Streptococcus pneumoniae serotype 3 (SPN3)

Streptococcus pneumoniae serotype 3 is a specific capsular type of the bacterium *Streptococcus pneumoniae*, distinguished by its thick, mucoid polysaccharide capsule. This capsule confers high virulence and enables the bacterium to evade host immune responses more effectively than many other pneumococcal serotypes[1][3][7]. Serotype 3 is associated with severe clinical manifestations such as empyema and invasive pneumococcal disease in both children and adults[1][4][7]. It exhibits unique biological properties including increased capsular shedding, which reduces opsonophagocytosis by sequestering antibodies away from the bacterial surface[1][3]. Serotype 3 strains are genetically diverse but are most commonly found within clonal complexes such as CC180 (ST180) globally; other genotypes like ST505 have been reported regionally[2][4][5][6]. These strains often show resistance to macrolides (such as erythromycin), typically via acquisition of genes like ermB or mefA, while generally remaining susceptible to β-lactam antibiotics—though there is evidence for increasing resistance over time in some lineages[2][4][5][6]. Despite inclusion in conjugate vaccines (PCV13), vaccine-induced immunity against this serotype has been suboptimal due to poor immunogenicity of its capsule and ongoing clonal expansion post-vaccine introduction[5]. The thick capsule also impedes complement deposition and phagocytosis, contributing further to immune evasion[1][5]. Note: "Streptococcus pneumoniae serotype 3" refers to a bacterial strain/serovar rather than a molecular target such as an enzyme or receptor. It is not considered a therapeutic target itself but rather an infectious agent; thus, "is_target" should be set to false and "is_incorrect" set to true for this context.

Other names

Pneumococcus serotype 3S. pneumoniae serotype 3Type 3 pneumococcus

Inhibition of cell wall synthesis (for β-lactams and vancomycin)