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Updated: Apr 20, 2026
Experimental Human Pneumococcal Carriage
Published on: February 15, 2013
Identifying an appropriate PCV for use in Senegal, recent insights concerning Streptococcus pneumoniae NP carriage
Fatim Ba1, Abdoulaye Seck2, Mamadou Bâ3
1Medical Laboratory, Pasteur Institute, Dakar, Senegal. lafatiz@gmail.com.
Insights
Streptococcus pneumoniae carriage and infection rates are high in young children in Dakar, with prevalent serotypes covered by current pneumococcal conjugate vaccines (PCV). Low antibiotic resistance was observed, but high case-fatality underscores the need for PCV introduction and surveillance.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Microbiology
Background:
- Sub-Saharan Africa faces high rates of pneumococcal nasopharyngeal carriage (40-60%) and disease incidence.
- The Global Alliance for Vaccines and Immunization (GAVI) and WHO support Pneumococcal Conjugate Vaccine (PCV) introduction in developing countries.
- Pneumococcal infections exhibit high incidence and case fatality rates in Africa.
Purpose of the Study:
- To investigate nasopharyngeal pneumococcal carriage and infection in children under 5 years old in Dakar.
- To determine serotypes, antibiotic susceptibility, and minimum inhibitory concentrations of Streptococcus pneumoniae.
- To compare current findings with historical Senegalese literature (1972-2013).
Main Methods:
- Nasopharyngeal swabs collected from 264 children in Dakar (2007-2008).
- Serotyping, antibiotic susceptibility testing, and minimum inhibitory concentration determination for Streptococcus pneumoniae.
- Literature review of 6 Senegalese publications (1972-2013) for comparative analysis.
Main Results:
- 50% of children (132/264) had positive nasopharyngeal cultures for Streptococcus pneumoniae.
- Prevalent serotypes included 6B, 19F, 23F, 14, and 6A. Reduced susceptibility to penicillin (15%) and fluoroquinolones (3%) was noted.
- Among 196 infections, 31.6% yielded Streptococcus pneumoniae. Serogroup 1 was most prevalent. PCV-7, PCV-10, and PCV-13 coverages were 36.2%, 66%, and 70.2% respectively. Case-fatality was 42.4%.
Conclusions:
- High carriage and disease rates by vaccine-contained serotypes confirm findings from other sub-Saharan African countries pre-PCV.
- Low rates of antimicrobial resistance observed in this sample.
- High case-fatality necessitates prioritizing high-valency pneumococcal vaccine introduction and establishing surveillance systems.
Background:
Since 2000, the Global Alliance for Vaccines and Immunization (GAVI) and WHO have supported the introduction of the Pneumococcal Conjugate Vaccine (PCV) in the immunization programs of developing countries. The highest pneumococcal nasopharyngeal carriage rates have been reported (40-60%) in these countries, and the highest incidence and case fatality rates of pneumococcal infections have been demonstrated in Africa.
Methods:
Studies concerning nasopharyngeal pneumococcal carriage and pneumococcal infection in children less than 5 years old were conducted in Dakar from 2007 to 2008. Serotype, antibiotic susceptibility and minimum inhibitory concentrations were determined. In addition, among 17 overall publications, 6 manuscripts of the Senegalese literature published from 1972 to 2013 were selected for data comparisons.
Results:
Among the 264 children observed, 132 (50%) children generated a nasopharyngeal (NP) positive culture with Streptococcus pneumoniae. The five most prevalent serotypes, were 6B (9%), 19 F (9%), 23 F (7.6%), 14 (7.6%) and 6A (6.8%). Fifteen percent of the strains (20/132) showed reduced susceptibility to penicillin and 3% (4/132) showed reduced susceptibility to anti-pneumococcal fluoroquinolones. Among the 196 suspected pneumococcal infections, 62 (31.6%) Streptococcus pneumoniae were isolated. Serogroup 1 was the most prevalent serotype (21.3%), followed by 6B (14.9%), 23 F (14.9%) and 5 (8.5%). Vaccine coverage for PCV-7, PCV-10 and PCV-13, were 36.2% (17/47), 66% (31/47) and 70.2% (33/47) respectively. Reduced susceptibility to penicillin and anti-pneumococcal fluoroquinolones was 6.4% and 4.3%, respectively, and the overall lethality was 42.4% (14/33).
Conclusions:
This study confirms a high rate of carriage and disease caused by Streptococcus pneumoniae serotypes contained within the current generation of pneumococcal conjugate vaccines and consistent with reports from other countries in sub-Saharan Africa prior to PCV introduction. Antimicrobial resistance in this small unselected sample confirms a low rate of antibiotic resistance. Case-fatality is high. Introduction of a high valency pneumococcal vaccine should be a priority for health planners with the establishment of an effective surveillance system to monitor post vaccine changes.
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