Identification and Susceptibility Testing on Samples of Mycobacterium spp

Background: Tuberculosis is still a major global health problem. Human tuberculosis is caused by species of bacteria belonging to the Mycobacterium genus. In this study we determined mycobacterial species affecting patients from Botucatu, Brazil, and tested M. tuberculosis sensitivity to different drugs.
Methods: Data were obtained from Clinical Laboratory Analysis records at Botucatu Medical School University Hospital, UNESP. All samples were processed according to standard isolation procedures from the 2008 Brazil Ministry of Health Mycobacteria Manual, which consist of staining smears by the Ziehl-Neelsen technique and seeding cultures in the Löwenstein-Jensen medium.
Results: Samples were isolated from sputum (80.5%), bronchoalveolar lavage (13.8%), pleural fluid (4.6%), and cerebrospinal liquor (1.1%). Smears were evaluated in 87 cases and a total of 59 patients showed positive smears; 55 from 70 sputum samples and 4 from 12 bronchoalveolar lavage samples. No pleural fluid (4) or cerebrospinal liquor (1) samples showed positive smears. The most commonly identified strain was M. tuberculosis (61 cases); followed by M. avium and M. gordonae 2 cases each, and M. peregrinumand M. abscessus 1 case each. Mycobacteria were not identified in 20 patients. Only two strains of M. tuberculosis were multidrug resistant; one was resistant to isoniazid, rifampicin, and pyrazinamide. These two patients evolved to cure.
Conclusion: This study highlights a small but troubling percentage of multidrug resistant samples and reveals the occurrence of nontuberculous mycobacteria, emphasizing the importance of correctly identifying species and testing sensitivity to antibacilar drugs to assure an adequate therapy.