Streptococcus pneumoniae isolates expressing a capsule with epitopes of both serotypes 6A and 6B.

Four Streptococcus pneumoniae isolates expressing both 6A and 6B capsular serotypes were detected by a multiplex immunoassay. The sequence of WciP, a GT2-family glycosyltransferase, indicates that point mutation has compromised linkage specificity, allowing two alternative oligosaccharides to be synthesized. This finding highlights that mutation as well as recombination can mediate serotype change.