Molecular Typing of Streptococcus pneumoniae Serotypes Causing Childhood Pneumonia in Onitsha, Anambra State

Streptococcus pneumoniae is the leading bacterial cause of community-acquired pneumonia and meningitis in children under five, making it a principal target of childhood immunization programs. Post-vaccine serotype surveillance is critical to assess replacement phenomena and guide booster formulation decisions. This study molecularly typed S. pneumoniae serotypes isolated from children hospitalized with clinical pneumonia at Borromeo Hospital Onitsha, Anambra State, Southeast Nigeria. Nasopharyngeal swabs and blood samples from 100 pediatric pneumonia cases were processed on blood and chocolate agar. Pneumococcal isolates were confirmed by optochin sensitivity and bile solubility testing, and PCR-based capsular typing using serotype-specific primers was performed. S. pneumoniae was isolated from 38% of cases. Capsular typing revealed that vaccine-targeted serotypes (PCV13 coverage types) accounted for 62% of isolates, while non-vaccine serotypes, including 19A, 15B, and 23A, constituted 38% of characterized strains. Penicillin non-susceptibility was detected in 34% of isolates. The persistent circulation of vaccine-included serotypes despite PCV13 rollout suggests incomplete immunization coverage in Onitsha. Continued serotype surveillance is warranted to assess vaccine impact. Keywords: Streptococcus pneumoniae, serotyping, PCV13, childhood pneumonia, Anambra State.