Global trends of pulmonary infections with nontuberculous mycobacteria: a systematic review

Clinical analysis and risk factors associated with poor prognosis in nontuberculous mycobacterial infection

Recently, the incidence and prevalence of NTM have been increasing nationwide in many countries. This study aimed to identify risk factors associated with the prognosis and mortality of non-HIV nontuberculous mycobacterial disease patients. This retrospective study was conducted at Peking Union Medical College Hospital. The electronic medical records in the hospital's database from January 2013 to December 2022 were retrospectively reviewed. Relevant data, including clinical characteristics, laboratory findings, microbiological tests, treatments, and outcomes were collected and subjected to statistical analyses. The search identified 745 patients diagnosed with NTM infection, of whom 147 met the inclusion criteria. NTM pulmonary disease was the most commonly observed (n = 93; 63.3%), followed by disseminated infection (n = 43; 29.3%). The most frequent NTM species was Mycobacterium avium complex (55.8%), followed by Mycobacterium abscessus (21.2%). The incidence of Aspergillus and Pseudomonas aeruginosa infection was significantly higher in the NTM pulmonary disease group than in the disseminated NTM group. Cumulative mortality in the total patients was 24.49% at 5 years. High Charlson Comorbidity Index (CCI), high neutrophil-to-lymphocyte-ratio (NLR), haematological disease, and disseminated infection were identified as independent predictors of unfavourable outcomes. The area under the curve (AUC) values for NLR and neutrophil-to-monocyte-plus-lymphocyte-ratio (NMLR) were 0.751 and 0.763 with optimal cut-off values of 9.50 and 3.83, respectively, for prediction of mortality in patients with NTM disease.

The Influencing Factors of Extensive Lung Lesions and Cavities in Patients With Non-Tuberculous Mycobacterial Lung Disease

Aims/Background The resolution of non-tuberculous mycobacterial (NTM) lung disease is associated with the extent of pulmonary lesions and the presence of lung cavities. This study aims to identify factors influencing the development of extensive lung lesions and cavities in patients with NTM lung disease, thereby generating valuable insights for the management and treatment of NTM lung disease. Methods Retrospective analysis was conducted on clinical data from 198 hospitalized patients with NTM lung disease at the Department of Tuberculosis, The Second Hospital of Nanjing, between 2022 and 2023. Patient data like age, gender, past medical history, nutritional risk screening 2002 (NRS-2002) score, lymphocyte count, peripheral blood neutrophil-to-lymphocyte ratio (NLR), pulmonary computed tomography (CT) imaging findings (including extent of lung lesions and presence of cavities), and T cell subsets count were gathered through electronic medical records and hospital information system (HIS) system. Univariate and multivariate logistic regression analyses were carried out with extensive lung lesions and cavities as dependent variables and other factors as independent variables. Results Among the 198 patients, 138 (69.7%) exhibited extensive lung lesions, while cavities were observed in 76 individuals (38.4%). Based on the results of logistic regression analysis, a high NLR (OR = 4.685 [1.176-18.663], p = 0.029) and an NRS-2002 score ≥3 (OR = 12.082 [3.726-39.183], p < 0.001) were identified as risk factors for the development of extensive lung lesions in patients with NTM lung disease. Furthermore, elevated NLR (OR = 3.454 [1.483-8.047], p = 0.004) was associated with an increased risk of cavities in patients with NTM lung disease. Conclusion In patients with NTM lung disease, high NLR is the risk factor for extensive lung lesions and formation of pulmonary cavities, whereas malnutrition elevates the risk for prevalent lung lesions. Early intervention and active monitoring of these related indicators are necessary to prevent disease progression and enhance overall cure rates.

Targeting Autophagy as a Strategy for Developing New Host-Directed Therapeutics Against Nontuberculous Mycobacteria

Nontuberculous mycobacteria (NTMs) are increasingly being recognized as opportunistic pathogens in clinical practice because of their innate resistance to antimicrobial treatment and the widespread increase in multidrug-resistant strains on a global scale. NTMs pose a tremendous infection management challenge, especially in individuals with pre-existing lung conditions, as well as those who are immunocompromised. NTMs' capability to evade or suppress the immune responses of their host is a key feature that makes them a cause of persistent chronic infection. Autophagy, an essential cellular defense mechanism that delivers and breaks down intracellular materials in lysosomes, protects the host from mycobacterial infection. Initial studies have revealed encouraging therapeutic strategies that augment endogenous autophagic mechanisms or block harmful host responses, thus having the potential to decrease intracellular mycobacterial infection, including that caused by multidrug-resistant strains. This review discusses how NTMs can evade autophagic mechanisms and considers the possibilities of using autophagy-inducing agents to develop novel therapeutic strategies to combat NTM infection.

Moving Beyond the Silos of Opportunistic Pathogen and Disinfection Byproduct Research to Improve Drinking Water System Management

Drinking water opportunistic pathogens (OPs) and disinfection byproducts (DBPs) both pose risks to public health, and their variable occurrence from source to tap complicates efforts to control them simultaneously. Management of OPs and DBPs is further hindered by the historical division between microbial and chemical research. This review brings together the current knowledge regarding OPs and DBPs, identifies factors that influence the occurrence of both, and highlights areas where research is needed to better understand their health risks. First, we examine the current understanding of how OPs and DBPs are jointly influenced by physicochemical parameters, source water characteristics, treatment processes including disinfection, and distribution system properties. Temperature, for example, can affect OP and DBP occurrence, where higher temperatures can promote the growth of some OPs, such as Legionella pneumophila, but temperature's effect on DBPs is species-dependent. Methods for quantifying the risks associated with OPs (quantitative microbial risk assessment) and DBPs (chemical risk assessment) are compared, finding that the numerous assumptions and data gaps associated with each method limit comparability across contaminant types. We highlight the urgent need to fill existing data gaps and develop a more unified risk framework so as to move toward holistic assessment of microbial and chemical risks. This review provides suggestions for future research, highlighting ways that researchers might utilize established practices in OP or DBP studies to further our understanding of the other. For example, analysis of source water organic matter composition, which has advanced our understanding of DBP formation, could be utilized to elucidate how source water characteristics influence OPs. This review bridges the gap between the OP and DBP disciplines, arguing that collaboration between the two is needed to address the pressing challenges facing water systems today.

Comprehensive Management Algorithm for Mycobacterium avium Complex Pulmonary Disease in the Real-World Setting

The management of Mycobacterium avium complex pulmonary disease (MAC-PD) is challenging because of limited efficacy and frequent adverse events associated with standard treatments. The 2020 guidelines from the American Thoracic Society, European Respiratory Society, European Society of Clinical Microbiology and Infectious Diseases, and Infectious Diseases Society of America provide recommendations, but real-world adherence is often hindered by these issues, leading many patients to be unable to complete standard therapy. This review proposes a comprehensive management algorithm for MAC-PD, emphasizing multidisciplinary approaches and integrating nonantimicrobial management before, during, and after drug treatment to enhance patient outcomes. When a patient presents with chronic respiratory symptoms suggestive of nontuberculous mycobacteria, clinicians should follow a guideline-based approach to diagnosis, as diagnostic delays are common because of nonspecific symptoms. Proper evaluation should determine the disease phenotype (existence of cavitary lesions), as it influences treatment choices. Airway clearance, nutritional support, and management of underlying conditions are essential nonantimicrobial components. Regular outpatient monitoring helps detect disease progression and optimize treatment. Treatment strategies vary based on disease severity. For noncavitary nodular bronchiectatic disease, a thrice-weekly regimen is preferred because of better tolerability. Severe cases or those with cavitary forms may require daily treatment with additional aminoglycosides. Amikacin liposome inhalation suspension is recommended for patients not responding to standard regimens after 6 months. Recent research addresses drug intolerance, suggesting alternatives such as a two-drug regimen without rifamycin in certain cases. Consultation with nontuberculous mycobacteria specialists is advised for complex cases, particularly those with macrolide resistance or requiring surgical intervention. The algorithm emphasizes shared decision making, patient education, and family support to improve adherence and outcomes.

Rifampicin-Induced Lung Injury in Mycobacterium shinjukuense Infection: A Case Report

A 70-year-old woman with sputum and cough was diagnosed with nontuberculous mycobacterial pulmonary disease based on multiple cultures of Mycobacterium shinjukuense and computed tomography (CT) findings of bilateral nodular shadows and bronchiectasis. Treatment was initiated with ethambutol and azithromycin, and rifampicin was added 1 month later. Three weeks after rifampicin therapy, she developed fever and fatigue, and CT revealed bilateral non-segmental infiltrates and a reversed halo sign indicative of organising pneumonia. Rifampicin was discontinued due to suspected rifampicin-induced lung injury, and a subsequent bronchial lung biopsy confirmed organising pneumonia. The patient's fever resolved with discontinuation of rifampicin, and chest imaging showed resolution of the infiltrates. Continuation with ethambutol and azithromycin did not result in fever or new shadows. We need to consider the possibility of drug-induced lung injury when new shadows appear during nontuberculous mycobacterial treatment regimens.

Clinical characteristics and diagnostic practices in nontuberculous mycobacterial pulmonary disease: Insights from Denmark

BACKGROUND

Clinical characteristics of patients with nontuberculous mycobacterial pulmonary disease (NTM-PD) in Denmark are undescribed. This study investigated clinical characteristics and diagnostic practices in patients with pulmonary NTM isolates.

METHODS

Patients in Central Region Denmark from 2016 to 2021 were identified using mycobacterial reference laboratory data, and hospital records were reviewed for demographics, comorbidities, risk factors, and diagnostic details. Diagnostic guideline criteria for NTM-PD were assessed, and clinical characteristics were compared between those who met the criteria and those who did not.

RESULTS

Among 193 patients, M. avium complex (56 %), M. gordonae (15 %), and M. xenopi (11 %) were most common. Symptoms included cough (62 %), expectoration (51 %), dyspnea (43 %), and systemic symptoms (42 %), with 36 % experiencing symptoms for over 6 months. The median time from first hospital contact to receipt of the first sample yielding NTM was 14 days (IQR: 42). Forty-five percent (n = 87) of patients were initially seen in a fast-track pulmonary cancer referral pathway. Fifty-three percent (n = 103) met the diagnostic criteria for NTM-PD. This was associated with older age, lower BMI and FEV1, a higher comorbidity burden, longer time to diagnostic sampling, and higher bacterial loads.

CONCLUSIONS

In Denmark, a high percentage of patients met the NTM-PD criteria compared to other studies, which may be attributed to a high prevalence of structural lung disease and delayed disease presentation and diagnosis. Many patients were initially seen in a fast-track pulmonary cancer pathway, which could be leveraged to improve the diagnostic pathway of NTM-PD.

Assessment of Healthcare Professionals' Knowledge Regarding Nontuberculosis Mycobacterial Infections at Debre Tabor Comprehensive Specialized Hospital, Northwest Ethiopia, 2024: A Cross-Sectional Study

BACKGROUND

Nontuberculosis mycobacteria (NTM) are environmental pathogens that can cause pulmonary infections, especially among the immunocompromised population. There is limited research on healthcare professionals' knowledge of NTM infections in Ethiopia. This study aimed to evaluate healthcare professionals' knowledge about NTM infections at Debre Tabor Comprehensive Specialized Hospital (DTCSH).

METHODS

A cross-sectional study was conducted from March 5 to July 30, 2024 at DTCSH to evaluate the knowledge of 292 healthcare professionals on NTM infections. A semi-structured questionnaire was used for data collection, and the data were analyzed using SPSS version 25. The study's findings were presented through texts, tables, and figures.

RESULTS

Of all the participants, 160 (54.8%) were male, and the majority 153 (52.4%) were 36-45 years old. Nurses made up the largest professional group, 127 (43.5%). Approximately 59% of healthcare professionals showed good knowledge of NTM infections. In this study, a higher percentage of female [92 (69.7%)] participants demonstrated good knowledge compared to males [83 out of 160 males (51.9%)]. Similarly, 35 doctors (89.7%) and 80 nurses (63%) demonstrated favorable knowledge. Only 52.4% could distinguish between NTM and Mycobacterium tuberculosis infections. Notably, 77.4% recognized that NTM infections are more common in immunocompromised individuals, yet only 20.5% knew that NTM species are not typically treated with anti-tuberculosis drugs.

CONCLUSION

The knowledge gaps among healthcare professionals regarding NTM infections necessitate focused educational initiatives to improve their ability to manage these infections. The focused training is essential for enhancing the management and identification of NTM infections.

Combined dual β-lactams and diazabicyclooctane β-lactamase inhibitor is highly effective against Mycobacterium abscessus species in vitro

OBJECTIVE

Mycobacterium abscessus pulmonary disease is a refractory infectious disease. Developing an effective treatment is urgent as the number of patients infected with M. abscessus species (MABS) is increasing worldwide. We previously reported that nacubactam, a diazabicyclooctane (DBO) β-lactamase inhibitor, could inhibit MABS β-lactamase. Few reports have indicated that dual β-lactams are effective with a DBO β-lactamase inhibitor against MABS. The objective of this study was to determine which dual β-lactams have high antibacterial activity against MABS in the presence and absence of nacubactam.

METHODS

Antimicrobial susceptibility tests were conducted through a checkerboard assay of 27 β-lactams using the broth microdilution method for three subspecies-type strains and 20 clinical isolates of MABS. The number of intracellular and extracellular bacteria was measured using human macrophages infected with M. abscessus treated with effective combinations confirmed in susceptibility tests.

RESULTS

In antimicrobial susceptibility tests, 91 combinations of dual β-lactams with nacubactam exhibited synergistic effects on M. abscessus JCM13569. Among them, the combination of cefazolin, cefotiam, cefoxitin, or cefuroxime with imipenem and nacubactam exhibited highly synergistic effects, resulting in low MICs against MABS clinical isolates. Without nacubactam, the combination of imipenem and cefoxitin showed the lowest MIC. In experiments using human macrophages infected with M. abscessus, these dual β-lactam combinations reduced the number of intracellular and extracellular bacteria compared with those of single β-lactams.

CONCLUSIONS

The combination of cefazolin, cefotiam, cefoxitin, or cefuroxime with imipenem and nacubactam was highly effective against MABS. Without nacubactam, the combination of cefoxitin and imipenem was effective.

An Antibody-Recruiting Molecule Enhances Fcγ Receptor-Mediated Uptake and Killing of Mycobacterial Pathogens by Macrophages

Mycobacteria, which include the infectious agents for tuberculosis (TB) and nontuberculous mycobacteria (NTM) disease, pose a critical health challenge due to traits that allow them to evade host immune clearance and antibiotic action. Toward a novel immunotherapy approach for mycobacteria, we previously reported an antibody-recruiting molecule (ARM) strategy to specifically modify the surface glycans of mycobacteria with exogenous haptens, marking the bacteria for opsonization by endogenous antibodies and enhancing the antibody-mediated immune response. We showed that the ARM, a trehalose-dinitrophenyl conjugate (Tre-DNP), exploited a conserved metabolic pathway to metabolically label the surface of nonpathogenic Mycobacterium smegmatis with DNP, recruited anti-DNP antibodies to the bacterial surface, and enhanced phagocytosis of the bacteria by THP-1 cells. Here, we extend these findings by investigating the ability of the Tre-DNP ARM strategy to increase macrophage-mediated phagocytosis and killing of different pathogenic mycobacterial species and interrogating mechanisms associated with the outcome. We show that Tre-DNP successfully modified the surface of multiple pathogens, including Mycobacterium tuberculosis and the NTM species Mycobacterium abscessus and Mycobacterium avium, and that phagocytosis and killing of intracellular bacteria by differentiated THP-1 cells is significantly enhanced for all species. Furthermore, we find that enhanced uptake is dependent upon the Fcγ receptor (FcγR) and enhanced killing correlates with sustained production of reactive oxygen species (ROS) and increased phagosome-lysosome fusion. Overall, our data demonstrate that Tre-DNP efficiently promotes ingestion of mycobacteria by human macrophages via the FcγR and enhances host effector responses against the pathogen. Thus, ARMs are tools that can be exploited for the purposes of (i) conducting mechanistic studies on immune recognition and elimination of mycobacterial pathogens and (ii) developing immune-targeting strategies against mycobacterial pathogens.

Cell Death Mechanisms in Mycobacterium abscessus Infection: A Double-Edged Sword

Infections caused by non-tuberculous mycobacteria (NTM), such as Mycobacterium abscessus, elicit diverse cell death mechanisms including apoptosis, necrosis, and pyroptosis, which play key roles in immunopathogenesis. NTM can manipulate these cell death pathways to evade host immune responses, ensuring their intracellular survival and persistence. Apoptosis may aid in antigen presentation and immune activation, while necrosis and pyroptosis trigger excessive inflammation, leading to tissue damage. Autophagy, a crucial cellular defense mechanism, is often induced in response to NTM infection; however, M. abscessus has evolved mechanisms to inhibit autophagic processes, enhancing its ability to survive within host cells. This manipulation of cell death pathways, particularly the dysregulation of autophagy and ferroptosis, contributes to chronic infection, immune evasion, and tissue damage, complicating disease management. Understanding these mechanisms offers potential therapeutic targets for improving treatment strategies against M. abscessus infections.

In vitro, intracellular and in vivo synergy between amoxicillin, imipenem and relebactam against Mycobacterium abscessus

OBJECTIVES

Mycobacterium abscessus is the most frequent of the rapidly growing mycobacteria responsible for lung infections in patients suffering from cystic fibrosis and COPD. Imipenem is currently recommended in the treatment of these infections in spite of β-lactamase production. Since the targets of β-lactams include transpeptidases of both the l,d and d,d specificities, we tested, in vitro, intracellularly and in vivo, a combination of two β-lactams active on these enzymes, amoxicillin and imipenem, alone or in combination with the β-lactamase inhibitor relebactam.

METHODS

Drug combinations were evaluated against M. abscessus CIP 104536T and clinical isolates (n = 35) by determining MICs, FIC indices and time-killing. Drug combinations were also evaluated in macrophages and in mice.

RESULTS

In the presence of relebactam, synergy between amoxicillin and imipenem was observed against both M. abscessus CIP 104536T and the clinical isolates. Against M. abscessus CIP 104536T, the addition of 1 mg/L imipenem and 4 mg/L relebactam led to a decrease in the MIC of amoxicillin from 64 to 1 mg/L. The triple combination was active in vitro and intracellularly (a 4.30 decrease in the log10 cfu/mL and 82% killing, respectively). The triple combination was effective in reducing log10 cfu in mouse organs and mouse spleen weights, and in preventing losses in mouse weights.

CONCLUSIONS

The amoxicillin/imipenem/relebactam combination was synergistic in vitro and effective in vivo against M. abscessus. Since these drugs are clinically available, the triple combination should be considered by clinicians and further evaluated based on the reporting of the patient outcomes.

Paediatric cervicofacial lymphadenitis caused by non-tuberculous mycobacteria: nation-wide overview in the period 2000-2020

PURPOSE

Cervicofacial lymphadenitis caused by non-tuberculous mycobacteria (NTM) is a rare but increasing infection in children worldwide. The purpose of this study was to analyse and evaluate all microbiologically proven cases of NTM lymphadenitis in children under the age 14 years in Slovenia.

METHODS

Between 2000 and 2020, we retrospectively reviewed laboratory and medical records for basic demographic and microbiological data. Different clinical samples were collected in medical centres and regional hospitals from all over Slovenia.

RESULTS

In the period before mandatory BCG vaccination was discontinued (2000-2005), we did not observe any case of paediatric NTM lymphadenitis. After discontinuation of non-selective BCG vaccination of new-borns (2006-2020), we identified 55 cases of microbiologically confirmed NTM lymphadenitis in BCG-unvaccinated children with median age 26.0 months (range: 15.0-75.0 months). Mean annual incidence of paediatric NTM lymphadenitis accounted for 1.26 (range: 0.35-2.38) per 100,000 children. The main causative agents were Mycobacterium avium (38/55; 69.1%) and M. intracellulare (9/55; 16.4%). We did not find any M. chimaera isolate. Since 2006, each year we microbiologically confirm sporadic cases of paediatric NTM lymphadenitis, a condition not diagnosed before.

CONCLUSIONS

After discontinuation of universal BCG vaccination in March 2005, first cases of paediatric NTM lymphadenitis appeared. Several possible reasons could be attributed to observed trend and further multinational observational studies are warranted to explore possible causal relationships.

Bibliometric Analysis of Nontuberculous Mycobacteria Research in South Korea

BACKGROUND

Current research on nontuberculous mycobacteria (NTM) is multidisciplinary, necessitating proper organization to obtain comprehensive insight. Therefore, a bibliometric analysis was performed to identify NTM research characteristics in South Korea.

METHODS

The Web of Science was searched for NTM articles authored by Koreans at Korean institutions until March 2023. We collected data on authors, publication year, article type, study design, research area, citations, research institutes, and funding sources.

RESULTS

Of the 28,092 articles on NTM, Koreans authored 868. After excluding 167 unrelated studies, 701 relevant articles were analyzed. The first study was from 1992, with publication rates markedly increasing from 2004 onward. Basic research constituted 41.3% (n=290) of the papers, whereas clinical research represented 44.7% (n=313). Basic research consisted mostly of biochemistry studies (n=73, 10.4%), whereas clinical research primarily involved retrospective studies (n=118, 16.8%). Fifty-four institutions participated in NTM research, with the top five contributing to 71% (n=498) of the publications. The National Research Foundation of Korea was the most significant funding source, supporting 181 studies (32.5% of funded articles). Citation analysis revealed a median citation count of 10 (interquartile range, 3 to 13), with clinical research dominating the top-cited articles and a rise in publications in high-impact journals over time.

CONCLUSION

The quality and quantity of NTM research in South Korea has improved. However, it is concentrated in a few institutions and is largely funded by a few sources. Future research should use more diverse funding sources, be conducted in more institutions, and prioritize prospective study designs to enhance the understanding and treatment of NTM.

Machine learning-based model assists in differentiating Mycobacterium avium Complex Pulmonary Disease from Pulmonary Tuberculosis: A Multicenter Study

The number of Mycobacterium avium-intracellulare complex pulmonary disease patients is increasing globally. Distinguishing Mycobacterium avium-intracellulare complex pulmonary disease from pulmonary tuberculosis is difficult due to similar manifestations and characteristics. We aimed to build and validate a machine learning model using clinical data and computed tomography features to differentiate them. This multi-centered, retrospective study included 169 patients diagnosed with Mycobacterium avium-intracellulare complex and pulmonary tuberculosis from date to date. Data were analyzed, and logistic regression, random forest, and support vector machine models were established and validated. Performance was evaluated using receiver operating characteristic and precision-recall curves. In total, 84 patients with Mycobacterium avium-intracellulare complex pulmonary disease and 85 with pulmonary tuberculosis were analyzed. Patients with Mycobacterium avium-intracellulare complex pulmonary disease were older. Hemoptysis rate, cavity number and morphology, bronchiectasis type, and distribution differed. The support vector machine model performed better. In the training set, the area under the curve was 0.960, and in the validation set it was 0.885. The precision-recall curve showed high accuracy and low recall for the support vector machine model. The support vector machine learning-based model, which integrates clinical data and computed tomography imaging features, exhibited excellent diagnostic performance and can assist in differentiating Mycobacterium avium-intracellulare complex pulmonary disease from pulmonary tuberculosis.

Macrophage Differentiation and Metabolic Adaptation in Mycobacterial Infections

The adaptation of macrophages-the most common tissue-resident immune cells-to metabolic and microbial cues with high local variability is essential for the maintenance of organ integrity. In homeostasis, macrophages show largely predictable tissue-specific differentiation, as recently revealed by multidimensional methods. However, chronic infections with human-adapted pathogens substantially contribute to the differentiation complexity of tissue macrophages, which has been only partially resolved. Specifically, the response to mycobacterial species-which range from Mycobacterium tuberculosis (with highest specificity for humans, broad organ tropism, yet tissue-specific disease phenotypes) to environmental mycobacteria with humans as accidental hosts-may serve as a paradigm of tissue macrophage adaptation mechanisms. While mycobacterial species-specific tissue preferences are partially related to the mode of acquisition and pathogen characteristics, evolutionary convergence with macrophages driven by metabolic features of the target organ likely contributes to infection resistance and immunopathology. In this review, we unravel the mechanisms of tissue-specific macrophage differentiation and its limitations in mycobacterial infections.

An Integrated Mycobacterial CT Imaging Dataset with Multispecies Information

The increasing global incidence of nontuberculous mycobacterial (NTM) pulmonary disease highlights the need for rapid diagnostic methods to guide timely treatment and prevent antibiotic misuse. While bacterial culture remains the gold standard for diagnosis, its extended turnaround time compromises clinical decision-making. Computed tomography (CT), with its high sensitivity for lung lesions and rapid imaging capabilities, has emerged as a critical diagnostic tool. AI-assisted CT interpretation shows particular promise for improving NTM detection, yet progress has been hindered by limited datasets due to disease rarity. We address this gap by introducing the first comprehensive CT dataset combining 430 NTM and 871 tuberculosis cases, supplemented with clinical parameters including demographics, symptoms, and mycobacterial species data. This resource aims to catalyze AI algorithm development for differential diagnosis, ultimately enhancing precision in NTM management through advanced machine learning applications.

Advances in isoxazole chemistry and their role in drug discovery

Isoxazoles are a class of five-membered heterocyclic compounds that have gained significant attention in medicinal chemistry due to their diverse biological activities and therapeutic potential. Recent advances in isoxazole chemistry have led to the development of novel synthetic strategies, enabling the creation of a wide array of isoxazole derivatives with enhanced bioactivity and selectivity. This review explores the latest progress in isoxazole synthesis, highlighting key methodologies such as transition metal-catalyzed cycloadditions, green chemistry approaches, and regioselective functionalization techniques. These advances have not only improved the efficiency of isoxazole synthesis but have also facilitated the design of more complex and bioactive derivatives. In addition to their synthetic advances, isoxazoles have demonstrated a broad spectrum of biological activities, including antimicrobial, anticancer, anti-inflammatory, and neuroprotective effects, making them attractive candidates in drug discovery. This review discusses the structural modifications that enhance their pharmacological properties and their potential for developing therapies for diseases such as cancer, neurodegenerative disorders, and infections. Moreover, we examine the emerging trends in isoxazole-based drug discovery, such as the development of multi-targeted therapies and personalized medicine approaches. The evolving role of isoxazoles in drug discovery underscores their continued importance in modern pharmaceutical research and their potential to address unmet medical needs.

Non-Invasive Mycobacterium avium Detection Using 99mTc-GSA on Single-Photon Emission Computed Tomography

Background: The prevalence of nontuberculous mycobacteria (NTM) infection is on the rise, surpassing that of pulmonary tuberculosis in Japan. Current standard therapy for NTM infection involves long-term treatment of at least 1.5 years, with low success rates and a high relapse rate. 99mTc-diethylenetriaminepentaacetic acid-galactosyl-human serum albumin (99mTc-GSA) is used for human liver imaging. In this study, we utilized 99mTc-GSA as a probe to detect Mycobacterium avium (M. avium), a major pathogen in NTM pulmonary diseases (NTM-PDs). Our aim was to investigate the non-invasive detection of M. avium using 99mTc-GSA on Single-Photon Emission Computed Tomography (SPECT). Methods: The accumulation of 99mTc-GSA in M. avium was investigated in vitro. In vivo, SPECT images were obtained after the administration of 99mTc-GSA to an M. avium thigh infection model. Subsequently, the contrast difference in accumulated 99mTc-GSA between infected and non-infected thighs was calculated using SPECT imaging. Furthermore, SPECT images were obtained for thighs infected with varying bacterial loads, and the accumulation was compared between them. Results: In vitro, we observed that 99mTc-GSA accumulates in M. avium. In vivo, SPECT images demonstrated the specific accumulation of 99mTc-GSA at the infection site, with this accumulation being correlated with the bacterial load. Conclusions: 99mTc-GSA specifically accumulates in M. avium, and SPECT can be used to monitor the distribution and quantity of M. avium in animals. By utilizing these measures, 99mTc-GSA can be targeted to the site of infection and used as a bacterial probe.

Genomic insights into the plasmidome of non-tuberculous mycobacteria

BACKGROUND

Non-tuberculous mycobacteria (NTM) are a diverse group of environmental bacteria that are increasingly associated with human infections and difficult to treat. Plasmids, which might carry resistance and virulence factors, remain largely unexplored in NTM.

METHODS

We used publicly available complete genome sequence data of 328 NTM isolates belonging to 125 species to study gene content, genomic diversity, and clusters of 196 annotated NTM plasmids. Furthermore, we analyzed 3755 draft genome assemblies from over 200 NTM species and 5415 short-read sequence datasets from six clinically relevant NTM species or complexes including M. abscessus, M. avium complex, M. ulcerans complex and M. kansasii complex, for the presence of these plasmids.

RESULTS

Between one and five plasmids were present in approximately one-third of the complete NTM genomes. The annotated plasmids varied widely in length (most between 10 and 400 kbp) and gene content, with many genes having an unknown function. Predicted gene functions primarily involved plasmid replication, segregation, maintenance, and mobility. Only a few plasmids contained predicted genes that are known to confer resistance to antibiotics commonly used to treat NTM infections. Out of 196 annotated plasmid sequences, 116 could be grouped into 31 clusters of closely related sequences, and about one-third were found across multiple NTM species. Among clinically relevant NTM, the presence of NTM plasmids showed significant variation between species, within (sub)species, and even among strains within (sub)lineages, such as dominant circulating clones of Mycobacterium abscessus.

CONCLUSIONS

Our analysis demonstrates that plasmids are a diverse and heterogeneously distributed feature in NTM bacteria. The frequent occurrence of closely related putative plasmid sequences across different NTM species suggests they may play a significant role in NTM evolution through horizontal gene transfer at least in some groups of NTM. However, further in vitro investigations and access to more complete genomes are necessary to validate our findings, elucidate gene functions, identify novel plasmids, and comprehensively assess the role of plasmids in NTM.

Effective killing of Mycobacterium abscessus biofilm by nanoemulsion delivery of plant phytochemicals

Mycobacterium is an acid-fast, aerobic, non-motile, and biofilm-forming bacterium. The increasing prevalence of mycobacterial infections makes it necessary to find new methods to combat the resistance of bacteria to conventional antibiotics. Mycobacterium abscessus is an emerging pathogen that is intrinsically drug resistant due to several factors, including an impermeable cell envelope, drug efflux pumps, target-modifying enzymes, and the ability to form thick, robust biofilms. Phytochemicals are promising antimicrobials; however, their poor solubility in water and their inability to penetrate biofilms render them inefficient in killing bacterial biofilms. In this study, we demonstrate the efficacy of polymer-stabilized phytochemical nanoemulsions in killing M. abscessus biofilms. These nanoemulsions improve the solubility and stability of the phytochemicals and enable biofilm penetration and eradication. We show that the phytochemical emulsions effectively eliminated M. abscessus in an in vitro biofilm model and killed non-replicating persister cells in the Wayne hypoxia model. These nanoemulsions were also effective in vivo in a wound infection model. These findings demonstrate the potential of polymer-stabilized phytochemical nanoemulsions as a promising alternative to conventional antibiotics for the treatment of mycobacterial infections.

IMPORTANCE

Mycobacterium abscessus is among the opportunistic bacterial pathogens that cause nontuberculous mycobacterial diseases. The infection caused by M. abscessus is difficult to treat because the bacterium is resistant to many of the currently available antibiotics, limiting chemotherapeutic strategies. Furthermore, it forms biofilms in clinically relevant settings, making the infection difficult to treat. Many phytochemicals have potent antimicrobial activities, but their hydrophobicity limits clinical applications. In this study, we tested a new drug delivery strategy where hydrophobic plant phytochemicals were emulsified with a biodegradable nanosponge. We show that the emulsification makes phytochemicals such as carvacrol and eugenol more effective against M. abscessus biofilms. We further demonstrate that nanoemulsified phytochemicals can kill hypoxia-induced dormant M. abscessus and effectively improve skin wound infection in mice. Our data pave the way to use phytochemical nanosponge as a platform to create synergy by combining other antimycobacterial drugs.

Relationship between age, sex, geography and incidence of nontuberculous mycobacteria in Denmark from 1991 to 2022

Objectives

We investigated age, sex and geographical differences in nontuberculous mycobacteria (NTM) incidence in Denmark.

Methods

A nationwide register-based study of all patients with NTM isolates in Denmark from 1991 to 2022 based on centralised microbiological data from the International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark. A Poisson regression model was used to calculate incidence rates (IRs) and rate ratios (IRRs).

Results

4123 patients had NTM isolated for the first time. Their median age was 59 years (interquartile range 33-72), which increased over time. Males were younger than females. The proportion of females increased significantly over time. The type of NTM and patient age were closely associated. Pulmonary NTM isolation was increasingly common with higher age, while extrapulmonary NTM isolation was mainly seen in small children. Pulmonary NTM IRs were almost twice as high for females in 2008-2022 compared to 1991-2007 (IRR 1.9, 95% CI 1.7-2.1, p<0.001), with increases mainly seen in older age groups. The increase was less pronounced for males (IRR 1.3, 95% CI 1.1-1.4, p<0.001). There were considerable geographical differences, with age- and sex-adjusted NTM IRs being 10-40% higher in countryside, provincial and catchment municipalities than in the capital.

Conclusion

Age, sex and geography are essential determinants in NTM epidemiology. We found that rates of pulmonary NTM have been increasing, particularly in older females, while changes for males were less pronounced. Finally, we observed considerable geographical differences in NTM IRs in Denmark, with higher rates in less populated municipalities.

Diagnostics, resistance and clinical relevance of non-tuberculous mycobacteria unidentified at the species level by line probe assays: a bi-national study

OBJECTIVES

While the reported incidence of non-tuberculous mycobacterial (NTM) infections is increasing, the true prevalence remains uncertain due to limitations in diagnostics and surveillance. The emergence of rare and novel species underscores the need for characterization to improve surveillance, detection, and management.

METHODS

We performed whole-genome sequencing (WGS) and/or targeted deep-sequencing using the Deeplex Myc-TB assay on all NTM isolates collected in Slovakia and the Czech Republic between the years 2019 to 2023 that were unidentifiable at the species level by the routine diagnostic line probe assays (LPA) GenoType CM/AS and NTM-DR. Minimal inhibitory concentrations against amikacin, ciprofloxacin, moxifloxacin, clarithromycin, and linezolid were determined, and clinical data were collected.

RESULTS

Twenty-eight cultures from different patients were included, of which 9 (32.1%) met the clinically relevant NTM disease criteria. The majority of those had pulmonary involvement, while two children presented with lymphadenitis. Antimycobacterial resistance rates were low. In total, 15 different NTM species were identified, predominantly rare NTM like M. neoaurum, M. kumamotonense and M. arupense. Notably, clinically relevant M. chimaera variants were also identified with WGS and Deeplex-Myc TB, which, unlike other M. chimaera strains, appeared to be undetectable by LPA assays. Deeplex detected four mixed infections that were missed by WGS analysis. In contrast, WGS identified two novel species, M. celatum and M. branderi, which were not detected by Deeplex-Myc TB. Importantly, one of these novel species strains was associated with clinically relevant pulmonary disease.

DISCUSSION

Our study demonstrates the clinical relevance of uncommon NTM and the effectiveness of targeted deep-sequencing combined with WGS in identifying rare and novel NTM species.

Multimodal machine learning-based model for differentiating nontuberculous mycobacteria from mycobacterium tuberculosis

Objective

To develop and evaluate the effectiveness of multimodal machine learning approach for the differentiation of NTM from MTB.

Methods

The clinical data and CT images of 175 patients were retrospectively obtained. We established clinical data-based model, radiomics-based model, and multimodal (clinical plus radiomics) model gradually using 5 machine learning algorithms (Logistic, XGBoost, AdaBoost, RandomForest, and LightGBM). Optimal algorithm in each model was selected after evaluating the differentiation performance both in training and validation sets. The model performance was further verified using external new MTB and NTM patient data. Performance was also compared with the existing approaches and model.

Results

The clinical data-based model contained age, gender, and IL-6, and the RandomForest algorithm achieved the optimal learning model. Two key radiomics features of CT images were identified and then used to establish the radiomics model, finding that model from Logistic algorithm was the optimal. The multimodal model contained age, IL-6, and the 2 radiomics features, and the optimal model was from LightGBM algorithm. The optimal multimodal model had the highest AUC value, accuracy, sensitivity, and negative predictive value compared with the optimal clinical or radiomics models, and its' favorable performance was also verified in the external test dataset (accuracy = 0.745, sensitivity = 0.900). Additionally, the performance of multimodal model was better than that of the radiologist, NGS detection, and existing machine learning model, with an increased accuracy of 26, 4, and 6%, respectively.

Conclusion

This is the first study to establish multimodal model to distinguish NTM from MTB and it performs well in differentiating them, which has the potential to aid clinical decision-making for experienced radiologists.

AgNP-Containing Niosomes Functionalized with Fucoidan Potentiated the Intracellular Killing of Mycobacterium abscessus in Macrophages

Intracellular pathogens represent a challenge for therapy because the antibiotics used need to diffuse into the cytoplasm to target the pathogens. The situation is more complicated in the mycobacteria family because members of this family infect and multiply within macrophages, the cells responsible for clearing microorganisms in the body. In addition, mycobacteria members are enclosed inside pathogen-containing vesicles or phagosomes. The treatments of these pathogens are aggravated when these pathogens acquire resistance to antibiotic molecules. As a result, new antimicrobial alternatives are needed. Niosomes are vesicles composed of cholesterol and nonionic surfactants that can be used for antibiotic encapsulation and delivery. The current study developed a systematic formulation of niosomes to determine the best option for niosome functionalizing for precise delivery to the intracellular pathogen Mycobacterium abscessus. Silver nanoparticles (AgNPs) were synthesized using gallic acid as an antibacterial agent. Then, niosomes were prepared and characterized, following the encapsulation of AgNPs functionalized with a single-chain antibody screened against the cell wall glycopeptidolipid of Mycobacterium abscessus. For a precise delivery of the cargo into macrophages, the niosomes were also functionalized with the polysaccharide fucoidan, taken specifically by the scavenger receptor class A expressed on the surface of macrophages. Results of the study showed a steady decrease in the intracellular pathogen load after 48 h post-infection. In conclusion, this system could be developed into a platform to target other types of intracellular pathogens and as an option for antimicrobial therapy.

Heme alters biofilm formation in Mycobacterium abscessus

Mycobacterium abscessus (Mabs) is commonly found in the cystic fibrosis (CF) lung. During infection, Mabs can form biofilms in the lung which reduce both the ability of the immune response to clear infection and the effectiveness of antibiotic therapy. In the CF lung, heme and hemoglobin levels are increased and may provide both iron and heme to Mabs cells. In this work, we show that exogenous heme altered Mabs biofilm formation and measured the effects of exogenous heme on protein level and metabolism in Mabs. Our findings suggest that heme impacts iron homeostasis in Mabs and affects other aspects of its metabolism, highlighting the potential role of heme as a critical nutrient for Mabs growth and biofilm formation.IMPORTANCEMycobacterium abscessus (Mabs) is commonly found in the cystic fibrosis (CF) lung, where Mabs can form biofilms that can reduce the efficacy of antibiotics. During infection, the CF lung can have more than 10 times the extracellular heme than that of a healthy lung. We have found that extracellular heme can change the way Mabs cells grow and form biofilms, which may have implications for pathogenesis.

Clinically significant hemoptysis and all-cause mortality in patients with nontuberculous mycobacterial pulmonary disease

BACKGROUND

Hemoptysis is one of the major symptoms in patients with nontuberculous mycobacterial pulmonary disease (NTM-PD). However, its prevalence, incidence, and impact on long-term prognosis remain uncertain. We evaluated the incidence of clinically significant hemoptysis, and determined its association with mortality in patients with NTM-PD.

METHODS

Patients enrolled in a prospective observational cohort (NCT01616745) between July 2011 and May 2023 were analyzed. We evaluated risk factors for clinically significant hemoptysis-defined as hemoptysis events requiring interventions such as bronchial artery embolization or surgical resection-and its association with all-cause mortality.

RESULTS

Among 506 patients from the ongoing cohort, 43 patients (8.5 %) experienced clinically significant hemoptysis during a median follow-up of 5.1 years. The overall incidence of clinically significant hemoptysis was 2.1 (95 % confidence interval [CI]; 1.5-2.9) cases per 100 person-years. Identified risk factors included a history of tuberculosis (incidence rate ratio [IRR], 1.91; 95 % CI, 1.02-3.60), higher C-reactive protein (CRP) (IRR, 1.20 for 1 mg/dl increase; 95 % CI, 1.01-1.43), and lower % predicted forced vital capacity (FVC) (IRR, 0.81 for 10 % increase; 95 % CI, 0.66-0.98). Clinically significant hemoptysis was independently associated with an increased risk of all-cause mortality (adjusted hazard ratio, 2.39; 95 % CI, 1.31-4.36).

CONCLUSION

In patients with NTM-PD, those with history of tuberculosis, higher CRP levels, and lower % predicted FVC were at a higher risk of subsequent clinically significant hemoptysis. Importantly, clinically significant hemoptysis was associated with an elevated risk of all-cause mortality.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT01616745.

Clinical Management and Outcomes of Nontuberculous Mycobacterial Infections in Solid Organ Transplant Recipients: A Multinational Case-control Study

BACKGROUND

The management and outcomes of nontuberculous mycobacterial (NTM) infections in solid organ transplant (SOT) recipients are poorly characterized. We aimed to describe the management and 1-y mortality of these patients.

METHODS

Retrospective, multinational, 1:2 matched case-control study included SOT recipients aged 12 y old or older diagnosed with NTM infection between January 1, 2008, and December 31, 2018. Controls were matched on transplanted organs, NTM treatment center, and posttransplant survival at least equal to the time to NTM diagnosis. The primary aim was 1-y mortality after NTM diagnosis. Differences between cases and controls were compared using the log-rank test, and Cox regression models were used to identify factors associated with mortality at 12 mo among cases.

RESULTS

In 85 patients and 169 controls, the median age at the time of SOT was 54 y (interquartile range, 40-62 y), 59% were men, and the lungs were the most common site of infection after SOT (57.6%). One-year mortality was significantly higher in cases than in controls (20% versus 3%; P < 0.001), and higher mortality was associated with lung transplantation (hazard ratio 3.27; 95% confidence interval [1.1-9.77]; P = 0.034). Median time (interquartile range) from diagnosis to treatment initiation (20 [4-42] versus 11 [3-21] d) or the reduction of net immunosuppression (36% versus 45%, hazard ratio 1.35 [95% CI, 0.41-4.43], P = 0.618) did not differ between survivors and those who died.

CONCLUSIONS

NTM disease in SOT recipients is associated with a higher mortality risk, especially among lung transplant recipients. Time to NTM treatment and reduction in net immunosuppression were not associated with mortality.

First recorded isolation of Mycobacterium kansasii in a nonendemic setting

Nontuberculous mycobacteria (NTM) are a diverse group of environmental mycobacteria found ubiquitously in soil and water, causing infections that typically arise from environmental exposure rather than person-to-person transmission. This case report documents the first known detection of Mycobacterium kansasii in our region, emphasizing the clinical challenges and diagnostic complexities associated with NTM infections. The case involves a 37-year-old male with a significant smoking history who presented with progressively worsening cough, significant weight loss, and bilateral cavitary lung lesions. Initial diagnostic efforts, including tests for tuberculosis and malignancy, were inconclusive. However, subsequent bronchoalveolar lavage confirmed the presence of M. kansasii, leading to a year-long treatment regimen. This report signifies a critical step in recognizing the burden of NTM infections in region, a region where comprehensive epidemiological data are lacking. The rising global incidence of NTM lung disease and its association with underlying lung conditions and immunocompromised states further underscore the importance of this case, particularly given the diagnostic overlap with more common conditions like tuberculosis. This case calls attention to the need for optimized local diagnostic criteria and the potential for NTM to be a causative agent of community-acquired pneumonia.

Revisiting the potential of natural products in antimycobacterial therapy: advances in drug discovery and semisynthetic solutions

Natural products have been pivotal in treating mycobacterial infections with early antibiotics such as streptomycin, forming the foundation of tuberculosis therapy. However, the emergence of multidrug-resistant and extensively drug-resistant Mycobacterium species has intensified the need for novel antimycobacterial agents. In this review, we revisit the historical contributions of natural products to antimycobacterial drug discovery and highlight recent advances in the field. We assess the application of molecular networking and the exploration of unculturable bacteria in identifying new antimycobacterial compounds such as amycobactin and levesquamides. We also highlight the role of semisynthesis in optimizing natural products, exemplified by sequanamycins and spectinomycin analogs that evade M. tuberculosis' intrinsic resistance. Finally, we discuss emerging technologies that are promising to accelerate the discovery and development of next-generation antimycobacterial therapies. Despite ongoing challenges, these innovative approaches offer renewed hope in addressing the growing crisis of drug-resistant mycobacterial infections.

CRISPR-Cas12a-based detection and differentiation of Mycobacterium spp

Mycobacterium species cause several vital human diseases, including tuberculosis and non-tuberculous mycobacterial infections, which are treated with different drug regimens Therefore, accurate and rapid diagnosis is essential for effective treatment and controlling the spread of these pathogens. This study aims to develop an isothermal method combining RPA and CRISPR-Cas12a techniques, named as MyTRACK, to detect and differentiate major clinical mycobacteria at the species level. The assay has no cross-reactivity with limit of detection of 1 to 100 copies/reaction for various targeted mycobacteria. The results demonstrated 100 % specificity and 92.59 % to 100 % sensitivity in clinical isolates and were consistent with the culture technique with LPA for clinical samples. The MyTRACK assay is an effective, portable, rapid, and accurate screening method for mycobacterial detection and identification, especially in low-resource clinical settings.

Lung CT-based multi-lesion radiomic model to differentiate between nontuberculous mycobacteria and Mycobacterium tuberculosis

BACKGROUND

Nontuberculous mycobacterial lung disease (NTM-LD) and Mycobacterium tuberculosis lung disease (MTB-LD) are difficult to distinguish based on conventional imaging examinations. In recent years, radiomics has been used to discriminate them. However, existing radiomic methods mainly focus on specific lesion types, and have limitations in handling the presence of multiple lesion types that vary among different patients.

PURPOSE

We aimed to establish a radiomic model based on multiple lesion types in the patient's CT scans, and analyzed the importance of different lesion types in distinguishing the two diseases.

METHODS

120 NTM-LD and 120 MTB-LD patients were retrospectively enrolled in this study and randomly split into the training (168) and testing (72) sets. A total of 1037 radiomic features were extracted separately for each lesion type. The univariate analysis, least absolute shrinkage, and selection operator were used to select the significant radiomic features. The radiomic signature score (Radscore) from each lesion type was estimated and aggregated to construct the multi-lesion feature vector for each patient. A multi-lesion radiomic (MLR) model was then established using the random forest classifier, which can estimate importance coefficients for different lesion types. The performances of the MLR model and single radomic models were investigated by the receiver operating characteristic curve (ROC). The impact of the predicted lesion importance was also evaluated in subjective imaging diagnosis.

RESULTS

The MLR model achieved an area under the curve (AUC) of 90.2% (95% CI: 86.2% 94.1%) in differentiating NTM-LD and MTB-LD, outperforming the models using specific lesion types following existing radiomic models by 1% to 13%. Among different lesion types, tree-in-bud pattern demonstrated the highest distinguishing value, followed by consolidation, nodules, and lymph node enlargement. Given the estimated lesion importance, two senior radiologists exhibited improved accuracy in diagnosis, with an increased accuracy of 8.33% and 8.34%, respectively.

CONCLUSIONS

This is the first radiomic study to use multiple lesion types to distinguish NTM-LD and MTB-LD. The developed MLR model performed well in differentiating the two diseases, and the lesion types with high importance exhibited the potential to assist experienced radiologists in clinical decision-making.

Development and evaluation of multiplex real-time PCR for rapid identifying major pathogenic mycobacteria from pulmonary and extrapulmonary clinical samples in eastern China

Background

Diseases caused by M. tuberculosis (MTB) and non-tuberculous mycobacteria (NTM) have similar clinical symptoms but require different treatments. Rapid and accurate identification of MTB and NTM is essential for proper patient management and treatment.

Methods

To develop and assess a multiplex real-time fluorescence PCR (Multiplex PCR) method for rapid identification of MTB, M. avium complex (MAC), M. chelonae-M. abscessus group (MCAG), and M. kansasii in clinical samples. The specificity and limit of detection (LOD) were tested using standard strains and clinical isolates. The accuracy of the Multiplex PCR was validated with DNA from 228 known clinical samples confirmed by Targeted next-generation sequencing (tNGS). Additionally, 901 consecutive clinical samples were assessed to evaluate the Multiplex PCR's diagnostic performance in detecting mycobacteria in pulmonary and extrapulmonary samples.

Results

LOD of the four mycobacteria ranged from 11.7 to 360.0 CFU/mL in water, 43.8-922.0 CFU/mL in sputum, and 53.2-859.3 CFU/mL in sputum mixed infection, with 98.7 % sample detection accuracy and 100 % strains identification accuracy. Based on the composite reference standard, the sensitivity of the Multiplex PCR for detecting tuberculosis in pulmonary and extrapulmonary samples was comparable to Xpert (p > 0.05) and higher than Culture, especially in extrapulmonary samples (P < 0.0001). For NTM detection in pulmonary samples, the sensitivity was slightly lower than Culture (P > 0.05) but higher than CapitalBio RT-PCR (P < 0.05). Overall, the Multiplex PCR showed significantly higher sensitivity for mycobacterial diseases compared to the other three methods (P < 0.01), with a specificity of 96 %.

Conclusions

The Multiplex PCR demonstrated excellent diagnostic performance in both pulmonary and extrapulmonary samples, offering a low-cost, rapid identifying tool for major pathogenic mycobacteria in eastern China.

Growing Challenges of Lung Infections with Non-tuberculous Mycobacteria in Immunocompromised Patients: Epidemiology and Treatment

Non-tuberculous mycobacteria (NTM) are increasingly recognized as opportunistic pathogens in humans and animals, particularly affecting those with compromised immune systems. These bacteria encompass a diverse group of mycobacterial species that are responsible for a range of infections, with pulmonary and skin-related conditions being the most common. The rise in NTM infections in recent years is a growing concern for healthcare, highlighting the urgent need to improve our understanding of NTM epidemiology and treatment strategies. This article reviews the NTM species associated with lung infections in immunocompromised patients and underscores the critical importance of advancing diagnostic and therapeutic approaches. The review is based on a thorough analysis of scientific literature from databases such as PubMed, Scopus, and ScienceDirect, covering studies up to June 2024. Through this comprehensive analysis, the article aims to provide detailed insights into the complexities of NTM diseases and spur further research and innovation in combating these challenging infections.

Recombinant interleukin-7 treatment of refractory Mycobacterium avium complex lung disease (IMPULSE-7): a pilot phase II, single-center, randomized, clinical trial

Background

Nontuberculous mycobacteria disease is an emerging opportunistic infection that is often refractory to therapy. Interleukin 7 (IL-7) is a pleiotropic cytokine with broad-ranging effects that enhance immunity and augment monocyte/macrophage anti-Mycobacterium avium killing in vitro.

Objectives

This study evaluated IL-7 in patients with refractory Mycobacterium avium complex lung disease (MAC-LD).

Design

Prospective, single-center, randomized, study of IL-7 in patients with refractory MAC-LD.

Methods

Randomization (two sets of 4 weekly IL-7 injections) was stratified based on the presence of pulmonary cavities. The primary outcome was sputum culture conversion to negative within 6 months. Exploratory outcomes included investigation of potential molecular mechanisms of immunosuppression via single-cell RNA sequencing (scRNA-seq).

Results

Of the eight participants enrolled, six completed the IL-7 regimen, one completed one 4-week therapy, and one received a single dose of IL-7. All six participants who completed the regimen showed an increased absolute lymphocyte count (ALC), yet none converted their sputum culture to negative at 6 months. Similarly, there were no differences in secondary outcomes compared to baseline. IL-7 was well tolerated, and two participants showed an increase in time-positivity for MAC in their sputum culture. scRNA-seq revealed increased expression of genes involved in immunosuppressive pathways.

Conclusion

In adults with refractory MAC-LD, IL-7 did not result in sputum culture conversion. IL-7 reversed the underlying lymphopenia associated with MAC-LD and led to a sustained increase in ALC. The study was limited by a small sample size, and although a longer course of IL-7 combined with newer antimicrobials for may warrant further investigation, structural lung disease may be a stronger predictor of cure than immune dysfunction in MAC-LD.

Trial registration

The trial was registered in clinicaltrials.gov (NCT04154826).

Four novel nontuberculous mycobacteria species: Mycobacterium wendilense sp. nov., Mycobacterium burgundiense sp. nov., Mycobacterium kokjensenii sp. nov. and Mycobacterium holstebronense sp. nov. revived from a historical Danish strain collection

Four novel nontuberculous mycobacteria were discovered from a historical strain collection at the International Reference Laboratory of Mycobacteriology at Statens Serum Institut in Copenhagen, Denmark. Phylogenetic analysis combining the 16S rrs, internal transcribed spacer and 23S rrl elements, as well as a single-copy core-gene (hsp65, rpoB+C, secA and tuf) analysis of these freeze-dried mycobacteria, clinically isolated from gastric lavage samples between 1948 and 1955, showed to be associated with type strains grouping within the Terra and Fortuitum-Vaccae clade. Phenotypic characteristics, biochemical properties and fatty acid and mycolic acid profiles supported the classification as novel strains. A genomic comparison to the closest related type strain was done by calculating average nucleotide identity and in silico DNA:DNA hybridization values, which showed 87.9% and 33.0% for Mu0050, 85.2% and 27.4% for Mu0053, 85.3% and 27.6% for Mu0083 and 93.3% and 50.1% for Mu0102, respectively. The names proposed for the new species are Mycobacterium wendilense sp. nov. (Mu0050T=ITM 501390T=CCUG 77525T), Mycobacterium burgundiense sp. nov. (Mu0053T=ITM 501391T=CCUG 77526T), Mycobacterium kokjensenii sp. nov. (Mu0083T=ITM 501392T=CCUG 77527T) and Mycobacterium holstebronense sp. nov. (Mu0102T=ITM 501393T=CCUG 77528T).

Pulmonary nontuberculous mycobacterial infections among women with cystic fibrosis and non-cystic fibrosis bronchiectasis

Nontuberculous mycobacteria (NTM) are ubiquitous, opportunistic pathogens that can cause lung disease in people with non-cystic fibrosis bronchiectasis (NCFB) and cystic fibrosis (CF). The incidence of NTM pulmonary infections and lung disease has continued to increase worldwide over the last decade among both groups. Notably, women with NCFB NTM pulmonary disease (NTM-PD) bear a disproportionate burden with NTM rates increasing in this population as well as having consistently higher incidence of NTM-PD compared to men. In contrast, among people with CF, an overall increased risk among women has not been observed. In the United States, the majority of people with CF are taking highly effective cystic fibrosis transmembrane conductance regulator (CFTR) modulators, and these numbers are increasing worldwide. The long-term impact of CFTR modulator medications on NTM infections is not entirely understood. Guidelines for the screening, diagnosis, and management of NTM-PD exist for people with NCFB and CF, but do not consider unique implications relevant to women. This review highlights aspects of NTM-PD among women with NCFB and CF, including the epidemiology of NTM infection, special considerations for treatment, and unmet research needs relevant to women with NTM-PD.

Evaluation of a Commercial Multiplex Real-Time PCR with Melting Curve Analysis for the Detection of Mycobacterium tuberculosis Complex and Five Nontuberculous Mycobacterial Species

BACKGROUND

Accurate and timely diagnosis of mycobacterial infections, including Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM), is crucial for effective disease management.

METHODS

This study evaluated the performance of the NeoPlex TB/NTM-5 Detection Kit (NeoPlex assay, Seongnam, Republic of Korea), a multiplex real-time PCR assay that incorporates melting curve analysis, compared with the line-probe assay (LPA). The NeoPlex assay could simultaneously detect and differentiate MTBC from five other NTM species: Mycobacterium intracellulare, Mycobacterium avium, Mycobacterium kansasii, Mycobacterium abscessus, and Mycobacterium massiliense. A total of 91 acid-fast bacillus culture-positive samples, comprising 36 MTBC and 55 NTM isolates, were collected from the Korea University Anam Hospital.

RESULTS

The NeoPlex assay successfully detected nucleic acids in 87 of the 91 isolates (95.6%). Notably, it identified additional mycobacterial nucleic acids not detected by the LPA in eight isolates. These findings were confirmed via DNA sequencing. The assay had 100% sensitivity and specificity for M. intracellulare, M. abscessus, M. massilense, NTM, and MTBC, whereas it had 100% specificity and sensitivity of 90.9% and 75.0% for M. avium and M. kansasii, respectively.

CONCLUSIONS

These results highlight the potential of the NeoPlex assay to enhance rapid and accurate diagnosis of mycobacterial infections, particularly in settings in which prompt treatment initiation is essential.

Susceptibility Patterns in Clinical Isolates of Mycobacterium avium Complex from a Hospital in Southern Spain

The incidence of infections caused by the Mycobacterium avium complex (MAC) has risen significantly, posing diagnostic and therapeutic challenges. This study analyzed 134 clinical isolates of the Mycobacterium avium complex from southern Spain, performing in vitro antimicrobial susceptibility testing using a commercial microdilution technique to generate additional data, refine treatment strategies, and improve patient outcomes. Phenotypic susceptibility testing revealed clarithromycin and amikacin as the most effective antibiotics, with susceptibility rates exceeding 90%, while linezolid and moxifloxacin exhibited limited activity, with resistance rates of 49.3% and 41.8%. A comparative analysis between M. avium and M. intracellulare showed significant differences in resistance to amikacin and linezolid, with M. avium exhibiting higher resistance rates. Additionally, species-specific differences were observed in MIC distributions for ethionamide, ciprofloxacin, and streptomycin. Our data reveal regional variability in resistance patterns, particularly for moxifloxacin and linezolid, which exhibit differing resistance rates compared to studies from other regions. The significant MIC differences for several antibiotics between M. avium and M. intracellulare underscore the importance of species-level identification and the heterogeneity in resistance mechanisms within MAC.

Metformin improves Mycobacterium avium infection by strengthening macrophage antimicrobial functions

Introduction

The incidence and prevalence of infections with non-tuberculous mycobacteria such as Mycobacterium avium (Mav) are increasing. Prolonged drug regimens, inherent antibiotic resistance, and low cure rates underscore the need for improved treatment, which may be achieved by combining standard chemotherapy with drugs targeting the host immune system. Here, we examined if the diabetes type 2 drug metformin could improve Mav-infection.

Methods

Metformin was administered to C57BL/6 mice infected intranasally with Mav and C57BL/6 mice were infected intranasally with Mav and treated with metformin over 3 weeks. Organ bacterial loads and lung pathology, inflammatory cytokines and immune cell profiles were assessed. For mechanistic insight, macrophages infected with Mav were treated with metformin alone or in combination with inhibitors for mitochondrial ROS or AMPK and assessed for bacterial burden and phagosome maturation.

Results and discussion

Three weeks of metformin treatment significantly reduced the lung mycobacterial burden in mice infected with Mav without major changes in the overall lung pathology or immune cell composition. Metformin treatment had no significant impact on tissue inflammation except for a tendency of increased lung IFNγ and infiltration of Mav-specific IFNγ-secreting T cells. Metformin did, however, boost the antimicrobial capacity of infected macrophages directly by modulating metabolism/activating AMPK, increasing mitochondrial ROS and phagosome maturation, and indirectly by bolstering type I immunity. Taken together, our data show that metformin improved the control of Mav-infection in mice, mainly by strengthening antimicrobial defenses in macrophages, and suggest that metformin has potential as an adjunct treatment of Mav infections.

Toward better cures for Mycobacterium abscessus lung disease

SUMMARYThe opportunistic pathogen Mycobacterium abscessus (Mab) causes fatal lung infections that bear similarities-and notable differences-with tuberculosis (TB) pulmonary disease. In contrast to TB, no antibiotic is formally approved to treat Mab disease, there is no reliable cure, and the discovery and development pipeline is incredibly thin. Here, we discuss the factors behind the unsatisfactory cure rates of Mab disease, namely intrinsic resistance and persistence of the pathogen, and the use of underperforming, often parenteral and toxic, repurposed drugs. We propose preclinical strategies to build injectable-free sterilizing and safe regimens: (i) prioritize oral bactericidal antibiotic classes, with an initial focus on approved agents or advanced clinical candidates to provide immediate options for desperate patients, (ii) test drug combinations early, (iii) optimize novel leads specifically for M. abscessus, and (iv) consider pharmacokinetic-pharmacodynamic targets at the site of disease, the lung lesions in which drug tolerant bacterial populations reside. Knowledge and tool gaps in the preclinical drug discovery process are identified, including validated mouse models and computational platforms to enable in vitro mouse-human translation. We briefly discuss recent advances in clinical development, the need for readouts and biomarkers that correlate with cure, and clinical trial concepts adapted to the uniqueness of Mab patient populations for new regimen development. In an era when most pharmaceutical firms have withdrawn from antimicrobial drug discovery, the breakthroughs needed to fill the regimen development pipeline will likely come from partnerships between academia, biotech, pharma, non-profit organizations, and governments, with incentives that reward cooperation.

Biochip-Based Identification of Mycobacterial Species in Russia

Infections caused by nontuberculous mycobacteria (NTM) are rising globally throughout the world. The number of species isolated from clinical samples is steadily growing, which demands the implementation of a robust diagnostic method with wide specificity. This study was carried out in in 2022-2024 in three clinical antituberculosis centers in the biggest cities of Russia: Moscow, Saint Petersburg, and Novosibirsk. We developed the DNA hybridization assay 'Myco-biochip' that allows the identification of 79 mycobacterial species and analyzed 3119 samples from 2221 patients. Sixty-eight mycobacterial species were identified in clinics, including the three novel species phylogenetically related to M. duvalii, M. lentiflavum, and M. talmoniae. The identification of a close relative of M. talmoniae adds to the existence of separate clade between M. terrae, M. triviale complexes and other slow-growing Mycobacteria, which supports the thesis against the splitting of Mycobacteria into five separate genera. Adding to the list of potentially pathogenic species, we identified M. adipatum and M. terramassiliense, which were previously described as natural habitats. The diversity of acid-fast bacilli identified in TB-suspected persons was not limited to the Mycobacteria genus and also includes species from genera Nocardia, Gordonia, Corynebacterium, Tsukamurella, and Rhodococcus of the order Mycobacteriales. The revealed bacterial diversity in patients with suspected NTM-diseases requires the implementation of relevant species identification assays as the first step in the laboratory diagnostic pipeline.

Risk of mycobacterial infections in a cohort of silicosis patients with autoimmune rheumatic diseases

OBJECTIVE

To evaluate the incidence rates of mycobacterial infections in silicosis patients with systemic autoimmune rheumatic disease (ARD).

METHODS

This was a retrospective cohort of silicosis patients between January of 1999 and December of 2023. We compared the incidence of tuberculosis and nontuberculous mycobacterial disease (NTM) in patients with silicosis with and without ARD. We also compared the tuberculosis incidence in the overall cohort with general Brazilian population estimates.

RESULTS

The study comprised 369 silicosis patients, of whom 35 (9.5%) had ARD. Having ARD did not affect the cumulative incidence of mycobacterial diseases. The risk of tuberculosis was higher in the cohort when compared with that in the adult Brazilian male population (age-adjusted incidence rate ratio = 20.46; 95% CI 14.89-28.13).

CONCLUSIONS

In this cohort of patients with silicosis, ARD was not associated with the incidence of mycobacterial diseases.

Multidrug tolerance conferred by loss-of-function mutations in anti-sigma factor RshA of Mycobacterium abscessus

Low-level drug resistance in noncanonical pathways can constitute steppingstones toward acquisition of high-level on-target resistance mutations in the clinic. To capture these intermediate steps in Mycobacterium abscessus (Mab), we performed classic mutant selection experiments with moxifloxacin at twofold its minimum inhibitory concentration (MIC) on solid medium. We found that low-level resistance emerged reproducibly as loss-of-function mutations in RshA (MAB_3542c), an anti-sigma factor that negatively regulates activity of SigH, which orchestrates a response to oxidative stress in mycobacteria. Since oxidative stress is generated in response to many antibiotics, we went on to show that deletion of rshA confers low to moderate resistance-by measure of MIC-to a dozen agents recommended or evaluated for the treatment of Mab pulmonary infections. Interestingly, this moderate resistance was associated with a wide range of drug tolerance, up to 1,000-fold increased survival of a ΔrshA Mab mutant upon exposure to several β-lactams and DNA gyrase inhibitors. Consistent with the putative involvement of the SigH regulon, we showed that addition of the transcription inhibitor rifabutin (RBT) abrogated the high-tolerance phenotype of ΔrshA to representatives of the β-lactam and DNA gyrase inhibitor classes. In a survey of 10,000 whole Mab genome sequences, we identified several loss-of-function mutations in rshA as well as non-synonymous polymorphisms in two cysteine residues critical for interactions with SigH. Thus, the multidrug multiform resistance phenotype we have uncovered may not only constitute a step toward canonical resistance acquisition during treatment but also contribute directly to treatment failure.

A loading dose of clofazimine to rapidly achieve steady-state-like concentrations in patients with nontuberculous mycobacterial disease

OBJECTIVES

Clofazimine is a promising drug for the treatment of nontuberculous mycobacterial (NTM) diseases. Accumulation of clofazimine to reach steady-state plasma concentrations takes months. A loading dose may reduce the time to steady-state-like concentrations. We evaluated the pharmacokinetics (PK), safety and tolerability of a loading dose regimen in patients with NTM disease.

METHODS

Adult participants received a 4-week loading dose regimen of 300 mg clofazimine once daily, followed by a maintenance dose of 100 mg once daily (combined with other antimycobacterial drugs). Blood samples for PK analysis were collected on three occasions. A population PK model for clofazimine was developed and simulations were performed to assess the time to reach steady-state-like (target) concentrations for different dosing regimens.

RESULTS

Twelve participants were included. The geometric mean peak and trough clofazimine concentrations after the 4-week loading phase were 0.87 and 0.50 mg/L, respectively. Adverse events were common, but mostly mild and none led to discontinuation of clofazimine. Our loading dose regimen reduced the predicted median time to target concentrations by 1.5 months compared to no loading dose (3.8 versus 5.3 months). Further time benefit was predicted with a 6-week loading dose regimen (1.4 versus 5.3 months).

CONCLUSION

A 4-week loading dose regimen of 300 mg once daily reduced the time to target clofazimine concentrations and was safe and well-tolerated. Extending the loading phase to 6 weeks could further decrease the time to target concentrations. Using a loading dose of clofazimine is a feasible strategy to optimize treatment of NTM disease.

CLINICAL TRIALS REGISTRATION

NCT05294146.

Epidemiology of nontuberculous mycobacteria in the Finger Lakes region of New York

Clinical-epidemiologic data for all nontuberculous mycobacteria isolated in the 9 County Finger Lakes region of NY from 226 patients between 04/01/2018-03/31/2020 were retrospectively analyzed. Only 51% of patients meeting diagnostic criteria were treated, while 25% not meeting diagnostic criteria were also treated, indicating important knowledge gaps and research opportunities.

Vertical stratification of the water microbiome in an electric water heater tank: implications for premise plumbing opportunistic pathogens

Hot water systems are the most frequent environment associated with the prevalence and growth of opportunistic premise plumbing pathogens (OPPPs). Previous studies identified water heaters as a source of waterborne diseases and concluded that design variables may contribute to their prevalence. A multifaceted approach was used to investigate the vertical stratification of the microbiome and selected OPPPs in an electric water heater tank connected to a home plumbing system simulator. Results show that the microbiome is highly diverse with evidence of temperature stratification and temporal structuring influenced by the partial drainage of the tank. Representatives of the Mycobacterium spp. were the most prevalent taxa, followed by Legionella spp., and a relatively low prevalence of free-living amoeba Vermamoeba vermiformis. Higher concentrations of Legionella pneumophila at the bottom of the tank indicated the potential growth and protection of this opportunistic pathogen at this location. Overall, partial drainage of the water tank (60% of the tank capacity) did not significantly mitigate the microbiome and selected OPPPs. The outcome of this study sheds light on the role of vertical stratification on water quality and demonstrates the resilience of the microbial community residing in an electric water heater tank and the implications for public health.

Increasing trends of non-tuberculous mycobacteria clinical isolates in Guangzhou, China

Non-tuberculous mycobacteria (NTM) are one of major public health concern. The current study aimed to find the prevalence trends of NTM in Guangzhou, China from January 2018 to December 2023. A total of 26,716 positive mycobacterial cultures were collected. Thirty-six specimens with incomplete personal information were excluded. The remaining 26,680 specimens were identified using a gene chip method. 16,709 isolates were Mycobacterium tuberculosis (MTB) (62.63 %), and 9,971 were NTM (37.37 %). 43.43 % (4,330/9,971) of NTM isolates were male, and 56.57 % (5,641/9,971) were female (χ2 = 24.36, P < 0.05), a male to female ratio of approximately 1:1.30. Infections in individuals with aged 40 years and above was higher (77.63 %) than below 40 years (22.37 %) (χ2 = 4.94, P = 0.026). The annual NTM isolation rates from 2018 to 2023 were 32.03 %, 34.00 %, 36.27 %, 38.58 %, 38.99 %, and 43.24 %, respectively, showing an increasing trend (χ2 for trend = 0.097, P < 0.05) (R = 0.097, P < 0.05). Out of 9,971 NTM isolates, 8,881 cases include only five common NTM species (MAC, M. abscessus/M. chelonae, M. kansasii, M. fortuitum, and M. gordonae). The overall NTM isolation rate was 37.37 %. The NTM isolation rate was significantly higher than the national average, showing an increasing trend over the last six years.

Progress in the study of mefloquine as an antibiotic adjuvant for combination bacterial inhibition treatment

Antimicrobial resistance is among the greatest threats to public health globally, and drug repurposing strategies may be advantageous to addressing this problem. Mefloquine, a drug traditionally used to treat malaria, has emerged as a promising antibiotic adjuvant, due to its ability to enhance the effectiveness of conventional antibiotics against resistant bacterial strains. In this paper, we first outline the enhancement properties of mefloquine and its mechanisms of action as an adjuvant antibiotic against multidrug-resistant bacteria. Mefloquine exhibits synergistic bacteriostatic effects when combined with colistin, β-lactams, antituberculosis drugs, quinolones, and linezolid. Potential mechanisms underlying its synergistic effects include inhibition of antibiotic efflux, disruption of bacterial cell membrane integrity, and disturbance of biofilm formation. In addition, we explore the bacteriostatic effects of several mefloquine derivatives against Mycobacterium tuberculosis and some fungi. Further, we summarize the findings of recent studies on other aspects of mefloquine activity, including its antiviral and antitumor effects. Finally, the advantages and challenges of mefloquine use as an antibiotic adjuvant in combination with antibiotics for bacterial inhibition are discussed. Overall, mefloquine shows excellent potential as an antibiotic adjuvant therapy against multidrug-resistant bacteria and is a promising candidate for combination therapy; however, further studies are needed to fully elucidate its mechanism of action and address the challenges associated with its clinical application.

Exploring the Chemical Space of Mycobacterial Oxidative Phosphorylation Inhibitors Using Molecular Modeling

Mycobacteria are opportunistic intracellular pathogens that have plagued humans and other animals throughout history and still are today. They manipulate and hijack phagocytic cells of immune systems, enabling them to occupy this peculiar infection niche. Mycobacteria exploit a plethora of mechanisms to resist antimicrobials (e. g., waxy cell walls, efflux pumps, target modification, biofilms, etc.) thereby evolving into superbugs, such as extensively drug-resistant tuberculosis (XDR TB) bacilli and the emerging pathogenic Mycobacterium abscessus complex. This review summarizes the mechanisms of action of some of the surging antimycobacterial strategies. Exploiting the fact that mycobacteria are obligate aerobes and the differences between their oxidative phosphorylation pathways versus their human counterpart opens a promising avenue for drug discovery. The polymorphism of respiratory complexes across mycobacterial pathogens imposes challenges on the repositioning of antimycobacterial agents to battle the rise in nontuberculous mycobacterial infections. In silico strategies exploiting mycobacterial respiratory machinery data to design novel therapeutic agents are touched upon. The potential druggability of mycobacterial respiratory elements is reviewed. Future research addressing the health challenges associated with mycobacterial pathogens is discussed.