W.C.M. de Lange

Drug resistance beyond extensively drug-resistant tuberculosis: individual patient data meta-analysis

The broadest pattern of tuberculosis drug resistance for which a consensus definition exists is extensively drug-resistant tuberculosis (XDR-TB). It is not known if additional drug resistance portends worsened patient outcomes. This study compares treatment outcomes of XDR-TB patients with and without additional resistance to explore the need for a new definition. Individual patient data on XDR-TB outcomes were included in a meta-analysis comparing outcomes between XDR-alone and three non-mutually exclusive XDR-TB patient groups: XDR plus resistance to all the second-line injectables (sli) capreomycin and kanamycin/amikacin (XDR+2sli); XDR plus resistance to second-line injectables and to ≥1 Group 4 drug, i.e. : ethionamide/prothionamide, cycloserine/terizidone or PAS (XDR+sliG4); and XDR+sliG4 plus resistance to ethambutol and/or pyrazinamide (XDR+sliG4EZ). Of 405 XDR-TB cases, 301 were XDR-alone; 68 XDR+2sli; 48 XDR+sliG4; and 42 XDR+sliG4EZ. In multivariate analysis, the odds of cure were significantly lower in XDR+2sli (adjusted Odds Ratio (aOR): 0.4; 95% Confidence Interval: 0.2–0.8) compared to XDR-alone, while odds of failure+death were higher in all XDR patients with additional resistance (aOR range: 2.6–2.8). Patients with additional resistance beyond XDR-TB showed poorer outcomes. Limitations in availability, accuracy and reproducibility of current DST methods preclude the adoption of a useful definition beyond the one currently used for XDR-TB.The broadest pattern of tuberculosis (TB) drug resistance for which a consensus definition exists is extensively drug-resistant (XDR)-TB. It is not known if additional drug resistance portends worsened patient outcomes. This study compares treatment outcomes of XDR-TB patients with and without additional resistance in order to explore the need for a new definition. Individual patient data on XDR-TB outcomes were included in a meta-analysis comparing outcomes between XDR alone and three nonmutually exclusive XDR-TB patient groups: XDR plus resistance to all the second-line injectables (sli) and capreomycin and kanamycin/amikacin (XDR+2sli) XDR plus resistance to second-line injectables and to more than one group 4 drug, i.e. ethionamide/protionamide, cycloserine/terizidone or para-aminosalicylic acid (XDR+sliG4) and XDR+sliG4 plus resistance to ethambutol and/or pyrazinamide (XDR+sliG4EZ). Of 405 XDR-TB cases, 301 were XDR alone, 68 XDR+2sli, 48 XDR+sliG4 and 42 XDR+sliG4EZ. In multivariate analysis, the odds of cure were significantly lower in XDR+2sli (adjusted OR 0.4, 95% CI 0.2–0.8) compared to XDR alone, while odds of failure and death were higher in all XDR patients with additional resistance (adjusted OR 2.6–2.8). Patients with additional resistance beyond XDR-TB showed poorer outcomes. Limitations in availability, accuracy and reproducibility of current drug susceptibility testing methods preclude the adoption of a useful definition beyond the one currently used for XDR-TB.

Clinical relevance of non-tuberculous mycobacteria isolated in the Nijmegen-Arnhem region, The Netherlands

Background: The frequency of clinical isolation of non-tuberculous mycobacteria (NTM) in the Netherlands is increasing, but its clinical relevance is often uncertain. Objective: To assess the frequency and clinical relevance of isolation of NTM in four associated hospitals in a single region in the Netherlands. Methods: Medical files of all patients from whom NTM were isolated between January 1999 and January 2005 were reviewed retrospectively. Diagnostic criteria for non-tuberculous mycobacterial disease published by the American Thoracic Society (ATS) were used to determine clinical relevance. Results: 232 patients were found, from whom NTM were isolated from the respiratory tract in 91% of cases. Patients were mostly white men, with an average age of 60 years and pre-existing pulmonary disease. Fifty-three of 212 patients (25%) with pulmonary isolates met the ATS diagnostic criteria for pulmonary NTM disease; this percentage differed by species. Most patients were treated with rifampicin, ethambutol and clarithromycin. Treatment outcome for pulmonary NTM disease was suboptimal but differed by species: overall, improvement was seen in 67% of treated patients, but in only 50% of those with pulmonary M avium disease. Lymphadenitis was the most common extrapulmonary disease type. Conclusions: Twenty-five per cent of all patients with pulmonary NTM isolates met the ATS criteria. Clinical relevance differs by species. NTM isolation increases over time. Species distribution differs from that of neighbouring countries and the M avium complex isolates have traits different from those reported in the USA. Adherence to diagnostic and treatment guidelines can be improved.

Clinical relevance of Mycobacterium malmoense isolation in the Netherlands

Uncertainty exists about the clinical relevance of Mycobacterium malmoense isolation, especially in pulmonary samples. We therefore determined clinical relevance, treatment and outcome of M. malmoense isolation in the Netherlands. A retrospective medical file study was conducted for all patients in the Netherlands from whom Mycobacterium malmoense had been isolated between January 2002 and January 2006. Diagnostic criteria for nontuberculous mycobacterial (NTM) disease published by the American Thoracic Society (ATS) were used to determine clinical relevance. Treatment was compared with guidelines published by the British Thoracic Society. In total, 51 patients were found from whom M. malmoense was isolated. Of these, 40 (78%) patients had pulmonary isolates and 32 (80%) of them met the ATS diagnostic criteria. Cavitary disease was most common (n = 28; 88%). Patients with pulmonary disease were mostly males, with an average age of 56 yrs and pre-existing chronic obstructive pulmonary disease. Cervical lymphadenitis was the most common extrapulmonary disease type. Adherence to treatment guidelines was poor. A good clinical response to treatment was observed in 70% and 73% of patients treated for pulmonary and extrapulmonary disease, respectively. In conclusion, M. malmoense is a clinically highly relevant NTM in the Netherlands causing serious pulmonary morbidity. Adherence to treatment guidelines is not satisfactory.

Low plasma concentrations of rifampicin in tuberculosis patients in Indonesia

SETTING Although rifampicin is a key drug in tuberculosis treatment, little is known about its quality and bioavailability in countries endemic for tuberculosis. High drug levels may lead to increased toxicity, while low drug levels may predispose to treatment failure and relapse. OBJECTIVE To investigate possible variations in the bioavailability of plasma rifampicin in tuberculosis patients in Indonesia. DESIGN Plasma concentrations of rifampicin and the rifampicin content of drug formulations in use were measured among 62 non-selected tuberculosis patients in Jakarta, Indonesia. RESULTS Plasma concentrations of rifampin were generally low: 70% of patients had 2-hour plasma concentrations (Cmax) below 4 mg/L. No toxic plasma concentrations of rifampicin (>20 mg/L) were found. The strongest predictive factor for the magnitude of rifampicin concentrations was the drug manufacturer. The rifampicin content of the different drug preparations used was normal (90.5-103.6% of the reference standard). No association was found between low plasma rifampicin concentrations and delayed sputum conversion or treatment failure. CONCLUSION The unexpectedly low plasma concentrations of rifampicin in this setting are most likely due to reduced bioavailability of local drug preparations, as the rifampicin content of the drug preparations was found to be normal. The clinical significance of these findings remains to be determined.

Dried Blood Spot Analysis for Therapeutic Drug Monitoring of Linezolid in Patients with Multidrug-Resistant Tuberculosis

ABSTRACT Linezolid is a promising antimicrobial agent for the treatment of multidrug-resistant tuberculosis (MDR-TB), but its use is limited by toxicity. Therapeutic drug monitoring (TDM) may help to minimize toxicity while adequate drug exposure is maintained. Conventional plasma sampling and monitoring might be hindered in many parts of the world by logistical problems that may be solved by dried blood spot (DBS) sampling. The aim of this study was to develop and validate a novel method for TDM of linezolid in MDR-TB patients using DBS sampling. Plasma, venous DBS, and capillary DBS specimens were obtained simultaneously from eight patients receiving linezolid. A DBS sampling method was developed and clinically validated by comparing DBS with plasma results using Passing-Bablok regression and Bland-Altman analysis. This study showed that DBS analysis was reproducible and robust. Accuracy and between- and within-day precision values from three validations presented as bias and coefficient of variation (CV) were less than 17.2% for the lower limit of quantification and less than 7.8% for other levels. The method showed a high recovery of approximately 95% and a low matrix effect of less than 8.7%. DBS specimens were stable at 37°C for 2 months and at 50°C for 1 week. The ratio of the concentration of linezolid in DBS samples to that in plasma was 1.2 (95% confidence interval [CI], 1.12 to 1.27). Linezolid exposure calculated from concentrations DBS samples and plasma showed good agreement. In conclusion, DBS analysis of linezolid is a promising tool to optimize linezolid treatment in MDR-TB patients. An easy sampling procedure and high sample stability may facilitate TDM, even in underdeveloped countries with limited resources and where conventional plasma sampling is not feasible.

The impact of nontuberculous mycobacteria on management of presumed pulmonary tuberculosis.

AbstractBackground: The presence of nontuberculous mycobacteria (NTM) in sputum or bronchial washings may cause diagnostic problems which affect clinical management. Patients and Methods: In a retrospective analysis of 135 patients in a Dutch tuberculosis center, patients with NTM isolates were thoroughly investigated. Colonization or contamination by NTM was differentiated from true lung disease. Results: 25 HIV-seronegative and two HIV-seropositive patients with NTM were identified. NTM were a likely cause of disease in only 14 (52%) patients. In 15 (55%), their presence led to preliminary diagnosis and treatment of tuberculosis. Unnecessary or inappropriate treatment was instituted in 17 (63%) patients with NTM. In two patients, detection of NTM in sputum also led to delay in diagnosing malignant disease. Conclusion: In this series, NTM in sputum or bronchial washings poorly reflected disease and often led to diagnostic and therapeutic errors. Although it is common knowledge that the presence of NTM should be considered in smear-positive patients, this apparently is a diagnostic pitfall in clinical practice. Reliable DNA-based techniques and better communication between physicians and microbiologists may improve management of suspected mycobacterial infections.

Group 5 drugs for multidrug-resistant tuberculosis: individual patient data meta-analysis

The role of so-called “group 5” second-line drugs as a part of antibiotic therapy for multidrug-resistant tuberculosis (MDR-TB) is widely debated. We performed an individual patient data meta-analysis to evaluate the effectiveness of several group 5 drugs including amoxicillin/clavulanic acid, thioacetazone, the macrolide antibiotics, linezolid, clofazimine and terizidone for treatment of patients with MDR-TB. Detailed individual patient data were obtained from 31 published cohort studies of MDR-TB therapy. Pooled treatment outcomes for each group 5 drug were calculated using a random effects meta-analysis. Primary analyses compared treatment success to a combined outcome of failure, relapse or death. Among 9282 included patients, 2191 received at least one group 5 drug. We found no improvement in treatment success among patients taking clofazimine, amoxicillin/clavulanic acid or macrolide antibiotics, despite applying a number of statistical approaches to control confounding. Thioacetazone was associated with increased treatment success (OR 2.6, 95% CI 1.1–6.1) when matched controls were selected from studies in which the group 5 drugs were not used at all, although this result was heavily influenced by a single study. The development of more effective antibiotics to treat drug-resistant TB remains an urgent priority. A meta-analysis of patient data found that group 5 drugs have limited benefit in treating patients with MDR-TB http://ow.ly/TIrH304QBci

Propensity Score-Based Approaches to Confounding by Indication in Individual Patient Data Meta-Analysis: Non-Standardized Treatment for Multidrug Resistant Tuberculosis

Background In the absence of randomized clinical trials, meta-analysis of individual patient data (IPD) from observational studies may provide the most accurate effect estimates for an intervention. However, confounding by indication remains an important concern that can be addressed by incorporating individual patient covariates in different ways. We compared different analytic approaches to account for confounding in IPD from patients treated for multi-drug resistant tuberculosis (MDR-TB). Methods Two antibiotic classes were evaluated, fluoroquinolones—considered the cornerstone of effective MDR-TB treatment—and macrolides, which are known to be safe, yet are ineffective in vitro. The primary outcome was treatment success against treatment failure, relapse or death. Effect estimates were obtained using multivariable and propensity-score based approaches. Results Fluoroquinolone antibiotics were used in 28 included studies, within which 6,612 patients received a fluoroquinolone and 723 patients did not. Macrolides were used in 15 included studies, within which 459 patients received this class of antibiotics and 3,670 did not. Both standard multivariable regression and propensity score-based methods resulted in similar effect estimates for early and late generation fluoroquinolones, while macrolide antibiotics use was associated with reduced treatment success. Conclusions In this individual patient data meta-analysis, standard multivariable and propensity-score based methods of adjusting for individual patient covariates for observational studies yielded produced similar effect estimates. Even when adjustment is made for potential confounding, interpretation of adjusted estimates must still consider the potential for residual bias.

Pharmacokinetic Evaluation of Sulfamethoxazole at 800 Milligrams Once Daily in the Treatment of Tuberculosis.

ABSTRACT For treatment of multidrug-resistant tuberculosis (MDR-TB), there is a scarcity of antituberculosis drugs. Co-trimoxazole is one of the available drug candidates, and it is already frequently coprescribed for TB-HIV-coinfected patients. However, only limited data are available on the pharmacokinetic (PK) and pharmacodynamic (PD) parameters of co-trimoxazole in TB patients. The objective of this study was to evaluate the PK parameters and in vitro PD data on the effective part of co-trimoxazole: sulfamethoxazole. In a prospective PK study in patients infected with drug-susceptible Mycobacterium tuberculosis (drug-susceptible TB patients) (age, >18), sulfamethoxazole-trimethoprim (SXT) was administered orally at a dose of 960 mg once daily. One-compartment population pharmacokinetic modeling was performed using MW\Pharm 3.81 (Mediware, Groningen, The Netherlands). The area under the concentration-time curve for the free, unbound fraction of a drug (ƒAUC)/MIC ratio and the period in which the free concentration exceeded the MIC (fT > MIC) were calculated. Twelve patients received 960 mg co-trimoxazole in addition to first-line drugs. The pharmacokinetic parameters of the population model were as follows (geometric mean ± standard deviation [SD]): metabolic clearance (CLm), 1.57 ± 3.71 liters/h; volume of distribution (V), 0.30 ± 0.05 liters · kg lean body mass−1; drug clearance/creatinine clearance ratio (fr), 0.02 ± 0.13; gamma distribution rate constant (ktr_po), 2.18 ± 1.14; gamma distribution shape factor (n_po), 2.15 ± 0.39. The free fraction of sulfamethoxazole was 0.3, but ranged between 0.2 and 0.4. The median value of the MICs was 9.5 mg/liter (interquartile range [IQR], 4.75 to 9.5), and that of theƒAUC/MIC ratio was 14.3 (IQR, 13.0 to 17.5). The percentage of ƒT > MIC ranged between 43 and 100% of the dosing interval. The PK and PD data from this study are useful to explore a future dosing regimen of co-trimoxazole for MDR-TB treatment. (This study has been registered at ClinicalTrials.gov under registration no. NCT01832987.)

Pharmacokinetics of 2,000 Milligram Ertapenem in Tuberculosis Patients

ABSTRACT Ertapenem is a carbapenem antibiotic with activity against Mycobacterium tuberculosis. Dose simulations in a hollow-fiber infection model showed that 2,000 mg once daily is an appropriate dose to be tested in clinical studies. Before using this dose in a phase II study, the aim of this prospective pharmacokinetic study was to confirm the pharmacokinetics of 2,000 mg once daily in tuberculosis (TB) patients. Twelve TB patients received a single intravenous dose of 2,000 mg ertapenem as a 30-min infusion. Blood samples were collected at 0, 0.5, 1, 2, 3, 4, 8, 12, and 24 h postadministration. Drug concentrations were measured using a validated liquid chromatography-tandem mass spectrometry assay. A large interindividual variation in the pharmacokinetics of ertapenem was observed. The median (interquartile range) area under the plasma concentration-time curve to infinity (AUC0–∞) was 2,032 (1,751 to 2,346) mg · h/liter, the intercompartmental clearance (CL12) was 1.941 (0.979 to 2.817) liters/h, and the volume of distribution in the central compartment (V1) was 1.514 (1.064 to 2.210) liters. A more than dose-proportional increase in AUC was observed compared to results reported for 1,000 mg ertapenem in multidrug-resistant TB patients. Based on a MIC of 1.0 mg/liter, 11 out of 12 patients would have reached the target value of unbound drug exceeding the MIC over 40% of the time (f40% T>MIC). In conclusion, this study shows that 2,000 mg ertapenem once daily in TB patients reached the expected f40% T>MIC for most of the patients, and exploration in a phase 2 study can be advocated.