Few eligible for the newly recommended short course MDR-TB regimen at a large Mumbai private clinic

Drug resistance and epidemiological success of modern Mycobacterium tuberculosis lineages in western India

BACKGROUND

Transmission is contributing to the slow decline of tuberculosis (TB) incidence globally. Drivers of TB transmission in India, the country estimated to carry a quarter of the World's burden, are not well studied. We conducted a genomic epidemiology study to compare epidemiological success, host factors and drug resistance (DR) among the four major Mycobacterium tuberculosis (Mtb) lineages (L1-4) circulating in Pune, India.

METHODS

We performed whole-genome sequencing (WGS) of Mtb sputum culture-positive isolates from participants in two prospective cohort studies and predicted genotypic susceptibility using a validated random forest model. We used maximum likelihood estimation to build phylogenies. We compared lineage specific phylogenetic and time-scaled metrics to assess epidemiological success.

RESULTS

Of the 642 isolates that underwent WGS, 612 met sequence quality criteria. Most isolates belonged to L3 (44.6%). The majority (61.1%) of multidrug-resistant isolates belonged to L2 (P < 0.001). In molecular dating, L2 demonstrated a higher rate and more recent resistance acquisition. We measured higher clustering, and time-scaled haplotypic density (THD) for L4 and L2 compared to L3 and/or L1 suggesting higher epidemiological success. L4 demonstrated higher THD and clustering (OR 5.1 (95% CI 2.3-12.3) in multivariate models controlling for host factors and DR.

CONCLUSION

L2 shows a higher frequency of DR and both L2 and L4 demonstrate evidence of higher epidemiological success than L3 or L1 in the study setting. Our findings highlight the need for contact tracing around TB cases, and heightened surveillance of TB DR in India.

Pharmacokinetic analysis of linezolid for multidrug resistant tuberculosis at a tertiary care centre in Mumbai, India

Linezolid is an oxazolidinone used to treat multidrug-resistant tuberculosis (MDR-TB), including in the recently-endorsed shorter 6-month treatment regimens. Due to its narrow therapeutic index, linezolid is often either dose-adjusted or discontinued due to intolerance or toxicity during treatment, and the optimal balance between linezolid efficacy and toxicity remains unclear. India carries a significant burden of MDR-TB cases in the world, but limited information on the pharmacokinetics of linezolid and minimum inhibitory concentration (MIC) distribution is available from Indian MDR-TB patients. We enrolled participants from a tertiary care centre in Mumbai, India, treated for MDR-TB and receiving linezolid daily doses of 600 or 300 mg. Pharmacokinetic visits were scheduled between 1 and 15 months after treatment initiation to undergo intensive or sparse blood sampling. Linezolid concentration versus time data were analysed using non-linear mixed-effects modelling, with simulations to evaluate doses for different scenarios. We enrolled 183 participants (121 females), with a median age of 26 years (interquartile range [IQR] 21-35), weight 55.0 kg (IQR 45.6-65.8), and fat-free mass 38.7 kg (IQR 32.7-46.0). Linezolid pharmacokinetics was best described by a one-compartment model with first-order elimination allometrically scaled by fat-free mass and transit compartment absorption. The typical clearance value was 3.81 L/h. Simulations predicted that treatment with 300 mg daily achieves a high probability of target attainment (PTA) when linezolid MIC was ≤0.25 mg/L (61.5% of participant samples tested), while 600 mg daily would be required if MIC were 0.5 mg/L (29% of samples). While linezolid 300 mg daily is predicted to achieve effective targets for the majority of adults with MDR-TB, it failed to achieve the therapeutic target for 21% participants. A dose of 600 mg had a PTA >90% for all susceptible samples, but with a higher likelihood of exceeding toxicity thresholds (31% vs 9.6%). These data suggest potential benefit to individualized dosing taking host and microbial characteristics into account to improve the likelihood of treatment efficacy while minimizing risk of toxicity from linezolid for the treatment of MDR-TB. Further prospective evaluation in different clinical settings is urgently needed to inform safety and efficacy of these lower doses.

Integrating services for HIV and multidrug-resistant tuberculosis: A global cross-sectional survey among ART clinics in low- and middle-income countries

Tuberculosis (TB) is the leading cause of death among PLHIV and multidrug-resistant-TB (MDR-TB) is associated with high mortality. We examined the management for adult PLHIV coinfected with MDR-TB at ART clinics in lower income countries. Between 2019 and 2020, we conducted a cross-sectional survey at 29 ART clinics in high TB burden countries within the global IeDEA network. We used structured questionnaires to collect clinic-level data on the TB and HIV services and the availability of diagnostic tools and treatment for MDR-TB. Of 29 ART clinics, 25 (86%) were in urban areas and 19 (66%) were tertiary care clinics. Integrated HIV-TB services were reported at 25 (86%) ART clinics for pan-susceptible TB, and 14 (48%) clinics reported full MDR-TB services on-site, i.e. drug susceptibility testing [DST] and MDR-TB treatment. Some form of DST was available on-site at 22 (76%) clinics, while the remainder referred testing off-site. On-site DST for second-line drugs was available at 9 (31%) clinics. MDR-TB treatment was delivered on-site at 15 (52%) clinics, with 10 individualizing treatment based on DST results and five using standardized regimens alone. Bedaquiline was routinely available at 5 (17%) clinics and delamanid at 3 (10%) clinics. Although most ART clinics reported having integrated HIV and TB services, few had fully integrated MDR-TB services. There is a continued need for increased access to diagnostic and treatment options for MDR-TB patients and better integration of MDR-TB services into the HIV care continuum.

Cycloserine did not increase depression incidence or severity at standard dosing for multidrug-resistant tuberculosis

In 2018 cycloserine was elevated to World Health Organization (WHO) group B status for multidrug-resistant tuberculosis (MDR-TB), and is recommended in longer MDR-TB treatment regimens [1]. Inclusion of cycloserine is associated with improved MDR-TB treatment success and reduced mortality, but is limited by treatment-associated depression, psychosis and neuropathy, forcing 9% of patients to stop therapy [1–3]. Cycloserine also demonstrates wide interindividual pharmacokinetic variation, with significant food and drug interactions, leaving nearly half of patients with inappropriate drug levels [4, 5]. Optimal dosing is unknown [6], but modelling studies suggest doses from 250 mg to 750 mg twice daily, with 500 mg twice daily for paucibacillary disease and 750 mg twice daily for cavitary pulmonary disease [7]. Therefore, clinicians must balance the known benefits of cycloserine with the dearth of susceptibility- and drug-monitoring capacity and the spectre of treatment-limiting side-effects. To evaluate the impact of cycloserine prescription and dose on incident depression during MDR-TB treatment, we analysed longitudinal cohort data from India.

In a longitudinal cohort of MDR-TB patients receiving individualised, DST-based treatment, neither the inclusion of cycloserine in a multidrug regimen nor the dose used (up to 750 mg daily) significantly increased incidence of depression during treatment https://bit.ly/3GtQmOH

Empiric Addition of Quinolones to First-Line Tuberculosis Treatment Is Associated With Increased Odds of XDR-TB

Background

Multidrug-resistant tuberculosis (MDR-TB) represents a significant clinical and public health challenge worldwide. Out of concern for possible resistance, some providers prescribe first- and second-line tuberculosis treatment together before completing drug susceptibility testing (DST), which may increase emergent resistance.

Methods

MDR-TB patients at an Indian referral center were enrolled in an observational cohort. Participants with drug susceptibility test (DST) results were categorized as prescribed fluoroquinolones, streptomycin, both, or neither with first-line treatment before DST. Odds of additional resistance to fluoroquinolones and aminoglycosides (XDR-TB) were calculated in association with empiric combined first- and second-line treatment before DST.

Results

Of 494 participants, 130 (26.3%) received a fluoroquinolone or streptomycin with first-line drugs before DST. Odds of XDR-TB were associated with fluoroquinolone prescription before DST [odds ratio (OR): 2.19, 95% confidence interval (CI): 1.26–3.76). The association with XDR-TB persisted in multivariable analysis (adjusted OR: 2.43, 95% CI: 1.19-4.91). Combined empiric first- and second-line treatment before DST was not associated with eventual outcomes.

Conclusion

Many participants received empiric combined first- and second-line drugs before DST, which was associated with XDR-TB. To minimize emerging resistance, treatment-associated side effects, and provide the best possible care, this approach should be discouraged in favor of early DST and DST-guided TB treatment.

Increased Moxifloxacin Dosing Among Patients With Multidrug-Resistant Tuberculosis With Low-Level Resistance to Moxifloxacin Did Not Improve Treatment Outcomes in a Tertiary Care Center in Mumbai, India

Background

Mycobacterium tuberculosis (Mtb) strains resistant to isoniazid and rifampin (multidrug-resistant tuberculosis [MDR-TB]) are increasingly reported worldwide, requiring renewed focus on the nuances of drug resistance. Patients with low-level moxifloxacin resistance may benefit from higher doses, but limited clinical data on this strategy are available.

Methods

We conducted a 5-year observational cohort study of MDR-TB patients at a tertiary care center in India. Participants with Mtb isolates resistant to isoniazid, rifampin, and moxifloxacin (at the 0.5 µg/mL threshold) were analyzed according to receipt of high-dose moxifloxacin (600 mg daily) as part of a susceptibility-guided treatment regimen. Univariable and multivariable Cox proportional hazard models assessed the relationship between high-dose moxifloxacin and unfavorable treatment outcomes.

Results

Of 354 participants with MDR-TB resistant to moxifloxacin, 291 (82.2%) received high-dose moxifloxacin. The majority experienced good treatment outcomes (200 [56.5%]), which was similar between groups (56.7% vs 54.0%, P = .74). Unfavorable outcomes were associated with greater extent of radiographic disease, lower initial body mass index, and concurrent treatment with fewer drugs with confirmed phenotypic susceptibility. Treatment with high-dose moxifloxacin was not associated with improved outcomes in either unadjusted (hazard ratio [HR], 1.2 [95% confidence interval {CI}, .6–2.4]) or adjusted (HR, 0.8 [95% CI, .5–1.4]) models but was associated with joint pain (HR, 3.2 [95% CI, 1.2–8.8]).

Conclusions

In a large observational cohort, adding high-dose (600 mg) moxifloxacin to a drug susceptibility test–based treatment regimen for MDR-TB was associated with increased treatment-associated side effects without improving overall outcomes and should be avoided for empiric treatment of moxifloxacin-resistant MDR-TB.

The pipeline of new molecules and regimens against drug-resistant tuberculosis

The clinical development and regulatory approval of bedaquiline, delamanid and pretomanid over the last decade brought about significant progress in the management of drug-resistant tuberculosis, providing all-oral regimens with favorable safety profiles. The Nix-TB and ZeNix trials of a bedaquiline - pretomanid - linezolid regimen demonstrated for the first time that certain forms of drug-resistant tuberculosis can be cured in the majority of patients within 6 months. Ongoing Phase 3 studies containing these drugs may further advance optimized regimen compositions. Investigational drugs in clinical development that target clinically validated mechanisms, such as second generation oxazolidinones (sutezolid, delpazolid, TBI-223) and diarylquinolines (TBAJ-876 and TBAJ-587) promise improved potency and/or safety compared to the first-in-class drugs. Compounds with novel targets involved in diverse bacterial functions such as cell wall synthesis (DrpE1, MmpL3), electron transport, DNA synthesis (GyrB), cholesterol metabolism and transcriptional regulation of ethionamide bioactivation pathways have advanced to early clinical studies with the potential to enhance antibacterial activity when added to new or established anti-TB drug regimens. Clinical validation of preclinical in vitro and animal model predictions of new anti-TB regimens may further improve the translational value of these models to identify optimal anti-TB therapies.

Controlling the drug-resistant tuberculosis epidemic in India: challenges and implications

India has a higher tuberculosis (TB) burden than any other country, accounting for an estimated one-fourth of the global burden. Drug-resistant tuberculosis (DR-TB) presents a major public health problem in India. Patients with DR-TB often require profound changes in their drug regimens, which are invariably linked to poor treatment adherence and sub-optimal treatment outcomes compared to drug-sensitive TB. The challenge of addressing DR-TB is critical for India, as India contributes over 27% of global DR-TB cases. In recent decades, India has been proactive in its battle against TB, even implementing a revised National Strategic Plan to eliminate TB by 2025. However, to achieve this ambitious goal, the country will need to take a multifaceted approach with respect to its management of DR-TB. Despite concerted efforts made by the National TB Elimination Program, India faces substantial challenges with regard to DR-TB care, especially in peripheral and resource-limited endemic zones. This article describes some of the major challenges associated with mitigating the growing DR-TB epidemic in India and their implications.

Fluroquinolone drug resistance among MDR-TB patients increases the risk of unfavourable interim microbiological treatment outcome: An observational study

OBJECTIVES

Sputum culture conversion at the end of the intensive phase of multidrug-resistant tuberculosis (MDR-TB) treatment is a key predictor for successful treatment outcome. This observational study was undertaken to assess the interim microbiological outcome of a cohort of rifampicin-resistant (RR)-TB patients with variable resistance to second-line drugs.

METHODS

During Jan-Apr 2018, we consecutively enrolled 100 RR-TB patients, who underwent phenotypic drug susceptibility testing (DST) to assess baseline resistance to second-line drugs. Following RR-TB diagnosis, these patients were started on MDR-TB treatment. After 6 months of treatment, sputum culture conversion status was determined. Data were analysed to assess the impact of resistance to second-line drugs on culture conversion.

RESULTS

DST of 100 RR-TB patients showed a high resistance to fluoroquinolones (FQs; levofloxacin 56%; moxifloxacin 44%) followed by kanamycin (8%) and capreomycin (6%). None of the patients were resistant to the other drugs tested (amikacin, clofazimine and linezolid). At 6-month treatment follow-up, 28 patients had been lost to follow-up and eight had died. Microbiological outcome was obtained from the remaining 64 patients, but successful culture conversion was achieved in only 62.5% of the patients. FQ resistance was found to be a strong predictor (P<0.001) for unfavourable microbiological outcome.

CONCLUSION

The rate of FQ resistance in RR/MDR-TB is high and has strong association with unsuccessful interim microbiological outcome of conventional MDR-TB treatment.

Clinical features associated with linezolid resistance among multidrug resistant tuberculosis patients at a tertiary care hospital in Mumbai, India

Background

Multidrug-resistant tuberculosis (MDR-TB) is an increasing problem worldwide, and 24% occurs in India. Linezolid is associated with improved MDR-TB treatment outcomes but causes significant side-effects and drug susceptibility testing (DST) is rarely available. This study assessed whether clinical factors could predict linezolid resistance.

Methods

An observational cohort of adults and adolescents with MDR-TB at a tertiary care hospital in Mumbai, India was analyzed for clinical, laboratory, and radiographic findings associated with linezolid resistance.

Results

In total, 343 MDR-TB patients had linezolid DST performed, and 23 (6.7%) had linezolid-resistant MDR-TB. Univariable analysis associated linezolid resistance with underweight (odds ratio (OR)–1.07, 95% confidence interval (CI):1.01–1.12); number of previous providers (OR:1.03, 95% CI:1.00–1.05); previous treatment with linezolid (OR:1.12, 95% CI:1.06–1.05), bedaquiline (OR:1.55, 95% CI:1.22–1.98), or clofazimine (OR:1.08 95% CI:1.03–1.16); cavitary disease (OR:1.10, 95% CI:1.04–1.16) and percent lung involvement (OR:1.02, 95% CI:1.01–1.03) on radiograph. DST associated linezolid resistance with resistance to fluoroquinolones (OR:1.08, 95% CI:1.01–1.14), injectables (OR:1.09, 95% CI:1.03–1.15), ethionamide (OR:1.09, 95% CI:1.03–1.15), and PAS (OR:1.13, 95% CI:1.06–1.21). In multivariate analysis, only prior linezolid and percent lung involvement were associated with linezolid resistance.

Conclusion

To maximize treatment benefits while minimizing toxicity, DST remains an important tool to identify linezolid resistance.