Declining Trends of Pneumococcal Meningitis in Gambian Children After the Introduction of Pneumococcal Conjugate Vaccines

Abstract

Background: Acute bacterial meningitis remains a major cause of childhood mortality in sub-Saharan Africa. We document findings from hospital-based sentinel surveillance of bacterial meningitis among children <5 years of age in The Gambia, from 2010 to 2016.

Methods: Cerebrospinal fluid (CSF) was collected from children admitted to the Edward Francis Small Teaching Hospital with suspected meningitis. Identification of Streptococcus pneumoniae (pneumococcus), Neisseria meningitidis (meningococcus), and Haemophilus influenzae was performed by microbiological culture and/or polymerase chain reaction where possible. Whole genome sequencing was performed on pneumococcal isolates.

Results: A total of 438 children were admitted with suspected meningitis during the surveillance period. The median age of the patients was 13 (interquartile range, 3-30) months. Bacterial meningitis was confirmed in 21.4% (69/323) of all CSF samples analyzed. Pneumococcus, meningococcus, and H. influenzae accounted for 52.2%, 31.9%, and 16.0% of confirmed cases, respectively. There was a significant reduction of pneumococcal conjugate vaccine (PCV) serotypes, from 44.4% in 2011 to 0.0% in 2014, 5 years after PCV implementation. The majority of serotyped meningococcus and H. influenzae belonged to meningococcus serogroup W (45.5%) and H. influenzae type b (54.5%), respectively. Meningitis pathogens were more frequently isolated during the dry dusty season of the year. Reduced susceptibility to tetracycline, trimethoprim-sulfamethoxazole, and chloramphenicol was observed. No resistance to penicillin was found.

Conclusions: The proportion of meningitis cases due to pneumococcus declined in the post-PCV era. However, the persistence of vaccine-preventable meningitis in children aged <5 years is a major concern and demonstrates the need for sustained high-quality surveillance.

Keywords: Haemophilus influenzae; Neisseria meningitidis; Streptococcus pneumoniae; pediatric bacterial meningitis; pneumococcal conjugate vaccines.

Figure 1.

Summary of cerebrospinal fluid collection and processing for invasive bacterial disease surveillance in The Gambia (2010–2016). Abbreviations: CSF, cerebrospinal fluid; PCR, polymerase chain reaction.

Figure 2.

Distribution of pathogens associated with pediatric bacterial meningitis in The Gambia (2010–2016). Thirteen-valent pneumococcal conjugate vaccine (PCV13) types include serotypes 1, 5, 6A/6B, 14, 19A, and 23F; non-PCV13 serotypes include 8, 11A, and 3 nontypeable pneumococci by real-time polymerase chain reaction.

Figure 3.

Seasonality of meningitis pathogens in The Gambia (2010–2016).

Figure 4.

Phylogeny and antibiogram of pneumococcal isolates associated with childhood bacterial meningitis. Isolates cultured from blood (n = 14); lungs (n = 6), and pus (n = 1) are included to contextualize the isolates cultured from cerebrospinal fluid specimens (n = 20). Resistance and intermediate resistance were confirmed by Etest. Abbreviations: CHL, chloramphenicol; CSF, cerebrospinal fluid; CTX, cefotaxime; ERY, erythromycin; PEN, penicillin; SXT, trimethoprim-sulfamethoxazole; TET, tetracycline.