Emergence of additional drug resistance during treatment of multidrug-resistant tuberculosis in China: a prospective cohort study

Impact of financial support on treatment outcomes of multidrug-resistant tuberculosis: A population-based, retrospective cohort study in Shanghai, China

Background

To date, the prolonged treatment duration and expensive second-line anti-tuberculosis drugs (SLDs) for multidrug-resistant tuberculosis (MDR-TB) can impose a significant financial burden, which may negatively impact treatment outcomes. This study examines the effect of a subsidy policy on treatment outcomes of MDR-TB patient..

Methods

We collected demographic and drug resistance data of all registered MDR-TB patients between April 2011 and December 2019 in Shanghai, China. Documentation of financial support received was routinely maintained until December 2021. We employed multivariate logistic regression to assess the association between financial support and treatment outcomes, estimating odds ratios (ORs) and their corresponding 95% confidence intervals (CIs).

Results

Of the 865 patients, 70.6% (611/865) achieved treatment success. The median amount compensated under the subsidy policy was 2359 United States dollar (USD), with an interquartile range from 1116 to 5652 USD. A positive association was found between benefiting from the subsidy policy and higher rate of treatment success, with an adjusted OR of 2.95 (95% CI, 2.03-4.28). Among the 641 patients covered by the policy, the adjusted OR comparing those with higher versus lower reimbursement was 1.74 (95% CI, 1.16-2.61).

Conclusions

Financial support policies for MDR-TB patients demonstrate a positive influence on treatment outcomes.

Genetic factors associated with acquired phenotypic drug resistance and its compensatory evolution during tuberculosis treatment

OBJECTIVES

We elucidated the factors, evolution, and compensation of antimicrobial resistance (AMR) in Mycobacterium tuberculosis (MTB) isolates under dual pressure from the intra-host environment and anti-tuberculosis (anti-TB) drugs.

METHODS

This retrospective case-control study included 337 patients with pulmonary tuberculosis from 15 clinics in Tianjin, China, with phenotypic drug susceptibility testing results available for at least two time points between January 1, 2009 and December 31, 2016. Patients in the case group exhibited acquired AMR to isoniazid (INH) or rifampicin (RIF), while those in the control group lacked acquired AMR. The whole-genome sequencing (WGS) was conducted on 149 serial longitudinal MTB isolates from 46 patients who acquired or reversed phenotypic INH/RIF-resistance during treatment. The genetic basis, associated factors, and intra-host evolution of acquired phenotypic INH/RIF-resistance were elucidated using a combined analysis.

RESULTS

Anti-TB interruption duration of ≥30 days showed association with acquired phenotypic INH/RIF resistance (aOR = 2·2, 95% CI, 1·0-5·1) and new rpoB mutations (p = 0·024). The MTB evolution was 1·2 (95% CI, 1·02-1·38) single nucleotide polymorphisms per genome per year under dual pressure from the intra-host environment and anti-TB drugs. AMR-associated mutations occurred before phenotypic AMR appearance in cases with acquired phenotypic INH (10 of 16) and RIF (9 of 22) resistances.

DISCUSSION

Compensatory evolution may promote the fixation of INH/RIF-resistance mutations and affect phenotypic AMR. The TB treatment should be adjusted based on gene sequencing results, especially in persistent culture positivity during treatment, which highlights the clinical importance of WGS in identifying reinfection and AMR acquisition before phenotypic drug susceptibility testing.

Tuberculosis: The success tale of less explored dormant Mycobacterium tuberculosis

Mycobacterium tuberculosis (M.tb) is an intracellular pathogen that predominantly affects the alveolar macrophages in the respiratory tract. Upon infection, the activation of TLR2 and TLR4- mediated signaling pathways leads to lysosomal degradation of the bacteria. However, bacterium counteracts the host immune cells and utilizes them as a cellular niche for its survival. One distinctive mechanism of M.tb to limit the host stress responses such as hypoxia and nutrient starvation is induction of dormancy. As the environmental conditions become favorable, the bacteria resuscitate, resulting in a relapse of clinical symptoms. Different bacterial proteins play a critical role in maintaining the state of dormancy and resuscitation, namely, DevR (DosS), Hrp1, DATIN and RpfA-D, RipA, etc., respectively. Existing knowledge regarding the key proteins associated with dormancy and resuscitation can be employed to develop novel therapies. In this review we aim to highlight the current knowledge of bacterial progression from dormancy to resuscitation and the gaps in understanding the transition from dormant to active state. We have also focused on elucidating a few therapeutic strategies employed to prevent M.tb resuscitation.

Antibiotic resistance acquisition versus primary transmission in the presentation of extensively drug-resistant tuberculosis

Mycobacterium tuberculosis is the leading cause of mortality worldwide due to a single bacterial pathogen. Of concern is the negative impact that the COVID-19 pandemic has had on the control of tuberculosis (TB) including drug-resistant forms of the disease. Antimicrobial resistance increases the likelihood of worsened outcomes in TB patients including treatment failure and death. Multidrug-resistant (MDR) strains, resistant to first-line drugs isoniazid and rifampin, and extensively drug-resistant (XDR) strains with further resistance to second-line drugs (SLD), threaten control programs designed to lower TB incidence and end the disease as a public health challenge by 2030, in accordance with UN Sustainable Development Goals. Tackling TB requires an understanding of the pathways through which drug resistance emerges. Here, the roles of acquired resistance mutation, and primary transmission, are examined with regard to XDR-TB. It is apparent that XDR-TB can emerge from MDR-TB through a small number of additional resistance mutations that occur in patients undergoing drug treatment. Rapid detection of resistance, to first-line drugs and SLD, at the initiation of and during treatment, and prompt adjustment of regimens are required to ensure treatment success in these patients. Primary transmission is predicted to make an increasing contribution to the XDR-TB caseload in the future. Much work is required to improve the implementation of the World Health Organization-recommended infection control practices and block onward transmission of XDR-TB patients to contacts including health-care workers. Finally, limiting background resistance to fluoroquinolones in pre-XDR strains of M. tuberculosis will necessitate better antimicrobial stewardship in the broader use of this drug class.

Potentiating the Anti-Tuberculosis Efficacy of Peptide Nucleic Acids through Combinations with Permeabilizing Drugs

The emergence of antimicrobial resistance warrants for the development of improved treatment approaches. In this regard, peptide nucleic acids (PNAs) have shown great promise, exhibiting antibiotic properties through the targeting of cellular nucleic acids. We aimed to study the efficacy of PNA as an anti-tuberculosis agent. Since the efficacy of PNA is limited by its low penetration into the cell, we also investigated combinatorial treatments using permeabilizing drugs to improve PNA efficacy. Various concentrations of anti-inhA PNA, permeabilizing drugs, and their combinations were screened against extracellular and intracellular mycobacteria.0.625 to 5 μM anti-inhA PNA was observed to merely inhibit the growth of extracellular M. smegmatis, while low intracellular bacterial load was reduced by 2 or 2.5 log-fold when treated with 2.5 or 5 μM PNA, respectively. Anti-inhA PNA against M. tuberculosis H37Ra exhibited bactericidal properties at 2.5 and 5 μM and enabled a slight reduction in intracellular M. tuberculosis at concentrations from 2.5 to 20 μM. Of the permeabilizing drugs tested, ethambutol showed the most permeabilizing potential and ultimately potentiated anti-inhA PNA to the greatest extent, reducing its efficacious concentration to 1.25 μM against both M. smegmatis and M. tuberculosis. Furthermore, an enhanced clearance of 1.3 log-fold was observed for ethambutol-anti-inhA PNA combinations against intracellular M. tuberculosis. Thus, permeabilizing drug-PNA combinations indeed exhibit improved efficacies. We therefore propose that anti-inhA PNA could improve therapy even when applied in minute doses as an addition to the current anti-tuberculosis drug regimen.

IMPORTANCE Peptide nucleic acids have great potential in therapeutics as anti-gene/anti-sense agents. However, their limited uptake in cells has curtailed their widespread application. Through this study, we explore a PNA-drug combinatorial strategy to improve the efficacy of PNAs and reduce their effective concentrations. This work also focuses on improving tuberculosis treatment, which is hindered by the emergence of antimicrobial-resistant strains of Mycobacterium tuberculosis. It is observed that the antibacterial efficacy of anti-inhA PNA is enhanced when it is combined with permeabilizing drugs, particularly ethambutol. This indicates that the addition of even small concentrations of anti-inhA PNA to the current TB regimen could potentiate their therapeutic efficiency. We hypothesize that this system would also overcome isoniazid resistance, since the resistance mutations lie outside the designed anti-inhA PNA target site.