Abdissa, Alemseged (2005) Characterization of Group a Streptococci Isolated from Throat of Healthy School Children in Ethiopia. Masters thesis, Addis Ababa University.
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Abstract
Post-streptococcal complications such as acute rheumatic fever (ARF) are reported to be common among Ethiopian children. Little is known, however, about the epidemiology of b-hemolytic streptococci, and Group A streptococci (GAS) in Ethiopia. A total of 937 randomly selected healthy schoolchildren residing in Addis Ababa (n=491), Gondar (n=265) and Dire-Dawa (n=181) were studied during a period November 2004 and January 2005. Throat specimens were collected and b-hemolytic streptococci were isolated on Columbia blood agar supplemented with Colistin-oxolonic acid. Gram reaction, catalase test Bacitracin susceptibility test and serological test were used to differentiate the organisms. In addition biochemical testing (API) was used to identify the species of isolates that could not be serogrouped. GAS were the predominant b-hemolytic streptococci with a proportion of 55% in Addis Ababa, 61% in Gondar, and 47% in Dire-Dawa of the serogroups. The carrier rate of GAS in healthy schoolchildren was 10.8% in Addis Ababa, 8.7% in Gondar and 9.4% in Dire- Dawa. Seven isolates that were nongroupable confirmed to be Streptococcus constellatus with API biochemical testing. Molecular (emm gene) typing was performed on 82 GAS isolates and 44 different emm types were detected. Among the 82 isolates 18 strains belonged to 13 new, previously undescribed emm subtypes. Known rheumatogenic strains accounted for 56% of isolates in Addis Ababa, 35% in Gondar and 0% in Dire-Dawa. Of the emm types prevalent in the study communities, 60% were not included in the 26 valent vaccine that was formulated for western countries. The distribution of emm types described in this study was compared with the study conducted on isolates collected 13 years ago in Addis Ababa, only 3/20 emm types identified in earlier study had been represented in the present study. Moreover, the type, which was predominant in the previous study, was not detected in the current one and the type that was predominant in our study was not detected in the previous one. In conclusion, Group A was the most frequent serogroup among b-hemolytic streptococci isolated from throat swabs of healthy schoolchildren in the selected three sites of Ethiopia and the carriage rate of GAS ranged from 8.7 to 10.8%. Tremendous diversity of emm types was observed in this first large scale emm type survey in Africa, and a significant proportion of them are known to be rheumatogenic. The association of the prevalent emm types not previously linked to rheumatic fever needs to be explored particularly in Dire-Dawa.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Beta-hemolytic streptococci, Group A Streptococci, Streptococcus pyogenes, M protein, emm typing |
| Subjects: | Q Science > Q Science (General) Q Science > QR Microbiology |
| Divisions: | Africana |
| Depositing User: | Vincent Mpoza |
| Date Deposited: | 29 Jun 2018 07:43 |
| Last Modified: | 29 Jun 2018 07:43 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/6124 |
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