in adults is the result of reducing the number of pneumococcal infection sources among children (herd immunity).
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