The genetic population structure of Mycobacterium bovis strains isolated from cattle slaughtered at the Yaoundé and Douala abattoirs in Cameroon.

Bovine tuberculosis is still prevalent and under-evaluated in cattle destined for human consumption in Cameroon. Potential reservoirs of the disease include livestock imported from countries endemic for bovine tuberculosis, such as Nigeria and Chad, and potential residual reservoirs in local livestock and wildlife. Few studies have been done in Cameroon to genotype the Mycobacterium tuberculosis complex (MTC) strains responsible for bovine tuberculosis. The aim of this work is to describe the population structure of MTC strains isolated from cattle, using spoligotyping as the genotyping method. Out of 218 organs or tissues from cattle with suspected tuberculosis lesions, 90 MTC strains were isolated and underwent molecular typing; among them, 86 strains were identified as M. bovis and four strains as M. tuberculosis. The M. tuberculosis strains belonged to rare M. tuberculosis lineages of the U family; among the M. bovis strains SB0944 was the most prevalent. Eight new spoligotype patterns were identified, representing 33% (30/90) of all isolates. Among these new spoligotypes, SB1955 was dominant. The spoligotype patterns of 85 M. bovis strains lacked spacer 30, a common characteristic of the M. bovis lineage African 1, described earlier in Cameroon, Chad, Mali and Nigeria. This study shows ongoing tuberculosis transmission involving M. bovis lineages not previously described as the leading cause of disease. It also shows a possible reverse zoonosis from humans to cattle.