Molecular Typing of Mycobacteria Isolated from Tuberculosis Patients at Debre Birhan Referral Hospital, North Shoa
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Date
2011-07
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Addis Ababa University
Abstract
Introduction: Tuberculosis (TB) is one of the major killers among infectious diseases in the world. Each year an estimated 8.9 to 9.9 million incident cases and approximately 1.55 to 2.32 million deaths due to TB occur worldwide. Ethiopia ranks 7th in the list of world’s 22 high burden countries for TB with incidence estimated at 379 persons per 100,000 persons for all forms of TB. Based on preliminary assessment about the disease and the research gap in
the study setting, a cross-sectional study was carried out from November 2010 to June 2011 on 99 smear positive pulmonary and 98 smear negative extrapulmonary TB patients at Debre Birhan Referral Hospital.
Objective: Molecular characterization of Mycobacterium strains implicated in tuberculosis.
Materials and methods: Structured questionnaire, acid fast bacilli smear staining, culture, deletion typing and spoligotyping were used in the study.
Results: The proportional distribution of TB disease and isolates were not varied substantially (p>0.05) either with age, sex, residence area, occupation, previous contact with TB patients, previous treatment with antibiotics or antimycobacterial drugs, habit of raw animal product consumption or with close contact with livestock for both pulmonary and extrapulmonary TB combined. Out of 99 sputum and 98 fine needle aspirate samples, 80.80% (80/99) and 36.73% (36/98) of them were culture positive respectively. Speciation of isolates using region of difference-9 (RD9) deletion typing showed that 90.00% (72/80) of the isolates from sputum and 88.89% (32/36) of the isolates from fine needle aspirate were M. tuberculosis, while only 1.25% (1/80) and 2.78% (1/36) were M.bovis respectively. Further characterization of 97 M. tuberculosis isolates to the strain level usingspoligo typing resulted in the identification of 25 clusters that constituted 80.41% (78/97) of the isolates tested out of which 17 clusters were new to Ethiopia. The most dominant spoligotypes were spoligo international typing number (ST) 149, 53 and 37 that accounted 32.99% (32/97) of the total spoligotypes identified. Comparison of our spoligo types with international spoligotype database, SpolDB4, showed 19 newspoligotypes which were clustered into nine clusters and have never been reported from elsewhere in the world. Analysis of non-clustered (new) spoligotypes and their source indicated that 35.71% (10/28) of the isolates from extrapulmonary sources were unique, compared with 13.04% (9/69) of the pulmonary isolates. Classifying strains on the bases of phylogeny of M. tuberculosis using SPOTCLUST software revealed that they belonged to Euro-American, East-African Indian and Mycobacterium africanum lineages. The most viii prevalent lineage in the current investigation was Euro-American constituting 69.07% (67/97) of the strains analyzed.
Conclusion: This research has shown the presence of several clusters and new strains of M. tuberculosis circulating both in pulmonary and extrapulmonary TB patients in Ethiopia. As mapping the population structure of M. tuberculosis is vital to understand the transmission and disease dynamics TB and set appropriate control measure, further similar studies are
recommended.
Key words: RD9 Typing, Spoligotyping, Mycobacterium family, Mycobacterium lineage, Tuberculosis, Debre Birhan Referral Hospital
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Keywords
RD9 Typing, Spoligotyping, Mycobacterium family, Mycobacterium lineage