Use of Multiplex Allele-Specific Polymerase Chain Reaction (MAS-PCR) to Detect Multidrug-Resistant Tuberculosis in Panama

The frequency of individual genetic mutations conferring drug resistance (DR) to Mycobacterium tuberculosis has not been studied previously in Central America, the place of origin of many immigrants to the United States. The current gold standard for detecting multidrug-resistant tuberculosis (MDR-TB) is phenotypic drug susceptibility testing (DST), which is resource-intensive and slow, leading to increased MDR-TB transmission in the community. We evaluated multiplex allele-specific polymerase chain reaction (MAS-PCR) as a rapid molecular tool to detect MDR-TB in Panama. Based on DST, 67 MDR-TB and 31 drug-sensitive clinical isolates were identified and cultured from an archived collection. Primers were designed to target five mutation hotspots that confer resistance to the first-line drugs isoniazid and rifampin, and MAS-PCR was performed. Whole-genome sequencing confirmed DR mutations identified by MAS-PCR, and provided frequencies of genetic mutations. DNA sequencing revealed 70.1% of MDR strains to have point mutations at codon 315 of the katG gene, 19.4% within mabA-inhA promoter, and 98.5% at three hotspots within rpoB. MAS-PCR detected each of these mutations, yielding 82.8% sensitivity and 100% specificity for isoniazid resistance, and 98.4% sensitivity and 100% specificity for rifampin resistance relative to DST. The frequency of individual DR mutations among MDR strains in Panama parallels that of other TB-endemic countries. The performance of MAS-PCR suggests that it may be a relatively inexpensive and technically feasible method for rapid detection of MDR-TB in developing countries

Flow-chart showing available drug susceptibility testing (DST), sequencing, and multiplex allele-specific PCR (MAS-PCR) results for the 98 archived isolates from Panama.

<p>Flow-chart showing available drug susceptibility testing (DST), sequencing, and multiplex allele-specific PCR (MAS-PCR) results for the 98 archived isolates from Panama.</p

Pairwise comparisons of the three drug resistance detection techniques (DST, DNA sequencing, and MAS-PCR) in detecting INH and RIF resistance.

<p>Pairwise comparisons of the three drug resistance detection techniques (DST, DNA sequencing, and MAS-PCR) in detecting INH and RIF resistance.</p

Distinct band patterns indicate drug resistance profile of isolates.

<p>A. Loci where each allele-specific primer binds are indicated, along with the expected product size if the locus is wild-type. The two common mutations that confer resistance to INH and the three common mutations that confer resistance to RIF are boxed separately. B. Band patterns indicate drug resistance profile of isolates. Expected PCR products have been color-coded in the same way as in A. Lane 1: H37Rv reference strain (wild-type at all 5 loci); Lane 2: <i>mabA-inhA</i> −15C→T and RpoB D516F double mutant; Lane 3: KatG S315T and RpoB H526Y double mutant; Lane 4: KatG S315G and RpoB 531L double mutant; Lane 5: <i>mabA-inhA</i> −15C→T, KatG S315T and RpoB H526D triple mutant; lane 6: <i>mabA-inhA</i> −15C→T, KatG S315T and RpoB S531L triple mutant; Lane 7: Molecular ladder.</p