Drug-Resistant tuberculosis - primary transmission and management

Risk factors for diagnosis and treatment delay among patients with multidrug-resistant tuberculosis in Hunan Province, China

BACKGROUND

Multidrug-resistant tuberculosis (MDR-TB) is a global health threat associated with high morbidity and mortality rates. Diagnosis and treatment delays are associated with poor treatment outcomes in patients with MDR-TB. However, the risk factors associated with these delays are not robustly investigated, particularly in high TB burden countries such as China. Therefore, this study aimed to measure the length of diagnosis and treatment delays and identify their risk factors among patients with MDR-TB in Hunan province.

METHODS

A retrospective cohort study was conducted using MDR-TB data from Hunan province between 2013 and 2018. The main outcomes of the study were diagnosis and treatment delay, defined as more than 14 days from the date of symptom to diagnosis confirmation (i.e., diagnosis delay) and from diagnosis to treatment commencement (i.e., treatment delay). A multivariable logistic regression model was fitted, and an adjusted odds ratio (AOR) with a 95% confidence interval (CI) was used to identify factors associated with diagnosis and treatment delay.

RESULTS

In total, 1,248 MDR-TB patients were included in this study. The median length of diagnosis delays was 27 days, and treatment delays were one day. The proportion of MDR-TB patients who experienced diagnosis and treatment delay was 62.82% (95% CI: 60.09-65.46) and 30.77% (95% CI: 28.27-33.39), respectively. The odds of experiencing MDR-TB diagnosis delay among patients coming through referral and tracing was reduced by 41% (AOR = 0.59, 95% CI: 0.45-0.76) relative to patients identified through consultations due to symptoms. The odds of experiencing diagnosis delay among ≥ 65 years were 65% (AOR = 0.35, 0.14-0.91) lower than under-15 children. The odds of developing treatment delay among foreign nationalities and people from other provinces were double (AOR = 2.00, 95% CI: 1.31-3.06) compared to the local populations. Similarly, the odds of experiencing treatment delay among severely ill patients were nearly 2.5 times higher (AOR = 2.49, 95% CI: 1.41-4.42) compared to patients who were not severely ill. On the other hand, previously treated TB cases had nearly 40% (AOR = 0.59, 95% CI: 0.42-0.85) lower odds of developing treatment delay compared with new MDR-TB cases. Similarly, other ethnic minority groups had nearly 40% (AOR = 0.57, 95% CI: 0.34-0.96) lower odds of experiencing treatment delay than the Han majority.

CONCLUSIONS

Many MDR-TB patients experience long diagnosis and treatment delays in Hunan province. Strengthening active case detection can significantly reduce diagnosis delays among MDR-TB patients. Moreover, giving attention to patients who are new to MDR-TB treatment, are severely ill, or are from areas outside Hunan province will potentially reduce the burden of treatment delay among MDR-TB patients.

Lymphocyte-Related Immunological Indicators for Stratifying Mycobacterium tuberculosis Infection

Background

Easily accessible tools that reliably stratify Mycobacterium tuberculosis (MTB) infection are needed to facilitate the improvement of clinical management. The current study attempts to reveal lymphocyte-related immune characteristics of active tuberculosis (ATB) patients and establish immunodiagnostic model for discriminating ATB from latent tuberculosis infection (LTBI) and healthy controls (HC).

Methods

A total of 171 subjects consisted of 54 ATB, 57 LTBI, and 60 HC were consecutively recruited at Tongji hospital from January 2019 to January 2021. All participants were tested for lymphocyte subsets, phenotype, and function. Other examination including T-SPOT and microbiological detection for MTB were performed simultaneously.

Results

Compared with LTBI and HC, ATB patients exhibited significantly lower number and function of lymphocytes including CD4⁺ T cells, CD8⁺ T cells and NK cells, and significantly higher T cell activation represented by HLA-DR and proportion of immunosuppressive cells represented by Treg. An immunodiagnostic model based on the combination of NK cell number, HLA-DR⁺CD3⁺ T cells, Treg, CD4⁺ T cell function, and NK cell function was built using logistic regression. Based on receiver operating characteristic curve analysis, the area under the curve (AUC) of the diagnostic model was 0.920 (95% CI, 0.867-0.973) in distinguishing ATB from LTBI, while the cut-off value of 0.676 produced a sensitivity of 81.48% (95% CI, 69.16%-89.62%) and specificity of 91.23% (95% CI, 81.06%-96.20%). Meanwhile, AUC analysis between ATB and HC according to the diagnostic model was 0.911 (95% CI, 0.855-0.967), with a sensitivity of 81.48% (95% CI, 69.16%-89.62%) and a specificity of 90.00% (95% CI, 79.85%-95.34%).

Conclusions

Our study demonstrated that the immunodiagnostic model established by the combination of lymphocyte-related indicators could facilitate the status differentiation of MTB infection.

The fourth national anti-tuberculosis drug resistance survey in Peru

BACKGROUND: Peru has one of the highest burdens of multidrug-resistant tuberculosis (MDR-TB), but universal drug susceptibility testing (DST) has not yet been achieved.OBJECTIVE: To estimate the proportion of drug resistance among smear-positive TB patients in Peru.DESIGN: From September 2014 to March 2015, we performed a national drug resistance survey of patients aged ≥15 years; TB was diagnosed based on sputum smear positivity. We performed DST at the National Reference Laboratory of the Peruvian National Institute of Health, Lima, Peru, using the proportion method in Middlebrook 7H10 agar for four first-line drugs and six second-line drugs, and the Wayne method for pyrazinamide.RESULTS: Of the 1908 new and 272 previously treated patients included in the analysis, 638 (29.3%) patients had resistance to at least one first-line drug. MDR-TB was diagnosed in 7.3% of new and 16.2% of previously treated patients (P < 0.001). There were five (0.2%) patients with extensively drug-resistant TB.CONCLUSION: MDR-TB has increased to 7.3% in new patients from 5.3% in the previous survey, indicating that resistance to anti-tuberculosis drugs is increasing in Peru. Ongoing community transmission of resistant strains highlights an urgent need for early diagnosis, optimised treatment and effective contact tracing of MDR-TB patients.

Transmission of drug-resistant tuberculosis in HIV-endemic settings

The emergence and expansion of the multidrug-resistant tuberculosis epidemic is a threat to the global control of tuberculosis. Multidrug-resistant tuberculosis is the result of the selection of resistance-conferring mutations during inadequate antituberculosis treatment. However, HIV has a profound effect on the natural history of tuberculosis, manifesting in an increased rate of disease progression, leading to increased transmission and amplification of multidrug-resistant tuberculosis. Interventions specific to HIV-endemic areas are urgently needed to block tuberculosis transmission. These interventions should include a combination of rapid molecular diagnostics and improved chemotherapy to shorten the duration of infectiousness, implementation of infection control measures, and active screening of multidrug-resistant tuberculosis contacts, with prophylactic regimens for individuals without evidence of disease. Development and improvement of the efficacy of interventions will require a greater understanding of the factors affecting the transmission of multidrug-resistant tuberculosis in HIV-endemic settings, including population-based molecular epidemiology studies. In this Series article, we review what we know about the transmission of multidrug-resistant tuberculosis in settings with high burdens of HIV and define the research priorities required to develop more effective interventions, to diminish ongoing transmission and the amplification of drug resistance.

The never-ending story of the fight against tuberculosis: from Koch's bacillus to global control programs

Tuberculosis (TB) is one of the oldest diseases known to affect humanity, and is still a major public health problem. It is caused by the bacillus Mycobacterium tuberculosis (MT), isolated in 1882 by Robert Koch. Until the 1950s, X rays were used as a cheap method of diagnostic screening together with the tuberculin skin sensitivity test. In the diagnosis and treatment of TB, an important role was also played by surgery. The late Nineteenth century saw the introduction of the tuberculosis sanatorium, which proved to be one of the first useful measures against TB. Subsequently, Albert Calmette and Camille Guérin used a non-virulent MT strain to produce a live attenuated vaccine. In the 1980s and 1990s, the incidence of tuberculosis surged as a major opportunistic infection in people with HIV infection and AIDS; for this reason, a combined strategy based on improving drug treatment, diagnostic instruments and prevention was needed.

Update on trends in childhood tuberculosis

PURPOSE OF REVIEW

Although tuberculosis (TB) causes much morbidity and mortality in children, diagnosis and treatment remain challenging. Recently, children have gained increasing attention in research and clinical trials driving improved contact management, case identification and treatment of both drug-susceptible and drug-resistant TB. This review highlights some recent advances.

RECENT FINDINGS

The tuberculin skin test is the most widely used test to distinguish Mycobacterium tuberculosis (M. tuberculosis) infection from active TB, however, using M. tuberculosis-specific, antigenic stimulation of CD4 and CD8 cells appear more effective. The use of Xpert MTB/RIF to identify M. tuberculosis in clinical samples, together with novel sampling methods have in part, overcome the difficulty of sampling and increased case identification capacity. Advances in treating both drug-susceptible and drug-resistant childhood TB show promise in being more paediatric friendly and improving adherence. Dosing strategies for drug-sensitive TB have improved with dispersible fixed drug combinations now available. In the treatment and prevention of drug-resistant TB, however, research involving the use of newer and more effective drugs currently recommended for adults, are still ongoing in children.

SUMMARY

The World Health Organization aims to end the TB epidemic by 2035 whereas the United Nations' Sustainable Developmental Goals sets this ambitious target for 2030. Therefore, adequate funding and implementing effective national TB programs must be prioritized, particularly in high-burden, low-income settings.