To establish a molecular epidemiological baseline for the strains causing tuberculosis in Nigeria, a survey of isolates from humans and cattle was carried out. Spoligotyping and variable-number ...tandem-repeat analysis revealed that the majority of tuberculosis disease in humans in Ibadan, southwestern Nigeria, is caused by a single, closely related group of Mycobacterium tuberculosis strains. Using deletion typing, we show that approximately 13% of the disease in humans in this sample was caused by strains of Mycobacterium africanum and Mycobacterium bovis rather than M. tuberculosis. Molecular analysis of strains of M. bovis recovered from Nigerian cattle show that they form a group of closely related strains that show similarity to strains from neighboring Cameroon. Surprisingly, the strains of M. bovis recovered from humans do not match the molecular type of the cattle strains, and possible reasons for this are discussed. This is the first molecular analysis of M. tuberculosis complex strains circulating among humans and cattle in Nigeria, the results of which have significant implications for disease control.
The early genes of bacteriophage T2 are partially excluded from the progeny of crosses between the related bacteriophages T2 and T4. This is due to complete exclusion from the progeny of six ...exclusion-sensitive sites in T2. A mutation exr(56)1 in the sensitive site near T2 gene 56 renders the site partially resistant against exclusion. This paper describes the mapping of the exr(56)1 mutation. The mutation was mapped between two clusters of amber 56 mutations in T2, but mapping was not completely unequivocal. Additional evidence for location of exr(56)1 within gene 56 was provided by the decrease in the activity of the gene 56 product (dCTPase: EC 3.6.1.12) induced by T2 exr(56)1 strains. The location of exr(56)1 within an essential gene contradicts the exclusion model proposed by Russell & Huskey (1974).
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