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

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.

Genetic biodiversity of Mycobacterium tuberculosis complex strains from patients with pulmonary tuberculosis in Cameroon.

We analyzed DNA polymorphisms in 455 Mycobacterium tuberculosis complex isolates from 455 patients to evaluate the biodiversity of tubercle bacilli in Ouest province, Cameroon. The phenotypic and genotypic identification methods gave concordant results for 99.5% of M. tuberculosis isolates (413 strains) and for 90% of Mycobacterium africanum isolates (41 strains). Mycobacterium bovis was isolated from only one patient. Analysis of regions of difference (RD4, RD9, and RD10) proved to be an accurate and rapid method of distinguishing between unusual members of the M. tuberculosis complex. Whereas M. africanum strains were the etiologic agent of tuberculosis in 56% of cases 3 decades ago, our results showed that these strains now account for just 9% of cases of tuberculosis. We identified a group of closely genetically related M. tuberculosis strains that are currently responsible for >40% of smear-positive pulmonary tuberculosis cases in this region of Cameroon. These strains shared a spoligotype lacking spacers 23, 24, and 25 and had highly related IS6110 ligation-mediated (LM) PCR patterns. They were designated the "Cameroon family." We did not find any significant association between tuberculosis-causing species or strain families and patient characteristics (sex, age, and human immunodeficiency virus status). A comparison of the spoligotypes of the Cameroon strains with an international spoligotype database (SpolDB3) containing 11,708 patterns from >90 countries, showed that the predominant spoligotype in Cameroon was limited to West African countries (Benin, Senegal, and Ivory Coast) and to the Caribbean area.

Snapshot of moving and expanding clones of Mycobacterium tuberculosis and their global distribution assessed by spoligotyping in an international study.

The present update on the global distribution of Mycobacterium tuberculosis complex spoligotypes provides both the octal and binary descriptions of the spoligotypes for M. tuberculosis complex, including Mycobacterium bovis, from >90 countries (13,008 patterns grouped into 813 shared types containing 11,708 isolates and 1,300 orphan patterns). A number of potential indices were developed to summarize the information on the biogeographical specificity of a given shared type, as well as its geographical spreading (matching code and spreading index, respectively). To facilitate the analysis of hundreds of spoligotypes each made up of a binary succession of 43 bits of information, a number of major and minor visual rules were also defined. A total of six major rules (A to F) with the precise description of the extra missing spacers (minor rules) were used to define 36 major clades (or families) of M. tuberculosis. Some major clades identified were the East African-Indian (EAI) clade, the Beijing clade, the Haarlem clade, the Latin American and Mediterranean (LAM) clade, the Central Asian (CAS) clade, a European clade of IS6110 low banders (X; highly prevalent in the United States and United Kingdom), and a widespread yet poorly defined clade (T). When the visual rules defined above were used for an automated labeling of the 813 shared types to define nine superfamilies of strains (Mycobacterium africanum, Beijing, M. bovis, EAI, CAS, T, Haarlem, X, and LAM), 96.9% of the shared types received a label, showing the potential for automated labeling of M. tuberculosis families in well-defined phylogeographical families. Intercontinental matches of shared types among eight continents and subcontinents (Africa, North America, Central America, South America, Europe, the Middle East and Central Asia, and the Far East) are analyzed and discussed.

Global distribution of Mycobacterium tuberculosis spoligotypes.

We present a short summary of recent observations on the global distribution of the major clades of the Mycobacterium tuberculosis complex, the causative agent of tuberculosis. This global distribution was defined by data-mining of an international spoligotyping database, SpolDB3. This database contains 11708 patterns from as many clinical isolates originating from more than 90 countries. The 11708 spoligotypes were clustered into 813 shared types. A total of 1300 orphan patterns (clinical isolates showing a unique spoligotype) were also detected.