Evolution and clonal traits of Mycobacterium tuberculosis complex in Guinea-Bissau

Two hundred twenty-nine consecutive isolates of Mycobacterium tuberculosis complex from patients with pulmonary tuberculosis in Guinea-Bissau, which i s located in West Africa,,were analyzed for clonal origin by biochemical ty ping and DNA fingerprinting, By using four biochemical tests (resistance to thiophene-2-carboxylic acid hydrazide, niacin production, nitrate reductas e test, and pyrazinamidase test), the isolates could be assigned to five di fferent biovars, The characteristics of four strains conformed fully with t he biochemical criteria for M bovis, while those of 85 isolates agreed with the biochemical criteria for M. tuberculosis. The remaining 140 isolates c ould be allocated into one of three biovars (biovars 2 to 4) representing a spectrum between the classical bovine (biovar 1) and human (biovar 5) tube rcle bacilli. By using two genotyping methods, restriction fragment Length polymorphism analysis with IS6110 (IS6110 RFLP analysis) and spoligotyping, the isolates could be separated into three groups (groups A to C) of the M . tuberculosis complex. Group A (n = 95), which contained the majority of c lassical human M. tuberculosis isolates, had large numbers of copies of IS6 110 elements (mean number of copies, 9) and a distinctive spoligotyping pat tern that Lacked spacers 33 to 36, Isolates of the major group, group B (n = 119), had fewer IS6110 copies (mean copy number, 5) and a spoligotyping p attern that lacked spacers 7 to 9 and 39 and mainly comprised isolates of b iovars 1 to 4, Group C isolates (n = 15) had one to three IS6110 copies, ha d a spoligotyping pattern that lacked spacers 29 to 34, and represented bio var 3 to 5 isolates. Four isolates whose biochemical characteristics confor med with those of M. bovis clustered,vith the group B isolates and had spol igotype patterns that differed from those previously reported for M. bovis, in that they possessed spacers 40 to 43, Interestingly, isolates of group B and, to a certain extent, also isolates of group C showed a high degree o f variability in biochemical traits, despite genotypic identity in terms of IS6110 RFLP and spoligotype patterns. We hypothesize that isolates of grou ps B and C have their evolutionary origin in West Africa, while group A iso lates are of European descent.