domingo, 20 de septiembre de 2015

Strain features and distributions in pneumococci from children with invasive disease before and after 13 valent conjugate vaccine implementation in... - PubMed - NCBI

2015 Sep 9. pii: S1198-743X(15)00813-7. doi: 10.1016/j.cmi.2015.08.027. [Epub ahead of print]

Strain features and distributions in pneumococci from children with invasive disease before and after 13 valent conjugate vaccine implementation in the United States.

Metcalf BJ1, Gertz RE Jr1, Gladstone RA2, Walker H1, Sherwood LK1, Jackson D1, Li Z1, Law C1, Hawkins PA1, Chochua S1, Sheth M3, Rayamajhi N1, Bentley SD2, Kim L1, Whitney CG1, McGee L1, Beall B4; Active Bacterial Core surveillance team.

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Abstract

The effect of second generation pneumococcal conjugate vaccines on invasive pneumococcal disease (IPD) strain distributions have not yet been well described. We analyzed IPD isolates recovered from children <5 years of age through Active Bacterial Core surveillance before (2008-2009; n=828) and after (2011-2013; n=600) 13-valent vaccine (PCV13) implementation. We employed conventional testing, PCR/electrospray ionization mass spectrometry, and whole genome sequence (WGS) analysis to identify serotypes, resistance features, genotypes, and pilus types. PCV13, licensed in February of 2010, effectively targeted all major 19A and 7F genotypes and decreased antimicrobial resistance primarily due to removal of the 19A/ST320 complex. The strain complex contributing most to remaining β-lactam resistance during 2011-2013 was 35B/ST558. Significant emergence of non-vaccine clonal complexes was not evident. Due to the removal of vaccine serotype strains, positivity for one or both pilus types (PI-1 and PI-2) decreased in the post PCV13 years 2011-2013 relative to 2008-2009 (decreases of 32-55% for PI-1, > 95% for PI-2 and combined PI-1 + PI-2). β-lactam susceptibility phenotypes correlated consistently with transpeptidase region sequence combinations of the three major penicillin binding proteins (PBPs) determined through WGS. Other major resistance features were predictable by DNA signatures from WGS. Multilocus sequence data combined with PBP combinations identified progeny, serotype donors, and recipient strains in serotype switch events. PCV13 decreased all PCV13 serotype clones and concurrently decreased strain subsets with resistance and/or adherence features conducive for successful carriage. Our results serve as a reference describing key features of current pediatric IPD strains in the United States after PCV13 implementation.