Among Rochester NY children, a dramatic increase in nasopharyngeal colonization by non-vaccine serotypes 35B and 15A pneumococci occurred after introduction of PCV13. During years 2010-2013 serotype 35B infrequently caused acute otitis media compared to serotype 15A
We investigated differences in 14 virulence genes between 35B and 15A strains in-vitro and 9 host innate cytokine gene responses in the nasopharynx of children using RT-PCR, normalized with two housekeeping genes, as possible explanations for the difference in virulence.
: Seven of 14 virulence genes were differentially regulated when comparing 35B and 15A strains. ComA, phtD and phtE were upregulated, ciaR, pcpA, nanA and CapD were downregulated. LuxS comD, spxB, spsA, lytA, lytB and Ply showed no difference. In the nasopharyngx, IL17 and IL23 production were >10 fold higher during 35B colonization compared to 15A colonization.
Low AOM case/carriage ratio of 35B from 2010-2013 in Rochester NY children was associated with differential regulation of known virulence factors and mucosal immunological responses.