Background: Infections with Streptococcus pneumoniae are endemic worldwide. It is a public health problem and responsible for 1.6 million of 8.8 million annual deaths of children under 5 years of age, with 50% occurring in sub-Saharan Africa. This descriptive study was done to determine the prevalent S. pneumoniae serotypes responsible for infections at Ahmadu Bello University Teaching Hospital, Shika-Zaria, Nigeria. 

Materials and methods: Clinical specimens of blood, cerebrospinal fluid and aspirates from abscess, ear swab, throat swab, pus and sputa were collected over a period of 18 months from 420 patients with pneumonia, meningitis, septicemia and otitis media. Specimens were cultured on 5% defibrinated sheep blood agar and chocolate agar. Incubation was done aerobically in a CO-enriched atmosphere at 37°C for 18-24 h. 

Isolates of S. pneumoniae were identified by standard biochemical techniques using Gram reaction, catalase test, Optochin disc and bile solubility tests. Antimicrobial susceptibility was determined by the modified Kirby-Bauer disc diffusion method with Mueller-Hinton agar supplemented with 5% sheep blood. Serotyping was done using the slide agglutination method (Denka Seiken Co. Ltd., Japan). The serotype final results were recorded as matching, discordant or non-typeable. 

Results: A total of 420 patients participated in this study, in which 227 were males (54%) and 193 were females (46%). Participants’ ages ranged from 2 days to 85 years. S. pneumoniae isolates were mainly from blood 12 (52.2%) and sputum 6 (26.1%). Samples with most isolates were from the pediatric age group of 15 years (65.2%). The serotypes identified were 6, 19 and 20 which were all from blood, as none of the strains from sputum was typeable.

Conclusion: The major S. pneumoniae serotypes found in this study were 6, 19 and 20. 

Keywords: Capsule, Serotype, Streptococcus pneumoniae, Northern Nigeria