Selective pressure: Rise of the nonencapsulated pneumococcus

Pneumococci can fail to express capsule if there is a disruption, mutation, or deletion of genes in the capsular polysaccharide biosynthesis (cps) locus Although classically considered avirulent, recent emergence of genetically divergent NESp strains has generated interest in how these bacteria are persisting and evolving Interestingly, a subgroup of NESp encodes novel virulence-associated proteins in the cps locus These novel proteins compensate for lack of capsule expression by increasing NESp colonization of the host and enhancing virulence during OM and pneumonia in animal models of infection