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Open Access Research article

Distinct genotypic profiles of the two major clades of Mycobacterium africanum

Sidra E Gonçalves Vasconcellos1, Richard C Huard2*, Stefan Niemann3, Kristin Kremer4, Adalberto R Santos1, Philip N Suffys1* and John L Ho5

Author Affiliations

1 Laboratory of Molecular Biology Applied to Mycobacteria, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Avenida Brasil 4365, Manguinhos - 21040-900, Rio de Janeiro, Brazil

2 Clinical Microbiology Service and the Department of Pathology, New York-Presbyterian Hospital, Columbia University Medical Center, 622 West 168th Street, New York City, NY, USA

3 National Reference Center for Mycobacteria, Forschungszentrum, Parkallee 18, D-23845, Borstel, Germany

4 Mycobacteria Reference Laboratory, (CIb/LIS), National Institute for Public Health and the Environment, 3720 Bilthoven, the Netherlands

5 Division of International Medicine and Infectious Diseases, Department of Medicine, Joan and Sanford I. Weill Medical College of Cornell University, 1300 York Avenue, New York City, NY, USA

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BMC Infectious Diseases 2010, 10:80  doi:10.1186/1471-2334-10-80

Published: 29 March 2010

Abstract

Background

Mycobacterium tuberculosis is the principal etiologic agent of human tuberculosis (TB) and a member of the M. tuberculosis complex (MTC). Additional MTC species that cause TB in humans and other mammals include Mycobacterium africanum and Mycobacterium bovis. One result of studies interrogating recently identified MTC phylogenetic markers has been the recognition of at least two distinct lineages of M. africanum, known as West African-1 and West African-2.

Methods

We screened a blinded non-random set of MTC strains isolated from TB patients in Ghana (n = 47) for known chromosomal region-of-difference (RD) loci and single nucleotide polymorphisms (SNPs). A MTC PCR-typing panel, single-target standard PCR, multi-primer PCR, PCR-restriction fragment analysis, and sequence analysis of amplified products were among the methods utilized for the comparative evaluation of targets and identification systems. The MTC distributions of novel SNPs were characterized in the both the Ghana collection and two other diverse collections of MTC strains (n = 175 in total).

Results

The utility of various polymorphisms as species-, lineage-, and sublineage-defining phylogenetic markers for M. africanum was determined. Novel SNPs were also identified and found to be specific to either M. africanum West African-1 (Rv1332523; n = 32) or M. africanum West African-2 (nat751; n = 27). In the final analysis, a strain identification approach that combined multi-primer PCR targeting of the RD loci RD9, RD10, and RD702 was the most simple, straight-forward, and definitive means of distinguishing the two clades of M. africanum from one another and from other MTC species.

Conclusion

With this study, we have organized a series of consistent phylogenetically-relevant markers for each of the distinct MTC lineages that share the M. africanum designation. A differential distribution of each M. africanum clade in Western Africa is described.