Multicenter Evaluation of Bactec MGIT 960 System for Second-Line Drug Susceptibility Testing of Mycobacterium tuberculosis Complex

Microbial Diseases Laboratory, CDPH, 850 Marina Bay Parkway, Richmond, CA 94804, USA.
Journal of clinical microbiology (Impact Factor: 3.99). 10/2009; 47(11):3630-4. DOI: 10.1128/JCM.00803-09
Source: PubMed


The Bactec MGIT 960 system for testing susceptibility to second-line drugs was evaluated with 117 clinical strains in a multicenter
study. The four drugs studied were levofloxacin, amikacin, capreomycin, and ethionamide. The critical concentration established
for levofloxacin and amikacin was 1.5 μg/ml, that established for capreomycin was 3.0 μg/ml, and that established for ethionamide
was 5.0 μg/ml. The overall level of agreement between the agar proportion method and the MGIT 960 system was 96.4%, and the
levels of agreement for the individuals drugs were 99.1% for levofloxacin, 100% for amikacin, 97.4% for capreomycin, and 88.9%
for ethionamide. The rate of reproducibility of the drug susceptibility testing results between the participating laboratories
was 99.5%.

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    • "The MICs for LEV were recommended between 0.5 and 2.0 μg/mL in previous papers [22, 23]. According to Sanders's paper, they tested MICs with both pansusceptible and resistant strain. "
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    ABSTRACT: Many laboratories validate DST of the second-line drugs by BACTEC MGIT 960 system. The objective of this study is to evaluate the critical concentration and perform DST for the 2nd line drugs. We evaluated 193 clinical strains of M. tuberculosis isolated from patients in South Korea. Testing the critical concentration of six second-line drugs was performed by MGIT 960 and compared with L-J proportion method. The critical concentration was determined to establish the most one that gave the difference between drug resistance and susceptibility in MGIT960 system. Good agreement of the following concentrations was found: Concordance was 95% for 0.5 μ g/mL of moxifloxacin; 93.6%, 1.0 μ g/mL of levofloxacin; 97.5%, 2.5 μ g/mL of kanamycin; 90.6%, 2.5 μ g/mL of capreomycin; 86.2%, 5.0 μ g/mL of ethionamide; and 90.8%, 2.0 μ g/mL of ρ-aminosalicylic acid. The critical concentrations of the four drugs, moxifloxacin, levofloxacin, kanamycin, and capreomycin, were concordant and reliable for testing 2nd line drug resistance. Further study of ethionamide and ρ -aminosalicylic acid is required.
    Full-text · Article · Mar 2013
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    • "The BACTEC MGIT 960 system has shown good concordance with the standard proportion method [15-18]. Currently, there is no commercially available kit for performing DST of second-line anti-TB drugs using the BACTEC MGIT 960 system [20,21]. This is inconvenient because the working solutions of each drug should be prepared by the users, making these tests more error-prone due to procedural inaccuracies. "
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    ABSTRACT: Background The increasing problem of multi-drug-resistant (MDR) tuberculosis (TB) [ie resistant to at least isoniazid (INH) and rifampicin (RIF)] is becoming a global problem. Successful treatment outcome for MDR-TB depends on reliable and accurate drug susceptibility testing of first-line and second-line anti-TB drugs. Method Consecutive M. tuberculosis isolates identified as MDR-TB during August 2007 to January 2008 using the BACTEC MGIT 960 systems and the agar proportion method were included in this study. Susceptibility testing of MDR-TB isolates against ethambutol (EMB) and streptomycin (STR) as well as two second-line anti-TB drugs, kanamycin (KAN) and ofloxacin (OFX) was performed using the BACTEC MGIT 960 systems at a routine diagnostic laboratory. The results were compared to those obtained by the agar proportion method. Result The agreement between the BACTEC MGIT 960 system and the agar proportion method was 44% for EMB, 61% for STR and 89% for both KAN and OFX. The sensitivity and specificity of the BACTEC MGIT 960 system using the agar proportion method as a gold standard was 92% and 37% for EMB, 95% and 37% for STR, 27% and 97% for KAN and 84% and 90% for OFX, respectively. Conclusions The BACTEC MGIT 960 system showed acceptable sensitivity for EMB, STR, and OFX; however, the BACTEC MGIT 960 system was less specific for EMB and STR and demonstrated a low sensitivity for KAN. The lower agreement found between the two methods suggests the unreliability of the BACTEC MGIT 960 system for the drugs tested. The reasons for the lower agreement between the two methods need to be investigated and further studies are needed in this setting to confirm the study finding.
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    ABSTRACT: A technique based on the null field method is developed to investigate the resonant frequencies and the quality factors of composite dielectric resonators. Numerical results are compared with previously published calculations and experiments whenever possible, which show that the present technique is an effective and flexible one for investigating dielectric resonators with relatively complicated geometries.
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