ABSTRACT
SETTINGS: The new Anyplex™ II MTB/MDR/XDR PCR assay enables the joint analysis of mutations conferring resistance to first- and second-line anti-tuberculosis drugs and the detection of Mycobacterium tuberculosis. OBJECTIVES: To evaluate the performance of the new Anyplex assay in detecting mutations that confer resistance to first- and second-line drugs in M. tuberculosis cultures. DESIGN: Results obtained using the new technique were compared with those obtained by phenotypic drug susceptibility testing (DST) and with two GenoType tests for the detection of mutations: GenoType(®) MTBDRplus and GenoType(®) MTBDRsl. RESULTS: For rifampicin resistance mutations, Anyplex displayed 97% sensitivity and 100% specificity compared with 100% and 100% for MTBDRplus. For isoniazid (INH) resistance, Anyplex displayed 61% sensitivity and 98% specificity compared with 62% and 98% for MTBDRplus. For second-line drugs, Anyplex recorded 95% sensitivity and 99% specificity in the detection of resistance to quinolones compared with 100% and 98% for the MTBDRsl. While both techniques displayed 100% specificity for aminoglycoside resistance mutations, sensitivity was 100% for Anyplex and 88% for MTBDRsl. CONCLUSIONS: Results obtained using Anyplex agreed strongly with those obtained using the two GenoType molecular techniques and with phenotypic DST, except in the case of INH, due to the large number of genes involved in resistance to this drug.
Subject(s)
Antitubercular Agents/pharmacology , Drug Resistance, Multiple, Bacterial/genetics , Isoniazid/pharmacology , Mycobacterium tuberculosis/drug effects , Mycobacterium tuberculosis/genetics , Rifampin/pharmacology , Genotype , Microbial Sensitivity Tests , Mutation , Sensitivity and SpecificityABSTRACT
SETTINGS: Molecular methods frequently used in laboratories can now give us useful information about low growth bacteria. OBJECTIVE: To evaluate the new GenoType MTBDRplus assay for its ability to detect mutations in the 81-bp hotspot region of the rpoB gene, mutations in codon 315 of the katG gene and alterations in the inhA promoter region. DESIGN: Prospective resistance to rifampicin (RMP) and isoniazid (INH) study using Mycobacterium tuberculosis positive specimens and cultures comparing the results of GenoType MTBDRplus with those obtained phenotypically with the Bactec MGIT (Mycobacterial Growth Indicator Tube) 960. RESULTS: In 59 specimens (18 smear microscopy samples and 41 solid and liquid medium cultures), mutations were detected in all of 36 M. tuberculosis strains phenotypically resistant to RMP (100%), and in 35 of 37 strains phenotypically resistant to INH (94.59%). The new assay prompted a 21.6% increase in the direct detection of INH resistance in the strains studied, due to the incorporation of inhA promoter region probes in the test. CONCLUSIONS: The GenoType MTBDRplus assay is a valid method for detecting the most common mutations in strains resistant to RMP and INH. However, further phenotypic testing is required, as the assay failed to detect 100% of INH and RMP resistance.
