So-called capsular switching
might have contributed to increasing non-PCV7 serotype disease (28).
meningitidis core genome amino acid sequences showed that all 22 sequenced CC4821 strains were closely related, irrespective of serogroup, ST, and PorA type, which indicated capsular switching
between serogroups C and B.
However, this association could be disrupted because of capsular switching
caused mainly by recombination of capsular genetic loci.
also is associated with recombination of PBP genes, considering that pbp1a and pbp2x genes which mediate [beta]-lactam resistance, are positioned at both ends of the cps region.
has been observed among pneumococcal serotypes after the 7-valent pneumococcal conjugate vaccine was introduced in the United States, although the substantial declines in incidence of pneumococcal disease were maintained overall (25).
Some of these clones, namely, cc11 and cc32, have undergone capsular switching
, which occurs through transformation and horizontal gene transfer, enables N.
Although the mechanism is not completely clear, available data indicate that capsular switching
from serotypes 6A, 23F, 19F, or 19A to serotype 6D is possible; this switching could occur in addition to replacement of the wciN gene into the 6B capsule gene locus.
However, capsular switching
of vaccine serotypes under selective pressure by PCV7 is one of the mechanisms underlying the expansion of serotype 19A (4,11-13).
Certain serotypes that are frequently involved in capsular switching
and penicillin resistance attributable to high competence should be further studied.
These strains exhibited capsular switching
and were highly similar to the Spanish 23F clone.
The population-based collections of isolates from ABCs are used to evaluate subtyping methods (24), identify genetic mechanisms of antimicrobial resistance, determine vaccine formulations (25,26), and assess capsular switching
among organisms (for vaccines based on capsular types) (27,28).