Modified protocol for drug susceptibility testing of MGIT cultures of Mycobacterium tuberculosis by the MGIT 960

• Published in: Diagnostic microbiology and infectious disease 2017-02, Vol.87 (2), p.108-111
• Main Authors: Adami, Aline Gois, Gallo, Juliana Failde, Pinhata, Juliana Maira Watanabe, Martins, Maria Conceição, Giampaglia, Carmen Maria Saraiva, de Oliveira, Rosangela Siqueira
• Format: Article
• Language: English
• Subjects: Antitubercular Agents - pharmacology; Diagnostics; Drug resistance; Infectious Disease; Internal Medicine; MGIT 960; Microbial Sensitivity Tests - methods; Mycobacterium tuberculosis; Mycobacterium tuberculosis - drug effects; Mycobacterium tuberculosis - isolation & purification; Predictive Value of Tests; Sensitivity and Specificity; Time Factors; Tuberculosis; Tuberculosis - diagnosis; Tuberculosis - microbiology
• ISSN: 0732-8893; 1879-0070
• DOI: 10.1016/j.diagmicrobio.2016.10.023

Abstract A rapid detection of resistance in Mycobacterium tuberculosis is crucial for management and control of tuberculosis. This study evaluated a more rapid and cost-effective drug susceptibility testing (DST) protocol using primary isolates of M. tuberculosis in mycobacteria growth indicator tube (MGIT). Ninety-four M. tuberculosis isolates in MGIT were subjected to DST by the manufacturer's method, i.e., primary isolates were subcultured and DST was performed from positive cultures for a maximum of 5 days; and by our modified method, i.e., DST was performed directly from primary MGIT cultures positive for more than 5 days. Results were concordant for 76 (81%) isolates. Agreement between both methods was 92.0%, 98.9%, 97.7%, and 95.5% for streptomycin, isoniazid, rifampicin, and ethambutol, respectively. Six isolates failed to grow on the recommended method, including 3 resistant isolates. Not performing subculture of primary M. tuberculosis isolates yields reliable results, decreasing the turnaround time and the cost of the test.