Acquired rifampicin resistance in thrice-weekly antituberculosis therapy: impact of HIV and antiretroviral therapy

Association between HIV and acquisition of rifamycin resistance with first-line TB treatment: a systematic review and meta-analysis

BACKGROUND

Multi-drug or rifamycin-resistant tuberculosis (MDR/RR-TB) is an important public health concern, including in settings with high HIV prevalence. TB drug resistance can be directly transmitted or arise through resistance acquisition during first-line TB treatment. Limited evidence suggests that people living with HIV (PLHIV) might have an increased risk of acquired rifamycin-resistance (ARR).

METHODS

To assess HIV as a risk factor for ARR during first-line TB treatment, a systematic review and meta-analysis was conducted. ARR was defined as rifamycin-susceptibility at treatment start with rifamycin-resistance diagnosed during or at the end of treatment, or at recurrence. PubMed/MEDLINE, CINAHL, Cochrane Library, and Google Scholar databases were searched from inception to 23 May 2024 for articles in English; conference abstracts were also searched from 2004 to 2021. The Mantel-Haenszel random-effects model was used to estimate the pooled odds ratio of any association between HIV and ARR among individuals receiving first-line TB treatment.

RESULTS

Ten studies that included data collected between 1990 and 2014 were identified: five from the United States, two from South Africa and one each from Uganda, India and Moldova. A total of 97,564 individuals were included across all studies, with 13,359 (13.7%) PLHIV. Overall, 312 (0.32%) acquired rifamycin-resistance, among whom 115 (36.9%) were PLHIV. The weighted odds of ARR were 4.57 (95% CI, 2.01-10.42) times higher among PLHIV compared to HIV-negative individuals receiving first-line TB treatment.

CONCLUSION

The available data, suggest that PLHIV have an increased ARR risk during first-line TB treatment. Further research is needed to clarify specific risk factors, including advanced HIV disease and TB disease severity. Given the introduction of shorter, 4-month rifamycin-based regimens, there is an urgent need for additional data on ARR, particularly for PLHIV.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022327337.

Acquired rifamycin resistance among patients with tuberculosis and HIV in new York City, 2001-2023

Introduction

Acquired rifamycin resistance (ARR) in tuberculosis (TB) has been associated with HIV infection and can necessitate complicated TB treatment regimens, particularly in people living with HIV (PLWH). This work examines clinical characteristics and treatment outcomes of PLWH who developed ARR from 2001 to 2023 in New York City (NYC) to inform best practices for treating these patients.

Methods

PLWH who developed ARR 2001-2023 were identified from the NYC TB registry.

Results

Sixteen PLWH developed ARR; 15 were diagnosed 2001-2009 and the 16th was diagnosed in 2017. Median CD4 count was 48/mm3. On initial presentation, 14 had positive sputum cultures; of these, 12 culture-converted prior to developing ARR. Ten patients completed a course of TB treatment but subsequently relapsed; in six of these cases, ARR was discovered upon relapse, triggering treatment with a non-rifamycin-containing regimen, while in the other four, ARR was discovered during a second round of rifamycin-containing treatment. Three patients were lost to follow-up during their initial course of TB treatment and later returned to care; after being restarted on a rifamycin-containing regimen, ARR was discovered. Finally, three patients culture-converted during their first course of treatment but subsequently had cultures that grew rifamycin-resistant Mycobacterium tuberculosis prior to treatment completion, leading to changes in their treatment regimens. Among the 16 patients, eight died before being cured of TB, seven successfully completed treatment, and one was lost to follow-up.

Conclusions

PLWH should be monitored closely for the development of ARR during treatment for TB, and sputum culture conversion should be interpreted cautiously in this group. Collecting a final sputum sample may be especially important for PLWH, as treatment failure and relapse were common in this population. The decrease in the number of cases of ARR among PLWH during the study period may reflect the decrease in the total number of PLWH diagnosed with TB in NYC in recent years, improved immune status of PLWH due to increased uptake of antiretroviral drugs, and improvements in the way anti-TB regimens are designed for PLWH (such as recommending daily rather than intermittent rifamycin dosing).

Tuberkulose im Erwachsenenalter

Die Tuberkulose ist in Deutschland eine seltene, überwiegend gut behandelbare Erkrankung. Weltweit ist sie eine der häufigsten Infektionserkrankungen mit ca. 10 Millionen Neuerkrankungen/Jahr. Auch bei einer niedrigen Inzidenz in Deutschland bleibt Tuberkulose insbesondere aufgrund der internationalen Entwicklungen und Migrationsbewegungen eine wichtige Differenzialdiagnose. In Deutschland besteht, aufgrund der niedrigen Prävalenz der Erkrankung und der damit verbundenen abnehmenden klinischen Erfahrung, ein Informationsbedarf zu allen Aspekten der Tuberkulose und ihrer Kontrolle. Diese Leitlinie umfasst die mikrobiologische Diagnostik, die Grundprinzipien der Standardtherapie, die Behandlung verschiedener Organmanifestationen, den Umgang mit typischen unerwünschten Arzneimittelwirkungen, die Besonderheiten in der Diagnostik und Therapie resistenter Tuberkulose sowie die Behandlung bei TB-HIV-Koinfektion. Sie geht darüber hinaus auf Versorgungsaspekte und gesetzliche Regelungen wie auch auf die Diagnosestellung und präventive Therapie einer latenten tuberkulösen Infektion ein. Es wird ausgeführt, wann es der Behandlung durch spezialisierte Zentren bedarf.

Die Aktualisierung der S2k-Leitlinie „Tuberkulose im Erwachsenenalter“ soll allen in der Tuberkuloseversorgung Tätigen als Richtschnur für die Prävention, die Diagnose und die Therapie der Tuberkulose dienen und helfen, den heutigen Herausforderungen im Umgang mit Tuberkulose in Deutschland gewachsen zu sein.

Whole Genome Sequencing Assessing Impact of Diabetes Mellitus on Tuberculosis Mutations and Type of Recurrence in India

BACKGROUND

Evidence describing the impact of diabetes mellitus (DM) on the recurrence and mutation rate of Mycobacterium tuberculosis (Mtb) is limited.

METHODS

This study was nested in 3 cohort studies of tuberculosis (TB) patients with and without DM in India. Paired Mtb isolates recovered at baseline and treatment failure/recurrence underwent whole genome sequencing. We compared acquisition of single-nucleotide polymorphisms (SNPs), TB drug resistance mutations, and type of recurrence (endogenous reactivation [<8 SNPs] or exogenous reinfection [≥8 SNPs]) by DM status.

RESULTS

Of 1633 enrolled in the 3 parent cohorts, 236 (14.5%) had microbiologically confirmed TB treatment failure/recurrence; 76 Mtb isolate pairs were available for sequencing (22 in TB-DM and 54 in TB-only). The SNP acquisition rate was overall was 0.43 (95% confidence interval [CI], .25-.64) per 1 person-year (PY); 0.77 (95% CI, .40-1.35) per 1 PY, and 0.44 (95% CI, .19-.86) per 1 PY at treatment failure and recurrence, respectively. Significant difference in SNP rates by DM status was seen at recurrence (0.21 [95% CI, .04-.61]) per 1 PY for TB-only vs 1.28 (95% CI, .41-2.98) per 1 PY for TB-DM; P = .02). No significant difference in SNP rates by DM status was observed at treatment failure. Acquired TB drug resistance was seen in 4 of 18 (22%) in TB-DM vs 4 of 45 (9%) in TB-only (P = .21). Thirteen (17%) participants had exogenous reinfection; the reinfection rate at recurrence was 25% (3/12) for TB-DM vs 17% (4/24) in TB-only (P = .66).

CONCLUSIONS

Considerable intrahost Mtb mutation rates were present at recurrence among patients with DM in India. One-fourth of patients with DM had exogenous reinfection at recurrence.

Potential contribution of HIV during first-line tuberculosis treatment to subsequent rifampicin-monoresistant tuberculosis and acquired tuberculosis drug resistance in South Africa: a retrospective molecular epidemiology study

Background

South Africa has a high burden of rifampicin-resistant tuberculosis (including multidrug-resistant [MDR] tuberculosis), with increasing rifampicin-monoresistant (RMR) tuberculosis over time. Resistance acquisition during first-line tuberculosis treatment could be a key contributor to this burden, and HIV might increase the risk of acquiring rifampicin resistance. We assessed whether HIV during previous treatment was associated with RMR tuberculosis and resistance acquisition among a retrospective cohort of patients with MDR or rifampicin-resistant tuberculosis.

Methods

In this retrospective cohort study, we included all patients routinely diagnosed with MDR or rifampicin-resistant tuberculosis in Khayelitsha, Cape Town, South Africa, between Jan 1, 2008, and Dec 31, 2017. Patient-level data were obtained from a prospective database, complemented by data on previous tuberculosis treatment and HIV from a provincial health data exchange. Stored MDR or rifampicin-resistant tuberculosis isolates from patients underwent whole-genome sequencing (WGS). WGS data were used to infer resistance acquisition versus transmission, by identifying genomically unique isolates (single nucleotide polymorphism threshold of five). Logistic regression analyses were used to assess factors associated with RMR tuberculosis and genomic uniqueness.

Findings

The cohort included 2041 patients diagnosed with MDR or rifampicin-resistant tuberculosis between Jan 1, 2008, and Dec 31, 2017; of those, 463 (22·7%) with RMR tuberculosis and 1354 (66·3%) with previous tuberculosis treatment. In previously treated patients, HIV positivity during previous tuberculosis treatment versus HIV negativity (adjusted odds ratio [OR] 2·07, 95% CI 1·35–3·18), and three or more previous tuberculosis treatment episodes versus one (1·96, 1·21–3·17) were associated with RMR tuberculosis. WGS data showing MDR or rifampicin-resistant tuberculosis were available for 1169 patients; 360 (30·8%) isolates were identified as unique. In previously treated patients, RMR tuberculosis versus MDR tuberculosis (adjusted OR 4·96, 3·40–7·23), HIV positivity during previous tuberculosis treatment (1·71, 1·03–2·84), and diagnosis in 2013–17 (1·42, 1·02–1·99) versus 2008–12, were associated with uniqueness. In previously treated patients with RMR tuberculosis, HIV positivity during previous treatment (adjusted OR 5·13, 1·61–16·32) was associated with uniqueness as was female sex (2·50 [1·18–5·26]).

Interpretation

These data suggest that HIV contributes to rifampicin-resistance acquisition during first-line tuberculosis treatment and that this might be driving increasing RMR tuberculosis over time. Large-scale prospective cohort studies are required to further quantify this risk.

Funding

Swiss National Science Foundation, South African National Research Foundation, and Wellcome Trust.

Assessing the impacts of short-course multidrug-resistant tuberculosis treatment in the Southeast Asia Region using a mathematical modeling approach

This study aimed to predict the impacts of shorter duration treatment regimens for multidrug-resistant tuberculosis (MDR-TB) on both MDR-TB percentage among new cases and overall MDR-TB cases in the WHO Southeast Asia Region. A deterministic compartmental model was constructed to describe both the transmission of TB and the MDR-TB situation in the Southeast Asia region. The population-level impacts of short-course treatment regimens were compared with the impacts of conventional regimens. Multi-way analysis was used to evaluate the impact by varying programmatic factors (eligibility for short-course MDR-TB treatment, treatment initiation, and drug susceptibility test (DST) coverage). The model predicted that overall TB incidence will be reduced from 246 (95% credible intervals (CrI), 221–275) per 100,000 population in 2020 to 239 (95% CrI, 215–267) per 100,000 population in 2035, with a modest reduction of 2.8% (95% CrI, 2.7%–2.9%). Despite the slight reduction in overall TB infections, the model predicted that the MDR-TB percentage among newly notified TB infections will remain steady, with 2.4% (95% CrI, 2.1–2.9) in 2020 and 2.5% (95% CrI, 2.3–3.1) in 2035, using conventional MDR-TB treatment. With the introduction of short-course regimens to treat MDR-TB, the development of resistance can be slowed by 38.6% (95% confidence intervals (CI), 35.9–41.3) reduction in MDR-TB case number, and 37.6% (95% CI, 34.9–40.3) reduction in MDR-TB percentage among new TB infections over the 30-year period compared with the baseline using the standard treatment regimen. The multi-way analysis showed eligibility for short-course treatment and treatment initiation greatly influenced the impacts of short-course treatment regimens on reductions in MDR-TB cases and percentage resistance among new infections. Policies which promote the expansion of short-course regimens and early MDR-TB treatment initiation should be considered along with other interventions to tackle antimicrobial resistance in the region.

Tuberculosis research conducted over the years at the ICMR-National Institute for Research in Tuberculosis (ICMR-NIRT)

This review article highlights some of the key research conducted at the ICMR-National Institute for Research in Tuberculosis (ICMR-NIRT) over the years since its inception in 1956 till the present. The research carried out in the field of tuberculosis at ICMR-NIRT has been a joint effort between the ICMR, NIRT, the TB control program in India with assistance from World Health Organization (WHO) and the National Institutes of Health (NIH), USA. The research carried out at ICMR-NIRT has helped to formulate the national guidelines for the control and the management of tuberculosis in India. The major highlights of the research carried out at ICMR-NIRT are provided in this manuscript.

Pathogenesis of Human Immunodeficiency Virus-Mycobacterium tuberculosis Co-Infection

Given that infection with Mycobacterium tuberculosis (Mtb) is the leading cause of death amongst individuals living with HIV, understanding the complex mechanisms by which Mtb exacerbates HIV infection may lead to improved treatment options or adjuvant therapies. While it is well-understood how HIV compromises the immune system and leaves the host vulnerable to opportunistic infections such as Mtb, less is known about the interplay of disease once active Mtb is established. This review explores how glutathione (GSH) depletion, T cell exhaustion, granuloma formation, and TNF-α upregulation, as a result of Mtb infection, leads to an increase in HIV disease severity. This review also examines the difficulties of treating coinfected patients and suggests further research on the clinical use of GSH supplementation.

Global access of rifabutin for the treatment of tuberculosis - why should we prioritize this?

INTRODUCTION

Rifabutin, a rifamycin of equivalent potency to rifampicin, has several advantages in its pharmacokinetic and toxicity profile, particularly in HIV co-infected patients on combined antiretroviral therapy (cART). In this commentary, we evaluate evidence supporting increased global use of rifabutin and highlight key recommendations for action.

DISCUSSION

Although extrapolation of data from HIV uninfected patients would suggest non-inferiority, there has been no randomized controlled study comparing rifabutin versus rifampicin in the outcomes of relapse-free cure, in drug susceptible tuberculosis (TB), in HIV co-infected patients on currently utilized cART regimens or in paediatric populations. An important advantage of rifabutin is that compared to the dose adjustments required with rifampicin, it can be co-administered with the integrase strand transfer inhibitors raltegravir or dolutegravir without the need for dose adjustments. This strategy would be easier to implement in a programmatic setting and would save costs. We have assessed cost incentives to utilize rifabutin and have estimated generic costs for a range of rifabutin dosage scenarios. Where facilities are present for drug re-challenge and monitoring for drug toxicity and cross-reactivity, rifabutin offers a switch alternative for adverse drug reactions (ADR)s attributed to rifampicin. This would negate the need to prolong treatment in the absence of a rifamycin as part of short-course multidrug therapy. There is evidence of incomplete cross-resistance to rifampicin and rifabutin. Rifabutin may be useful in rifampicin-resistant TB, in an estimated 20% of cases, based on phenotypic or genotypic rifabutin susceptibility testing.

CONCLUSIONS

Rifabutin should be available globally as a first-line rifamycin in HIV co-infected individuals and as a switch option in cases of rifampicin associated ADRs. Further studies are needed to ascertain the utility of rifabutin in rifampicin-resistant rifabutin-susceptible TB.

Management of Advanced HIV Disease

Great progress has been made in caring for persons with human immunodeficiency virus. However, a significant proportion of individuals still present to care with advanced disease and a low CD4 count. Careful considerations for selection of antiretroviral therapy as well as close monitoring for opportunistic infections and immune reconstitution inflammatory syndrome are vitally important in providing care for such individuals.

Does oxidative stress contribute to adverse outcomes in HIV-associated TB?

In HIV infection, oxidative stress is a pronounced phenomenon, with likely links to HIV-related pathologies and the progression of HIV infection per se. TB is an AIDS-defining condition. HIV-associated oxidative stress, like that associated with diabetes mellitus, might adversely impact the outcomes of TB, probably through increased propensity for generation of metabolically dormant mycobacterial persisters, alongside other mechanisms. This hypothesis might help in guiding the exploration of relevant research directions to improve the care of patients.

High prevalence of multi drug resistant tuberculosis in people living with HIV in Western India

BACKGROUND

Most studies assessing drug resistant tuberculosis (DRTB) in human immunodeficiency virus (HIV) co-infected patients in India have used conventional culture- based systems to diagnose DRTB that have a longer turnaround time leading to risk of amplification of resistance to an empirical regimen. We determined the prevalence of DRTB amongst people living with HIV (PLHIV) using the line probe assay and determined risk factors associated with the presence of multi drug resistant tuberculosis (MDRTB).

METHODS

A Cross-sectional study was undertaken at Poona Hospital and Research Center (PHRC) and the Institute of Infectious Diseases, two tertiary level private care centers in Pune, India. Consenting PLHIV with confirmed Pulmonary TB (PTB) and/or extra-pulmonary TB (EPTB) diagnosed based on detection of Mycobacterium TB by line probe assay (Geno Type MTBDRplus version 2) on clinical specimens were included. Those with documented past history of DRTB were excluded. Resistance against anti-TB drugs was determined by the same assay. The prevalence of any form of drug resistant TB (DRTB), MDRTB, Rifampicin resistant TB (RRTB) and Isoniazid (INH) mono-resistant TB were determined as the proportion of these amongst all included PLHIV-TB. A multivariate analysis was conducted to determine risk factors that were statistically associated with MDRTB, DRTB, RRTB and INH mono-resistant TB.

RESULTS

Two hundred PLHIV were recruited. The prevalence (95% CI) of MDRTB, INH mono- resistance and RR resistance was 12.5% (7.9-17.1%), 9% (6.9-11.2%) and 2.5% (1.4-3.6%), respectively. The prevalence (95% CI) of MDRTB among new and relapsed patients was 8.8% (6.5-11.1%) and 23.1% (17.2-28.9%), respectively. Tuberculosis relapse was the only factor significantly associated with MDRTB, DRTB and INH mono-resistant TB.

CONCLUSION

We document a high prevalence of drug resistance to anti-TB drugs including MDRTB among PLHIV in our setting using Geno Type MTBDRplus directly on clinical specimens. This validates the WHO recommendation of performing routine rapid molecular resistance testing prior to initiating anti-TB treatment among all PLHIV with presumptive TB. Using rapid molecular testing especially Geno Type MTBDRplus (that detects resistance to INH and Rifampicin simultaneously) reduces the turn-around time helping in optimizing treatment.

Daily vs Intermittent Antituberculosis Therapy for Pulmonary Tuberculosis in Patients With HIV: A Randomized Clinical Trial

IMPORTANCE

The benefit of daily over thrice-weekly antituberculosis therapy among HIV-positive patients with pulmonary tuberculosis (TB) who are receiving antiretroviral therapy remains unproven.

OBJECTIVE

To compare the efficacy and safety of daily, part-daily, and intermittent antituberculosis therapy regimens in the treatment of HIV-associated pulmonary TB.

DESIGN, SETTING, AND PARTICIPANTS

This open-label, randomized clinical trial was conducted by the National Institute for Research in Tuberculosis, south India. Adults infected with HIV with newly diagnosed, culture-positive, pulmonary TB were enrolled between September 14, 2009, and January 18, 2016.

INTERVENTIONS

Patients were randomized to daily, part-daily, and intermittent antituberculosis therapy regimens, stratified by baseline CD4 lymphocyte count and sputum smear grade. Antiretroviral therapy was initiated as per national guidelines. Clinical and sputum microbiological examinations of patients were performed monthly until 18 months after randomization. Adverse events were recorded using standard criteria.

MAIN OUTCOMES AND MEASURES

The primary outcome was favorable response, defined as treatment completion with all available sputum cultures negative for Mycobacterium tuberculosis during the last 2 months of treatment. Unfavorable responses included treatment failures, dropouts, deaths, and toxic effects among regimens.

RESULTS

Of 331 patients (251 [76%] male; mean [SD] age, 39 [9] years; mean [SD] HIV viral load, 4.9 [1.2] log10 copies/mL; and median [interquartile range] CD4 lymphocyte count, 138 [69-248] cells/μL), favorable responses were experienced by 91% (89 of 98), 80% (77 of 96), and 77% (75 of 98) in the daily, part-daily, and intermittent regimens, respectively. With the difference in outcome between daily and intermittent regimens crossing the O'Brien-Fleming group sequential boundaries and acquired rifampicin resistance emergence (n = 4) confined to the intermittent group, the data safety monitoring committee halted the study. A total of 18 patients died and 18 patients dropped out during the treatment period in the 3 regimens. Six, 4, and 6 patients in the daily, part-daily, and intermittent regimens, respectively, had TB recurrence.

CONCLUSIONS AND RELEVANCE

Among HIV-positive patients with pulmonary TB receiving antiretroviral therapy, a daily anti-TB regimen proved superior to a thrice-weekly regimen in terms of efficacy and emergence of rifampicin resistance.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00933790.

Executive Summary: Official American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America Clinical Practice Guidelines: Treatment of Drug-Susceptible Tuberculosis

The American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America jointly sponsored the development of this guideline for the treatment of drug-susceptible tuberculosis, which is also endorsed by the European Respiratory Society and the US National Tuberculosis Controllers Association. Representatives from the American Academy of Pediatrics, the Canadian Thoracic Society, the International Union Against Tuberculosis and Lung Disease, and the World Health Organization also participated in the development of the guideline. This guideline provides recommendations on the clinical and public health management of tuberculosis in children and adults in settings in which mycobacterial cultures, molecular and phenotypic drug susceptibility tests, and radiographic studies, among other diagnostic tools, are available on a routine basis. For all recommendations, literature reviews were performed, followed by discussion by an expert committee according to the Grading of Recommendations, Assessment, Development and Evaluation methodology. Given the public health implications of prompt diagnosis and effective management of tuberculosis, empiric multidrug treatment is initiated in almost all situations in which active tuberculosis is suspected. Additional characteristics such as presence of comorbidities, severity of disease, and response to treatment influence management decisions. Specific recommendations on the use of case management strategies (including directly observed therapy), regimen and dosing selection in adults and children (daily vs intermittent), treatment of tuberculosis in the presence of HIV infection (duration of tuberculosis treatment and timing of initiation of antiretroviral therapy), as well as treatment of extrapulmonary disease (central nervous system, pericardial among other sites) are provided. The development of more potent and better-tolerated drug regimens, optimization of drug exposure for the component drugs, optimal management of tuberculosis in special populations, identification of accurate biomarkers of treatment effect, and the assessment of new strategies for implementing regimens in the field remain key priority areas for research. See the full-text online version of the document for detailed discussion of the management of tuberculosis and recommendations for practice.

Pharmacokinetics and pharmacogenetics of anti-tubercular drugs: a tool for treatment optimization?

INTRODUCTION

WHO global strategy is to end tuberculosis epidemic by 2035. Pharmacokinetic and pharmacogenetic studies are increasingly performed and might confirm their potential role in optimizing treatment outcome in specific settings and populations. Insufficient drug exposure seems to be a relevant factor in tuberculosis outcome and for the risk of phenotypic resistance. Areas covered: This review discusses available pharmacokinetic and pharmacogenetic data of first and second-line antitubercular agents in relation to efficacy and toxicity. Pharmacodynamic implications of optimized drugs and new options regimens are reviewed. Moreover a specific session describes innovative investigations on drug penetration. Expert opinion: The optimal use of available antitubercular drugs is paramount for tuberculosis control and eradication. Whilst trials are still on-going, higher rifampicin doses should be reserved to treatment for tubercular meningitis. Therapeutic Drug Monitoring with limiting sampling strategies is advised in patients at risk of failure or with slow treatment response. Further studies are needed in order to provide definitive recommendations of pharmacogenetic-based individualization: however lower isoniazid doses in NAT2 slow acetylators and higher rifampicin doses in individuals with SLCO1B1 loss of function genes are promising strategies. Finally in order to inform tailored strategies we need more data on tissue drug penetration and pharmacological modelling.

Immunodeficiency and Intermittent Dosing Promote Acquired Rifamycin Monoresistance in Murine Tuberculosis

More-permissive preclinical models may be useful in evaluating antituberculosis regimens for their propensity to select drug-resistant mutants. To evaluate whether acquired rifamycin monoresistance could be recapitulated in mice and, if so, to evaluate the effects of immunodeficiency, intermittent dosing, and drug exposures, athymic nude and BALB/c mice were infected. Controls received daily rifapentine alone or 2 months of rifampin, isoniazid, pyrazinamide, and ethambutol, followed by 4 months of rifampin/isoniazid, either daily or twice weekly with one of two isoniazid doses. Test groups received the same intensive regimen followed by once-weekly rifapentine or isoniazid/rifapentine with rifapentine doses of 10, 15, or 20 mg/kg of body weight plus one of two isoniazid doses. All combination regimens rendered BALB/c mouse cultures negative but selected mutants resistant to isoniazid (8.5%, 12/140) or rifampin (3.5%, 5/140) in nude mice (P < 0.001). Intermittently dosed intensive-phase therapy selected isoniazid and rifampin resistance in 10% (8/80, P < 0.001) and 20% (16/80, P = 0.009) of nude mice, respectively, compared to 0% treated with a daily regimen. Once-weekly rifapentine-containing continuation-phase regimens selected rifampin-resistant mutants at a rate of 18.0% (18/100, P = 0.035 compared to rifampin/isoniazid regimens). Higher isoniazid doses in the intermittent-treatment control regimen and higher rifapentine doses in once-weekly regimens were associated with less selection of isoniazid resistance. Acquired resistance, including rifamycin monoresistance, was more likely to occur in nude mice despite administration of combination therapy. These results recapitulate clinical outcomes and indicate that nude mice may be useful for evaluating the ability of novel regimens to prevent the selection of resistance.

TB-HIV co-infection: a catastrophic comradeship

The symbiotic association of tuberculosis (TB) and HIV poses a challenge to human survival. HIV complicates every aspect of TB including presentation, diagnosis and treatment. HIV-TB patients encounter unique problems like drug-drug interactions, cumulative toxicity, immune reconstitution inflammatory syndrome (IRIS), lower plasma drug levels and emergence of drug resistance during treatment despite adherence. TB may also be overdiagnosed in HIV due to a number of diseases that closely resemble TB. Notable among them are non-tuberculous mycobacteria, Pneumocystis Jirovecii and Nocardia. Even though diagnostic procedures have improved over the years, patients in developing countries usually seek health care at later stage of the disease. Research data ascertains the duration of therapy for TB to be 6 months with rifampicin and isoniazid, reinforced with ethambutol and pyrazinamide in the first 2 months. The schedule of therapy is still debatable with daily regimens being preferred in the context of HIV. Many reasons exist for persistence of Mycobacterium Tuberculosis (M.TB) in sputum, or delayed-clearance of TB from sputum smears in HIV, apart from emergence of drug resistance and non-compliance. Acquired rifampicin resistance (ARR) is a unique phenomenon complicating HIV-associated TB when an intermittent regimen of antituberculosis therapy (ATT) is used without timely initiation of highly active antiretroviral therapy (HAART), especially in patients harbouring isoniazid-resistant strains Immune restoration is often incomplete ('swiss cheese' pattern) even with effective HAART if not started early. Immune reconstitution inflammatory syndrome (IRIS) is the paradoxical worsening of the patient's condition often with radiological deterioration, due to an enhanced immune response with HAART. IRIS occurs despite an effective virological suppression and a favourable response to ATT. The incidence of IRIS in HIV has reached up to 54%, requiring utilization of experts and tertiary care which forms an obstacle to the decentralization of patients in the ART programme. Research in HIV-TB immunology and management needs further exploration in order to understand the diseases and offer appropriate treatment. The following paragraphs provide scientific evidences generated through research that could potentially guide management.

Low Frequency of Acquired Isoniazid and Rifampicin Resistance in Rifampicin-Susceptible Pulmonary Tuberculosis in a Setting of High HIV-1 Infection and Tuberculosis Coprevalence

Background

We estimated the incidence of acquired isoniazid and rifampicin resistance in rifampicin-susceptible tuberculosis in a setting of high human immunodeficiency virus type 1 (HIV-1) infection and tuberculosis coprevalence.

Methods

GeneXpert MTB/RIF–confirmed patients with rifampicin-susceptible tuberculosis were recruited at antituberculosis treatment initiation in Khayelitsha, South Africa. Liquid culture and adherence assessment were performed at 2 and 5–6 months. MTBDRplus was performed on mycobacteria-positive cultures to ascertain acquired drug resistance (ADR). Spoligotyping and whole-genome sequencing were performed to ascertain homogeneity between baseline isolates and isolates with ADR. Baseline isolates were retrospectively tested for isoniazid monoresistance. An electronic database review was performed to ascertain tuberculosis recurrences.

Results

A total of 306 participants (62% with HIV-1 coinfection, of whom 71% received antiretroviral therapy) were recruited. Ascertainment of outcomes was complete for 284 participants. Five acquired a resistant Mycobacterium tuberculosis strain during or subsequent to treatment. One strain was confirmed to have ADR, 2 were confirmed as causing exogenous reinfection, and 2 were unrecoverable for genotyping. Incident ADR was estimated to have ranged from 0.3% (95% confidence interval [CI], .1%–1.9%; 1 of 284 participants) to 1% (95% CI, .2%–3%; 3 of 284 participants). Seventeen of 279 baseline isolates (6.1%; 95% CI, 3.6%–9.6%) had isoniazid monoresistance (13 of 17 had an inhA promoter mutation), but 0 of 17 had amplified resistance.

Conclusions

Treatment with standardized antituberculosis regimens dosed daily throughout, high uptake of antiretroviral therapy, and low prevalence of isoniazid monoresistance were associated with a low frequency of ADR.

Official American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America Clinical Practice Guidelines: Treatment of Drug-Susceptible Tuberculosis

The American Thoracic Society, Centers for Disease Control and Prevention, and Infectious Diseases Society of America jointly sponsored the development of this guideline for the treatment of drug-susceptible tuberculosis, which is also endorsed by the European Respiratory Society and the US National Tuberculosis Controllers Association. Representatives from the American Academy of Pediatrics, the Canadian Thoracic Society, the International Union Against Tuberculosis and Lung Disease, and the World Health Organization also participated in the development of the guideline. This guideline provides recommendations on the clinical and public health management of tuberculosis in children and adults in settings in which mycobacterial cultures, molecular and phenotypic drug susceptibility tests, and radiographic studies, among other diagnostic tools, are available on a routine basis. For all recommendations, literature reviews were performed, followed by discussion by an expert committee according to the Grading of Recommendations, Assessment, Development and Evaluation methodology. Given the public health implications of prompt diagnosis and effective management of tuberculosis, empiric multidrug treatment is initiated in almost all situations in which active tuberculosis is suspected. Additional characteristics such as presence of comorbidities, severity of disease, and response to treatment influence management decisions. Specific recommendations on the use of case management strategies (including directly observed therapy), regimen and dosing selection in adults and children (daily vs intermittent), treatment of tuberculosis in the presence of HIV infection (duration of tuberculosis treatment and timing of initiation of antiretroviral therapy), as well as treatment of extrapulmonary disease (central nervous system, pericardial among other sites) are provided. The development of more potent and better-tolerated drug regimens, optimization of drug exposure for the component drugs, optimal management of tuberculosis in special populations, identification of accurate biomarkers of treatment effect, and the assessment of new strategies for implementing regimens in the field remain key priority areas for research. See the full-text online version of the document for detailed discussion of the management of tuberculosis and recommendations for practice.

Current trends and intricacies in the management of HIV-associated pulmonary tuberculosis

Human immunodeficiency virus (HIV) epidemic has undoubtedly increased the incidence of tuberculosis (TB) globally, posing a formidable global health challenge affecting 1.2 million cases. Pulmonary TB assumes utmost significance in the programmatic perspective as it is readily transmissible as well as easily diagnosable. HIV complicates every aspect of pulmonary tuberculosis from diagnosis to treatment, demanding a different approach to effectively tackle both the diseases. In order to control these converging epidemics, it is important to diagnose early, initiate appropriate therapy for both infections, prevent transmission and administer preventive therapy. Liquid culture methods and nucleic acid amplification tests for TB confirmation have replaced conventional solid media, enabling quicker and simultaneous detection of mycobacterium and its drug sensitivity profile Unique problems posed by the syndemic include Acquired rifampicin resistance, drug-drug interactions, malabsorption of drugs and immune reconstitution inflammatory syndrome or paradoxical reaction that complicate dual and concomitant therapy. While the antiretroviral therapy armamentarium is constantly reinforced by discovery of newer and safer drugs every year, only a few drugs for anti tuberculosis treatment have successfully emerged. These include bedaquiline, delamanid and pretomanid which have entered phase III B trials and are also available through conditional access national programmes. The current guidelines by WHO to start Antiretroviral therapy irrespective of CD4+ cell count based on benefits cited by recent trials could go a long way in preventing various complications caused by the deadly duo. This review provides a consolidated gist of the advancements, concepts and updates that have emerged in the management of HIV-associated pulmonary TB for maximizing efficacy, offering latest solutions for tackling drug-drug interactions and remedial measures for immune reconstitution inflammatory syndrome.

Recent developments in genomics, bioinformatics and drug discovery to combat emerging drug-resistant tuberculosis

Emergence of drug-resistant tuberculosis (DR-TB) is a big challenge in TB control. The delay in diagnosis of DR-TB leads to its increased transmission, and therefore prevalence. Recent developments in genomics have enabled whole genome sequencing (WGS) of Mycobacterium tuberculosis (M. tuberculosis) from 3-day-old liquid culture and directly from uncultured sputa, while new bioinformatics tools facilitate to determine DR mutations rapidly from the resulting sequences. The present drug discovery and development pipeline is filled with candidate drugs which have shown efficacy against DR-TB. Furthermore, some of the FDA-approved drugs are being evaluated for repurposing, and this approach appears promising as several drugs are reported to enhance efficacy of the standard TB drugs, reduce drug tolerance, or modulate the host immune response to control the growth of intracellular M. tuberculosis. Recent developments in genomics and bioinformatics along with new drug discovery collectively have the potential to result in synergistic impact leading to the development of a rapid protocol to determine the drug resistance profile of the infecting strain so as to provide personalized medicine. Hence, in this review, we discuss recent developments in WGS, bioinformatics and drug discovery to perceive how they would transform the management of tuberculosis in a timely manner.

Burden of transmitted multidrug resistance in epidemics of tuberculosis: a transmission modelling analysis

Background

Multidrug-resistant tuberculosis (MDR-TB) can be acquired through de novo mutation during TB treatment or through transmission from other individuals with active MDR-TB. Understanding the balance between these two mechanisms is essential when allocating resources for MDR-TB.

Methods

We constructed a dynamic transmission model of an MDR-TB epidemic, allowing for both treatment-related acquisition and person-to-person transmission of resistance. We used national TB notification data to inform Bayesian estimates of the fraction of each country’s 2013 MDR-TB incidence that resulted from MDR transmission rather than treatment-related MDR acquisition.

Findings

Global estimates of 3·5% MDR-TB prevalence among new TB notifications and 20·5% among retreatment notifications translate into an estimate that resistance transmission rather than acquisition accounts for a median 96% (95% UR: 68–100%) of all incident MDR-TB, and 61% (16–95%) of incident MDR-TB in previously-treated individuals. The estimated percentage of MDR-TB resulting from transmission varied substantially with different countries’ notification data; for example, we estimated this percentage at 48% (30–75%) of MDR-TB in Bangladesh, versus 99% (91–100%) in Uzbekistan. Estimates were most sensitive to estimates of the transmissibility of MDR strains, the probability of acquiring MDR during tuberculosis treatment, and the responsiveness of MDR TB to first-line treatment.

Interpretation

Notifications of MDR prevalence from most high-burden settings are most consistent with the vast majority of incident MDR-TB resulting from transmission rather than new treatment-related acquisition of resistance. Merely improving the treatment of drug-susceptible TB is unlikely to greatly reduce future MDR-TB incidence. Improved diagnosis and treatment of MDR-TB – including new tests and drug regimens – should be highly prioritized.

Optimal Duration of Daily Antituberculosis Therapy before Switching to DOTS Intermittent Therapy to Reduce Mortality in HIV Infected Patients: A Duration-Response Analysis Using Restricted Cubic Splines

Compared with thrice-weekly intermittent antituberculosis therapy (ATT), the use of daily ATT during the intensive phase has shown improved survival in HIV infected patients with tuberculosis. However, the optimal duration of daily ATT before initiating intermittent ATT is not well known. In this study, we analysed the mortality of HIV-related tuberculosis according to the duration of daily ATT before switching to thrice-weekly ATT in patients who completed at least two months of treatment in an HIV cohort study. Statistical analysis was performed using Cox proportional hazard models. To relax the linearity assumption in regression models and to allow for a flexible interpretation of the relationship between duration of daily ATT and mortality, continuous variables were modelled using restricted cubic splines. The study included 520 HIV infected patients with tuberculosis and 8,724.3 person-months of follow-up. The multivariable analysis showed that the mortality risk was inversely correlated with the duration of daily ATT before switching to intermittent therapy during the first 30 days of ATT but, after approximately 30 days of treatment, differences were not statistically significant. The results of this study suggest that daily ATT should be given for at least 30 days before switching to intermittent ATT in HIV infected patients with tuberculosis.