Comparing mycobacterium tuberculosis complex susceptibility methods, a developing country’s experience

In spite of current diagnosis and treatment, Mycobacterium tuberculosis complex is still an important cause of mortality and morbidity. Uneffective drug combinations and patient incompliance lead to increasing drug resistance. This study by managing four different -non molecular- susceptibility methods was carried out to determine the susceptibility patterns of Mycobacterium tuberculosis complex isolates in central part of Turkey and to compare the methods. The susceptibility testing of 33 isolates were initially performed using the agar proportion method, the results of which were compared with the other three methods; BACTEC 460TB, MGIT 960, and Etest prospectively. According to the “gold standard” agar proportion method, none of the strains were resistant to STR or ETM, while two isolates were found to be resistant to both isoniazid and rifampicin. BACTEC 460 TB remains the reference method of choice, and for low-volume centers. The MGIT 960 system is more suited for high-volume laboratories but has a high risk of contamination. Etest may seem expensive and produces cumbersome results. Regardless of the test used, validation with the gold standard method should be performed periodically as well as in the event of a discordant result. There remains a need for further studies to establish whether available rapid tests will eventually become the gold standard

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