Prevalence and Clinical Characteristics of Nontuberculous Mycobacteria in Patients with Bronchiectasis: A Systematic Review and Meta-Analysis

Single-cell transcriptomics by clinical course of Mycobacterium avium complex pulmonary disease

Mycobacterium avium complex pulmonary disease (MAC-PD) has a heterogeneous clinical course. However, immune profiles associated with MAC-PD clinical course are limited. We performed single-cell RNA sequencing of peripheral blood mononuclear cells from 21 MAC-PD patients divided into three clinical courses: group A, spontaneous culture conversion; group B, stable disease without antibiotic treatment; and group C, progressive disease with antibiotic treatment. A lower proportion of NK cells and higher proportion of monocytes were noted in group C compared to combined groups A and B. The proportion of classical monocytes was higher in group C compared to groups A and B, while the proportion of non-classical monocytes decreased. EGR1, HSPA1A, HSPA1B, and CD83 were up-regulated in spontaneous culture conversion group A compared to progressive disease group C. Up-regulation of MYOM2 and LILRA4 and down-regulation of MT-ATP8, CD83, and CCL3L1 was found in progressive disease group C. PCBP1, FOS, RGCC, S100B, G0S2, AREG, and LYN were highly expressed in favorable treatment response compared to unfavorable response. Our findings may offer a comprehensive understanding of the host immune profiles that influence a particular MAC-PD clinical course and could suggest an immunological mechanism associated with the disease progression of MAC-PD.

Growing from common ground: nontuberculous mycobacteria and bronchiectasis

Bronchiectasis and nontuberculous mycobacteria (NTM) are intricately intertwined, with NTM capable of being both a cause and consequence of bronchiectatic disease. This narrative review focuses on the common ground of bronchiectasis and NTM pulmonary disease (NTM-PD) in terms of diagnostic approach, underlying risk factors and treatment strategies. NTM-PD diagnosis relies on a combination of clinical, radiological and microbiological criteria. Although their epidemiology is complicated by detection and reporting biases, the prevalence and pathogenicity of NTM species vary geographically, with Mycobacterium avium complex and Mycobacterium abscessus subspecies most frequently isolated in bronchiectasis-associated NTM-PD. Diagnosis of nodular bronchiectatic NTM-PD should prompt investigation of host factors, including disorders of mucociliary clearance, connective tissue diseases and immunodeficiencies, either genetic or acquired. Treatment of NTM-PD in bronchiectasis involves a multidisciplinary approach and considers the (sub)species involved, disease severity and comorbidities. Current guideline-based antimicrobial treatment of NTM-PD is considered long, cumbersome and unsatisfying in terms of outcomes. Novel treatment regimens and strategies are being explored, including rifampicin-free regimens and inclusion of clofazimine and inhaled antibiotics. Host-directed therapies, such as immunomodulators and cytokine-based therapies, might enhance antimycobacterial immune responses. Optimising supportive care, as well as pathogen- and host-directed strategies, is crucial, highlighting the need for personalised approaches tailored to individual patient needs. Further research is warranted to elucidate the complex interplay between host and mycobacterial factors, informing more effective management strategies.

Five-Year Outcomes among U.S. Bronchiectasis and NTM Research Registry Patients

Rationale: Nontuberculous mycobacteria (NTM) are prevalent among patients with bronchiectasis. However, the long-term natural history of patients with NTM and bronchiectasis is not well described. Objectives: To assess the impact of NTM on 5-year clinical outcomes and mortality in patients with bronchiectasis. Methods: Patients in the Bronchiectasis and NTM Research Registry with ⩾5 years of follow-up were eligible. Data were collected for all-cause mortality, lung function, exacerbations, hospitalizations, and disease severity. Outcomes were compared between patients with and without NTM at baseline. Mortality was assessed using Cox proportional hazards models and the log-rank test. Measurements and Main Results: In total, 2,634 patients were included: 1,549 (58.8%) with and 1,085 (41.2%) without NTM at baseline. All-cause mortality (95% confidence interval) at Year 5 was 12.1% (10.5%, 13.7%) overall, 12.6% (10.5%, 14.8%) in patients with NTM, and 11.5% (9.0%, 13.9%) in patients without NTM. Independent predictors of 5-year mortality were baseline FEV1 percent predicted, age, hospitalization within 2 years before baseline, body mass index, and sex (all P < 0.01). The probabilities of acquiring NTM or Pseudomonas aeruginosa were approximately 4% and 3% per year, respectively. Spirometry, exacerbations, and hospitalizations were similar, regardless of NTM status, except that annual exacerbations were lower in patients with NTM (P < 0.05). Conclusions: Outcomes, including exacerbations, hospitalizations, rate of loss of lung function, and mortality rate, were similar across 5 years in patients with bronchiectasis with or without NTM.

Epidemiology of Mycobacterium abscessus

BACKGROUND

Nontuberculous mycobacteria (NTM) are highly abundant in soil, dust, and water sources, making human-pathogen contact frequent and recurrent. NTM represents over 200 species/subspecies; some are considered strict or opportunistic pathogens. Mycobacterium abscessus, often regarded as one of the most antibiotic-resistant mycobacteria, is the second most frequent NTM pulmonary disease pathogen.

OBJECTIVES

To describe the epidemiology of M. abscessus through a literature review focusing on clinical aspects.

SOURCES

We conducted searches on PubMed and Web of Knowledge for articles published from 2010 to the present using the keywords 'Mycobacterium abscessus', 'Nontuberculous mycobacteria', and 'epidemiology'. Our search prioritized original reports on the occurrence of NTM and M. abscessus infection/disease.

CONTENT

Advanced molecular and genetic diagnostic techniques have refined the M. abscessus complex (MABC) microbiological classification over the last few decades. MABC can adhere to surfaces and form a biofilm. This characteristic and its resistance to common disinfectants allow these microorganisms to persist in the water distribution systems, becoming a constant reservoir. The frequency and manifestation of NTM species vary geographically because of environmental conditions and population susceptibility differences. MABC lung disease, the most frequent site of NTM infection in humans, is often seen in patients with underlying lung diseases such as bronchiectasis, whereas MABC disseminated disease is related to immunosuppression. Skin and soft tissue infections are associated with surgical or injection procedures. Epidemiological evidence suggests an overall increase in MABC infection and disease in the last decade.

IMPLICATIONS

Establishing the burden of this disease is challenging because of varying measures of incidence and prevalence, referral bias, and differences in medical practices and reporting. Furthermore, environmental and structural determinants, infection routes, and MABC pulmonary disease mechanisms require additional investigation. This review contributes to a better understanding of the epidemiology of MABC, which could inform clinical practice and future research.

Endotypes in bronchiectasis: moving towards precision medicine. A narrative review

Bronchiectasis is a highly complex entity that can be very challenging to investigate and manage. Patients are diverse in their aetiology, symptoms, risk of complications and outcomes. "Endotypes"- subtypes of disease with distinct biological mechanisms, has been proposed as a means of better managing bronchiectasis. This review discusses the emerging field of endotyping in bronchiectasis. We searched PubMed and Google Scholar for randomized controlled trials (RCT), observational studies, systematic reviews and meta-analysis published from inception until October 2022, using the terms: "bronchiectasis", "endotypes", "biomarkers", "microbiome" and "inflammation". Exclusion criteria included commentaries and non-English language articles as well as case reports. Duplicate articles between databases were initially identified and appropriately excluded. Studies identified suggest that it is possible to classify bronchiectasis patients into multiple endotypes deriving from their co-morbidities or underlying causes to complex infective or inflammatory endotypes. Specific biomarkers closely related to a particular endotype might be used to determine response to treatment and prognosis. The most clearly defined examples of endotypes in bronchiectasis are the underlying causes such as immunodeficiency or allergic bronchopulmonary aspergillosis where the underlying causes are clearly related to a specific treatment. The heterogeneity of bronchiectasis extends, however, far beyond aetiology and it is now possible to identify subtypes of disease based on inflammatory mechanisms such airway neutrophil extracellular traps and eosinophilia. In future biomarkers of host response and infection, including the microbiome may be useful to guide treatments and to increase the success of randomized trials. Advances in the understanding the inflammatory pathways, microbiome, and genetics in bronchiectasis are key to move towards a personalized medicine in bronchiectasis.

Case report: Intraabdominal infection of Mycobacterium syngnathidarum in an immunocompetent patient confirmed by whole-genome sequencing

Background

The taxonomic group of non-tuberculous mycobacteria (NTM) encompasses more than 190 species and subspecies, some of which can cause pulmonary and extrapulmonary diseases across various age groups in humans. However, different subspecies exhibit differential drug sensitivities, and traditional detection techniques struggle to accurately classify NTM. Therefore, clinicians need more effective detection methods to identify NTM subtypes, thus providing personalized medication for patients.

Case presentation

We present the case of a 47-year-old female patient diagnosed with an intraabdominal infection caused by Mycobacterium syngnathidarum. Despite computed tomography of the chest suggesting potential tuberculosis, tuberculosis infection was ruled out due to negative TB-DNA results for ascites fluid and sputum and limited improvement of lung lesions after treatment. Additionally, acid-fast staining and Lowenstein-Jensen culture results revealed the presence of mycobacterium in ascites fluid. Subsequent whole-genome sequencing (WGS) confirmed the DNA sequences of Mycobacterium syngnathidarum in colonies isolated from the ascites fluid, which was further corroborated by polymerase chain reaction and Sanger sequencing. Ultimately, the patient achieved a complete recovery following the treatment regimen targeting Mycobacterium syngnathidarum, which involved clarithromycin, ethambutol hydrochloride, pyrazinamide, rifampicin, and isoniazid.

Conclusion

This is the first reported case of Mycobacterium syngnathidarum infection in humans. Mycobacterium syngnathidarum was detected by WGS in this case, suggesting that WGS may serve as a high-resolution assay for the diagnosis of different subtypes of mycobacterium infection.

The performance of interferon gamma release assays in patients with nontuberculous mycobacterial infection: a systematic review and meta-analysis

BACKGROUND

The actual positive rate of interferon gamma release assays (IGRAs) in patients with nontuberculous mycobacteria (NTM) infections remains unclear. This review and meta-analysis present the prevalence of positive IGRAs (T-SPOT.TB and QuantiFERON [QFT] tests) among patients infected with NTM isolates (with or without ESAT-6/CFP-10).

METHODS

Several databases, including PubMed, Scopus, Embase, and Web of Science were searched (until June 18th, 2022). Studies that had the following data were included: (1) results of T-SPOT.TB, QuantiFERON (QFT) test, or both, (2) NTM species, and (3) NTM diseases, or NTM colonization. The metaprop command that incorporates a Freeman-Tukey double arcsine transformation is used for pooling proportions.

RESULTS

A total of 11 articles (n = 929) were deemed eligible for inclusion. Meta-analysis identified that the overall pooled positive and indeterminate rates of IGRA results in patients with NTM infections was 16% and 5%, respectively. Subgroup analysis showed that the positive rate of IGRAs in patients infected with NTM (without ESAT-6/CFP-10) was 7% (95% CI, 1%-18%), and 44% (95%CI, 22%-68%) in patients infected with NTM (with ESAT-6/CFP-10). In addition, the indeterminate rate of QFT (7%, 95% CI: 4%-12%) was higher than that of T-SPOT.TB (0%; 95% CI, 0%-2%) among the overall population with NTM infections.

CONCLUSIONS

The IGRAs have a moderate positive rate for the diagnosis of NTM (expressing ESAT-6/CFP-10) infections, and a significant indeterminate rate is observed among the overall population infected with NTM. However, these findings should be interpreted with caution because of the high heterogeneity among studies.

Bronchiectasis

Bronchiectasis is a final common pathway of a wide variety of underlying conditions including infectious, autoimmune, allergic, genetic and inflammatory conditions. Patients experience a chronic disease with variable clinical symptoms and course, but most experience cough, sputum production and recurrent exacerbations. Symptoms of bronchiectasis lead to poor quality of life and exacerbations are the major driver of morbidity and mortality. Patients are often chronically infected with bacteria with the most common being Pseudomonas aeruginosa and Haemophilus influenzae. Treatment of bronchiectasis includes standardised testing to identify the underlying cause with targeted treatment if immune deficiency, allergic bronchopulmonary aspergillosis or non-tuberculous mycobacterial infection, for example, are identified. Airway clearance is the mainstay of therapy for patients with symptoms of cough and sputum production. Frequently exacerbating patients may benefit from long term antibiotic or mucoactive therapies. Bronchiectasis is a heterogeneous disease and increasingly precision medicine approaches are advocated to target treatments most appropriately and to limit the emergence of antimicrobial resistance.

Nontuberculous mycobacterial pulmonary disease and the potential role of SPR720

INTRODUCTION

Nontuberculous mycobacteria infect patients who have structural lung disease or those who are immunocompromised. Nontuberculous mycobacterial pulmonary disease (NTM-PD) is increasing in prevalence. Treatment guidelines for Mycobacterium avium complex (MAC) pulmonary disease involve a three-drug regimen with azithromycin, ethambutol, and rifampin, and those of Mycobacterium abscessus complex (MAB) pulmonary disease involve a combination of three or more antimicrobials including macrolides, amikacin, and a β-lactam or imipenem. However, these regimens are poorly tolerated and generally ineffective.

AREAS COVERED

SPR720 is a novel therapeutic agent that has demonstrated activity against a range of NTM species, including MAC and MAB. Encouraging in vitro and pre-clinical data demonstrate that SPR720 is active both alone and in combination with standard-of-care agents, with no evidence of cross-resistance to such agents. It is generally well tolerated with mainly gastrointestinal and headache adverse events of mild or moderate severity.

EXPERT OPINION

Management of NTM-PD is challenging for many reasons including length of therapy, poor efficacy, drug intolerance, recurrence, and resistance development. The current antimicrobial management options for NTM-PD are limited in number and there exists a large unmet need for new treatments. SPR720 has encouraging data that warrant further study in the context of a multidrug regimen.

Bronchiectasis and obstructive lung diseases in primary antibody deficiencies and beyond: update on management and pathomechanisms

PURPOSE OF REVIEW

Pulmonary complications are among the most frequent manifestations in patients with primary antibody deficiency (PAD), contributing significantly to morbidity and mortality. Here, we focus on recent findings in obstructive pulmonary disease and bronchiectasis in PAD. Since specific data on patients with PAD is limited and management mostly follows general recommendations, this review also aims to summarize data from the immunocompetent population.

RECENT FINDINGS

Potential risk factors for the development and progression of bronchiectasis include reduced immunoglobulins and lower CD4 cells. In addition, Pseudomonas aeruginosa and an altered microbiome might contribute to local inflammation and disease progression. Findings on the contribution of neutrophils and eosinophils in the affected immunocompetent population require confirmation in PAD. Despite its high global burden, there is an extreme paucity of data on chronic obstructive pulmonary disease in PAD. Lower IgA and IgM are associated with asthma in PAD, but the heterogeneity of prevalence among PAD groups is poorly understood. Recent observations of non-IgE-mediated pathomechanisms in asthma may be of particular interest in PAD patients.

SUMMARY

Management of PAD patients with chronic lung disease requires a multidisciplinary team approach including immunology, pulmonology, infectious disease and physiotherapy. Diagnostic processes should be harmonized to ensure a more precise perspective on prevalence and disease courses.

Impacts of Nontuberculous Mycobacteria Isolates in Non-cystic Fibrosis Bronchiectasis: A 16-Year Cohort Study in Taiwan

Background

The prevalence of nontuberculous mycobacteria (NTM) in patients with chronic respiratory disease has increased. The implication of NTM in non-CF bronchiectasis remained controversial. This study investigated the impact of NTM in non-CF bronchiectasis in Taiwan.

Methods

Clinical manifestation, imaging, and microbiological data were retrieved from the Chang Gung Research Database, the largest electronic medical record-based database in Taiwan. Patients with bronchiectasis during 2001–2016 were included. Cox proportional hazard model was employed to compare outcomes between patients with negative and positive NTM isolates after 1:1 propensity score matching.

Results

A total of 19,647 non-CF bronchiectasis patients were enrolled and 11,492 patients were eligible for analysis after exclusion screening. Finally, patients with negative and positive NTM isolates—650 each—were analyzed after propensity score matching. The patients with negative NTM isolates were divided into three groups: Pseudomonas aeruginosa isolates (n = 53); fungus isolates (n = 26); and concomitant P. aeruginosa and fungus isolates (n = 8). The patients with positive NTM isolates were divided into five groups: single NTM isolate (n = 458); multiple NTM isolates (n = 60); concomitant NTM and P. aeruginosa isolates (n = 89); concomitant NTM and fungus isolates (n = 33); and concomitant NTM, P. aeruginosa, and fungus isolates (n = 10). Patients with P. aeruginosa isolates; concomitant NTM and P. aeruginosa isolates; concomitant NTM, P. aeruginosa, and fungus isolates had independently associated with respiratory failure and death. Patients with single or multiple NTM isolates were not related to ventilator use, but both were independent risk factor for mortality.

Conclusion

NTM, either combined with P. aeruginosa or fungus, exhibited more frequent exacerbations in non-CF bronchiectasis patients. Moreover, NTM predicted mortality in non-CF bronchiectasis patients and were also correlated to respiratory failure while concomitantly isolated with P. aeruginosa and fungus.