Project description:Rationale: The World Health Organization recommends the use of isoniazid (INH) alone or in combination with rifapentine to treat latent tuberculosis infections. The recent rise of drug-resistant tuberculosis has complicated the choice of treatment regimen for latent tuberculosis infection.Objectives: To evaluate the effects of INH preventive therapy on the contacts of patients with multidrug-resistant tuberculosis.Methods: In a prospective cohort study conducted between September 2009 and August 2012, we identified 4,500 index patients with tuberculosis and 14,044 tuberculosis-exposed household contacts who we followed for 1 year for the occurrence of incident tuberculosis disease. Although Peruvian national guidelines specify that INH preventive therapy should be provided to contacts aged 19 years old or younger, only half this group received INH preventive therapy.Measurements and Main Results: Among 4,216 contacts under 19 years of age, 2,106 contacts (50%) initiated INH preventive therapy at enrollment. The protective effect of INH was more extreme in contacts exposed to drug-sensitive tuberculosis (adjusted hazard ratio, 0.30; 95% confidence interval, 0.18-0.48) and to multidrug-resistant tuberculosis (adjusted hazard ratio, 0.19; 95% confidence interval, 0.05-0.66) compared with those exposed to mono-INH-resistant tuberculosis (adjusted hazard ratio, 0.80; 95% confidence interval, 0.23-2.80). In the second independent study, tuberculosis occurred in none of the 76 household contacts who received INH preventive therapy compared with 3% (8 of 273) of those who did not.Conclusions: Household contacts who received INH preventive therapy had a lower incidence of tuberculosis disease even when they had been exposed to an index patient with multidrug-resistant tuberculosis. INH may have a role in the management of latent multidrug-resistant tuberculosis infection.
Project description:IntroductionTraditionally, single critical concentrations of drugs are utilized for Mycobacterium tuberculosis (Mtb) drug susceptibility testing (DST); however, the level of drug resistance can impact treatment choices and outcomes. Mutations at the katG gene are the major genetic mutations in multidrug resistant (MDR) Mtb and usually associated with high level resistance. We assessed the minimum inhibitory concentrations (MICs) of MDR or rifampin resistant (RR) and isoniazid (INH) resistant Mtb isolates to determine the quantification of drug resistance among key anti-tuberculosis drugs.MethodsThe study was conducted on stored Mtb isolates collected as part of a national drug resistance survey in Ethiopia. MIC values were determined using Sensititre™ MYCOTB plates. A line probe assay (MTBDRplus) was also performed to identify genetic determinants of resistance for all isolates.ResultsMIC testing was performed on 74 Mtb isolates including 46 MDR, 2 RR and 26 INH phenotypically resistant isolates as determined by the Löwenstein Jensen (LJ) method. Four (15%) INH resistant Mtb isolates were detected as borderline rifampin resistance (MIC = 1 μg/ml) using MYCOTB MIC plates and no rifampin resistance mutations were detected by LPA. Among the 48 MDR/RR TB cases, 9 (19%) were rifabutin susceptible (MIC was between ≤0.25 and 0.5μg/ml). Additionally, the MIC for isoniazid was between 2-4 μg/ml (moderate resistance) for 58% of MDR TB isolates and 95.6% (n = 25) of the isolates had mutations at the katG gene.ConclusionOur findings suggest a role for rifabutin treatment in a subset of RR TB patients, thus potentially preserving an important drug class. The high proportion of moderate level INH resistant among MDR Mtb isolates indicates the potential benefit of high dose isoniazid treatment in a high proportion of katG gene harboring MDR Mtb isolates.
Project description:We report outcomes for a cohort of patients with multidrug-resistant tuberculosis who received high-dose isoniazid in Haiti. Patients who received high-dose isoniazid had a faster time to culture conversion and higher odds of successful outcome, despite high-level isoniazid resistance. This suggests high-dose isoniazid may have effectiveness even with phenotypic resistance.
Project description:BackgroundThe WHO-endorsed shorter-course regimen for MDR-TB includes high-dose isoniazid. The pharmacokinetics of high-dose isoniazid within MDR-TB regimens has not been well described.ObjectivesTo characterize isoniazid pharmacokinetics at 5-15 mg/kg as monotherapy or as part of the MDR-TB treatment regimen.MethodsWe used non-linear mixed-effects modelling to evaluate the combined data from INHindsight, a 7 day early bactericidal activity study with isoniazid monotherapy, and PODRtb, an observational study of patients on MDR-TB treatment including terizidone, pyrazinamide, moxifloxacin, kanamycin, ethionamide and/or isoniazid.ResultsA total of 58 and 103 participants from the INHindsight and PODRtb studies, respectively, were included in the analysis. A two-compartment model with hepatic elimination best described the data. N-acetyltransferase 2 (NAT2) genotype caused multi-modal clearance, and saturable first-pass was observed beyond 10 mg/kg dosing. Saturable isoniazid kinetics predicted an increased exposure of approximately 50% beyond linearity at 20 mg/kg dosing. Participants treated with the MDR-TB regimen had a 65.6% lower AUC compared with participants on monotherapy. Ethionamide co-administration was associated with a 29% increase in isoniazid AUC.ConclusionsMarkedly lower isoniazid exposures were observed in participants on combination MDR-TB treatment compared with monotherapy. Isoniazid displays saturable kinetics at doses >10 mg/kg. The safety implications of these phenomena remain unclear.
Project description:The molecular basis for isoniazid resistance in Mycobacterium tuberculosis is complex. Putative isoniazid resistance mutations have been identified in katG, ahpC, inhA, kasA, and ndh. However, small sample sizes and related potential biases in sample selection have precluded the development of statistically valid and significant population genetic analyses of clinical isoniazid resistance. We present the first large-scale analysis of 240 alleles previously associated with isoniazid resistance in a diverse set of 608 isoniazid-susceptible and 403 isoniazid-resistant clinical M. tuberculosis isolates. We detected 12 mutant alleles in isoniazid-susceptible isolates, suggesting that these alleles are not involved in isoniazid resistance. However, mutations in katG, ahpC, and inhA were strongly associated with isoniazid resistance, while kasA mutations were associated with isoniazid susceptibility. Remarkably, the distribution of isoniazid resistance-associated mutations was different in isoniazid-monoresistant isolates from that in multidrug-resistant isolates, with significantly fewer isoniazid resistance mutations in the isoniazid-monoresistant group. Mutations in katG315 were significantly more common in the multidrug-resistant isolates. Conversely, mutations in the inhA promoter were significantly more common in isoniazid-monoresistant isolates. We tested for interactions among mutations and resistance to different drugs. Mutations in katG, ahpC, and inhA were associated with rifampin resistance, but only katG315 mutations were associated with ethambutol resistance. There was also a significant inverse association between katG315 mutations and mutations in ahpC or inhA and between mutations in kasA and mutations in ahpC. Our results suggest that isoniazid resistance and the evolution of multidrug-resistant strains are complex dynamic processes that may be influenced by interactions between genes and drug-resistant phenotypes.
Project description:ContextResistance to isoniazid (INH) only (monoresistance), with drug susceptibility to rifampin, pyrazinamide, and ethambutol at diagnosis of tuberculosis (TB) disease, can increase the length of treatment.ObjectiveTo describe US trends in INH monoresistance and associated patient characteristics.DesignWe performed trend and cross-sectional analyses of US National Tuberculosis Surveillance System surveillance data. We used Joinpoint regression to analyze annual trends in INH monoresistance and logistic regression to identify patient characteristics associated with INH monoresistance.ParticipantsCulture-positive cases reported to National Tuberculosis Surveillance System during 1993-2016 with drug susceptibility test results to INH, rifampin, pyrazinamide, and ethambutol.Main outcome measures(1) Trends in INH monoresistance; (2) odds ratios for factors associated with INH monoresistance.ResultsIsoniazid monoresistance increased significantly from 4.1% of all TB cases in 1993 to 4.9% in 2016. Among US-born patients, INH monoresistance increased significantly from 2003 onward (annual percentage change = 2.8%; 95% confidence interval: 1.4-4.2). During 2003-2016, US-born persons with INH-monoresistant TB were more likely to be younger than 65 years; to be Asian; to be human immunodeficiency virus-infected; or to be a correctional facility resident at the time of diagnosis. Among non-US-born persons, INH resistance did not change significantly during 1993-2016 (annual percentage change = -0.3%; 95% confidence interval: -0.7 to 0.2) and was associated with being aged 15 to 64 years; being Asian, black, or Hispanic; or having a previous history of TB.ConclusionsINH-monoresistant TB has been stable since 1993 among non-US-born persons; it has increased 2.8% annually among US-born persons during 2003-2016. Reasons for this increase should be further investigated.
Project description:A reverse line blot DNA hybridization format for rapid detection of multidrug-resistant tuberculosis was developed. Simultaneous detection of rifampin and isoniazid resistance in clinical isolates of Mycobacterium tuberculosis was based on the same amplification/reverse hybridization principle of the widely used spoligotyping. The test involved probing nine DNA regions that are targets of common drug resistance-associated mutations in the genes rpoB, katG, and inhA. Addition of quaternary amine tetramethyl ammonium chloride to the hybridization buffer promoted multiple hybrid formations at a single annealing temperature irrespective of the different GC contents of probes. The assay was standardized using 20 well-documented strains from the Institute of Tropical Medicine (Belgium) and evaluated blindly in a central laboratory with 100 DNA samples that were obtained from cultured clinical isolates and shipped dried from three other countries. Compared with drug susceptibility testing, both sensitivity and specificity for rifampin resistance detection were 93.0% while for isoniazid the values were 87.7% and 97.7%, respectively. Compared with sequencing and GenoType MTBDRplus methods, sensitivity and specificity reached 96.4% and 95.5% for rifampin and 92.7% and 100% for isoniazid. Altogether, 40/45 (89%) multidrug-resistant isolates were correctly identified. Advantages of this in-house development include versatility, capacity to run up to 41 samples by triplicate in a single run, and reuse of the membrane at least 10 times. These features substantially reduce cost per reaction and make the assay an attractive tool for use in reference laboratories of countries that have a high burden of multidrug-resistant tuberculosis but that cannot afford expensive commercial tests because of limited resources.
Project description:Ethionamide is recommended as part of regimens to treat multidrug-resistant and rifampicin-resistant tuberculosis. This study was conducted to (i) describe the distribution of ethionamide MICs, (ii) describe the pharmacokinetics of ethionamide, and (iii) determine the probability of attaining target area under the concentration-time curve from 0 to 24 h (AUC0-24)/MIC values associated with suppression of resistant subpopulation and microbial kill. Participants received 15 to 20 mg of drug/kg of body weight of ethionamide daily (in 500- or 750-mg doses) as part of a multidrug regimen. Pretreatment MICs of ethionamide for Mycobacterium tuberculosis sputum isolates were determined using Sensititre MYCOTB MIC plates. Plasma concentrations of ethionamide (measured predose and at 2, 4, 6, 8, and 10 h postdose) were available for 84 patients. A one-compartment disposition model, including a liver compartment capturing hepatic extraction, best described ethionamide pharmacokinetics. Clearance and volume were allometrically scaled using fat-free mass. Isoniazid coadministration reduced ethionamide clearance by 31%, resulting in a 44% increase in AUC0-24. The median (range) MIC (n = 111) was 2.5 mg/liter (<0.3 to >40 mg/liter). Simulations showed increased daily doses of ethionamide (1,250 mg, 1,500 mg, and 1,750 mg for patients weighing ≤45 kg, 46 to 70 kg, and >70 kg, respectively) resulted in the probability of attaining an area under the concentration-time curve from 0 to 24 h for the free, unbound fraction of a drug (fAUC0-24)/MIC ratio of ≥42 in more than 90% of patients only at the lowest MIC of 0.3 mg/liter. The WHO-recommended doses of ethionamide do not achieve target concentrations even for the lowest MIC measured in the cohort.
Project description:RationaleIsoniazid-monoresistant tuberculosis (INH-monoresistant TB) is the most common drug-resistant TB type in the United States; however, its impact on TB treatment outcomes is not clear.ObjectivesThis study aims to understand 1) factors associated with INH-monoresistant TB and 2) the association between INH monoresistance and response to TB treatment.MethodsWe studied all patients with TB (age, ≥15 yr) reported to the Georgia State Electronic Notifiable Disease Surveillance System (SENDSS) from 2009 to 2014. INH-monoresistant TB was defined as a Mycobacterium tuberculosis isolate resistant to isoniazid only. Time to sputum culture conversion was defined as the time (measured in days) from TB treatment initiation to the date of the first consistently negative culture result reported to the SENDSS. Logistic regression and Cox proportional hazard models were used to estimate the odds and hazard rate of sputum culture conversion, all-cause mortality, and poor TB outcome among patients with INH-monoresistant TB.ResultsAmong 1,141 culture-confirmed patients with available drug susceptibility testing results, 998 (87.5%) were susceptible to TB first-line drugs, and 143 (12.5%) were patients with INH-monoresistant TB. In multivariable analysis, male sex (adjusted odds ratio [aOR], 1.62; 95% confidence interval [CI], 1.01-2.67) and homelessness (aOR, 5.55; 95% CI, 3.38-9.17) were associated with higher odds of INH-monoresistant TB. In the same multivariable model, older age (≥65 yr old) (aOR, 0.21; 95% CI, 0.07-0.55) and miliary disease (aOR, 0.19; 95% CI, 0.01-0.96) were associated with lower odds of INH-monoresistant TB. Among 1,116 patients with pulmonary TB, the median time to sputum culture conversion was 30 days (interquartile range, 13-58). The rate of culture conversion was similar among patients with and without INH monoresistance (adjusted cause-specific hazard ratio, 1.15; 95% CI, 0.95-1.40). INH-monoresistant TB was not significantly associated with poor TB treatment outcomes (aOR, 1.61; 95% CI, 0.67-3.70) or mortality during TB treatment (aOR, 1.72; 95% CI, 0.58-4.94).ConclusionsOur findings suggest that compared with drug-susceptible TB, patients in Georgia with INH-monoresistant TB have a similar response to TB treatment including culture conversion rate, final TB treatment outcome, and all-cause mortality.