[Comparison of two methods for the detection of antituberculous drug susceptibility in Mycobacterium tuberculosis complex isolates: sensititre MycoTB MIC plate and the indirect agar proportion methods].

Tuberculosis is still one of the most important public health problems worldwide. Due to the increase of multidrug-resistant (MDR) tuberculosis and extensively drug-resistant (XDR) tuberculosis cases, fast, practical and standardized methods need to be developed for the determination of drug resistance in Mycobacterium tuberculosis complex. The aim of this study was to compare the Sensititre MycoTB plate method with the gold standard agar proportion method (APM); in order to determine if the Sensititre MycoTB plate method is effective enough to be used instead of the APM. A total of 100 M.tuberculosis complex isolates, 36 with different resistance patterns and 64 sensitive to all first-line agents stored in culture collection of Ege University Faculty of Medicine Microbiology Department Laboratory, were used in the study. The susceptibility of rifampin, isoniazid, ethambutol, streptomycin, ofloxacin, moxifloxacin, amikacin, rifabutin, para-aminosalicylic acid, ethionamide, cycloserine and kanamycin for all the isolates were determined by APM and Sensititre MycoTB plate methods. APM was performed as defined by CLSI, Sensititre MycoTB plate method was performed as instructed by the manufacturer. Results were assessed in 95% confidence interval and sensitivity, specificity and categorical agreement values were determined. Results were obtained in 14 days using the Sensititre MycoTB plate method. Sensitivity and the specificity of the Sensititre MycoTB was between 86-100% and 95-100% respectively, while the categorical agreement between the two methods were 95-100% for the drugs tested. The sensitivities of the drugs were 100% except ethambutol and ethionamide. The specificity values for both of the drugs and categorical agreement were over 95%. All the drugs were in the 95% confidence interval (p< 0.001) and the greatest difference between the lower and upper levels of sensitivity and specificity confidence limits was found in ethambutol and ethionamide. MDR was detected in 16 isolates with the APM and in 20 isolates with the Sensititre MycoTB plate method. None of the isolates had XDR [in addition to MDR resistance against any fluoroquinolones and at least one of the second-line parenteral drugs (amikacin, kanamycin or capreomycin)]. As a result, owing to the short incubation period (14 days), high sensitivity, specificity and categorical agreement values, and the possibility for evaluating both first- and second-line agents and the quantitative values of drugs; the Sensititre MycoTB method was determined as an effective method that can be used especially in laboratories where the rate of MDR-TB isolates are high.