Kelly E. Dooley

Tuberculosis and diabetes mellitus: convergence of two epidemics

The link between diabetes mellitus and tuberculosis has been recognised for centuries. In recent decades, tuberculosis incidence has declined in high-income countries, but incidence remains high in countries that have high rates of infection with HIV, high prevalence of malnutrition and crowded living conditions, or poor tuberculosis control infrastructure. At the same time, diabetes mellitus prevalence is soaring globally, fuelled by obesity. There is growing evidence that diabetes mellitus is an important risk factor for tuberculosis and might affect disease presentation and treatment response. Furthermore, tuberculosis might induce glucose intolerance and worsen glycaemic control in people with diabetes. We review the epidemiology of the tuberculosis and diabetes epidemics, and provide a synopsis of the evidence for the role of diabetes mellitus in susceptibility to, clinical presentation of, and response to treatment for tuberculosis. In addition, we review potential mechanisms by which diabetes mellitus can cause tuberculosis, the effects of tuberculosis on diabetic control, and pharmacokinetic issues related to the co-management of diabetes and tuberculosis.

TMC207: the first compound of a new class of potent anti-tuberculosis drugs

Disease caused by Mycobacterium tuberculosis continues as a global epidemic: over 2 billion people harbor latent TB infection, and more than 9 million new TB cases, of whom 500,000 are multidrug-resistant (MDR), and nearly 2 million deaths are estimated to occur each year. New drugs are required to shorten treatment duration of drug-sensitive TB and for the treatment of MDR-TB. TMC207 is a first-in-class diarylquinoline compound with a novel mechanism of action, the inhibition of bacterial ATP synthase, and potent activity against drug-sensitive and drug-resistant TB. It has bactericidal and sterilizing activity against M. tuberculosis and other mycobacterial species, but little activity against other bacteria. In a Phase II efficacy study conducted in patients with MDR-TB taking TMC207 plus a standard background regimen, the drug appeared to be safe and well tolerated, and showed significant efficacy after 2 months of treatment with conversion rates of sputum culture of 48% (vs 9% in the placebo group). Given the product development partnership between Tibotec and the TB Alliance, the strategies of using TMC207 in shorter first-line regimens or using it in second-line regimens for drug-resistant M. tuberculosis infections are both being pursued. No clinical data of TMC207 in TB patients with HIV coinfection have been published; drug-drug interaction studies with antiretrovirals are being conducted. Finally, the remarkable sterilizing capacity of TMC207 also makes it an attractive drug in the strategy of TB elimination. Current and future studies will determine the role of TMC207 in a shortened treatment regimen for drug-sensitive TB, a more effective and better-tolerated regimen for MDR-TB, the treatment of latent TB infection, and intermittent-TB treatment regimens.

Empiric Treatment of Community-Acquired Pneumonia with Fluoroquinolones, and Delays in the Treatment of Tuberculosis

Fluoroquinolones, which are widely used to treat community-acquired pneumonia, also have excellent in vitro activity against Mycobacterium tuberculosis. A retrospective cohort study was conducted among adults with culture-confirmed tuberculosis to assess the effect of empiric fluoroquinolone therapy on delays in the treatment of tuberculosis. Sixteen (48%) of 33 patients received fluoroquinolones for presumed bacterial pneumonia before tuberculosis was diagnosed and treated. There were no differences between the group who did and the group who did not receive fluoroquinolones, except that patients who received fluoroquinolones were more likely to present with shortness of breath. Among patients treated empirically with fluoroquinolones, the median time between presentation to the hospital and initiation of antituberculosis treatment was 21 days (interquartile range, 5-32 days); among those who were not, it was 5 days (interquartile range, 1-16 days; P=.04). Initial empiric therapy with a fluoroquinolone was associated with a delay in the initiation of appropriate antituberculosis treatment.

The epidemiology, pathogenesis, transmission, diagnosis, and management of multidrug-resistant, extensively drug-resistant, and incurable tuberculosis

Global tuberculosis incidence has declined marginally over the past decade, and tuberculosis remains out of control in several parts of the world including Africa and Asia. Although tuberculosis control has been effective in some regions of the world, these gains are threatened by the increasing burden of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis. XDR tuberculosis has evolved in several tuberculosis-endemic countries to drug-incurable or programmatically incurable tuberculosis (totally drug-resistant tuberculosis). This poses several challenges similar to those encountered in the pre-chemotherapy era, including the inability to cure tuberculosis, high mortality, and the need for alternative methods to prevent disease transmission. This phenomenon mirrors the worldwide increase in antimicrobial resistance and the emergence of other MDR pathogens, such as malaria, HIV, and Gram-negative bacteria. MDR and XDR tuberculosis are associated with high morbidity and substantial mortality, are a threat to health-care workers, prohibitively expensive to treat, and are therefore a serious public health problem. In this Commission, we examine several aspects of drug-resistant tuberculosis. The traditional view that acquired resistance to antituberculous drugs is driven by poor compliance and programmatic failure is now being questioned, and several lines of evidence suggest that alternative mechanisms-including pharmacokinetic variability, induction of efflux pumps that transport the drug out of cells, and suboptimal drug penetration into tuberculosis lesions-are likely crucial to the pathogenesis of drug-resistant tuberculosis. These factors have implications for the design of new interventions, drug delivery and dosing mechanisms, and public health policy. We discuss epidemiology and transmission dynamics, including new insights into the fundamental biology of transmission, and we review the utility of newer diagnostic tools, including molecular tests and next-generation whole-genome sequencing, and their potential for clinical effectiveness. Relevant research priorities are highlighted, including optimal medical and surgical management, the role of newer and repurposed drugs (including bedaquiline, delamanid, and linezolid), pharmacokinetic and pharmacodynamic considerations, preventive strategies (such as prophylaxis in MDR and XDR contacts), palliative and patient-orientated care aspects, and medicolegal and ethical issues.

Safety, tolerability, and pharmacokinetics of the HIV integrase inhibitor dolutegravir given twice daily with rifampin or once daily with rifabutin: Results of a phase 1 study among healthy subjects

Background:Cotreatment of tuberculosis (TB) and HIV among coinfected patients is now the standard of care. Rifampin (RIF) is a standard part of TB treatment but is a potent inducer of drug metabolizing enzymes. This study evaluated the effect of RIF or rifabutin (RBT) on the pharmacokinetics of the investigational HIV integrase inhibitor, dolutegravir (DTG). Methods:Phase I pharmacokinetic drug interaction study. In arm 1, healthy subjects received 50 mg of DTG once daily for 7 days (period 1), then 50 mg of DTG twice daily for 7 days (period 2), then 50 mg of DTG twice daily together with 600 mg of RIF once daily for 14 days (period 3). In arm 2, subjects received 50 mg of DTG once daily for 7 days (period 1) then 50 mg of DTG once daily together with 300 mg of RBT once daily for 14 days (period 2). PK sampling was performed at the end of each period. Results:In arm 1, comparing period 3 to period 1, the geometric mean ratio (GMR) for the 24-hour area under the time–concentration curve (AUC0–24) was 1.33 [90% confidence interval (CI): 1.14 to 1.53], and the GMR for the trough (C&tgr;) was 1.22 (90% CI: 1.01 to 1.48). Comparing period 2 to period 1 in arm 2, the GMR for the AUC0–24 was 0.95 (90% CI: 0.82 to 1.10), and the GMR for the C&tgr; was 0.70 (90% CI: 0.57 to 0.87). Conclusions:Regimens including twice-daily DTG and RIF or once-daily DTG and RBT may represent a new treatment option for patients who require concomitant treatment of HIV and TB.

Fluoroquinolone Resistance in Patients with Newly Diagnosed Tuberculosis

Fluoroquinolones are widely used for the treatment of bacterial infections and are also second-line therapy for tuberculosis. However, fluoroquinolone resistance in patients with newly diagnosed cases of tuberculosis is not routinely assessed. We performed in vitro susceptibility testing of Mycobacterium tuberculosis to fluoroquinolones for all culture-confirmed tuberculosis cases in adults that were diagnosed at Johns Hopkins Hospital (Baltimore) between January 1998 and March 2002. Fifty-five patients were included in the study; 19 received fluoroquinolone monotherapy before the initiation of antituberculosis therapy. Two of 55 M. tuberculosis isolates (4%; 95% CI, 1%-13%) had decreased susceptibility to fluoroquinolones, including 2 of 19 of those from patients who had received fluoroquinolones (11%; 95% CI, 1%-33%) and 0 of 36 isolates from those who had not (95% CI, 0%-10%). The 2 fluoroquinolone-resistant M. tuberculosis strains were both from patients with acquired immunodeficiency syndrome and a CD4+ lymphocyte count of <50 cells/mm3. The incidence of M. tuberculosis fluoroquinolone resistance in this small sample of patients with newly diagnosed tuberculosis was high, particularly among patients with prior fluoroquinolone exposure.

World Health Organization Group 5 Drugs for the Treatment of Drug-Resistant Tuberculosis: Unclear Efficacy or Untapped Potential?

BACKGROUND Treatment of multidrug-resistant or extensively drug-resistant tuberculosis (DR-tuberculosis) is challenging because commonly used second-line drugs are poorly efficacious and highly toxic. Although World Health Organization group 5 drugs are not recommended for routine use because of unclear activity, some may have untapped potential as more efficacious or better tolerated alternatives. METHODS We conducted an exhaustive review of in vitro, animal, and clinical studies of group 5 drugs to identify critical research questions that may inform their use in current treatment of DR-tuberculosis and clinical trials of new DR-tuberculosis regimens. RESULTS Clofazimine may contribute to new short-course DR-tuberculosis regimens. Beta-lactams merit further evaluation-specifically optimization of dose and schedule. Linezolid appears to be effective but is frequently discontinued due to toxicity. Thiacetazone is too toxic to warrant further evaluation. Mycobacterium tuberculosis has intrinsic inducible resistance to clarithromycin. CONCLUSIONS Clofazimine and beta-lactams may have unrealized potential in the treatment of DR-tuberculosis and warrant further study. Serious toxicities or intrinsic resistance limit the utility of other group 5 drugs. For several group 5 compounds, better understanding of structure-toxicity relationships may lead to better-tolerated analogs.

Risk factors for tuberculosis treatment failure, default, or relapse and outcomes of retreatment in Morocco

BackgroundPatients with tuberculosis require retreatment if they fail or default from initial treatment or if they relapse following initial treatment success. Outcomes among patients receiving a standard World Health Organization Category II retreatment regimen are suboptimal, resulting in increased risk of morbidity, drug resistance, and transmission.. In this study, we evaluated the risk factors for initial treatment failure, default, or early relapse leading to the need for tuberculosis retreatment in Morocco. We also assessed retreatment outcomes and drug susceptibility testing use for retreatment patients in urban centers in Morocco, where tuberculosis incidence is stubbornly high.MethodsPatients with smear- or culture-positive pulmonary tuberculosis presenting for retreatment were identified using clinic registries in nine urban public clinics in Morocco. Demographic and outcomes data were collected from clinical charts and reference laboratories. To identify factors that had put these individuals at risk for failure, default, or early relapse in the first place, initial treatment records were also abstracted (if retreatment began within two years of initial treatment), and patient characteristics were compared with controls who successfully completed initial treatment without early relapse.Results291 patients presenting for retreatment were included; 93% received a standard Category II regimen. Retreatment was successful in 74% of relapse patients, 48% of failure patients, and 41% of default patients. 25% of retreatment patients defaulted, higher than previous estimates. Retreatment failure was most common among patients who had failed initial treatment (24%), and default from retreatment was most frequent among patients with initial treatment default (57%). Drug susceptibility testing was performed in only 10% of retreatment patients. Independent risk factors for failure, default, or early relapse after initial treatment included male gender (aOR = 2.29, 95% CI 1.10-4.77), positive sputum smear after 3 months of treatment (OR 7.14, 95% CI 4.04-13.2), and hospitalization (OR 2.09, 95% CI 1.01-4.34). Higher weight at treatment initiation was protective. Male sex, substance use, missed doses, and hospitalization appeared to be risk factors for default, but subgroup analyses were limited by small numbers.ConclusionsOutcomes of retreatment with a Category II regimen are suboptimal and vary by subgroup. Default among patients receiving tuberculosis retreatment is unacceptably high in urban areas in Morocco, and patients who fail initial tuberculosis treatment are at especially high risk of retreatment failure. Strategies to address risk factors for initial treatment default and to identify patients at risk for failure (including expanded use of drug susceptibility testing) are important given suboptimal retreatment outcomes in these groups.

Drug Interactions Involving Combination Antiretroviral Therapy and Other Anti-Infective Agents: Repercussions for Resource-Limited Countries

The scale-up of antiretroviral treatment (ART) in resource-poor countries has been impressive, both in its scope and in its impact. In 2003, 400,000 people in resource-limited settings were receiving antiretroviral drugs (ARVs); by 2006, this number had increased to 2 million people [1]. Treatment of common infections occurring with HIV is also increasing, as most HIV-infected persons live in areas where infectious diseases such as tuberculosis (TB) and malaria are prevalent. The use of over-the-counter and natural health products is also pervasive [2]. Therefore, the management of HIV infection in these settings will require multiple concurrent medications, with a potential for drug interactions and overlapping toxicities. Although in recent years there has been a significant expansion in access to ARVs in resource-poor countries, options are limited in most areas. In 2006, 95% of individuals receiving first-line ARVs in resource-poor settings were being treated with 1 of 4 fixed-dose regimens: stavudine (d4T) lamivudine (3TC) nevirapine (NVP); zidovudine (AZT) 3TC NVP; d4T 3TC efavirenz (EFV); or AZT 3TC EFV [1]. Currently, the World Health Organization (WHO) recommends a first-line regimen that includes a thiacytadine analogue (either 3TC or emtricitabine), a companion nucleoside reverse-transcriptase inhibitor (NRTI) (either AZT, tenofovir [TDF], abacavir [ABC], or d4T), and a nonNRTI (NNRTI) (either EFV or NVP) [3]. Second-line regimens include 2 previously unused NRTIs (didanosine, TDF, ABC, 3TC, and/or AZT) coupled with either a ritonavir (RTV)– boosted protease inhibitor (PI) (either lopinavir, saquinavir, indinavir, atazanavir, or fosamprenavir) or unboosted nelfinavir. Available antimicrobial drugs such as itraconazole, ketoconazole, clarithromycin, and rifampin have serious interactions or overlapping toxicities with ARVs. Cost, as well as political and infrastructural constraints, limits access to drugs—such as fluconazole, azithromycin, and rifabutin—that have fewer interactions [4]. Thus, even when drug interactions are well characterized, clinicians caring for HIV-infected patients have few options. Now that HIV treatment is available in many resource-limited countries, clinicians must understand the basic principles of drug metabolism. In this review, we describe new insights into mechanisms of CYP450 induction and inhibition. In addition, we provide a comprehensive review of the major interactions between ARVs recommended by WHO as firstor second-line therapy for HIV in resource-limited settings and drugs used to treat TB, malaria, and fungal, bacterial, and parasitic diseases.

Daily Rifapentine for Treatment of Pulmonary Tuberculosis. A Randomized, Dose-Ranging Trial

RATIONALE Rifapentine has potent activity in mouse models of tuberculosis chemotherapy but its optimal dose and exposure in humans are unknown. OBJECTIVES We conducted a randomized, partially blinded dose-ranging study to determine tolerability, safety, and antimicrobial activity of daily rifapentine for pulmonary tuberculosis treatment. METHODS Adults with sputum smear-positive pulmonary tuberculosis were assigned rifapentine 10, 15, or 20 mg/kg or rifampin 10 mg/kg daily for 8 weeks (intensive phase), with isoniazid, pyrazinamide, and ethambutol. The primary tolerability end point was treatment discontinuation. The primary efficacy end point was negative sputum cultures at completion of intensive phase. MEASUREMENTS AND MAIN RESULTS A total of 334 participants were enrolled. At completion of intensive phase, cultures on solid media were negative in 81.3% of participants in the rifampin group versus 92.5% (P = 0.097), 89.4% (P = 0.29), and 94.7% (P = 0.049) in the rifapentine 10, 15, and 20 mg/kg groups. Liquid cultures were negative in 56.3% (rifampin group) versus 74.6% (P = 0.042), 69.7% (P = 0.16), and 82.5% (P = 0.004), respectively. Compared with the rifampin group, the proportion negative at the end of intensive phase was higher among rifapentine recipients who had high rifapentine areas under the concentration-time curve. Percentages of participants discontinuing assigned treatment for reasons other than microbiologic ineligibility were similar across groups (rifampin, 8.2%; rifapentine 10, 15, or 20 mg/kg, 3.4, 2.5, and 7.4%, respectively). CONCLUSIONS Daily rifapentine was well-tolerated and safe. High rifapentine exposures were associated with high levels of sputum sterilization at completion of intensive phase. Further studies are warranted to determine if regimens that deliver high rifapentine exposures can shorten treatment duration to less than 6 months. Clinical trial registered with www.clinicaltrials.gov (NCT 00694629).