Genetic diversity of Mycobacterium tuberculosis Complex in Jos, Nigeria

Abstract

Background: Nigeria has a high tuberculosis incidence, and genotyping studies of Mycobacterium tuberculosis Complex (MTC) in the country are necessary in order to improve our understanding of the epidemic.

Methods: Isolates of MTC were isolated from cases of pulmonary tuberculosis in Jos, North Central region of Nigeria during 2006-2008. Drug susceptibility test (DST) was performed on 77 of 111 isolates by proportion method on Lowenstein Jensen (LJ) slope while genotyping of mycobacterial DNA was performed by spoligotyping. The SpolDB4 database and the model-based program 'spotclust' were used to assign isolates to families, subfamilies and variants.

Results: A total of 111 pulmonary isolates from consecutive tuberculosis patients in the city of Jos, Plateau State, Nigeria were spoligotyped. A total of 84 (76%) of the isolates belonged to the Latin American Mediterranean (LAM) family. Of these, 78 isolates were assigned to the LAM10 lineage. Among these, 66 exhibited identical spoligopatterns. Drug susceptibility profiles obtained were not consistently associated with any spoligopattern.

Conclusions: The dominance of few M. tuberculosis lineages suggests either a high rate of transmission, frequent import of closely related strains, or a highly conserved genotype. It remains to be confirmed whether the predominance of identical LAM10 represent an outbreak.Spoligotyping was useful to gain an overall understanding of the local TB epidemic. This study demonstrated that the incidence of TB in Jos, Nigeria may be caused by a few successful M. tuberculosis families, dominated by the LAM10 family.

Figure 1

Spoligopatterns and identity of Mycobacterium tuberculosis complex strains from Jos, Nigeria. Genetic similarity and spoligopattern of M. tuberculosis Complex isolates from Jos in Nigeria. The population demonstrates a high degree of homogeneity and dominance of LAM10.