Changes in capsule and drug resistance of Pneumococci after introduction of PCV7, Japan, 2010-2013

Area of Science:

• Microbiology
• Epidemiology
• Vaccinology

Background:

• The 7-valent pneumococcal conjugate vaccine (PCV7) was introduced in Japan to reduce invasive pneumococcal disease (IPD).
• Changes in antibiotic resistance patterns of Streptococcus pneumoniae serotypes following vaccination are crucial for public health surveillance.
• Understanding serotype and genotype shifts is essential for monitoring vaccine effectiveness and antimicrobial resistance.

Purpose of the Study:

• To investigate the changes in serotypes and genotypes responsible for beta-lactam and macrolide resistance in Streptococcus pneumoniae isolates from Japanese children with IPD post-PCV7 introduction.
• To track the trends of antibiotic resistance in both vaccine-type and non-vaccine-type pneumococcal strains over a three-year period.

Main Methods:

• Prospective surveillance of invasive pneumococcal disease (IPD) across 341 Japanese hospitals from April 2010 to March 2013.
• Collection and serotyping/genotyping of Streptococcus pneumoniae isolates.
• Analysis of antimicrobial resistance patterns, focusing on beta-lactam and macrolide resistance genes (e.g., erm(B)).

Main Results:

• The proportion of vaccine serotypes among infectious isolates significantly decreased from 73.3% to 14.7% over the study period.
• Genotypic penicillin-resistant Streptococcus pneumoniae strains within vaccine serotypes also declined annually.
• Non-vaccine serotypes, including 19A, 15A, 15B, 15C, and 24, showed an increase, particularly in 2012.
• Notable increases in genotypic penicillin-resistant isolates of serotypes 15A and 35B were observed.
• Macrolide resistance mediated by the erm(B) gene rose in serotypes 15A, 15B, 15C, and 24.

Conclusions:

• The introduction of PCV7 in Japan led to a decrease in vaccine-type pneumococcal isolates and associated resistance.
• There is a concerning rise in non-vaccine serotypes exhibiting increased resistance to penicillin and macrolides, necessitating ongoing surveillance.
• The shift towards resistant non-vaccine serotypes highlights the need for updated vaccination strategies and antimicrobial stewardship.