Analysis of discrepant results between phenotypic and genotypic drug susceptibility tests of Mycobacterium tuberculosis isolates at tertiary teaching hospitals: a preliminary result = Analysis of discrepant results between phenotypic and genotypic drug susceptibility tests of Mycobacterium tuberculosis isolates at tertiary teaching hospitals: a preliminary result

다국어 초록 (Multilingual Abstract)

Background: South Korea is an intermediate tuberculosis (TB) burden country with high rates of anti-TB drug resistance. We identified patterns of anti-TB drug resistance in Mycobacterium tuberculosis (MTB) isolates and evaluated results of phenotypic and genotypic drug susceptibility tests (DST).
Methods: One hundred forty four patients with pulmonary TB were recruited into a prospective observational cohort study at two hospitals from December 2016 to June 2017. We determined the drug susceptibility of MTB isolates by using conventional phenotypic DST and GenoType MTBDRplus assay.
Results: Among 92 patients with culture-positive pulmonary TB, 14 (15.2%) patients with drug-resistant TB were identified on the phenotypic DST; 11 had any isoniazid (INH) resistance, 1 had rifampicin (RFP) monoresistance, 1 had streptomycin monoresistance, and 1 had multidrug-resistance. Two patients had INH resistance on the MTBDRplus assay, but no drug resistance on the phenotypic DST. The sensitivity and specificity of the MTBDRplus assay were respectively 72.7% and 96.7% for the detection of INH resistance; 100.0% and 98.6% for the detection of RFP resistance. Among 72 patients who had both phenotypic and genotypic DSTs, discordant results were found in 5 (6.9%) patients with INH resistance and 1 (1.4%) patient with RFP resistance.
Conclusions: The specificity of the MTBDRplus assay in detecting INH and RIF resistance was high. Because of frequent discordant results of INH resistance between phenotypic and genotypic DSTs, physician needs to be careful in interpreting their results.