P. R. Donald

Tuberculous meningitis: a uniform case definition for use in clinical research

Tuberculous meningitis causes substantial mortality and morbidity in children and adults. More research is urgently needed to better understand the pathogenesis of disease and to improve its clinical management and outcome. A major stumbling block is the absence of standardised diagnostic criteria. The different case definitions used in various studies makes comparison of research findings difficult, prevents the best use of existing data, and limits the management of disease. To address this problem, a 3-day tuberculous meningitis workshop took place in Cape Town, South Africa, and was attended by 41 international participants experienced in the research or management of tuberculous meningitis. During the meeting, diagnostic criteria were assessed and discussed, after which a writing committee was appointed to finalise a consensus case definition for tuberculous meningitis for use in future clinical research. We present the consensus case definition together with the rationale behind the recommendations. This case definition is applicable irrespective of the patients age, HIV infection status, or the resources available in the research setting. Consistent use of the proposed case definition will aid comparison of studies, improve scientific communication, and ultimately improve care.

Randomized Pilot Trial of Eight Weeks of Bedaquiline (TMC207) Treatment for Multidrug-Resistant Tuberculosis: Long-Term Outcome, Tolerability, and Effect on Emergence of Drug Resistance

ABSTRACT The 2-year follow-up results for a randomized placebo-controlled study of 47 patients with multidrug-resistant pulmonary tuberculosis treated with either the new diarylquinoline TMC207, recently renamed bedaquiline, or placebo, added to the first 8 weeks of a background regimen, are presented. Bedaquiline significantly reduced the time to culture conversion over 24 weeks (hazard ratio, 2.253; 95% confidence interval, 1.08 to 4.71; P = 0.031). With the exception of nausea reported in 26% of patients receiving bedaquiline and none receiving placebo, adverse events occurred at similar frequencies in both groups of patients: bilateral hearing impairment, extremity pain, acne, and noncardiac chest pain occurred in 13 and 21%, 17 and 13%, 9 and 17%, and 4 and 17% of patients, respectively, receiving bedaquiline or placebo. Excluding resistance to ethambutol and ethionamide, only one patient receiving bedaquiline acquired resistance to companion drugs, but five patients receiving placebo (4.8% versus 21.7%; P = 0.18) acquired resistance to companion drugs, and resistance to ofloxacin was acquired in four patients receiving placebo and none receiving bedaquiline (0% versus 22%; 0 = 0.066). In all, 23 patients (49%), including 13 receiving placebo (54%) and 10 receiving bedaquiline (44%), discontinued the study prior to its completion, 12 during the first 24 weeks of treatment. Eight subjects were withdrawn for noncompliance or default, and seven withdrew consent, citing the rigorous program of investigations for safety and pharmacokinetic monitoring. Bedaquiline may contribute to the management of multidrug-resistant tuberculosis by effecting more rapid sputum culture negativity and by preventing acquired resistance to companion drugs.

Early Bactericidal Activity and Pharmacokinetics of the Diarylquinoline TMC207 in Treatment of Pulmonary Tuberculosis

ABSTRACT Tibotec Medicinal Compound 207 (TMC207) is a novel diarylquinoline with a unique mode of action that targets mycobacterial ATP synthase. TMC207 exhibits high in vitro activity against mycobacterial strains either susceptible or resistant to all first-line and many second-line drugs, including fluoroquinolones, and has shown exceptional in vivo activity against several mycobacterial species in different animal models. In this early bactericidal activity study, 75 treatment-naïve patients with smear-positive pulmonary tuberculosis were randomized to once-daily oral TMC207 (25 mg, 100 mg, or 400 mg), 600 mg rifampin (RIF), or 300 mg isoniazid (INH) for 7 days. Sixteen-hour overnight sputum collected at baseline and on each treatment day was plated in serial dilutions on selective agar plates. The bactericidal activity was expressed as the log10 decrease in CFU/ml sputum/day. Pharmacokinetic sampling was performed on day 7 of TMC207 administration up to 24 h postdose. The decreases in log10 CFU counts (± standard deviation) from baseline to day 7 were 0.04 ± 0.46 for 25 mg TMC207 (n = 14), 0.26 ± 0.64 for 100 mg TMC207 (n = 14), 0.77 ± 0.58 for 400 mg TMC207 (n = 14), 1.88 ± 0.74 for INH (n = 11), and 1.70 ± 0.71 for RIF (n = 14). Significant bactericidal activity of 400 mg TMC207 was observed from day 4 onward and was similar in magnitude to those of INH and RIF over the same period. The pharmacokinetics of TMC207 were linear across the dose range. In summary, TMC207 demonstrated bactericidal activity with a delayed onset and was well tolerated, and no study drug-related serious adverse events occurred.

Twenty Years of Pediatric Tuberculous Meningitis: A Retrospective Cohort Study in the Western Cape of South Africa

OBJECTIVE. Tuberculous meningitis is the most severe extrapulmonary complication of tuberculosis, with high morbidity and mortality rates. The objective of this study was to assess the relationship between presenting clinical characteristics and outcome of pediatric tuberculous meningitis. PATIENTS AND METHODS. We present a retrospective cohort study of all of the children diagnosed with tuberculous meningitis in a large university hospital in South Africa between January 1985 and April 2005. We compared demographic, clinical, and diagnostic characteristics with clinical outcome after 6 months of treatment. RESULTS. We included 554 patients. Common characteristics on admission were young age (82%; <5 years), stage II or III tuberculous meningitis (97%), nonspecific symptoms existing for >1 week (58%), poor weight gain or weight loss (91%), loss of consciousness (96%), motor deficit (63%), meningeal irritation (98%), raised intracranial pressure (23%), brainstem dysfunction (39%), and cranial nerve palsies (27%). Common features of tuberculous meningitis on computed tomography scan of the brain were hydrocephalus (82%), periventricular lucency (57%), infarctions (32%), and basal meningeal enhancement (75%). Clinical outcome after 6 months was as follows: normal (16%), mild sequelae (52%), severe sequelae (19%), and death (13%). All of the patients diagnosed with stage I tuberculous meningitis had normal outcome. Factors associated with poor outcome in univariate analyses were as follows: African ethnicity, young age, HIV coinfection, stage III tuberculous meningitis, absence of headache and vomiting, convulsions, decreased level of consciousness, motor deficits, cranial nerve palsies, raised intracranial pressure, brainstem dysfunction and radiographic evidence of hydrocephalus, periventricular lucency, and infarction. Ethnicity, stage of disease, headache, convulsions, motor function, brainstem dysfunction, and cerebral infarctions were independently associated with poor outcome in multivariate logistic regression analysis. CONCLUSIONS. Tuberculous meningitis starts with nonspecific symptoms and is often only diagnosed when brain damage has already occurred. Earlier diagnosis will improve outcome significantly. We were able to identify presenting variables independently associated with poor clinical outcome.

Early Bactericidal Activity of High-Dose Rifampin in Patients with Pulmonary Tuberculosis Evidenced by Positive Sputum Smears

ABSTRACT We studied the early bactericidal activity of twice the standard dose of rifampin in subjects with pulmonary tuberculosis evidenced by positive smears. The observed mean 2-day activity was almost double that reported at the standard dose. Further studies are warranted to establish whether higher rifampin doses might assist in shortening tuberculosis treatment.

Early Bactericidal Activity and Pharmacokinetics of PA-824 in Smear-Positive Tuberculosis Patients

ABSTRACT PA-824 is a novel nitroimidazo-oxazine being evaluated for its potential to improve tuberculosis (TB) therapy. This randomized study evaluated safety, tolerability, pharmacokinetics, and extended early bactericidal activity of PA-824 in drug-sensitive, sputum smear-positive, adult pulmonary tuberculosis patients. Fifteen patients per cohort received 1 of 4 doses of oral PA-824: 200, 600, 1,000, or 1,200 mg per day for 14 days. Eight subjects received once daily standard antituberculosis treatment as positive control. The primary efficacy endpoint was the mean rate of change in log CFU of Mycobacterium tuberculosis in sputum incubated on agar plates from serial overnight sputum collections, expressed as log10 CFU/day/ml (± standard deviation [SD]). The drug demonstrated increases that were dose linear but less than dose proportional in serum concentrations in doses from 200 to 1,000 mg daily. Dosing of 1,200 mg gave no additional exposure compared to 1,000 mg daily. The mean daily CFU fall under standard treatment was 0.148 (±0.055), consistent with that found in previous studies. The mean daily fall under PA-824 was 0.098 (±0.072) and was equivalent for all four dosages. PA-824 appeared safe and well tolerated; the incidence of adverse events potentially related to PA-824 appeared dose related. We conclude that PA-824 demonstrated bactericidal activity over the dose range of 200 to 1,200 mg daily over 14 days. Because maximum efficacy was unexpectedly achieved at the lowest dosage tested, the activity of lower dosages should now be explored.

Efficiency and safety of the combination of moxifloxacin, pretomanid (PA-824), and pyrazinamide during the first 8 weeks of antituberculosis treatment: a phase 2b, open-label, partly randomised trial in patients with drug-susceptible or drug-resistant pulmonary tuberculosis

BACKGROUND New antituberculosis regimens are urgently needed to shorten tuberculosis treatment. Following on from favourable assessment in a 2 week study, we investigated a novel regimen for efficacy and safety in drug-susceptible and multidrug-resistant (MDR) tuberculosis during the first 8 weeks of treatment. METHODS We did this phase 2b study of bactericidal activity--defined as the decrease in colony forming units (CFUs) of Mycobacterium tuberculosis in the sputum of patients with microscopy smear-positive pulmonary tuberculosis-at eight sites in South Africa and Tanzania. We enrolled treatment-naive patients with drug-susceptible, pulmonary tuberculosis, who were randomly assigned by computer-generated sequences to receive either 8 weeks of moxifloxacin, 100 mg pretomanid (formerly known as PA-824), and pyrazinamide (MPa100Z regimen); moxifloxacin, 200 mg pretomanid, and pyrazinamide (MPa200Z regimen); or the current standard care for drug-susceptible pulmonary tuberculosis, isoniazid, rifampicin, PZA, and ethambutol (HRZE regimen). A group of patients with MDR tuberculosis received MPa200Z (DRMPa200Z group). The primary outcome was bactericidal activity measured by the mean daily rate of reduction in M tuberculosis CFUs per mL overnight sputum collected once a week, with joint Bayesian non-linear mixed-effects regression modelling. We also assessed safety and tolerability by monitoring adverse events. This study is registered with ClinicalTrials.gov, number NCT01498419. FINDINGS Between March 24, 2012, and July 26, 2013 we enrolled 207 patients and randomly assigned them to treatment groups; we assigned 60 patients to the MPa100Z regimen, 62 to the MPa200Z regimen, and 59 to the HRZE regimen. We non-randomly assigned 26 patients with drug-resistant tuberculosis to the DRMPa200Z regimen. In patients with drug-susceptible tuberculosis, the bactericidal activity of MPa200Z (n=54) on days 0-56 (0·155, 95% Bayesian credibility interval 0·133-0·178) was significantly greater than for HRZE (n=54, 0·112, 0·093-0·131). DRMPa200Z (n=9) had bactericidal activity of 0·117 (0·070-0·174). The bactericidal activity on days 7-14 was strongly associated with bactericidal activity on days 7-56. Frequencies of adverse events were similar to standard treatment in all groups. The most common adverse event was hyperuricaemia in 59 (29%) patients (17 [28%] patients in MPa100Z group, 17 [27%] patients in MPa200Z group, 17 [29%] patients. in HRZE group, and 8 [31%] patients in DRMPa200Z group). Other common adverse events were nausea in (14 [23%] patients in MPa100Z group, 8 [13%] patients in MPa200Z group, 7 [12%] patients in HRZE group, and 8 [31%] patients in DRMPa200Z group) and vomiting (7 [12%] patients in MPa100Z group, 7 [11%] patients in MPa200Z group, 7 [12%] patients in HRZE group, and 4 [15%] patients in DRMPa200Z group). No on-treatment electrocardiogram occurrences of corrected QT interval more than 500 ms (an indicator of potential of ventricular tachyarrhythmia) were reported. No phenotypic resistance developed to any of the drugs in the regimen. INTERPRETATION The combination of moxifloxacin, pretomanid, and pyrazinamide, was safe, well tolerated, and showed superior bactericidal activity in drug-susceptible tuberculosis during 8 weeks of treatment. Results were consistent between drug-susceptible and MDR tuberculosis. This new regimen is ready to enter phase 3 trials in patients with drug-susceptible tuberculosis and MDR-tuberculosis, with the goal of shortening and simplifying treatment. FUNDING Global Alliance for TB Drug Development.

Isoniazid pharmacokinetics in children treated for respiratory tuberculosis.

Aims: To define the pharmacokinetics of isoniazid (INH) in children with tuberculosis in relation to the N-acetyltransferase 2 (NAT2) genotype. Methods: The first order elimination rate constant (k) and area under the concentration curve (AUC) were calculated in 64 children <13 years of age (median 3.8) with respiratory tuberculosis from INH concentrations determined 2–5 hours after a 10 mg/kg INH dose. The NAT2 genotype was determined; 25 children were classified as homozygous slow (SS), 24 as heterozygous fast (FS), and 15 as homozygous fast (FF) acetylators. Results: The mean (SD) k values of the genotypes differed significantly from one another: SS 0.254 (0.046), FS 0.513 (0.074), FF 0.653 (0.117). Within each genotype a median regression of k on age showed a significant decrease in k with age. The mean (SD) INH concentrations (mg/l) two hours after INH administration were SS 8.599 (1.974), FS 5.131 (1.864), and FF 3.938 (1.754). A within genotype regression of 2-hour INH concentrations on age showed a significant increase with age. A within genotype regression of 3-hour, 4-hour, and 5-hour concentrations on age also showed a significant increase with age in each instance. In ethnically similar adults, mean (SD) 2-hour INH concentrations (mg/l) for each genotype were significantly higher than the children’s: SS 10.942 (1.740), FS 8.702 (1.841), and FF 6.031 (1.431). Conclusions: Younger children eliminate INH faster than older children and, as a group, faster than adults, and require a higher mg/kg body weight INH dose to achieve serum concentrations comparable to adults.

Respiratory tuberculosis in childhood: the diagnostic value of clinical features and special investigations.

During a 16-month period children presenting to a pediatric outpatient facility from an area with a high tuberculosis incidence (> 400/100 000) and suspected of having respiratory tuberculosis (TB) were evaluated for close contact with adult pulmonary tuberculosis, weight loss, symptom duration, respiratory signs, lymphadenopathy and hepatosplenomegaly and by chest radiography and tuberculin testing (Mantoux or tine). Probable tuberculosis was diagnosed in 258 children and was confirmed in 109 (42%) patients with a mean age of 31 months by culture of Mycobacterium tuberculosis from gastric aspirate or another source. Eleven children with confirmed TB had a normal chest radiograph. After review of special investigations, clinical course and follow-up of the remaining 149 children, 86 children (58%) with a mean age of 32.4 months were considered to have probable TB and 63 (42%) with a mean age of 27 months not to have TB. Significantly fewer children in the “not TB” group than in the confirmed and probable TB groups had a close adult pulmonary tuberculosis contact (13 (21%) and 95 (49%), respectively; P < 0.01). There was no difference between the “not TB” group and the confirmed and probable TB groups in the proportion presenting with weight loss, cough or other respiratory symptoms, a symptom duration >2 weeks, the presence of bronchial breathing, wheeze, hepatomegaly or splenomegaly or peripheral lymphadenopathy. Final diagnoses in the “not TB” group included bacterial or viral pneumonia or bron-chopneumonia in 37, asthma often accompanied by segmental collapse in 9 and cavitating pneumonia in 3 children. On the one hand children in whom there were sufficient criteria to be considered probable cases of TB were subsequently thought not to have TB; on the other hand 11 (10%) of children with TB confirmed by culture of Mycobacterium tuberculosis from gastric aspirate had a normal chest radiograph.

The global burden of tuberculosis--combating drug resistance in difficult times.

Disturbingly, there were an estimated 500,000 cases of multidrug-resistant (MDR) tuberculosis in 2007, and 55 countries had reported cases of extensively drug-resistant (XDR) tuberculosis by the end of 2008. Dr. Peter Donald and Paul van Helden write that these figures highlight a potential threat to our ability to treat tuberculosis.