Genetic profiling of Mycobacterium tuberculosis in Tunisia: predominance and evidence for the establishment of a few genotypes

Abstract

Typing analyses of 378 Mycobacterium tuberculosis isolates collected between the years 2001 and 2005 from three northern representative regions of Tunisia revealed a highly homogeneous population. Indeed, 84.9 % of all tuberculosis (TB) cases were attributed to the Haarlem, LAM or T families. Strikingly, within each family, more than 60 % of TB cases were due to a single genotype. ST50 (Haarlem3) and ST42 (LAM9) genotypes were exceptionally predominant, representing 46.3 % of all typed isolates. ST50 showed an increased tendency for clustering and was more predominant in the extreme north of the country. By contrast, the more widespread ST42, which was apparently prevalent 17 years ago, displayed weak cluster individualization and a low transmission rate, consistent with its stable association with the Tunisian population. It is believed that both mass BCG vaccination, strictly applied for four decades, and the high endogamy rate that characterizes the Tunisian population could have profoundly shaped the population structure of M. tuberculosis by concurrently favouring the selection and accommodation of particular genotypes.

Unexpectedly High Proportion of Ancestral Manu Genotype Mycobacterium tuberculosis Strains Cultured from Tuberculosis Patients in Egypt

“…The Manu lineage was initially described as a new family from India in 2004 (16), and later, similar strains in small numbers were reported in a study from Madagascar (8), Soon afterwards, it was tentatively subdivided into the Manu1 (deletion of spacer 34), Manu2 (deletion of spacers 33 and 34), and Manu3 (deletion of spacers 34 to 36) sublineages; and it was suggested that this lineage could represent an ancestral clone of principal genetic group 1 strains (4). More recently, Manu lineage strains were reported from Saudi Arabia (2) and Tunisia (15).…”

Estimates of Genetic Variability of <i>Mycobacterium tuberculosis</i> Complex and Its Association with Drug Resistance in Cameroon

“…The factors that might contribute to the adaptability of M. tuberculosis strains or lineages to a particular population or zone are poorly understood. As hypothesized for the Tunisian family [15], mass BCG vaccination strictly applied for decades might have profoundly shaped the population structure of M. tuberculosis by concurrently favoring the selection and accommodation of particular genotypes, as the LAM10_ CAM family in our setting.…”

Spoligotype Profile of Mycobacterium tuberculosis Complex Strains from HIV-Positive and -Negative Patients in Nigeria: a Comparative Analysis

“…Soon afterwards, it was tentatively subdivided into the Manu1 (deletion of spacer 34), Manu2 (deletion of spacers 33 and 34), and Manu3 (deletion of spacers 34 to 36) sublineages, and it was suggested that it could represent an ancestral clone of principal genetic group (PGG) 1 strains (4). Manu lineage strains were reported from Saudi Arabia (2) and Tunisia (17) and more recently in a study from Egypt, where it represented as much as 27% of all isolates (15). However, according to a recent report, a fraction of Manu2 patterns could also arise due to mixed infection by a strain belonging to evolutionarily recent H, LAM, X, and T lineages with a Beijing strain, a risk that may be excluded by looking for genomic deletion of region of difference RD105, which is characteristic of the Beijing lineage (26).…”