Serotype distribution and resistant pattern of Streptococcus pneumoniae among under 5 attending clinic at a tertiary hospital

Abstract Background Streptococcus pneumoniae remains a significant cause of morbidity and mortality among children under five years of age, particularly in developing countries. This study assessed the prevalence, serotype distribution, and antimicrobial resistance patterns of S. pneumoniae among pediatric patients at Nnamdi Azikiwe University Teaching Hospital, Nnewi, Southeast Nigeria. A cross-sectional hospital-based study was conducted involving 392 children under five years. Demographic data and vaccination history were collected using structured questionnaires. Clinical specimens, including blood, sputum, and nasopharyngeal exudates, were cultured and tested for S. pneumoniae using standard microbiological techniques. Confirmed isolates underwent capsular serotyping via Quellung reaction targeting PCV13-covered serotypes. Antibiotic susceptibility testing was performed using the disc diffusion method in accordance with Clinical and Laboratory Standards Institute guidelines. Results Out of 392 collected samples, 43 isolates (11% at 95% confident interval) tested positive for S. pneumoniae : blood ( n = 9), sputum ( n = 23), and nasal exudate ( n = 11). We analyzed invasive and non-invasive isolates separately. Nine PCV13 serotypes were identified, with serotype 6 A (23.3%) being the most prevalent; non-PCV13 serotypes accounted for 18.6% (8/43). Antibiotic resistance was highest for ceftriaxone (35%) and amoxicillin-clavulanic acid (33%). Intermediate resistance was observed particularly for erythromycin (44%) and trimethoprim-sulfamethoxazole (35%). The highest susceptibility was noted for oxacillin (72%) and tetracycline (65%). All isolates exhibited resistance to at least one antibiotic. Conclusions Serotype 6 A was found in both vaccinated and unvaccinated children, consistent with the circulation of PCV13-covered and non-PCV13 serotypes. The active circulation of antibiotic-resistant S. pneumoniae strains among the pediatric population points to the need for continuous surveillance and tailored intervention strategies to combat resistance and improve vaccine coverage.