Fluoroquinolones: are they essential to treat multidrug-resistant tuberculosis?

Effectiveness, cost, and safety of four regimens recommended by WHO for RR/MDR-TB treatment: a cohort study in Eastern China

BACKGROUND

To compare the effectiveness, cost, and safety of four regimens recommended by the World Health Organization (WHO) for rifampicin resistance/multidrug-resistance tuberculosis (RR/MDR-TB) Treatment in Eastern China.

METHODS

We performed a cohort study among patients with RR/MDR between 2020 and 2022 in Jiangsu Province. The treatment success rate, cost, and drug adverse reaction rate were compared.

RESULTS

Between 2020 and 2022, 253 RR/MDR-TB patients were enrolled in the study. 37 (14.62%), 76 (30.04%), 74 (29.25%), and 66 (26.09%) patients had the short-term regimens, the new long-term oral regimens, the new long-term injectable regimens, and the traditional long-term regimens, respectively. The treatment success rate was the highest among patients treated with the short-term regimen (75.68%) and was the lowest among patients treated with the traditional long-term regimens (60.61%). The estimated mean cost per favorable outcome was 142.61 thousand Chinese Yuan (CNY), and the short-term regimens showed the lowest cost in the four regimes (88.51 thousand CNY vs. 174.24 thousand CNY, 144.00 thousand CNY, and 134.98 thousand CNY). Incremental cost-effectiveness ratios of the short-term regimens, the new long-term oral regimen, and the new long-term injectable regimens were -3083.04, 6040.09, and 819.68 CNY compared to the traditional long-term regimens.

CONCLUSIONS

For RR/MDR-TB patients in China who meet the criteria for short-term regimens, the short-term regimens were proven to be the most cost-effective of the four regimens recommended by WHO. For RR/MDR-TB patients in China who don't meet the criteria for short-term regimens, the new long-term injectable regimens are more cost-effective than the remaining two regimens.

Improved outcomes following addition of bedaquiline and clofazimine to a treatment regimen for multidrug-resistant tuberculosis

OBJECTIVE

To investigate if the addition of bedaquiline and clofazimine to a treatment regimen for multidrug-resistant tuberculosis (MDR-TB) could improve patient outcomes.

METHODS

A prospective, randomized, controlled study was conducted in patients with MDR-TB. Treatment was for 18 months. Patients in the experimental group received bedaquiline and clofazimine in addition to their regular treatment regimen whereas patients in the control group did not.

RESULTS

68 patients with MDR-TB were randomised to treatment, 34 to each group. At the end of treatment, cure rates were statistically significantly greater for the experimental group compared with the control group (82% vs. 56%). There was no difference between groups in the number of severe adverse events (3[9%]) in both groups and none were skin-related.

CONCLUSIONS

The addition of bedaquiline and clofazimine to the treatment regimen significantly improves outcomes for patients with MDR-TB. Clinicians should be aware of the clinical benefits of this addition but be mindful of contraindications and adverse effects.

Treatment Outcome of a Shorter Regimen Containing Clofazimine for Multidrug-resistant Tuberculosis: A Randomized Control Trial in China

BACKGROUND

The emergence of multidrug-resistant tuberculosis (MDR-TB) poses a serious obstacle to global TB control programs.

METHODS

We carried out a prospective, randomized, multicenter study in China that was focused on the potential of a shorter regimen containing clofazimine (CFZ) for the treatment of MDR-TB. There were 135 MDR-TB cases that met eligibility requirements and were randomly stratified into either the control group or experimental group. Patients in the control group received an 18-month treatment regimen, whereas patients in the experimental group received a 12-month treatment regimen containing CFZ.

RESULTS

At the completion of the treatment period, the difference in sputum-culture conversion rates between the experimental group and the control group was not significant. Notably, by the end of 3 months of treatment, 68.7% patients receiving the experimental regimen had sputum-culture conversion, as compared with 55.9% of those receiving the control regimen; this was a significant difference, suggesting an early sputum conversion (P = .04). There were 67 adverse events reported in 56 patients in this study, including 32 in the control group and 35 in the experimental group. No significant difference in the overall incidences of adverse events was observed between the 2 groups.

CONCLUSIONS

The MDR-TB patients treated with the shorter regimen containing CFZ had a comparable successful outcome rate when compared to those with the standard regimen. The patients assigned to the experimental group achieved more rapid sputum-culture conversion, reflecting superior antimicrobial activity against MDR-TB.

CLINICAL TRIALS REGISTRATION

Chinese Clinical Trial Registry ChiCTR 1800020391.

Towards tailored regimens in the treatment of drug-resistant tuberculosis: a retrospective study in two Italian reference Centres

Background

The increased incidence of drug-resistant TB is a major challenge for effective TB control. Limited therapeutic options and poor treatment outcomes of DR-TB may increase drug-resistance rates. The objective of the study is to retrospectively compare MDR-TB and pre-XDR-TB treatment regimens and outcomes in two large TB reference centres in Italy from January 2000 to January 2015.

Methods

A retrospective, multicentre study was conducted at the Regional TB Reference Centre Villa Marelli Institute (Milan) and at the Reference Center for MDR-TB and HIV-TB, Eugenio Morelli Hospital (Sondalo). The supra-national Reference Laboratory in Milan performed DST. Inclusion criteria were: age ≥ 18 and culture-confirmed diagnosis of MDR- or pre-XDR TB. Chi-square or Fisher exact test was used to detect differences in the comparison between treatment outcomes, therapeutic regimens, and drug-resistances. Computations were performed with STATA 15.

Results

A total of 134 patients were selected. Median (IQR) age at admission was 33 (26–41) years and 90 patients (67.2%) were male. Pulmonary TB was diagnosed in 124 (92.5%) patients. MDR- and pre-XDR-TB cases were 91 (67.9%) and 43 (32.1%), respectively. The WHO shorter MDR-TB regimen could have been prescribed in 16/84 (19.1%) patients. Treatment success was not statistically different between MDR- and pre-XDR-TB (81.3% VS. 81.4%; P = 0.99). Mortality in MDR-TB and pre-XDR-TB groups was 4.4 and 9.3%, respectively (P = 0.2). Median duration of treatment was 18 months and a total of 110 different regimens were administered. Exposure to linezolid, meropenem, and amikacin was associated with a better outcome in both groups (P = 0.001, P < 0.001, and P = 0.004, respectively).

Conclusions

Tailored treatment regimens based on DST results can achieve successful outcomes in patients with pre-XDR-TB.

Predicting the Outcomes of New Short-Course Regimens for Multidrug-Resistant Tuberculosis Using Intrahost and Pharmacokinetic-Pharmacodynamic Modeling

Short-course regimens for multidrug-resistant tuberculosis (MDR-TB) are urgently needed. Limited data suggest that the new drug bedaquiline (BDQ) may have the potential to shorten MDR-TB treatment to less than 6 months when used in conjunction with standard anti-TB drugs. However, the feasibility of BDQ in shortening MDR-TB treatment duration remains to be established. Mathematical modeling provides a platform to investigate different treatment regimens and predict their efficacy. We developed a mathematical model to capture the immune response to TB inside a human host environment. This model was then combined with a pharmacokinetic-pharmacodynamic model to simulate various short-course BDQ-containing regimens. Our modeling suggests that BDQ could reduce MDR-TB treatment duration to just 18 weeks (4 months) while still maintaining a very high treatment success rate (100% for daily BDQ for 2 weeks, or 95% for daily BDQ for 1 week during the intensive phase). The estimated time to bacterial clearance of these regimens ranges from 27 to 33 days. Our findings provide the justification for empirical evaluation of short-course BDQ-containing regimens. If short-course BDQ-containing regimens are found to improve outcomes, then we anticipate clear cost savings and a subsequent improvement in the efficiency of national TB programs.

Current Status of Fluoroquinolone Use for Treatment of Tuberculosis in a Tertiary Care Hospital in Korea

Background

Fluoroquinolones are considered important substitutes for the treatment of tuberculosis. This study investigates the current status of fluoroquinolone for the treatment of tuberculosis.

Methods

In 2009, a retrospective analysis was performed at one tertiary referral center for 953 patients diagnosed with tuberculosis.

Results

A total of 226 patients (23.6%), who received fluoroquinolone at any time during treatment for tuberculosis, were enrolled in this study. The most common reasons for fluoroquinolone use were adverse events due to other anti-tuberculosis drugs (52.7%), drug resistance (23.5%), and underlying diseases (16.8%). Moxifloxacin (54.0%, 122/226) was the most commonly administered fluoroquinolone, followed by levofloxacin (36.3%, 82/226) and ofloxacin (9.7%, 22/226). The frequency of total adverse events from fluoroquinolone-containing anti-tuberculosis medication was 22.6%, whereas fluoroquinolone-related adverse events were estimated to be 2.2% (5/226). The most common fluoroquinolone-related adverse events were gastrointestinal problems (3.5%, 8/226). There were no significant differences in the treatment success rate between the fluoroquinolone and fluoroquinolone-naïve groups (78.3% vs. 78.4%, respectively).

Conclusion

At our institution, fluoroquinolones are commonly used for the treatment of both multidrug-resistant tuberculosis and susceptible tuberculosis, especially as a substitute for adverse event-related drugs. Considering the low adverse event rates and the comparable treatment success rates, fluoroquinolones seem to be an invaluable drug for the treatment of tuberculosis.

Cost-effectiveness of bedaquiline in MDR and XDR tuberculosis in Italy

Objective: To evaluate the cost-effectiveness of bedaquiline plus background drug regimens (BR) for multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) in Italy. Methods: A Markov model was adapted to the Italian setting to estimate the incremental cost-effectiveness ratio (ICER) of bedaquiline plus BR (BBR) versus BR in the treatment of MDR-TB and XDR-TB over 10 years, from both the National Health Service (NHS) and societal perspective. Cost-effectiveness was evaluated in terms of life-years gained (LYG). Clinical data were sourced from trials; resource consumption for compared treatments was modelled according to advice from an expert clinicians panel. NHS tariffs for inpatient and outpatient resource consumption were retrieved from published Italian sources. Drug costs were provided by reference centres for disease treatment in Italy. A 3% annual discount was applied to both cost and effectiveness. Deterministic and probabilistic sensitivity analyses were conducted. Results: Over 10 years, BBR vs. BR alone is cost-effective, with ICERs of €16,639/LYG and €4081/LYG for the NHS and society, respectively. The sensitivity analyses confirmed the robustness of the results from both considered perspectives. Conclusion: In Italy, BBR vs. BR alone has proven to be cost-effective in the treatment of MDR-TB and XDR-TB under a range of scenarios.

New Antituberculosis Drugs: From Clinical Trial to Programmatic Use

Treatment of multidrug-resistant tuberculosis (MDR-TB) cases is challenging because it relies on second-line drugs that are less potent and more toxic than those used in the clinical management of drug-susceptible TB. Moreover, treatment outcomes for MDR-TB are generally poor compared to drug sensitive disease, highlighting the need for of new drugs. For the first time in more than 50 years, two new anti-TB drugs were approved and released. Bedaquiline is a first-in-class diarylquinoline compound that showed durable culture conversion at 24 weeks in phase IIb trials. Delamanid is the first drug of the nitroimidazole class to enter clinical practice. Similarly to bedaquiline results of phase IIb studies showed increased sputum-culture conversion at 2 months and better final treatment outcomes in patients with MDR-TB. Among repurposed drugs linezolid and carbapenems may represent a valuable drug to treat cases of MDR and extensively drug-resistant TB. The recommended regimen for MDR-TB is the combination of at least four drugs to which M. tuberculosis is likely to be susceptible for the duration of 20 months. Drugs are chosen with a stepwise selection process through five groups on the basis of efficacy, safety, and cost. Clinical phase III trials on new regimen are ongoing that could prove transformative against MDR-TB, by being shorter (six months), simpler (an all-oral regimen) and safer than current standard therapy. It is fundamental that the adoption of the new drugs is done responsibly to avoid inappropriate use. Concentration of in-patient MDR-TB treatment in specialized centers could be considered in countries with low numbers of cases in order to provide appropriate clinical case management and to prevent emergence of drug resistance.

Fluoroquinolone-resistant tuberculosis: implications in settings with weak healthcare systems

Fluoroquinolones (FQ) play an essential role in the treatment and control of multidrug-resistant tuberculosis (MDR-TB). They are also being evaluated as part of newer regimens under development for drug-sensitive TB. As newer FQ-based regimens are explored, knowledge of FQ resistance data from high TB burden countries becomes essential. We examine available FQ resistance data from high TB burden countries and demonstrate the need for comprehensive surveys to evaluate FQ resistance in these countries. The factors driving FQ resistance in such conditions and the cost of such resistance to weak healthcare systems are discussed. The need for a comprehensive policy for addressing the issue of FQ resistance is highlighted.

Benzotriazole: An overview on its versatile biological behavior

Discovered in late 1960, azoles are heterocyclic compounds class which constitute the largest group of available antifungal drugs. Particularly, the imidazole ring is the chemical component that confers activity to azoles. Triazoles are obtained by a slight modification of this ring and similar or improved activities as well as less adverse effects are reported for triazole derivatives. Consequently, it is not surprising that benzimidazole/benzotriazole derivatives have been found to be biologically active. Since benzimidazole has been widely investigated, this review is focused on defining the place of benzotriazole derivatives in biomedical research, highlighting their versatile biological properties, the mode of action and Structure Activity Relationship (SAR) studies for a variety of antimicrobial, antiparasitic, and even antitumor, choleretic, cholesterol-lowering agents.

Treatment outcome of multi-drug resistant tuberculosis in the United Kingdom: retrospective-prospective cohort study from 2004 to 2007

United Kingdom (UK) guidelines recommend at least 18 months treatment for patients with multidrug-resistant tuberculosis (MDR-TB). Prior to 2008, data on treatment outcome were only available at 12 months and therefore the proportion completing treatment was unknown. This retrospective-prospective cohort study reports on treatment outcomes for MDR-TB patients notified between 2004 and 2007 and examines factors associated with successful outcomes. 70.6% (144/204) completed treatment in 24 months or more, 6.9% (14) stopped treatment, 6.9% (14) died, 7.8% (16) were lost to follow up, 0.5% (1) relapsed and 4.4% (9) were transferred overseas. Following adjustment for age, being non-UK born, non-compliance and having co-morbidities, treatment with a fluoroquinolone (OR 3.09; 95% CI 1.21-7.88; p<0.05) or bacteriostatic drug (OR 4.23; 95% CI 1.60-11.18; p<0.05) were independently associated with successful treatment outcome. Treatment completion for MDR-TB cases remains below the World Health Organization (WHO) target. Our findings support current WHO guidelines for MDR-TB treatment. The UK should consider adopting individualised regimens based on WHO recommended drugs, taking into account drug sensitivities. Improving treatment completion rates will be key to tackling further drug resistance and transmission from untreated infectious cases.

Management of difficult multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis: update 2012

Multidrug-resistant (MDR) tuberculosis (TB) denotes bacillary resistance to at least isoniazid and rifampicin. Extensively drug-resistant (XDR) TB is MDR-TB with additional bacillary resistance to any fluoroquinolone and at least one second-line injectable drugs. Rooted in inadequate TB treatment and compounded by a vicious circle of diagnostic delay and improper treatment, MDR-TB/XDR-TB has become a global epidemic that is fuelled by poverty, human immunodeficiency virus (HIV) and neglect of airborne infection control. The majority of MDR-TB cases in some settings with high prevalence of MDR-TB are due to transmission of drug-resistant bacillary strains to previously untreated patients. Global efforts in controlling MDR-TB/XDR-TB can no longer focus solely on high-risk patients. It is difficult and costly to treat MDR-TB/XDR-TB. Without timely implementation of preventive and management strategies, difficult MDR-TB/XDR-TB can cripple global TB control efforts. Preventive strategies include prompt diagnosis with adequate TB treatment using the directly observed therapy, short-course (DOTS) strategy and drug-resistance programmes, airborne infection control, preventive treatment of TB/HIV, and optimal use of antiretroviral therapy. Management strategies for established cases of difficult MDR-TB/XDR-TB rely on harnessing existing drugs (notably newer generation fluoroquinolones, high-dose isoniazid, linezolid and pyrazinamide with in vitro activity) in the best combinations and dosing schedules, together with adjunctive surgery in carefully selected cases. Immunotherapy may also have a role in the future. New diagnostics, drugs and vaccines are required to meet the challenge, but science alone is insufficient. Difficult MDR-TB/XDR-TB cannot be tackled without achieving high cure rates with quality DOTS and beyond, and concurrently addressing poverty and HIV.

TBNET - Collaborative research on tuberculosis in Europe

Networking is a key feature of scientific success. The Tuberculosis Network European Trialsgroup (TBNET) was founded in 2006 as a non-profit, non-governmental peer-initiated scientific organization to collaboratively address research priorities in the area of tuberculosis in Europe. Today, TBNET is the largest tuberculosis research organization in Europe with nearly 500 members from 22 EU countries and 49 countries worldwide (www.tb-net.org). Apart from small multicenter basic research studies, a particular strength of TBNET is the performance of large collaborative projects, pan-European multicenter studies and database projects. In recent years, research from TBNET has substantially contributed to the understanding of the management, risk and prognosis of patients with multidrug (MDR) and extensively drug-resistant (XDR) tuberculosis and led to a better understanding of the clinical value of novel tests for the identification of adults and children with tuberculosis and latent infection with Mycobacterium tuberculosis. In 2009, two branches of TBNET were founded to specifically address tuberculosis in the pediatric population (ptbnet) and non-tuberculous mycobacterial diseases (NTM-NET). In addition to the research activities, TBNET is developing expert consensus documents for clinical management and provides training and capacity building especially for members from Eastern European countries, where tuberculosis is still a prevalent health problem.

Multidrug- and extensively drug-resistant TB in persons living with HIV

Multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) represent an emerging public health problem worldwide. The collision of the HIV epidemic with MDR- and XDR-TB has produced disastrous consequences for individual patients, with very high mortality rates reported in outbreaks among HIV-infected individuals. There is evidence of the importance of primary resistance among HIV-infected persons with XDR-TB, while the relevance of acquired resistance during inappropriate treatment among HIV-infected persons is uncertain, and TB case management of HIV-infected and -uninfected persons is based on similar standard practices to ensure treatment adherence. Current data show a limited geographical overlap of the XDR-TB and HIV epidemics: such data must be interpreted cautiously owing to the lack of adequate testing for both conditions. In fact, there are signs of an evolving epidemiological situation characterized by increased outbreak risk in concentrated areas owing to the extension of the HIV epidemic into areas of high MDR-TB prevalence and of the MDR-TB epidemic into areas of high HIV prevalence. There is a paucity of studies on treatment outcome among HIV-infected XDR-TB patients, and the only available report shows extremely high mortality rate and very short survival. Rapid diagnosis of TB and MDR-TB will be pivotal to reduce mortality among persons co-infected with HIV. However, while rapid diagnosis of MDR-TB is feasible with molecular assays on direct specimens, molecular approaches are still insensitive for XDR-TB diagnosis. There is speculative evidence that effective strategies for early HIV diagnosis and treatment will play a role in limiting the spread, and possibly improving the outcome of XDR-TB. Prevention is currently the mainstay of XDR-TB control in HIV communities. Strategies for infection control based on administrative procedures, environmental control and respiratory protection should be a priority for countries where both XDR-TB and HIV are prevalent. However, only the comprehensive implementation of the full Stop TB Strategy may be expected to curb the devastating impact of XDR-TB on HIV-infected persons.

Antimycobacterial drugs currently in Phase II clinical trials and preclinical phase for tuberculosis treatment

INTRODUCTION

In 2010, about 8.8 million new cases of tuberculosis were recorded and 1.1 million people died of tuberculosis worldwide. Although numbers are in decrease since 2006, tuberculosis still represents a global issue and a major public health threat, due to appearance of multidrug-resistant and extensively drug-resistant tuberculosis cases. Although anti-tuberculosis drugs currently used are effective against tuberculosis, they present however more and more limits, especially in treating complex cases of tuberculosis, increasing therefore the need to develop new tools and approaches to treat tuberculosis today.

AREAS COVERED

In this review, we describe anti-tuberculosis drugs in Phase II clinical trials and in preclinical phase that are likely to play a crucial role in the management of tuberculosis cases in a near future. SQ109, TMC207, nitroimidazoles, and oxazolidinones are currently in Phase II clinical trials while BDM31343, SQ641, CPZEN-45, RBx 8700, DC-159a, and BTZ043 are in preclinical phase.

CONCLUSION

These drugs, alone or in different combinations represent a promising future for the treatment of tuberculosis. Continual conjugative efforts between governments and private organizations worldwide are essential for building new strategies for discovery and the development of new anti-tuberculosis drugs.

Pyrazinamide may improve fluoroquinolone-based treatment of multidrug-resistant tuberculosis

The role of pyrazinamide in the current treatment of multidrug-resistant (MDR) tuberculosis (TB) is uncertain. From a territory-wide registry of MDR-TB cases diagnosed between 1995 and 2009, we assembled a cohort of 194 patients with MDR pulmonary TB given fluoroquinolone-containing regimens. Stratified by pyrazinamide use and susceptibility, there were 83 users with pyrazinamide-susceptible MDR-TB (subgroup A), 24 users with pyrazinamide-resistant MDR-TB (subgroup B), 40 nonusers with pyrazinamide-susceptible MDR-TB (subgroup C), and 47 nonusers with pyrazinamide-resistant MDR-TB (subgroup D). We estimated the adjusted risk ratio (ARR) of early sputum culture conversion (ARR-culture) that occurred within 90 days posttreatment and that of cure or treatment completion (ARR-success) that occurred by 2 years posttreatment due to pyrazinamide use with susceptibility. In comparison with subgroup B, ARR-culture and ARR-success were 1.38 (95% confidence interval [CI], 0.89 to 2.12) and 1.38 (95% confidence interval [CI], 0.88 to 2.17), respectively. Corresponding findings were 0.99 (95% CI, 0.81 to 1.22) and 0.99 (95% CI, 0.78 to 1.26) in comparison with subgroup C and 1.09 (95% CI, 0.84 to 1.42) and 0.94 (95% CI, 0.74 to 1.20) in comparison with subgroup D. Early culture conversion significantly increased the incidence proportion of cure or treatment completion by 71% (95% CI, 26% to 133%). Selection bias among pyrazinamide nonusers might have underestimated the role of pyrazinamide. Comparison of pyrazinamide users showed that pyrazinamide increased the incidence proportion of early culture conversion and that of cure or treatment completion by a best estimate of 38% for both. This magnitude of change exceeded the 15 to 20% increase in the 2-month culture conversion rate of drug-susceptible TB that results from adding pyrazinamide to isoniazid and rifampin. Pyrazinamide is likely important in fluoroquinolone-based treatment of MDR-TB.

Predictors of poor outcomes among patients treated for multidrug-resistant tuberculosis at DOTS-plus projects

The Objective of this analysis was to identify predictors of death, failure, and default among MDR-TB patients treated with second-line drugs in DOTS-plus projects in Estonia, Latvia, Philippines, Russia, and Peru, 2000-2004. Risk ratios (RR) with 95% confidence intervals (CI) were calculated using multivariable regression. Of 1768 patients, treatment outcomes were: cure/completed - 1156 (65%), died - 200 (11%), default - 241 (14%), failure - 118 (7%). Independent predictors of death included: age>45 years (RR = 1.90 (95%CI 1.29-2.80), HIV infection (RR = 4.22 (2.65-6.72)), extrapulmonary disease (RR = 1.54 (1.04-2.26)), BMI<18.5 (RR = 2.71 (1.91-3.85)), previous use of fluoroquinolones (RR = 1.91 (1.31-2.78)), resistance to any thioamide (RR = 1.59 (1.14-2.22)), baseline positive smear (RR = 2.22 (1.60-3.10)), no culture conversion by 3rd month of treatment (RR = 1.69 (1.19-2.41)); failure: cavitary disease (RR = 1.73 (1.07-2.80)), resistance to any fluoroquinolone (RR = 2.73 (1.71-4.37)) and any thioamide (RR = 1.62 (1.12-2.34)), and no culture conversion by 3rd month (RR = 5.84 (3.02-11.27)); default: unemployment (RR = 1.50 (1.12-2.01)), homelessness (RR = 1.52 (1.00-2.31)), imprisonment (RR = 1.86 (1.42-2.45)), alcohol abuse (RR = 1.60 (1.18-2.16)), and baseline positive smear (RR = 1.35 (1.07-1.71)). Patients with biomedical risk factors for treatment failure or death should receive heightened medical attention. To prevent treatment default, management of patients who are unemployed, homeless, alcoholic, or have a prison history requires extra measures to insure treatment completion.

Population pharmacokinetics and pharmacodynamics of ofloxacin in South African patients with multidrug-resistant tuberculosis

Despite the important role of fluoroquinolones and the predominant use of ofloxacin for treating multidrug-resistant tuberculosis in South Africa, there are limited data on ofloxacin pharmacokinetics in patients with multidrug-resistant tuberculosis, no ofloxacin pharmacokinetic data from South African patients, and no direct assessment of the relationship between ofloxacin pharmacokinetics and the MIC of ofloxacin of patient isolates. Our objectives are to describe ofloxacin pharmacokinetics in South African patients being treated for multidrug-resistant tuberculosis and assess the adequacy of ofloxacin drug exposure with respect to the probability of pharmacodynamic target attainment (area under the time curve/MIC ratio of at least 100). Sixty-five patients with multidrug-resistant tuberculosis were recruited from 2 hospitals in South Africa. We determined the ofloxacin MICs for the Mycobacterium tuberculosis isolates from baseline sputum specimens. Patients received daily doses of 800 mg ofloxacin, in addition to other antitubercular drugs. Patients underwent pharmacokinetic sampling at steady state. NONMEM was used for data analysis. The population pharmacokinetics of ofloxacin in this study has been adequately described. The probability of target attainment expectation in the study population was 0.45. Doubling the dose to 1,600 mg could increase this to only 0.77. The currently recommended ofloxacin dose appeared inadequate for the majority of this study population. Studies to assess the tolerability of higher doses are warranted. Alternatively, ofloxacin should be replaced with more potent fluoroquinolones.

Protecting the tuberculosis drug pipeline: stating the case for the rational use of fluoroquinolones

The use of fluoroquinolones (FQs) to treat lower respiratory tract infections (LTRI) other than tuberculosis (TB) allows selection of FQ-resistant TB when TB is misdiagnosed. This study maps national guidelines on the use of FQs for LRTI in Europe and determines the risk of FQ-resistant TB upon FQ treatment before TB diagnosis. A questionnaire was developed to map existing national LRTI and community-acquired pneumonia (CAP) guidelines. A systematic review and meta-analysis were performed to determine the risk of FQ-resistant TB if prescribed FQs prior to TB diagnosis. 15 (80%) out of 24 responding European Respiratory Society national delegates reported having national LRTI management guidelines, seven including recommendations on FQ use and one recommending FQs as the first-choice drug. 18 out of 24 countries had national CAP management guidelines, two recommending FQ as the drug of choice. Six studies investigating FQ exposure and the risk of FQ-resistant TB were analysed. TB patients had a three-fold higher risk of having FQ-resistant TB when prescribed FQs before TB diagnosis, compared to non FQ-exposed patients (OR 2.81, 95% CI 1.47-5.39). Although the majority of European countries hold national LRTI/CAP guidelines, our results suggest that a risk of developing FQ resistance exists. Further strengthening of, and adherence to, guidelines is needed to ensure rational use of FQs.

Characteristics and treatment outcomes of patients with MDR and XDR tuberculosis in a TB referral hospital in Beijing: a 13-year experience

Background

Information on treatment outcomes among hospitalized patients with multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) are scarce in China.

Methodology/Principal Findings

We conducted this retrospective study to analyze the characteristics and treatment outcomes in MDR- and XDR-TB patients in the 309 Hospital in Beijing, China during 1996–2009. Socio-demographic and clinical data were retrieved from medical records and analyzed. Logistic regression analysis was performed to identify risk factors associated with poor treatment outcomes and Cox proportional hazards regression model was further used to determine risk factors associated with death in TB patients. Among the 3,551 non-repetitive hospitalized TB patients who had drug susceptibility testing (DST) results, 716 (20.2%) had MDR-TB and 51 (1.4%) had XDR-TB. A total of 3,270 patients who had medical records available were used for further analyses. Treatment success rates (cured and treatment completed) were 90.9%, 53.4% and 29.2% for patients with non-MDR-TB, patients with MDR-TB excluding XDR-TB and patients with XDR-TB, respectively. Independent risk factors associated with poor treatment outcomes in MDR-TB patients included being a migrant (adjusted OR = 1.77), smear-positivity at treatment onset (adjusted OR = 1.94) and not receiving 3 or more potentially effective drugs (adjusted OR = 3.87). Independent risk factors associated with poor treatment outcomes in XDR-TB patients were smear-positivity at treatment onset (adjusted OR = 10.42) and not receiving 3 or more potentially effective drugs (adjusted OR = 14.90). The independent risk factors associated with death in TB patients were having chronic obstructive pulmonary disease (adjusted HR = 5.25) and having hypertension (adjusted HR = 4.31).

Conclusions/Significance

While overall satisfactory treatment success for non-MDR-TB patients was achieved, more intensive efforts should be made to better manage MDR- and XDR-TB cases in order to improve their treatment outcomes and to minimize further emergence of so-called totally drug-resistant TB cases.

Outcome of hospitalized MDR-TB patients: Israel 2000-2005

MDR-TB has emerged in Israel following an immigrations wave from the Former Soviet Union (FSU) and Ethiopia. The purpose of this study was to outline characteristics and outcome of hospitalized MDR-TB patients. We retrospectively summarized charts of MDR-TB patients hospitalized in the national referral tuberculosis centers from January 2000 to December 2005, and followed them for 2 years. One hundred thirty-two patients were identified with a median age of 40 years and male predominance (77%). The majority of the patients were immigrants from FSU (83%) and Ethiopia (7.6%). They were characterized by alcohol (25.8%) and IV drug abuse (23.5%), presented with advanced disease manifested by hypoalbuminemia (50.8%) and smear positivity (70.5%). Cure was achieved in 50.3% and 30.4% died. Factors independently associated with death were patients' age (OR = 1.036 for each year, 95%CI 1.0-1.1, p = 0.014), hypoalbuminemia (OR = 2.95, 95%CI 1.1-7.6, p = 0.025), smear positivity at diagnosis (OR = 3.7, 95%CI 1.2-11.4, p = 0.023), alcohol abuse (OR = 4.8, 95%CI 1.7-13.7, p = 0.004) and XDR-TB resistance pattern (OR 8.3, 95%CI 1.5-44.6, p = 0.014). This study brings out the poor prognosis of a highly vulnerable immigration population. Efforts should be focused on earlier diagnosis and treatment in a well controlled hospital environment and to professional support groups to attend to this population's special needs.

Best drug treatment for multidrug-resistant and extensively drug-resistant tuberculosis

Multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis are generally thought to have high mortality rates. However, many cases can be treated with the right combination and rational use of available antituberculosis drugs. This Review describes the evidence available for each drug and discusses the basis for recommendations for the treatment of patients with MDR and XDR tuberculosis. The recommended regimen is the combination of at least four drugs to which the Mycobacterium tuberculosis isolate is likely to be susceptible. Drugs are chosen with a stepwise selection process through five groups on the basis of efficacy, safety, and cost. Among the first group (the oral first-line drugs) high-dose isoniazid, pyrazinamide, and ethambutol are thought of as an adjunct for the treatment of MDR and XDR tuberculosis. The second group is the fluoroquinolones, of which the first choice is high-dose levofloxacin. The third group are the injectable drugs, which should be used in the following order: capreomycin, kanamycin, then amikacin. The fourth group are called the second-line drugs and should be used in the following order: thioamides, cycloserine, then aminosalicylic acid. The fifth group includes drugs that are not very effective or for which there are sparse clinical data. Drugs in group five should be used in the following order: clofazimine, amoxicillin with clavulanate, linezolid, carbapenems, thioacetazone, then clarithromycin.

Rapid assays for fluoroquinolone resistance in Mycobacterium tuberculosis: a systematic review and meta-analysis

OBJECTIVES

Multidrug-resistant tuberculosis has emerged as a global health threat. Given poor treatment outcomes of fluoroquinolone-resistant multidrug-resistant tuberculosis, there is a pressing need for rapid drug susceptibility testing of multidrug-resistant Mycobacterium tuberculosis against fluoroquinolones. This review aims at evaluating these rapid assays.

METHODS

PubMed and OvidSP were used to search MEDLINE and EMBASE for publications in English regarding rapid assays that tested ofloxacin, levofloxacin or moxifloxacin. Studies were included only in the concurrent presence of sensitivity and specificity data. Summary estimates of sensitivity and specificity were generated by the bivariate random effects model when there were at least three sets of data under the same assay category that tested the same fluoroquinolone with reference to a standard test.

RESULTS

Of 108 articles identified, 24 articles were included in a meta-analysis of rapid assays that tested ofloxacin in culture isolates. Overall, rapid genotypic assays targeting gyrA only are significantly less specific (96% versus 99%) and non-significantly less sensitive (88% versus 94%) than rapid phenotypic assays. To test for the presence or absence of ofloxacin resistance to a certainty threshold of 90%, the required pre-test prevalence ranges of ofloxacin resistance for genotypic assays targeting gyrA only are 29%-47% overall, 36%-55% for PCR-DNA sequencing and 23%-44% for others. Corresponding ranges are 7%-65% for phenotypic assays overall and 3%-75% for Mycobacteria Growth Indicator Tube (MGIT).

CONCLUSIONS

Assuming that the mean pre-test prevalence of fluoroquinolone resistance in culture isolates of multidrug-resistant M. tuberculosis is approximately 20%, rapid genotypic assays other than PCR-DNA sequencing, targeting gyrA only, can reliably screen for ofloxacin resistance.

Early treatment outcomes and HIV status of patients with extensively drug-resistant tuberculosis in South Africa: a retrospective cohort study

BACKGROUND

Data from Kwazulu Natal, South Africa, suggest that almost all patients with extensively drug-resistant (XDR) tuberculosis are HIV-positive, with a fatal outcome. Since, there are few data for the treatment-related outcomes of XDR tuberculosis in settings with a high HIV prevalence, we investigated the associations of these diseases in such settings to formulate recommendations for control programmes.

METHODS

In a retrospective cohort study, we analysed the case records of patients (>16 years old) with XDR tuberculosis (culture-proven at diagnosis) between August, 2002, and February, 2008, at four designated provincial treatment facilities in South Africa. We used Cox proportional hazards regression models to assess risk factors associated with the outcomes-mortality and culture conversion.

FINDINGS

195 of 227 patients were analysed. 21 died before initiation of any treatment, and 174 patients (82 with HIV infection) were treated. 62 (36%) of these patients died during follow-up. The number of deaths was not significantly different in patients with or without HIV infection: 34 (41%) of 82 versus 28 (30%) of 92 (p=0.13). Treatment with moxifloxacin (hazard ratio 0.11, 95% CI 0.01-0.82; p=0.03), previous culture-proven multidrug-resistant tuberculosis (5.21, 1.93-14.1; p=0.001), and number of drugs used in a regimen (0.59, 0.45-0.78, p<0.0001) were independent predictors of death. Fewer deaths occurred in patients with HIV infection given highly active antiretroviral therapy than in those who were not (0.38, 0.18-0.80; p=0.01). 33 (19%) of 174 patients showed culture conversion, of which 23 (70%) converted within 6 months of initiation of treatment.

INTERPRETATION

In South Africa, patients with XDR tuberculosis, a substantial proportion of whom are not infected with HIV, have poor management outcomes. Nevertheless, survival in patients with HIV infection is better than previously reported. The priorities for the country are still prevention of XDR tuberculosis, and early detection and management of multidrug-resistant and XDR tuberculosis through strengthened programmes and laboratory capacity.

FUNDING

South African Medical Research Council, European Union Framework 7 program, and European Developing Countries Clinical Trials Partnership.

Drug-resistant tuberculosis: past, present, future

In a population of Mycobacterium tuberculosis, random chromosomal mutation that results in genetic resistance to anti-tuberculosis (TB) drugs occurs at a relatively low frequency. Anti-TB drugs impose selection pressure so that mycobacterial mutants gradually outnumber susceptible bacilli and emerge as the dominant strains. Resistance to two or more anti-TB drugs represents cumulative results of sequential mutation. The fourth report on global anti-TB drug resistance provides the latest data on the extent of such problem in the world. The median prevalence of multi-drug-resistant TB (MDR-TB) in new TB cases was 1.6%, and in previously treated TB cases 11.7%. Of the half a million MDR-TB cases estimated to have emerged in 2006, 50% were in China and India. The optimal duration of any given combination of anti-TB drugs for treatment of MDR- and extensively drug-resistant TB (XDR-TB) has not been defined in controlled clinical trials. Standardized treatment may be feasible for MDR-TB patients not previously treated with second-line drugs, but a different strategy needs to be applied in the treatment of MDR-TB patients who have received second-line drugs before. Unfortunately, the reliability of drug susceptibility testing of most second-line anti-TB drugs is still questionable. Drug-resistant TB is not necessarily less virulent. Findings from modelling exercise warned that if MDR-TB case detection and treatment rates increase to the World Health Organization target of 70%, without simultaneously increasing MDR-TB cure rates, XDR-TB prevalence could increase exponentially. Prevention of development of drug resistance must be accorded the top priority in the era of MDR-/XDR-TB.

Multidrug- and extensively drug-resistant tuberculosis, Germany

We evaluated risk factors and treatment outcomes associated with multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) in Germany in 2004-2006. In 177 (4%) of 4,557 culture-positive TB cases, Mycobacterium tuberculosis isolates were identified as MDR TB; an additional 7 (0.15%) met criteria for XDR TB. Of these 184 patients, 148 (80%) were born in countries of the former Soviet Union. In patients with XDR TB, hospitalization was longer (mean +/- SD 202 +/- 130 vs. 123 +/- 81 days; p = 0.015) and resistance to all first-line drugs was more frequent (36% vs. 86%; p = 0.013) than in patients with MDR TB. Seventy-four (40%) of these 184 patients received treatment with linezolid. Treatment success rates ranged from 59% for the entire cohort (59% for MDR TB and 57% for XDR TB) to 87% for those with a definitive outcome (n = 125; 89% for MDR TB and 80% for XDR TB). Extensive drug susceptibility testing and availability of second- and third-line drugs under inpatient management conditions permit relatively high treatment success rates in MDR- and XDR TB.

Treatment of extensively drug-resistant tuberculosis in Tomsk, Russia: a retrospective cohort study

BACKGROUND

Mycobacterium tuberculosis strains that cause untreatable drug-resistant disease are a threat worldwide. We describe the treatment, management, and outcomes of patients with extensively drug-resistant tuberculosis in Tomsk, Russia.

METHODS

We undertook a retrospective cohort study of 608 patients with multidrug resistant tuberculosis who had treatment in civilian or prison services, between Sept 10, 2000, and Nov 1, 2004, according to the treatment strategy recommended by WHO. Clinical characteristics, management practices, and treatment outcomes of patients with extensively drug-resistant (XDR) tuberculosis and non-extensively drug-resistant (non-XDR) tuberculosis are described. The main outcome was the frequency of poor and favourable outcomes at the end of treatment.

FINDINGS

Of 608 patients with multidrug resistant tuberculosis, 29 (4.8%) patients had baseline XDR tuberculosis. Treatment failure was more common in patients with XDR tuberculosis than in those with non-XDR tuberculosis (31%vs 8.5%, p=0.0008). 48.3% of patients with XDR tuberculosis and 66.7% of patients with non-XDR tuberculosis had treatment cure or completion (p=0.04). The frequency and management of adverse events did not differ between patients with XDR and non-XDR tuberculosis.

INTERPRETATION

The chronic features of tuberculosis in these patients suggest that extensively drug-resistant tuberculosis may be acquired through previous treatments that include second-line drugs. Aggressive management of this infectious disease is feasible and can prevent high mortality rates and further transmission of drug-resistant strains of Mycobacterium tuberculosis.