Characterization of Streptococcus pneumoniae detected in clinical respiratory tract samples in southern Sweden 2 to 4 years after introduction of PCV13.

Objective: To determine the serotype distribution and antimicrobial resistance of Streptococcus pneumoniae associated with mucosal infections in patients of all ages, 2 to 4 years after the transition from a 10-valent pneumococcal conjugate vaccine (PCV10) to PCV13 in the childhood immunization programme.
Methods: Background information and antimicrobial susceptibility data regarding all respiratory tract, middle ear, and conjunctival samples positive for growth of S. pneumoniae (n = 2,131) were collected during 18 months in 2016-2018. Available corresponding bacterial isolates were serotyped by PCR and/or antisera (n = 1,858).
Results: In total, 17% of isolates were covered by PCV13, predominantly represented by serotypes 3 (9%) and 19A (5%). The most common nonvaccine serotypes were 11A (10%), 23B (10%), 15A (6%) and 35F (5%). Isolates exhibiting serotype 15A or 23B were often multidrug-resistant (21%) or penicillin nonsusceptible (38%), respectively.
Conclusions: The overall proportion of serotype 19A was halved compared to a previous observation period when PCV10 was used (years 2011-2013), suggesting herd protection related to PCV13. The proportion of serotype 3 was, however, unchanged. Despite most nonvaccine serotypes causing mucosal infections have a low invasive potential, certain antibiotic resistant serotypes may pose a clinical problem.
Competing Interests: Declaration of Competing Interest Hans-Christian Slotved and Jonas Ahl report grants from Pfizer outside the submitted work. Kristian Riesbeck reports grants from Pfizer, during the conduct of the study; personal fees from GSK, personal fees from MSD, and grants from Pfizer, outside the submitted work. Remaining authors have nothing to disclose.
(Copyright © 2021. Published by Elsevier Ltd.)