ethionamide and Extensively-Drug-Resistant-Tuberculosis

The detection of pre-extensively (pre-XDR) and extensively drug-resistant tuberculosis (XDR-TB) is challenging. Drug-susceptibility tests for some anti-TB drugs, especially ethambutol (ETH) and ethionamide (ETO), are problematic due to overlapping thresholds to differentiate between susceptible and resistant phenotypes. We aimed to identify possible metabolomic markers to detect Mycobacterium tuberculosis (Mtb) strains causing pre-XDR and XDR-TB. The metabolic patterns of ETH- and ETO-resistant Mtb isolates were also investigated. Metabolomics of 150 Mtb isolates (54 pre-XDR, 63 XDR-TB and 33 pan-susceptible; pan-S) were investigated. Metabolomics of ETH and ETO phenotypically resistant subgroups were analyzed using UHPLC-ESI-QTOF-MS/MS. Orthogonal partial least-squares discriminant analysis revealed distinct separation in all pairwise comparisons among groups. Two metabolites (meso-hydroxyheme and itaconic anhydride) were able to differentiate the pre-XDR and XDR-TB groups from the pan-S group with 100% sensitivity and 100% specificity. In comparisons of the ETH and ETO phenotypically resistant subsets, sets of increased (ETH = 15, ETO = 7) and decreased (ETH = 1, ETO = 6) metabolites specific for the resistance phenotype of each drug were found. We demonstrated the potential for metabolomics of Mtb to differentiate among types of DR-TB as well as between isolates that were phenotypically resistant to ETO and ETH. Thus, metabolomics might be further applied for DR-TB diagnosis and patient management.

Topics: Antitubercular Agents; Drug Resistance, Multiple, Bacterial; Ethambutol; Ethionamide; Extensively Drug-Resistant Tuberculosis; Humans; Metabolome; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Tandem Mass Spectrometry; Tuberculosis, Multidrug-Resistant

Drug-resistant tuberculosis is an increasing healthcare challenge. Drug regimen building demands the use of different therapeutic groups, many of which harbor neurotoxicity as a side-effect, whether central or peripheral. Peripheral neuropathy is a major concern as it tends to be severe and usually irreversible. Anti-tubercular drugs that may contribute to peripheral neuropathy include INH, ethambutol, linezolid, cycloserine and para-amino salicylic acid. This potential adverse effect must be balanced against the intrinsically grave prognosis that drug resistant tuberculosis harbors. We present such a clinically challenging case of a 25 years-old female with extremely drug resistant tuberculosis whose treatment necessitated the use of several neurotoxic anti-tubercular drugs, leading to severe sensory peripheral neuropathy who did not improve despite the withdrawal of culprit drugs. She developed positive and negative sensory symptoms in both lower limbs. Nerve conduction studies were suggestive of sensory neuropathy affecting both lower limbs. Alternate causes of peripheral neuropathy including HIV, vasculitis, B12 deficiency and diabetes were ruled out. Despite drug withdrawal, the patient did not improve significantly. This case emphasizes the irreversibility of anti-tubercular therapy-induced peripheral neuropathy, demanding more rigorous clinical screening for the same while managing such patients.

Topics: Adult; Aminosalicylic Acid; Antitubercular Agents; Clofazimine; Cycloserine; Deprescriptions; Diarylquinolines; Ethionamide; Extensively Drug-Resistant Tuberculosis; Female; Humans; Kanamycin; Linezolid; Neural Conduction; Neurotoxicity Syndromes; Peripheral Nervous System Diseases; Pyrazinamide; Pyridoxine; Tuberculosis, Pulmonary

Drug resistance (DR) remains a major challenge for tuberculosis (TB) control. Whole-genome sequencing (WGS) provides the highest genetic resolution for genotypic drug-susceptibility tests (DST). We compared DST profiles of 60 Mycobacterium tuberculosis isolates which were drug resistant according to agar proportion tests (one poly DR-TB, 34 multidrug-resistant TB and 25 extensively drug-resistant TB). We additionally performed minimum inhibitory concentration (MIC) tests using Sensititre MYCOTBI plates (MYCOTB) and a WGS-based DST. Agreement between WGS-based DST and MYCOTB was high for all drugs except ethambutol (65%) and ethionamide (62%). Isolates harboring the -15 c/t inhA promoter mutation had a significantly lower MIC for isoniazid than did isolates with the katG Ser315Thr mutation (p < 0.001). Similar patterns were seen for ethambutol (embB Gly406Asp vs. embB Met306Ile), streptomycin (gid Gly73Ala vs. rpsL Lys43Arg), moxifloxacin (gyrA Ala90Val vs. gyrA Asp94Gly) and rifabutin (rpoB Asp435Phe/Tyr/Val vs. rpoB Ser450Leu). For genotypic heteroresistance, isolates with lower proportion of mapped read tended to has lower MIC of anti-TB drugs than those with higher proportion. These results emphasize the high applicability of WGS for determination of DR-TB and the association of particular mutations with MIC levels.

Topics: Adult; Antitubercular Agents; Drug Resistance, Bacterial; Ethambutol; Ethionamide; Extensively Drug-Resistant Tuberculosis; Female; Humans; Isoniazid; Male; Microbial Sensitivity Tests; Middle Aged; Mutation; Mycobacterium tuberculosis; Tuberculosis, Multidrug-Resistant; Whole Genome Sequencing

Antibiotic resistance is one of the biggest threats to human health globally. Alarmingly, multidrug-resistant and extensively drug-resistant

Topics: Animals; Antitubercular Agents; DNA; Drug Resistance, Multiple, Bacterial; Ethionamide; Extensively Drug-Resistant Tuberculosis; Humans; Isoxazoles; Mice; Mutation; Mycobacterium tuberculosis; Oxadiazoles; Piperidines; Protein Binding; Repressor Proteins; Spiro Compounds

Drug-resistant tuberculosis (TB) remains extremely difficult to treat because there are often few remaining active medications and limited diagnostic options to detect resistance. Resistance to isoniazid is typically caused by mutations in either katG or the inhA promoter. inhA mutations confer low-level resistance to isoniazid and cross-resistance to ethionamide while katG mutations confer high-level isoniazid resistance and no cross-resistance. Line Probe Assays (LPAs) that detect mutations in katG and inhA are currently performed on all positive TB cultures in KwaZulu-Natal province, South Africa, but the frequency of inhA mutations in drug-resistant TB patients has not been examined.. We sought to determine the proportion of patients who could potentially benefit from high-dose isoniazid and who may be resistant to ethionamide. We reviewed 994 LPA (Hain MTBDRplus) results at the TB reference laboratory in KwaZulu-Natal to determine the frequency of mutations in either katG or the inhA promoter. We stratified these results by drug-resistance category (i.e., MDR-TB, pre-XDR-TB, and XDR-TB) as determined by phenotypic drug-susceptibility testing.. Among MDR- and XDR-TB isolates, the prevalence of inhA mutations without a concurrent katG mutation was 14.8% and 10.3% respectively. The prevalence of inhA mutations with OR without a katG mutation was 30.3% and 82.8%, respectively.. More than 10% of patients with MDR- and XDR-TB may benefit from high-dose isoniazid. Although ethionamide is empirically included in all MDR- and XDR-TB regimens, nearly a third of MDR-TB patients and a majority of XDR-TB patients likely have resistance to ethionamide. Laboratories performing line probe assays should report specific band patterns so that clinicians may adjust treatment regimens accordingly.

Topics: Antitubercular Agents; Bacterial Proteins; Catalase; Ethionamide; Extensively Drug-Resistant Tuberculosis; Humans; Isoniazid; Mutation; Mycobacterium tuberculosis; Oxidoreductases; Prevalence; Promoter Regions, Genetic; South Africa; Tuberculosis, Multidrug-Resistant

The emergence of drug-resistant tuberculosis (TB) is a challenge to TB control in Europe. We evaluated second-line drug susceptibility testing in Mycobacterium tuberculosis isolates from patients with multidrug-resistant, pre-extensively drug-resistant (pre-XDR-TB) and XDR-TB at 23 TBNET sites in 16 European countries. Over 30% of bacilli from patients with pre-XDR-TB showed resistance to any fluoroquinolone and almost 70% to any second-line injectable drug. Respectively >90% and >80% of the XDR-TB strains tested showed phenotypic resistance to pyrazinamide and ethambutol. Resistance to prothionamide/ethionamide was high in bacilli from pre-XDR-TB patients (43%) and XDR-TB patients (49%).

Topics: Adult; Antitubercular Agents; Ethambutol; Ethionamide; Europe; Extensively Drug-Resistant Tuberculosis; Female; Fluoroquinolones; Humans; Logistic Models; Male; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Pyrazinamide

High mortality rates have been reported for patients co-infected with extensively drug-resistant tuberculosis (XDR-TB) and HIV, but treatment outcomes have not been reported. We report treatment outcomes for adult XDR TB patients in KwaZulu-Natal Province, South Africa. Initial data were obtained retrospectively, and outcomes were obtained prospectively during 24 months of treatment. A total of 114 XDR TB patients were treated (median 6 drugs, range 3-9 drugs); 82 (73%) were HIV positive and 50 (61%) were receiving antiretroviral therapy. After receiving treatment for 24 months, 48 (42%) of 114 patients died, 25 (22%) were cured or successfully completed treatment, 19 (17%) withdrew from the study, and 22 (19%) showed treatment failure. A higher number of deaths occurred among HIV-positive patients not receiving antiretroviral therapy and among patients who did not show sputum culture conversion. Culture conversion was a major predictor of survival but was poorly predictive (51%) of successful treatment outcome.

Topics: Adolescent; Adult; Antitubercular Agents; Coinfection; Cycloserine; Drug Therapy, Combination; Ethambutol; Ethionamide; Extensively Drug-Resistant Tuberculosis; Female; HIV Infections; Humans; Kaplan-Meier Estimate; Male; Middle Aged; Pyrazinamide; Retrospective Studies; Treatment Outcome; Tuberculosis, Pulmonary; Young Adult

Tuberculosis remains the second only to HIV as the leading cause of death by infectious disease worldwide, and was responsible for 1.4 million deaths globally in 2011. One of the essential drugs of the second-line antitubercular regimen is the prodrug ethionamide, introduced in the 1960s. Ethionamide is primarily used in cases of multi-drug resistant (MDR) and extensively drug resistant (XDR) TB due to severe adverse side effects. As a prodrug, ethionamide is bioactivated by EthA, a mono-oxygenase whose activity is repressed by EthR, a member of the TetR family of regulators. Previous studies have established that inhibition of EthR improves ethionamide potency. We report here the crystal structures of three EthR inhibitors at 0.8 Å resolution (3-oxo-3-{4-[3-(thiophen-2-yl)-1,2,4-oxadiazol-5-yl]piperidin-1-yl}propanenitrile (BDM31343), 4,4,4-trifluoro-1-{4-[3-(6-methoxy-1,3-benzothiazol-2-yl)-1,2,4-oxadiazol-5-yl]piperidin-1-yl}butanone (BDM41325) and 5,5,5-trifluoro-1-{4-[3-(4-methanesulfonylphenyl)-1,2,4-oxadiazol-5-yl]piperidin-1-yl}pentanone (BDM41907)), and the docking studies undertaken to investigate possible binding modes. The results revealed two distinct orientations of the three compounds in the binding channel, a direct consequence of the promiscuous nature of the largely lipophilic binding site.

Topics: Antitubercular Agents; Binding Sites; Crystallography, X-Ray; Ethionamide; Extensively Drug-Resistant Tuberculosis; Models, Molecular; Mycobacterium tuberculosis; Prodrugs

India with a major burden of multidrug-resistant tuberculosis (MDR-TB) does not have national level data on this hazardous disease. Since 2006, emergence of extensively drug-resistant TB (XDR-TB) is considered a serious threat to global TB control. This study highlights the demographic and clinical risk factors associated with XDR-TB in Delhi.. The study was conducted during April 2007 to May 2010. Six hundred eleven MDR-TB suspects were enrolled from four tertiary care hospitals, treating TB patients in Delhi and the demographic details recorded. Sputum samples were cultured using rapid, automated liquid culture system (MGIT 960). Drug susceptibility testing (DST) for Rifampicin (RIF) and Isoniazid (INH) was performed for all positive M. tuberculosis (M.tb) cultures. All MDR-TB isolates were tested for sensitivity to second-line drugs [Amikacin (AMK), Capreomycin (CAP), Ofloxacin (OFX), Ethionamide (ETA)].. Of 611, 483 patients were infected with MDR M. tuberculosis (M.tb) strains. Eighteen MDR-TB isolates (3.7%) were XDR M.tb strains. Family history of TB (p 0.045), socioeconomic status (p 0.013), concomitant illness (p 0.001) and previous intake of 2(nd) line injectable drugs (p 0.001) were significantly associated with occurrence of XDR-TB. Only two of the patients enrolled were HIV seropositive, but had a negative culture for M. tuberculosis. 56/483 isolates were pre-XDR M. tuberculosis, though the occurrence of pre-XDR-TB did not show any significant demographical associations.. The actual incidence and prevalence rate of XDR-TB in India is not available, although some scattered data is available. This study raises a concern about existence of XDR-TB in India, though small, signaling a need to strengthen the TB control program for early diagnosis of both tuberculosis and drug resistance in order to break the chains of transmission.

Topics: Adult; Amikacin; Antitubercular Agents; Capreomycin; Ethionamide; Extensively Drug-Resistant Tuberculosis; Female; Humans; Incidence; India; Isoniazid; Male; Mycobacterium tuberculosis; Ofloxacin; Prevalence; Rifampin; Risk Factors; Sputum; Tuberculosis, Pulmonary

We screened 194 Mycobacterium tuberculosis strains isolated from tuberculosis (TB) patients in Delhi and neighboring regions in India to identify the prevalence of extensive drug resistance (XDR) in clinical isolates. Among these, 104 isolates were found to be multidrug resistant (MDR), and 6 were identified as XDR isolates, which was later confirmed by antimicrobial susceptibility testing against the respective drug screening panel. Genotyping was carried out by amplifying and sequencing the following genes: rpoB (rifampin), katG (isoniazid), gyrA (fluoroquinolones), and rrs (amikacin, kanamycin, and capreomycin). Our analyses indicated that mutations at the hot spots of these genes were positively correlated with drug resistance in clinical isolates. The key mutation observed for rpoB was in the codon for amino acid position 531 (S531L), and other mutations were seen in the hot spot, including those encoding Q510P, L511H, D516V, and H526Y mutations. We identified S315T and R463L substitutions encoded in the katG locus. An S95T substitution encoded in the gyrA locus was the most common mutation observed in fluoroquinolone-resistant isolates. In addition, we saw D94G and D94N mutations encoded in the QRDR region. The 16S rRNA (rrs) gene encoded mainly the A1401G mutation and an additional mutation, G1484T, resulting in ribosomal modifications. Taken together, the data in this report clearly establish the presence of phenotypically distinct XDR strains in India by molecular profiling and further identify specific mutational hot spots within key genes of XDR-TB strains.

Topics: Amikacin; Antitubercular Agents; Bacterial Proteins; Capreomycin; DNA Gyrase; DNA Mutational Analysis; DNA-Directed RNA Polymerases; Extensively Drug-Resistant Tuberculosis; Fluoroquinolones; India; Isoniazid; Kanamycin; Microbial Sensitivity Tests; Mutation; Mycobacterium tuberculosis; Point Mutation; Polymerase Chain Reaction; Rifampin

Limited information about the prevalence of drug-resistant tuberculosis (TB) has been reported from India, the country with the world's highest burden of TB. We conducted a representative state-wide survey in the state of Gujarat (2005 population: 56 million).. Mycobacterium tuberculosis isolates from a representative sample of new and previously treated smear-positive pulmonary TB (PTB) cases were subjected to drug susceptibility testing (DST) against first-line drugs at a World Health Organization supranational reference laboratory. Isolates found to have at least both isoniazid (INH) and rifampicin (RMP) resistance (i.e., multidrug-resistant TB [MDR-TB]) were subjected to second-line DST.. Of 1571 isolates from new patients, 1236 (78.7%) were susceptible to all first-line drugs, 173 (11%) had any INH resistance and MDR-TB was found in 37 (2.4%, 95%CI 1.6-3.1). Of 1047 isolates from previously treated patients, 564 (54%) were susceptible to all first-line drugs, 387 (37%) had any INH resistance and MDR-TB was found in 182 (17.4%, 95%CI 15.0-19.7%). Among 216 MDR-TB isolates, 52 (24%) were ofloxacin (OFX) resistant; seven cases of extensively drug-resistant TB (XDR-TB) were found, all of whom were previously treated cases.. MDR-TB prevalence remains low among new TB patients in Gujarat, but is more common among previously treated patients. Among MDR-TB isolates, the alarmingly high prevalence of OFX resistance may threaten the success of the expanding efforts to treat and control MDR-TB.

Topics: Antitubercular Agents; Bacteriological Techniques; Colony Count, Microbial; Drug Resistance, Multiple, Bacterial; Ethionamide; Extensively Drug-Resistant Tuberculosis; Female; Humans; India; Isoniazid; Kanamycin; Male; Microscopy, Fluorescence; Mycobacterium tuberculosis; Ofloxacin; Population Surveillance; Prevalence; Rifampin; Sputum; Tuberculosis, Multidrug-Resistant