Molecular characterization of Mycobacterium tuberculosis in northeastern Ethiopia, Amhara Regional State
Fikru Gashaw1,2,3*, Aboma Zewde4, Endalkachew Tedla5, Biniam Wondale6, Yalemtsehay Mekonnen2, Berhanu Erko1, Nicol H.7, Gobena Ameni1
1 Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia; 2 Department of Microbial, Cellular and Molecular Biology, College of Natural and Computational Sciences, Addis Ababa University, Addis Ababa, Ethiopia,
3 Department of Biology, College of Natural and Computational Sciences, Kotebe Metropolitan University, Addis Ababa, Ethiopia
4 Ethiopian Public Health Institute, Addis Ababa, Ethiopia
5 Bikat Higher Diagnostic Laboratory, Amhara Regional State, Dessie, Ethiopia; 6 Department of Biology, College of Natural and Computational Sciences, Arbaminch University, Arbaminch, Ethiopia; 7 Emory University School of Medicine and Rollins School of Public Health, Atlanta, GA, USA
Background: Tuberculosis (TB) is a severe public health threat caused by different members of Mycobacterium tuberculosis complex (MTBC). Characterization of this Mycobacterium is not well established in Ethiopia. Thus, the aim of this study was to determine the diversity of Mycobacterium tuberculosis (M. tb) isolated from South Wollo and Oromia Special Zone in Amhara Regional State, northeastern Ethiopia.
Methods: A cross-sectional study was conducted using 384 smear positive pulmonary and extra-pulmonary tuberculosis cases. Clinical examination, ZiehlNeelsen staining, mycobacterial culture, region of difference (RD) 9-based polymerase chain reaction (PCR), spoligotyping and mycobacterial interspersed repetitive unit-variable-number tandem repeat (MIRU-VNTR) typing were used in the TB investigation. Descriptive statistical analysis was used to determine the proportion of positive samples, speciation, clustered and orphan isolates.
Results: Pulmonary tuberculosis (PTB) accounted for 74.5% (286/384) and the overall prevalence of the disease was highest in the 18–37 years age group. Culture positivity was confirmed in only 29.2% (112/384) of cases. Speciation of the isolates using RD9 revealed 77.7% (87/112) asM. tb. Spoligotyping of 112 isolates identified 92.9% (104/112) as interpretable spoligotyping patterns and 20.2% (21/104) of the isolates were grouped under 10 clustered strains while the remaining 79.8% (83/104) isolates were classified as singleton strains. On the other hand, 13.5% (14/104) of the isolates grouped under shared types and 86.5% (90/104) were orphan. In addition, spoligotyping identified 52.9%, 27.9% and 19.2% of the isolates as Euroamerican, Indio-oceanic and East African Indian lineages, respectively. DNA samples of 69 isolates were tested by 24-loci MIRU-VNTR typing and 56 had valid amplification products. Each of the 56 isolates had distinct MIRU-VNTR profile and, as a result, 56 different genotypes (strains) were detected.
Conclusion: All the strains identified from the study area were M. tuberculosis with a large proportion of genotypic diversities and more of of the isolates were orphan.