Serotype Distribution Pattern of Streptococcus pneumoniae Isolates from Invasive Infections at a University Teaching Hospital in Northern Nigeria

Abstract

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 18months 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 CO₂-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 nontypeable. 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.