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Published on: April 9, 2012
Rapid detection of rifampicin resistance in Mycobacterium tuberculosis by high-resolution melting curve analysis
B Malhotra1, S Goyal1, S Bhargava1
1Department of Microbiology and Immunology, Sawai Man Singh Medical College, Jaipur, India.
Setting:
High-resolution melting curve analysis (HRMA) can be used to screen for mutations in genes without the need for specific probes, with low turnaround time and high cost-effectiveness.
Objective:
To detect the sensitivity and specificity of a line-probe assay (LPA) and HRMA in comparison with BACTEC™ MGIT™ 960 for the detection of rifampicin (RMP) resistance.
Design:
A total of 219 Mycobacterium tuberculosis isolates tested by MGIT 960 for RMP susceptibility were tested with HRMA and LPA. Discordant samples were processed for sequencing of the RMP resistance-determining region (RRDR) of the rpoB gene.
Results:
HRMA identified 93 of 103 (90.3%) isolates that were resistant and 113/116 (97.4%) that were susceptible on MGIT 960, with a sensitivity and specificity of respectively 90.3% and 97.4%. HRMA identified 117/119 (98.3%) LPA-susceptible and 94/100 (94%) resistant isolates, with 98.3% specificity and 94% sensitivity. Two isolates that were susceptible on LPA but resistant on HRMA showed silent mutations at 539 and 541 codons on sequencing, while 6 isolates that were susceptible on HRMA but resistant on LPA showed D516V (n = 4) and H526C/D (n = 2) mutations. Four isolates (3.9%) that were resistant on MGIT were susceptible on all three genotypic methods, which could be due to mutations outside the RRDR or efflux pumps.
Conclusion:
HRMA shows good potential as a rapid screening tool for the detection of drug resistance.
