Pharmacokinetics of rifampicin in adult TB patients and healthy volunteers: a systematic review and meta-analysis.

Objectives: The objectives of this study were to explore inter-study heterogeneity in the pharmacokinetics (PK) of orally administered rifampicin, to derive summary estimates of rifampicin PK parameters at standard dosages and to compare these with summary estimates for higher dosages. Methods: A systematic search was performed for studies of rifampicin PK published in the English language up to May 2017. Data describing the Cmax and AUC were extracted. Meta-analysis provided summary estimates for PK parameter estimates at standard rifampicin dosages. Heterogeneity was assessed by estimation of the I2 statistic and visual inspection of forest plots. Summary AUC estimates at standard and higher dosages were compared graphically and contextualized using preclinical pharmacodynamic (PD) data. Results: Substantial heterogeneity in PK parameters was evident and upheld in meta-regression. Treatment duration had a significant impact on the summary estimates for rifampicin PK parameters, with Cmax 8.98 mg/L (SEM 2.19) after a single dose and 5.79 mg/L (SEM 2.14) at steady-state dosing, and AUC 72.56 mg·h/L (SEM 2.60) and 38.73 mg·h/L (SEM 4.33) after single and steady-state dosing, respectively. Rifampicin dosages of at least 25 mg/kg are required to achieve plasma PK/PD targets defined in preclinical studies. Conclusions: Vast inter-study heterogeneity exists in rifampicin PK parameter estimates. This is not explained by the available modifying variables. The recommended dosage of rifampicin should be increased to improve efficacy. This study provides an important point of reference for understanding rifampicin PK at standard dosages as efforts to explore higher dosing strategies continue in this field.

Pharmacokinetics, Tolerability, and Bacteriological Response of Rifampin Administered at 600, 900, and 1,200 Milligrams Daily in Patients with Pulmonary Tuberculosis.

In a multiple-dose-ranging trial, we previously evaluated higher doses of rifampin in patients for 2 weeks. The objectives of the current study were to administer higher doses of rifampin for a longer period to compare the pharmacokinetics, safety/tolerability, and bacteriological activity of such regimens. In a double-blind, randomized, placebo-controlled, phase II clinical trial, 150 Tanzanian patients with tuberculosis (TB) were randomized to receive either 600 mg (approximately 10 mg/kg of body weight), 900 mg, or 1,200 mg rifampin combined with standard doses of isoniazid, pyrazinamide, and ethambutol administered daily for 2 months. Intensive pharmacokinetic sampling occurred in 63 patients after 6 weeks of treatment, and safety/tolerability was assessed. The bacteriological response was assessed by culture conversion in liquid and solid media. Geometric mean total exposures (area under the concentration-versus-time curve up to 24 h after the dose) were 24.6, 50.8, and 76.1 mg · h/liter in the 600-mg, 900-mg, and 1,200-mg groups, respectively, reflecting a nonlinear increase in exposure with the dose (P < 0.001). Grade 3 adverse events occurred in only 2 patients in the 600-mg arm, 4 patients in the 900-mg arm, and 5 patients in the 1,200-mg arm. No significant differences in the bacteriological response were observed. Higher daily doses of rifampin (900 and 1,200 mg) resulted in a more than proportional increase in rifampin exposure in plasma and were safe and well tolerated when combined with other first-line anti-TB drugs for 2 months, but they did not result in improved bacteriological responses in patients with pulmonary TB. These findings have warranted evaluation of even higher doses of rifampin in follow-up trials. (This study has been registered at ClinicalTrials.gov under identifier NCT00760149.).

Ebola, fragile health systems and tuberculosis care: a call for pre-emptive action and operational research.

The Ebola outbreak that started in late 2013 is by far the largest and most sustained in history. It occurred in a part of the world where pre-existing health systems were already fragile, and these deteriorated further during the epidemic due to a large number of health worker deaths; temporary or permanent closure of health facilities; non-payment of health workers; intrinsic fear of contracting or being stigmatised by Ebola among the population, which negatively influenced health-seeking behaviour; enforced quarantine of Ebola-affected communities, restricting the access of vulnerable individuals to health facilities; and late response by the international community. There are also reports of drug and consumable stockouts due to deficiencies in the procurement and supply chain as a result of overriding Ebola-related priorities. Providing tuberculosis (TB) care and achieving favourable treatment outcomes require a fully functioning health system, accurate patient tracking and high patient adherence to treatment. Furthermore, as Ebola is easily transmitted through body fluids, the use of needles-essential for TB diagnosis and treatment-needs to be avoided during an outbreak. We highlight ways in which a sustained Ebola outbreak could jeopardise TB activities and suggest pre-emptive preventive measures while awaiting operational research evidence.

Molecular drug susceptibility testing in the Netherlands: performance of the MTBDRplus and MTBDRsl assays.

BACKGROUND: The performance of molecular drug susceptibility testing in countries with a low prevalence of drug resistance, such as the Netherlands, has not been adequately studied. OBJECTIVE: To evaluate the diagnostic accuracy of the GenoType(®) MTBDRplus and MTBDRsl assays to detect resistance to first- and second-line anti-tuberculosis drugs in the context of a nationwide screening programme in the Netherlands. RESULTS: The MTBDRplus assay had a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%, 99%, 80% and 100% for detecting rifampicin resistance. The sensitivity, specificity, PPV and NPV of either a katG or inhA mutation for detecting isoniazid resistance were 88%, 100%, 100% and 99%. The MTBDRsl assay had a sensitivity, specificity, PPV and NPV of 100%, 99%, 83%, and 100% for detecting moxifloxacin resistance; 62%, 71%, 58% and 74%, respectively, for detecting ethambutol resistance; 86%, 99%, 86% and 99% for detecting amikacin resistance; and 50%, 96%, 71% and 91% for detecting capreomycin resistance. CONCLUSION: The MTBDRplus and MTBDRsl assays may aid in decision making in tuberculosis treatment in low-level drug resistance settings and should preferably be used to exclude resistance.

Highly successful treatment outcome of multidrug-resistant tuberculosis in the Netherlands, 2000-2009.

SETTING: Resistance to the two key anti-tuberculosis drugs isoniazid and rifampicin is a characteristic of multidrug-resistant tuberculosis (MDR-TB). MDR-TB is a scourge requiring toxic, prolonged treatment and is associated with poor outcomes. The Netherlands is a country with a long-standing, integrated, well-resourced TB service where all patients are offered culture-confirmed diagnosis by a central reference laboratory. OBJECTIVE: To assess the treatment outcomes of MDR-TB patients over a period of 10 years in The Netherlands. DESIGN: Demographic, clinical and microbiological features of all patients with MDR-TB who started treatment in 2000-2009 in the Netherlands were analysed from national registry and patient records. RESULTS: Characteristics of the 113 MDR-TB patients were as follows: male/female ratio 1.57, 96% foreign born, median age 29 years, 96 (85%) pulmonary TB, 56 (50%) smear-positive, 14 (12%) human immunodeficiency virus (HIV) co-infected. Of the 104 (92%) patients who started MDR-TB treatment, 86% had a successful outcome using a median of six active drugs; eight underwent pulmonary surgery. HIV negativity was associated with successful outcome (adjusted OR 2.1, 95%CI 1.1-3.8). CONCLUSION: High success rates for MDR-TB treatment were achieved with close collaboration of all stakeholders, reaching the targets set for drug-susceptible TB. HIV remained an independent risk factor for unsuccessful treatment outcome.

An African woman with pulmonary cavities: TB or not TB?

Cavitary lung lesions in patients from developing countries are mostly caused by tuberculosis (TB). However, when TB cannot be confirmed, a primary lung abscess caused by anaerobic bacteria from the mouth should be considered, especially in patients with poor dentition. We present a case of a Sudanese woman with a cavitary lung lesion and severe gingivitis. Bulleidia extructa was isolated as a single pathogen from the pulmonary cavity.

Population pharmacokinetics and limited sampling strategy for first-line tuberculosis drugs and moxifloxacin.

Therapeutic drug monitoring (TDM) of tuberculosis (TB) drugs currently focuses on peak plasma concentrations, yet total exposure [area under the 24-h concentration-time curve (AUC0₋24)] is probably most relevant to the efficacy of these drugs. We therefore assessed population AUC0₋24 data for all four first-line TB drugs (rifampicin, isoniazid, pyrazinamide and ethambutol) as well as moxifloxacin and developed limited sampling strategies to estimate AUC0₋24 values conveniently. AUC0₋24 and other pharmacokinetic (PK) parameters were determined following intensive PK sampling in two Dutch TB referral centres. Best subset selection multiple linear regression was performed to derive limited sampling equations. Median percentage prediction error and median absolute percentage prediction error were calculated via jackknife analysis to evaluate bias and imprecision of the predictions. Geometric mean AUC0₋24 values for rifampicin, isoniazid, pyrazinamide, ethambutol and moxifloxacin were 41.1, 15.2, 380, 25.5 and 33.6 hmg/L, respectively. Limited sampling at various fixed sampling points enabled an accurate and precise prediction of AUC0₋24 values of all drugs separately and simultaneously. In the absence of clinically validated target values for AUC0₋24, average AUC0₋24 values can be used as reference values in TDM. Limited sampling of AUC0₋24 is feasible in many settings and allows for TDM to be performed at a larger scale.

Rapid diagnosis of pyrazinamide-resistant multidrug-resistant tuberculosis using a molecular-based diagnostic algorithm.

There is an urgent need for rapid and accurate diagnosis of pyrazinamide-resistant multidrug-resistant tuberculosis (MDR-TB). No diagnostic algorithm has been validated in this population. We hypothesized that pncA sequencing added to rpoB mutation analysis can accurately identify patients with pyrazinamide-resistant MDR-TB. We identified from the Dutch national database (2007-11) patients with a positive Mycobacterium tuberculosis culture containing a mutation in the rpoB gene. In these cases, we prospectively sequenced the pncA gene. Results from the rpoB and pncA mutation analysis (pncA added to rpoB) were compared with phenotypic susceptibility testing results to rifampicin, isoniazid and pyrazinamide (reference standard) using the Mycobacterial Growth Indicator Tube 960 system. We included 83 clinical M. tuberculosis isolates containing rpoB mutations in the primary analysis. Rifampicin resistance was seen in 72 isolates (87%), isoniazid resistance in 73 isolates (88%) and MDR-TB in 65 isolates (78%). Phenotypic reference testing identified pyrazinamide-resistant MDR-TB in 31 isolates (48%). Sensitivity of pncA sequencing added to rpoB mutation analysis for detecting pyrazinamide-resistant MDR-TB was 96.8%, the specificity was 94.2%, the positive predictive value was 90.9%, the negative predictive value was 98.0%, the positive likelihood was 16.8 and the negative likelihood was 0.03. In conclusion, pyrazinamide-resistant MDR-TB can be accurately detected using pncA sequencing added to rpoB mutation analysis. We propose to include pncA sequencing in every isolate with an rpoB mutation, allowing for stratification of MDR-TB treatment according to pyrazinamide susceptibility.

Pharmacokinetic studies in patients with nontuberculous mycobacterial lung infections.

Concentrations of antimycobacterial drugs are an intermediary link between doses administered and eventual response to the drugs. Few pharmacokinetic (PK) studies have focused on drug treatment for nontuberculous mycobacterial (NTM) disease, although a favourable treatment response occurs in just over 50% of patients despite drug treatment for ≥1 year. A prospective, descriptive PK study was performed to assess the plasma pharmacokinetics of rifampicin, ethambutol, clarithromycin, 14-OH-clarithromycin, azithromycin, isoniazid and moxifloxacin. Intensive PK sampling was performed in 14 patients with clinically relevant NTM lung disease. PK parameters were assessed and were compared with available data from the literature. Exposure to clarithromycin when combined with rifampicin was very low [area under the concentration-time curve over 12 h (AUC(0-12 h), geometric mean 2.6 h·mg/L, range 1.6-3.2 h·mg/L; peak concentration in plasma (C(max)), geometric mean 0.3 mg/L, range 0.1-0.7 mg/L]. The mean parent-to-metabolite ratios for clarithromycin to 14-OH-clarithromycin were 0.4 and 0.3 for AUC(0-12 h) and C(max), instead of the typical ratio of ca. 3, probably reflecting increased metabolism of clarithromycin to its (virtually inactive) 14-OH metabolite. Exposure to rifampicin was relatively high, with all patients having a rifampicin C(max) within the reference range. The majority of ethambutol C(max) values were within the reference range. The current study re-emphasises the relevant PK interaction between clarithromycin and rifampicin. This calls for a re-evaluation of dosing strategies in NTM lung disease, as suboptimal drug exposure may contribute to inadequate response to treatment of NTM disease.

Mycobacterium genavense in the Netherlands: an opportunistic pathogen in HIV and non-HIV immunocompromised patients. An observational study in 14 cases.

Mycobacterium genavense is an opportunistic non-tuberculous mycobacterium previously mostly associated with HIV-infected patients with CD4 counts below 100/µL. In this retrospective observational study of medical charts we studied all Dutch patients in whom M. genavense was detected between January 2002 and January 2010. Of the 14 patients identified, 13 (93%) showed clinically relevant M. genavense disease. All patients with M. genavense disease were severely immunocompromised, including HIV-infected patients, solid organ transplant recipients, those with chronic steroid use in combination with other immune modulating drugs, recipients of chemotherapy for non-Hodgkin lymphoma, and those with immunodeficiency syndromes. Two patients had non-disseminated pulmonary M. genavense disease. Of the 12 patients treated, eight (75%) showed a favourable outcome. Four patients died in this study, three despite treatment for M. genavense disease. We conclude that M. genavense is a clinically relevant pathogen in severely immunocompromised patients that causes predominantly disseminated disease with serious morbidity and mortality. M. genavense is increasingly seen among non-HIV immunocompromised patients.

The Cough Cylinder: a tool to study measures against airborne spread of (myco-) bacteria.

BACKGROUND: 'Covering your cough' reduces droplet number, but its effect on airborne pathogen transmission is less clear. The World Health Organization specifically recommends cough etiquette to prevent the spread of Mycobacterium tuberculosis, but implementation is generally poor and evidence supporting its value is lacking. METHODS: We constructed a model to assess 'real life' transmission risk by counting viable pathogens from aerosols produced by coughing patients, thus allowing the assessment of outward protection measures in a standardised fashion. During the validation process, we focused on rod-shaped bacteria as surrogates for M. tuberculosis. RESULTS: The Cough Cylinder enabled us to sample Pseudomonas aeruginosa, Escherichia coli and mycobacteria from aerosols produced by patients with cystic fibrosis, primary ciliary dyskinesia and tuberculosis. Pathogens in droplets and in airborne particles could be sampled. Delayed air sampling allowed specific measurement of persistent airborne particles. CONCLUSION: This novel experimental system allows measurement of aerosol pathogen spread in a highly standardised fashion. It also offers the possibility to assess the impact of different interventions to limit aerosol transmission.

Characterization of a novel variant of Mycobacterium chimaera.

In this study, nonchromogenic mycobacteria were isolated from pulmonary samples of three patients in the Netherlands. All isolates had identical, unique 16S rRNA gene and 16S-23S ITS sequences, which were closely related to those of Mycobacterium chimaera and Mycobacterium marseillense. The biochemical features of the isolates differed slightly from those of M. chimaera, suggesting that the isolates may represent a possible separate species within the Mycobacterium avium complex (MAC). However, the cell-wall mycolic acid pattern, analysed by HPLC, and the partial sequences of the hsp65 and rpoB genes were identical to those of M. chimaera. We concluded that the isolates represent a novel variant of M. chimaera. The results of this analysis have led us to question the currently used methods of species definition for members of the genus Mycobacterium, which are based largely on 16S rRNA or rpoB gene sequencing. Definitions based on a single genetic target are likely to be insufficient. Genetic divergence, especially in the MAC, yields strains that cannot be confidently assigned to a specific species based on the analysis of a single genetic target.

Xpert MTB/RIF®, a novel automated polymerase chain reaction-based tool for the diagnosis of tuberculosis.

There is an urgent need for new point of care tests for tuberculosis (TB). Xpert MTB/RIF® is a real-time polymerase chain reaction-based system that detects Mycobacterium tuberculosis DNA and rifampicin (RMP) resistance modulating mutations directly from clinical samples in 2 h. The sensitivity for detecting M. tuberculosis in culture-positive samples was 93.8% (60/64) and exceeded smear microscopy (40/64, 62.5%). The specificity for detecting M. tuberculosis was 92.0% (23/25) and for RMP resistance it was 100% (8/8). The test is simple to conduct and requires basic sputum handling facilities only. These characteristics render it a promising close-to-patient test for TB in various settings.

Low-level rifampicin-resistant Mycobacterium tuberculosis strains raise a new therapeutic challenge.

In an outbreak of multidrug-resistant tuberculosis, the outbreak strain had an Asp516Tyr rpoB gene mutation. Phenotypically, low-level rifampicin (RMP) resistance (minimum inhibitory concentration [MIC] 1-2 mg/l) was observed. Based on drug susceptibility test results, three patients were treated with 12-15 month rifabutin-based regimens and one with a 12-month RMP-based regimen. We retrospectively performed pharmacokinetic calculations to assess the potential for RMP treatment, from which we conclude that MICs for RMP up to 1 µg/ml may be safely overcome by applying 20 mg/kg RMP doses in treatment regimens.

Serum 25-hydroxy-vitamin D3 concentrations increase during tuberculosis treatment in Tanzania.

SETTING: Vitamin D deficiency is associated with susceptibility to active tuberculosis (TB) in many settings. In vitro studies and studies on human volunteers showed that two of the first-line anti-tuberculosis drugs, isoniazid and rifampicin, reduce 25-hydroxy vitamin D (25[OH]D) concentrations. OBJECTIVE: To study changes in vitamin D status during treatment of Tanzanian hospitalised patients with pulmonary TB (PTB). DESIGN: We compared serum 25[OH]D concentrations in 81 Tanzanian PTB patients before and after 2 months of treatment. RESULTS: Median serum 25[OH]D concentrations increased from 91 nmol/l at baseline to 101 nmol/l after 2 months of TB treatment (median increase 6.0 nmol/l, IQR -0.7-25.0, P = 0.001). Median serum parathyroid hormone concentrations increased from 1.6 to 2.0 pmol/l (median increase 0.46, IQR -0.2-1.1, P < 0.001). CONCLUSION: 25[OH]D serum concentrations increased during the first 2 months of TB treatment in 81 PTB patients in northern Tanzania. Improved dietary intake and increased sunlight exposure may have contributed to the increased 25[OH]D concentrations.

The changing pattern of clinical Mycobacterium avium isolation in the Netherlands.

SETTING: National Mycobacteria Reference Laboratory, The Netherlands. OBJECTIVE: To assess the role of factors other than laboratory improvements in the increasing frequency of isolation of non-tuberculous mycobacteria (NTM) in the Netherlands; laboratory improvements are often considered key factors in this increase. DESIGN: Laboratory database study. All clinically isolated NTM referred to the national reference laboratory between January 2000 and January 2007 were retrieved from the laboratory database and categorised by species, patient age group and sample origin. Data were compared with national demographic data. RESULTS: Clinical Mycobacterium avium isolates accounted for most of the increase in referred NTM. The number of respiratory M. avium samples in patients aged >40 years increased over time. This age group increased in size during the study. In this age group, the prevalence of chronic obstructive pulmonary disease (COPD) increased during the study period. M. avium isolation from lymph nodes in children remained stable, whereas extra-pulmonary M. avium isolation in the middle age group, including human immunodeficiency virus associated bloodstream isolates, decreased. CONCLUSIONS: The increasing NTM notification in the Netherlands is unlikely to have been a result of laboratory improvements alone: the ageing population with an increasing prevalence of COPD is likely as important. Environmental characteristics may specifically favour M.avium.