Diagnostic Performance of the GenoType MTBDRplus and MTBDRsl Assays to Identify Tuberculosis Drug Resistance in Eastern China

Background: The WHO recently has recommended the GenoType MTBDR plus version 1.0 and MTBDR sl version 1.0 assays for widespread use in countries endemic with drug-resistant tuberculosis. Despite this, these assays have rarely been evaluated in China, where the burden of drug-resistant tuberculosis is among the highest globally. Methods: Mycobacterium tuberculosis clinical isolates were obtained between January 2008 and December 2008. Isolates were tested for drug resistance against rifampicin (RFP) and isoniazid (INH) using the GenoType MTBDR plus assay and drug resistance against ethambutol (EMB), ofloxacin (OFX), and kanamycin (KM) using the Genotype MTBDR sl assay. These results were compared with conventional drug-susceptibility testing (DST). Results: Readable results were obtained from 235 strains by GenoType MTBDR plus assay. Compared to DST, the sensitivity of GenoType MTBDR plus assay to detect RFP, INH, and multidrug resistance was 97.7%, 69.9%, and 69.8%, respectively, whereas the specificity for detecting RFP, INH, and multidrug resistance was 66.7%, 69.2%, and 76.8%, respectively. The sensitivity and specificity of the GenoType MTBDR sl assay were 90.9% and 95.2% for OFX, 77.8% and 99.5% for KM, 63.7% and 86.4% for EMB, respectively. Mutations in codon S531L of the rpoB gene and codon S315T1 of KatG gene were dominated in multidrug-resistant tuberculosis (MDR-TB) strains. Conclusions: In combination with DST, application of the GenoType MTBDR plus and MTBDR sl assays may be a useful supplementary tool to allow a rapid and safe diagnosis of multidrug resistance and extensively drug-resistant tuberculosis.