AbstractThe differential diagnosis of Mycobacterium bovis is important in the control of transmission to the human population and also for treatment since M. bovis is naturally resistant to pyrazinamide. Eleven clinical isolates from the Fernando Fonseca Hospital with Spoligotypes indicative of M. bovis, through the absence of spacers 39-43 but that also counted with the absence of spacer 38, were analyzed. For the identification of these strains, the phenotypic analysis of pyrazinamide resistance and study of the polymorphisms of the pncA and gyrB genes were carried out. The study of the pncA polymorphism revealed that the strains analyzed did not contain the M. bovis specific mutation. In relation the gyrB polymorphisms, using the GenoType® MTBC kit, the strains were identified as belonging to the group M. tuberculosis, M. africanum subtipo II e M. canetti. The present investigation enabled us to define new genotypes on which future bacteriological studies should be based. Amongst these the study of the pncA polymorphism was considered important due to the immediate practical implications for the clinician. Evaluating transmission and defining groups of risk is an objective for which support from the veterinary services is considered relevant.Rev Port Pneumol 2005; XI (6): 533-556