Concordance between Molecular and Phenotypic Testing of Mycobacterium tuberculosis Complex Isolates for Resistance to Rifampin and Isoniazid in the United States

Abstract

Multidrug-resistant (MDR) isolates of Mycobacterium tuberculosis complex (MTBC) are defined by resistance to at least rifampin (RMP) and isoniazid (INH). Rapid and accurate detection of multidrug resistance is essential for effective treatment and interruption of disease transmission of tuberculosis (TB).T wo essential drugs for the first-line treatment of tuberculosis (TB) are rifampin (RMP) and isoniazid (INH). Isolates of Mycobacterium tuberculosis complex (MTBC) that are resistant to at least both these drugs are classified as multidrug resistant (MDR). Rapid and accurate detection of resistance to either RMP or INH is crucial for selection of treatment regimens and public health interventions. In 2012, the Centers for Disease Control and Prevention (CDC) reported 9,945 cases of TB in the United States (http://www.cdc.gov/tb/statistics/reports/2012/default.htm). For 7,188 of these cases, for which initial drug susceptibility to firstline antituberculosis drugs was reported, 660 (9.2%) were at least INH resistant, and 83 (1.2%) were MDR. The American Thoracic Society, CDC, and the Infectious Diseases Society of America have issued guidelines for treating INH-monoresistant TB (1). Early detection of RMP resistance, which correlates well with multidrug resistance, is critical for the initiation of effective second-line treatment regimens and interruption of disease transmission.CDC offers the molecular detection of drug resistance (MDDR) for mutations associated with resistance to RMP at the RMP resistance-determining region (RRDR) of the rpoB locus and with resistance to INH at the katG and inhA loci (2, 3). Other loci that are examined are embB (EMB resistance), pncA (pyrazinamide resistance), gyrA (fluoroquinolone resistance), rrs (kanamycin, amikacin, and capreomycin resistance), tlyA (capreomycin resistance), and eis (promoter region mutations associated with kanamycin resistance) (2). MDDR is available by request in coordination with state public health laboratories (PHL) for M. tuberculosis isolates and sediments meeting submission criteria (http://www.cdc.gov/tb/topic /laboratory/MDDRsubmissionform.pdf). Although molecular testing can rapidly detect mutations associated with drug resistance, it should complement, not supersede, conventional phenotypic drug susceptibility testing (DST) (4). Therefore, all submissions to MDDR undergo growth-based DST for a full panel of first-line and second-line drugs (4). Submitters receive a preliminary report with molecular test results and a final report upon completion of DST, with both the molecular and DST results and interpretive comments.In this study, we examined the concordances between molecular testing and DST for RMP and INH to determine the performance characteristics of CDC's MDDR service for rapid detection and confirmation of MDR TB. Through an electronic survey using a secure data collection instrument, we collected phenotypic DST results from state and local PHL for isolates submitted for testing at CDC. We examined the concordances between molecular ...

Multiplex detection of extensively drug resistant tuberculosis using binary deoxyribozyme sensors

“…Although NAATs cannot replace phenotypic drug testing they provide a quick alternative for the identification of drug resistance at the POC (Yakrus et al 2014). In addition to traditional PCR and hybridization based methods, there have been numerous reports of alternative technologies for ultrasensitive detection of nucleic acids (Lapitan et al 2015; Sun et al 2014).…”

Real-Life Clinical Practice of Using the Xpert MTB/RIF Assay in Thailand

“…In contrast, the Xpert MTB/RIF assay has been shown to detect silent mutations (nonfunctional gene) and missense mutations (nonfunctional protein), which have no clinical resistance [21]. The flaws of the phenotypic tests often fail to detect small amounts of resistant bacilli (false negative), which may have clinical significance, while the Xpert MTB/RIF may report rifampicin resistance regardless whether they are silent and/or missense mutations in the rpoB gene (false positive) [20,23]. As a result, the WHO guidelines recommend the use of alternative DST such as rpoB gene sequencing as the confirmatory test when there are discordant results from the genotypically defined Xpert MTB/RIF and the conventional mycobacterial culture [14].…”

“…In other words, none of the samples from the study had false-positive results for rifampicin resistance. However, it should be noted that discordant results between Xpert MTB/RIF and the conventional gold standard DST such as the MGIT has been reported [14,[20][21][22][23]. Discordant results are extremely problematic for physicians in determining the appropriate TB treatment.…”

A Comparison of the Sensititre MycoTB Plate, the Bactec MGIT 960, and a Microarray-Based Molecular Assay for the Detection of Drug Resistance in Clinical Mycobacterium tuberculosis Isolates in Moscow, Russia

“…The most frequent substitution found when analyzing resistance to RMP was the S531L substitution, which was associated with high-level resistance [10, 13, 30] and was found in strains resistant to both RMP and RFB with high MICs in most cases. However, several of these isolates had intermediate MICs for RMP and were susceptible to RFB, which was similar to earlier findings [31, 32, 33] and diminished the prognostic value of genetic tests based on rpoB locus analysis.…”