The Impact of Ten-valent Pneumococcal Conjugate Vaccine (pcv10) on Streptococcus Pneumoniae Nasopharyngeal Carriage Rate in Healthy Children: Phenotypic and Genetic Diversity of Isolates from Addis Ababa, Ethiopia
| dc.contributor.advisor | Woldeamanuel, Yimtubezinash (MD, MSc PhD) | |
| dc.contributor.author | Tsegaye, Wondewosen | |
| dc.date.accessioned | 2018-10-26T06:32:47Z | |
| dc.date.accessioned | 2023-11-05T09:35:57Z | |
| dc.date.available | 2018-10-26T06:32:47Z | |
| dc.date.available | 2023-11-05T09:35:57Z | |
| dc.date.issued | 2017-05 | |
| dc.description.abstract | Background: Streptococcus pneumoniae is among the most important human pathogens responsible for high morbidity and mortality rates. Nasopharyngeal colonisation is the necessary first step in the pathogenesis of associated invasive pneumococcal diseases. Ethiopia, introduced the ten valent pneumococcal conjugate vaccine (PCV10) in October 2011, and the vaccine is currently given at a “3+0” schedule: at the age of 6, 10 and 14 weeks without booster dose. However, there is lack of adequate baseline information on epidemiological factors for comparison in subsequent impact assessment. The aim of this study was to determine the impact of PCV10 vaccine on nasopharyngeal carriage and analyze the phenotypic and genetic diversity of pneumococcal isolates identified. Method: A total of 789 infants were enrolled at the age of six weeks when they came for the first PCV10 vaccine; and 206 were re-sampled at the age of nine months; and 201 at two years of age after the final dose of PCV10. Nasopharyngeal swab samples were taken for bacteriological analysis before vaccination at the age of six weeks, and after completion at the age of nine months and two years. Isolates were tested for commonly used antibiotics by the disc diffusion method, and the minimum inhibitory concentration was determined by E-test for those isolates that showed reduced susceptability to penicillin and resistance to erythromycin. A total of 422 pneumococcal isolates were serotyped and 325 isolates characterized by Pulsed Field Gel Electrophoresis (PFGE) and twelve isolates were analysed by multilocus sequence typing (MLST). Results: The carriage rate of S. pneumoniae at the age of six weeks, nine months and two years was 26.6%, 56.8% and 48.3% respectively. A total of 59 serotypes of S. pneumoniae were identified from 422 isolates, and serotype 6A, 34, 10A, 11A, 19F, 15B, 23F, and 15A dominated in decreasing order. The proportion of serotypes covered by PCV10 vaccine among the isolates at six weeks, nine months and two years were 20.2%, 11.1% and 10.3% respectively. Molecular typing of six-week and nine-month isolates further showed a presence of a high genetic diversity. Resistance rates ranged from none xvi to ceftriaxone and 4.3% for chloramphenicol to 27.7% for trimethoprim/sulfamethoxazole. Conclusion: This study highlights the presence of very diverse serotypes in the country, and PFGE and MLST results indicate a case of possible capsular switching event. A vaccine impact has been observed on with a reduction of carriage of vaccine types; but, like in similar other studies, non-vaccine type replacement were also demonstrated. The use of PCV13 would have an added value by increasing the coverage over additional nasopharyngeal carried isolates by at least 10% more. This work was conducted in Addis Ababa only and it is necessary to extend the investigation to other parts of the country and include clinical cases to have a complete picture of the impact of PCV on pneumococcal epidemiology. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/123456789/13272 | |
| dc.language.iso | en_US | en_US |
| dc.publisher | Addis Ababa Universty | en_US |
| dc.subject | Steptococcus pneumoniae, Serotypes, Genetic diversity, Pneumococcal conjugate vaccine, Addis Ababa | en_US |
| dc.title | The Impact of Ten-valent Pneumococcal Conjugate Vaccine (pcv10) on Streptococcus Pneumoniae Nasopharyngeal Carriage Rate in Healthy Children: Phenotypic and Genetic Diversity of Isolates from Addis Ababa, Ethiopia | en_US |
| dc.type | Thesis | en_US |