Objective: To determine primary and acquired resistance to pyrazinamide in Mycobacterium tuberculosis strains isolated in sputum samples from patients with pulmonary tuberculosis. Methods: This was a prospective, descriptive study conducted between April and November of 2011 at a referral hospital for tuberculosis in the city of Recife, Brazil. Cultures, drug sensitivity tests, and tests of pyrazinamidase activity were conducted in a private laboratory in Recife. Results: Of the 71 patients included in the study, 37 were treatment-naïve and 34 represented cases of retreatment. Pyrazinamide-resistant strains were isolated in 14 (41.2%) of the 34 patients who had previously been treated for tuberculosis and in none of the 37 treatment-naïve patients. Of the 14 isolates, 10 (90.9%) tested negative for pyrazinamidase activity. A total of 60 isolates tested positive for pyrazinamidase activity. Of those, 56 (93.3%) were found to be sensitive to pyrazinamide. Conclusions: The high frequency of pyrazinamide-resistant strains (41.2%) in patients previously treated for tuberculosis highlights the need for drug susceptibility testing prior to the adoption of a new treatment regimen.

Keywords: Mycobacterium tuberculosis; Pyrazinamide; Tuberculosis, multidrug-resistant