Molecular characteristics of strains of the cameroon family, the major group of Mycobacterium tuberculosis in a country with a high prevalence of tuberculosis - PubMed (original) (raw)

Molecular characteristics of strains of the cameroon family, the major group of Mycobacterium tuberculosis in a country with a high prevalence of tuberculosis

Sara Ngo Niobe-Eyangoh et al. J Clin Microbiol. 2004 Nov.

Abstract

A preliminary investigation of the genetic biodiversity of Mycobacterium tuberculosis complex strains in Cameroon, a country with a high prevalence of tuberculosis, described a group of closely related M. tuberculosis strains (the Cameroon family) currently responsible for more than 40% of smear-positive pulmonary tuberculosis cases. Here, we used various molecular methods to study the genetic characteristics of this family of strains. Cameroon family M. tuberculosis strains (i) are part of the major genetic group 2 and lack the TbD1 region like other families of epidemic strains, (ii) lack spacers 23, 24, and 25 in their direct repeat (DR) region, (iii) have an identical number of repeats in 8 of 12 variable-number tandem repeats of mycobacterial interspersed repetitive unit (MIRU-VNTR) loci, (iv) have similar IS6110-restriction fragment length polymorphism (RFLP) multiband patterns (10 to 15 copies) with seven common IS6110 bands, (v) do not have an IS6110 element in their DR locus, and (vi) have four IS6110 elements in open reading frames (adenylate cyclase, phospholipase C, moeY, and ATP binding genes). Analysis by spoligotyping, MIRU-VNTR, and IS6110-RFLP typing methods revealed differences not observed in previous studies; polymorphism as assessed by MIRU-VNTR typing was lower than suggested by spoligotyping, and in rare cases, strains with identical IS6110-RFLP patterns had spoligotypes differing by as much as 15 spacers. Our findings confirm the recent expansion of this family in Cameroon and indicate that the interpretation of molecular typing results has to be adapted to the characteristics of the strain population within each setting. The knowledge of this particular genotype, with its large involvement in tuberculosis in Cameroon, allows greater refinement of tuberculosis transmission studies by interpreting data in the context of this geographic area.

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Figures

FIG. 1.

FIG. 1.

Patterns of the 45 M. tuberculosis strains obtained by various typing methods. The genetic distances between strains depicted in the dendrogram are based upon combined IS_6110_-RFLP, MIRU-VNTR, and spoligotyping analysis using the same weight for each method. The dendrogram was constructed by UPGMA. Spoligotypes were published previously (20).

FIG. 2.

FIG. 2.

Schematic representation of combined analysis of the three kinds of spoligotyping patterns (Dra-Drb, Ris1-Dra, and Ris2-Drb). Open squares indicate the absence of a particular spacer, solid squares indicate the presence of a particular spacer, and diamond shapes indicate particular spacers not detected by spoligotyping but shown to be present by LR spoligotyping.

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