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Revista de la Facultad de Medicina

Print version ISSN 0120-0011


SIERRA PARADA, Claudia Rocío; SANCHEZ MORALES, Edgar Alberto; HENAO RIVEROS, Sandra Consuelo  and  SAAVEDRA RODRIGUEZ, Alfredo. Determining the susceptibility to first-line drugs in M. tuberculosis isolates using the mycobacteria growth indicator tube method. [online]. 2008, vol.56, n.1, pp.11-20. ISSN 0120-0011.

Background. The appearance of Mycobacterium tuberculosis isolates resistant to drugs has triggered the search for quicker and more reliable methods to determine the susceptibility to anti-tuberculosis drugs. Objective. To evaluate the susceptibility of M. tuberculosis isolates to anti-tuberculosis first line drugs by Mycobacterium growth indicator tube method (MGIT). Materials and methods. Forty-nine isolates of M. tuberculosis were tested, coming from the Mycobacteriology Laboratory of Microbiology Department of the Universidad Nacional de Colombia. The MGIT method was evaluated and compared in order to determine resistance or susceptibility to rifampicin, isoniazid, ethambutol and streptomycin with the gold standard method, the multiple proportion method (PM). Results. With the PM method, of 49 isolates, 26 (53.0%) were sensitive to all four antibiotics, 12 (24.5%) were resistant to one antibiotic and 11 (22.5%) to more than one antibiotic. Using the MGIT method, of 49 isolates, 31 (63.3%) were sensitive to all four antibiotics, 8 (16.3%) were resistant to one antibiotic and 10 (20.6%) were resistant to more than one antibiotic. The concordance percentages observed oscillated between 83.7% and 97.9% and the kappa index was between 0.61 and 0.83 for the different antibiotics analyzed. The sensitivity of the MGIT method to the rifampicin, isoniazid, ethambutol and streptomycin was of 88.9, 95.2, 62.5 and 58% respectively and specifity was of 97.7, 92.3, 98.8 y 98.4% respectively. Using the MGIT method, isolates resistant to M. tuberculosis were determined in an average time of 7.85 days. Conclusions. The MGIT method permits obtaining reliable results in less time than conventional methods with isoniazid and rifampicin which are the antibiotics that determine the multi-resistance of M tuberculosis and to a lesser degree to streptomycin and ethambutol.

Keywords : tuberculosis; MGIT; drug resistance; susceptibility.

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