Changes in the Molecular Epidemiology of Pediatric Bacterial Meningitis in Senegal After Pneumococcal Conjugate Vaccine Introduction

Abstract

Background: Bacterial meningitis is a major cause of mortality among children under 5 years of age. Senegal is part of World Health Organization-coordinated sentinel site surveillance for pediatric bacterial meningitis surveillance. We conducted this analysis to describe the epidemiology and etiology of bacterial meningitis among children less than 5 years in Senegal from 2010 and to 2016.

Methods: Children who met the inclusion criteria for suspected meningitis at the Centre Hospitalier National d'Enfants Albert Royer, Senegal, from 2010 to 2016 were included. Cerebrospinal fluid specimens were collected from suspected cases examined by routine bacteriology and molecular assays. Serotyping, antimicrobial susceptibility testing, and whole-genome sequencing were performed.

Results: A total of 1013 children were admitted with suspected meningitis during the surveillance period. Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus accounted for 66% (76/115), 25% (29/115), and 9% (10/115) of all confirmed cases, respectively. Most of the suspected cases (63%; 639/1013) and laboratory-confirmed (57%; 66/115) cases occurred during the first year of life. Pneumococcal meningitis case fatality rate was 6-fold higher than that of meningococcal meningitis (28% vs 5%). The predominant pneumococcal lineage causing meningitis was sequence type 618 (n = 7), commonly found among serotype 1 isolates. An ST 2174 lineage that included serotypes 19A and 23F was resistant to trimethoprim-sulfamethoxazole.

Conclusions: There has been a decline in pneumococcal meningitis post-pneumococcal conjugate vaccine introduction in Senegal. However, disease caused by pathogens covered by vaccines in widespread use still persists. There is need for continued effective monitoring of vaccine-preventable meningitis.

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

Figure 1.

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

Figure 2.

Distribution of pathogens associated with pediatric bacterial meningitis in Senegal (2010–2016).

Figure 3.

Temporal distribution of vaccine vs nonvaccine serotypes of pneumococcus by year (2010–2016). There was no serotyping result for all 5 pneumococcal meningitis cases in 2013; the sentinel site did not send CSF specimens for these cases to the WHO RRL. Abbreviations: CSF, cerebrospinal fluid; PCV-13, 13-valent pneumococcal conjugate vaccine; RRL, Regional Reference Laboratory; WHO, World Health Organization.

Figure 4.

Seasonality of meningitis pathogens in the Senegal (2010–2016).

Figure 5.

Phylogeny and antibiogram of pneumococcal isolates associated with childhood bacterial meningitis in Senegal. Pneumococcal isolates include those from 2009 (4 cases) to contextualize the isolates cultured from CSF specimens (39 cases). Resistance and intermediate resistance were confirmed by E-test. Abbreviations: C, chloramphenicol; CSF, cerebrospinal fluid; ERY, erythromycin; OX, oxacillin; PCV, pneumococcal conjugate vaccine; SXT, trimethoprim-sulfamethoxazole; TET, tetracycline.