Nontuberculous Mycobacteria Research Articles

Characterization of non-tuberculous mycobacterial pulmonary disease and pulmonary tuberculosis in patients with AFB smear-positive sputum: A retrospective comparative study

BackgroundDistinguishing nontuberculous mycobacteria pulmonary disease (NTM-PD) from pulmonary tuberculosis (PTB) is a challenge especially in patients with positive sputum smear of acid-fast bacilli (AFB). This study aimed to compare and identify the clinical characteristics between the two diseases among patients with positive sputum AFB. MethodsFrom February 2017 through March 2021, patients with positive sputum AFB were reviewed in two hospitals of China. Among them, clinical data of NTM-PD and PTB patients was collected and compared. Results76 cases of NTM-PD and 92 cases of PTB were included in our study. When compared with PTB, NTM-PD patients were older (59.2 ± 11.4 vs 44.2 ± 19.5 years, P < 0.001) and manifested more hemoptysis and dyspnea (28.9 % vs 14.1 %, P < 0.05; 48.7 % vs 17.4 %, P < 0.001 respectively). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) for Xpert were 85.9 %, 96.1 %, 96.3 %, 84.9 %, respectively, compared to 94.2 %, 81.1 %, 83.1 %, 93.5 %, respectively for T-spot in diagnosing PTB. In radiological features, NTM-PD affected more lobes (4.53 ± 0.89 vs 3.61 ± 1.41, P < 0.001) and showed more consolidation (50 % vs 32.6 %, P < 0.05), destroyed lung (22.7 % vs 9.8 %, P < 0.05), honeycomb lung (26.7 % vs 6.5 %, P < 0.001) but less nodules (80.3 % vs 95.7 %, P < 0.05), tree-in-bud sign (49.3 % vs 87 %, P < 0.001), and satellite nodules (14.5 % vs 90.2 %, P < 0.001) than PTB. Age (odds ratio [OR], 1.043; 95 % confidence interval [CI], 1.018–1.069, P < 0.05), hemoptysis (OR, 3.552; 95%CI, 1.421–8.729, P < 0.05), and dyspnea (OR, 2.631; 95%CI, 1.151–6.016, P < 0.05) were independently correlated with NTM infection. ConclusionsNTM-PD and PTB share similar clinical manifestations. Among them, advanced age, hemoptysis, and dyspnea are the independent predictors for NTM infection. Xpert is an efficiency analysis in discriminating between NTM-PD and PTB in patients with positive sputum AFB.

An alveolus lung-on-a-chip model of Mycobacterium fortuitum lung infection.

Lung disease due to non-tuberculous mycobacteria (NTM) is rising in incidence. While both two dimensional cell culture and animal models exist for NTM infections, a major knowledge gap is the early responses of human alveolar and innate immune cells to NTM within the human alveolar microenvironment. Here we describe development of a humanized, three-dimensional, alveolus lung-on-a-chip (ALoC) model of Mycobacterium fortuitum lung infection that incorporates only primary human cells such as pulmonary vascular endothelial cells in a vascular channel, and type I and II alveolar cells and monocyte-derived macrophages in an alveolar channel along an air-liquid interface. M. fortuitum introduced into the alveolar channel primarily infected macrophages, with rare bacteria inside alveolar cells. Bulk-RNA sequencing of infected chips revealed marked upregulation of transcripts for cytokines, chemokines and secreted protease inhibitors (SERPINs). Our results demonstrate how a humanized ALoC system can identify critical early immune and epithelial responses to M. fortuitum infection. We envision potential application of the ALoC to other NTM and for studies of new antibiotics.

Comparison of Power Ultrasound and NALC-NaOH Decontamination Methods for Stool Mycobacterial Culture: A Prospective Study.

Stool samples have been reported to be useful for the diagnosis of pulmonary tuberculosis (PTB), especially in patients who are unable to produce sputum. However, contamination limits the usefulness of stool specimens in mycobacterial culture. In this study, a novel decontamination method of power ultrasound (PU) was evaluated for mycobacterial isolation from suspected PTB cases. Stool samples (n = 650) were collected, and each sample was divided into approximately three equal groups. In addition to an AFB smear (Auramine O method), the stool samples were treated using different decontamination methods (NaOH-NALC vs. PU methods). The sensitivity (calculated against CRS) and contamination rates between the two methods were compared using McNemar's test. Of the 650 samples, 32 (4.92%) stool samples treated with the NaOH-NALC method were culture-positive, including Mycobacterium tuberculosis (M.TB; n = 21, 3.23%) and nontuberculous mycobacteria (NTM; n = 11, 1.69%). Sixty-one (9.38%) stool samples treated with the PU method were culture-positive, including M.TB (n = 37, 5.69%) and NTM (n = 24, 3.69%). Statistical analysis showed that a significant difference was found in the isolation rate of M.TB and NTM between the two methods (p < 0.05). Additionally, compared with the NALC-NaOH method (19.07%), stool samples treated with the PU method (13.23%) had a significantly lower contamination rate (p < 0.05). In conclusion, our findings suggest that the utilization of the PU method as a novel decontamination technique could significantly enhance the isolation rates of both NTM and M.TB when stool specimens are employed for culture. Compared to the NaOH-NALC method, this approach proves to be more effective in facilitating stool mycobacterial culture.

Rare Presentation of Non-Tuberculous Mycobacteria: A Case of Lung Infection with Pleural Effusion

Background: Non-tuberculous mycobacteria (NTM) are environmental organisms that can cause pulmonary infections, particularly in individuals with predisposing conditions. While NTM lung disease is increasingly recognized, pleural effusion as a complication remains uncommon, posing diagnostic and therapeutic challenges. This case emphasizes the importance of a high index of suspicion, comprehensive microbiological investigations, and bronchoscopy in the diagnosis of NTM lung disease with pleural effusion. Case presentation: We present the case of a 55-year-old male farmer with a history of smoking, who presented with progressive dyspnea, cough, and constitutional symptoms. Initial investigations suggested tuberculosis, but sputum tests were negative. Chest imaging revealed a right pleural effusion and cavitary lung lesions. Pleural fluid analysis showed an exudative pattern with elevated adenosine deaminase (ADA) but negative for acid-fast bacilli. Bronchoscopy with bronchoalveolar lavage culture yielded Mycobacterium other than tuberculosis (MOTT). The patient was diagnosed with NTM lung disease complicated by pleural effusion and initiated on multidrug therapy. Conclusion: This case highlights the diagnostic challenges of NTM lung disease, particularly when presenting with pleural effusion. A high index of suspicion, comprehensive microbiological investigations, and bronchoscopy are crucial for accurate diagnosis. Prompt initiation of appropriate multidrug therapy is essential for optimal outcomes.

MALDI-TOF mass spectrometry from nucleic acid: development and evaluation of a novel platform for identification of mycobacteria and detection of genetic markers of resistance.

Complete identification methods are critical for evaluating nontuberculous mycobacteria (NTM). Here, we describe a novel diagnostic method for identification of eight NTM, Mycobacterium tuberculosis complex, and three drug resistance markers using PCR/matrix-assisted, laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) from cultured organisms. With this technology, a multiplex end-point PCR is performed for targets of interest. Detection probes that are extended in the presence of a target are added. The extended probes have greater molecular weight and can be detected by MALDI-TOF MS. An AFB Primary Panel was designed to differentiate Mycobacterium avium; Mycobacterium intracellulare subsp. chimaera; Mycobacterium avium complex (other); Mycobacterium abscessus subsp. abscessus, bolletii, and massiliense; Mycobacterium kansasii, and M. tuberculosis complex. This design should cover 90% (3,483/3,691) of mycobacteria seen onsite. A development set of unblinded isolates (n = 217) was used to develop PCR primers, detection probes, and probe barcodes. It demonstrated 99.1% (215/217) agreement with reference methods. An evaluation set using blinded isolates (n = 320) showed an overall sensitivity of 94.3% (range by target: 90.0-100%). Overall specificity from negative media, non-target mycobacteria, and bacteria was 99.1% (108/109; range by target: 94.4-100%). Three drug resistance markers erm (41), rrl, and rrs demonstrated 100%, 91%, and 100% sensitivity, respectively, and >99% specificity. Limit of detection per target ranged from 2.2 × 103 to 9.9 × 106 CFU/mL. The AFB Primary Panel allows for mycobacterial speciation, subspeciation, and resistance mutation detection, which is essential for diagnosis, appropriate therapy, identifying outbreaks, and managing treatment-refractory disease. It can perform with high-throughput and high specificity and sensitivity from isolates.IMPORTANCEEven closely related mycobacteria can have unique treatment patterns, but differentiating these organisms is a challenge. Here, we tested an innovative platform that combines two commonly used technologies and creates something new: matrix-assisted, laser-desorption ionization time-of flight mass spectrometry was performed on PCR amplicons instead of on proteins. This created a robust system with the advantages of PCR (high discriminatory power, high throughput, detection of resistance) with the advantages of mass spectrometry (more targets, lower operational cost) in order to identify closely related mycobacterial organisms.

Genomic Epidemiology of Mycobacterium abscessus on the Island of Montréal Not Suggestive of Healthcare-associated Person-to-Person Transmission.

Mycobacterium abscessus complex (MABC), an opportunistic nontuberculous mycobacteria (NTM), can lead to poor clinical outcomes in pulmonary infections. Conflicting data exist on person-to-person transmission of MABC within and across healthcare facilities. To investigate further, a comprehensive retrospective study across five healthcare institutions on the Island of Montréal was undertaken. We analyzed the genomes of 221 MABC isolates obtained from 115 individuals (2010-2018) to identify possible links. Genetic similarity, defined as ≤25 single-nucleotide polymorphisms (SNPs), was investigated through a blinded epidemiological inquiry. Bioinformatics analyses identified 28 sequence types (STs), including globally observed dominant circulating clones (DCCs). Further analysis revealed 210 isolate pairs within the SNP threshold. Among these pairs, there was one possible lab contamination where isolates from different patients processed in the same lab differed by only 2 SNPs. There were 37 isolate pairs from patients who had provided specimens from the same hospital; however, epidemiological analysis found no evidence of healthcare-associated person-to-person transmission between these patients. Additionally, pan-genome analysis showed higher discriminatory power than core genome analysis for examining genomic similarity. Genomics alone is insufficient to establish MABC transmission, particularly considering the genetic similarity and wide distribution of DCCs, although pan-genome analysis has the potential to add further insight. Our findings indicate that MABC infections in Montréal are unlikely attributable to healthcare-associated person-to-person transmission.

The Canadian Bronchiectasis and Nontuberculous Mycobacteria Registry: A Study Protocol

BackgroundBronchiectasis is a complex, chronic disease with geographic and ethnic diversity. While the most substantial cohort studies have been conducted in Europe and the USA, Canada also faces considerable challenges. The Comprehensive Canadian Bronchiectasis and Nontuberculous Mycobacterial Infection Registry aims to: (1) outline the clinical characteristics and natural history of bronchiectasis in Canada; (2) identify risk factors contributing to disease progression within Canadians; (3) integrate comprehensive clinical information to better understand the phenotypes of bronchiectasis; (4) support the development of large-scale, randomized controlled trials in Canada.MethodsThe Canadian Bronchiectasis and Nontuberculous Mycobacterial Infection Registry is an ongoing prospective, longitudinal, multi-center, observational cohort study. It aims to enroll at least 2000 participants to collect data such as medical history, etiological assessments, lung function tests, microbiological profiles, radiographic evaluations, comorbidities and quality of life (QoL) metrics. Participants will undergo annual follow-ups to gather longitudinal information regarding outcomes, treatments and changes in QoL. The inclusion criteria are a diagnosis of bronchiectasis by clinical history and computed tomography and/or pulmonary nontuberculous mycobacterial (NTM) infection as defined by ATS/IDSA guidelines. The study's protocol received ethical approval from the lead site, the University of Calgary, with future additional approval from local ethics committees at all participating centers.DiscussionThe outcomes of the registry will be instrumental in uncovering the clinical traits and natural history of bronchiectasis. This longitudinal study will be used for analysis to form evidence-based clinical practices and serve as a resource in Canada to inform future studies in NTM and bronchiectasis.

Chemical optimization and derivatization of micrococcin p2 to target multiple bacterial infections: new antibiotics from thiopeptides.

Antimicrobial resistance poses a significant threat to humanity, and the development of new antibiotics is urgently needed. Our research has focused on thiopeptide antibiotics such as micrococcin P2 (MP2) and derivatives thereof as new anti-infective agents. Thiopeptides are sulfur-rich, structurally complex substances that exhibit potent activity against Gram-positive pathogens and Mycobacteria species, including clinically resistant strains. The clinical development of thiopeptides has been hampered by the lack of efficient synthetic platforms to conduct detailed structure-activity relationship studies of these natural products. The present contribution touches upon efficient synthetic routes to MP2 that laid the groundwork for clinical translation. The medicinal chemistry campaign on MP2 has been guided by computational molecular dynamic simulations and parallel investigations to improve drug-like properties, such as enhancing the aqueous solubility and optimizing antibacterial activity. Such endeavors have enabled identification of promising lead compounds, AJ-037 and AJ-206, against Mycobacterium avium complex (MAC). Extensive in vitro studies revealed that these compounds exert potent activity against MAC species, a subspecies of non-tuberculous mycobacteria (NTM) that proliferate inside macrophages. Two additional pre-clinical candidates have been identified: AJ-024, for the treatment of Clostridioides difficile infections, and AJ-147, for methicillin-resistant Staphylococcus aureus impetigo. Both compounds compare quite favorably with current first-line treatments. In particular, the ability of AJ-147 to downregulate pro-inflammatory cytokines adds a valuable dimension to its clinical use. In light of above, these new thiopeptide derivatives are well-poised for further clinical development.

The autophagy-targeting compound V46 enhances antimicrobial responses to Mycobacteroides abscessus by activating transcription factor EB

Mycobacteroides abscessus (Mabc) is a rapidly growing nontuberculous mycobacterium that poses a considerable challenge as a multidrug-resistant pathogen causing chronic human infection. Effective therapeutics that enhance protective immune responses to Mabc are urgently needed. This study introduces trans-3,5,4′-trimethoxystilbene (V46), a novel resveratrol analogue with autophagy-activating properties and antimicrobial activity against Mabc infection, including multidrug-resistant strains. Among the resveratrol analogues tested, V46 significantly inhibited the growth of both rough and smooth Mabc strains, including multidrug-resistant strains, in macrophages and in the lungs of mice infected with Mabc. Additionally, V46 substantially reduced Mabc-induced levels of pro-inflammatory cytokines and chemokines in both macrophages and during in vivo infection. Mechanistic analysis showed that V46 suppressed the activation of the protein kinase B/Akt-mammalian target of rapamycin signaling pathway and enhanced adenosine monophosphate-activated protein kinase signaling in Mabc-infected cells. Notably, V46 activated autophagy and the nuclear translocation of transcription factor EB, which is crucial for antimicrobial host defenses against Mabc. Furthermore, V46 upregulated genes associated with autophagy and lysosomal biogenesis in Mabc-infected bone marrow-derived macrophages. The combination of V46 and rifabutin exerted a synergistic antimicrobial effect. These findings identify V46 as a candidate host-directed therapeutic for Mabc infection that activates autophagy and lysosomal function via transcription factor EB.

Forecasting climate-associated non-tuberculous mycobacteria (NTM) infections in the UK using international surveillance data and machine learning.

Nontuberculous mycobacteria (NTM) cause skin and lung infections, have high mortality rates, and are resistant to a range of antibiotics and water treatment methods. As NTM reside in environmental reservoirs, they are sensitive to environmental conditions. The suitability of their environmental reservoirs can increase as a result of climate change, subsequently increasing environmental exposure and infection rates. NTM infections are not generally notifiable, including in the UK, but sustained increases have been observed in regions that report NTM infection rates. To assess the burden of NTM infections in the UK under projected climate change, we examined the relationship between climate variables and available NTM surveillance data internationally. Statistically significant increases were found in regions where NTM infections are notifiable, which were positively associated with increased precipitation and temperatures. A random forest regressor was trained using supervised learning from international NTM surveillance data and linked climate variables. The random forest model was applied to UK climate projections, projecting a 6.2% increase in NTM infection rates over the next 10 years, with notable regional variation. Our random forest model predicts that the forecasted impacts of climate change in the UK, including increasing temperatures and frequency of heavy rainfall, will lead to increases in NTM infection rates. Robust surveillance in the future is necessary to increase data available to train models, increasing our predictive power in forecasting climate-associated NTM trends. Our results highlight a novel aspect of how climate change will impact health outcomes in the UK.

Isolation and identification of non-tuberculous mycobacteria from aquarium fish in Ilam, Iran

Non-tuberculous mycobacteria (NTM) are among the most important pathogens in wild, captive, marine, and freshwater fish species. So, it is important to consider fish as the primary source of infection for aquarium fish and humans. The present study analyzed the occurrence of NTM in aquarium fish in Ilam, west of Iran. In total, 50 samples of infected fish were collected from different aquariums. Following initial sample processing, sediment of each sample was inoculated into Lowenstein-Jensen and Herrold egg media. The positive colonies were investigated with, growth rate, pigmentation, colony morphology, niacin accumulation, nitrate reduction, catalase activity, urease activity, and arylsulfatase activity. Also, molecular identification was carried out by sequencing of heat shock protein 65 kD gene (hsp65) sequence analysis. According to our results, NTM were isolated from 13 samples (26%), comprising 6 (46.2%) rapid growing, and 7 (53.8%) slow growing mycobacteria. In addition, Mycobacterium marinum was the most common NTM isolated in ornamental fish, which is potentially dangerous for both fish and humans. In conclusion, the current study indicates that ornamental fish play a significant role as a source of NTM.

Berberine enhances the antibacterial activity of thymoquinone, carvacrol and thymol against multi-drug resistant nontuberculous mycobacteria

Berberine enhances the antibacterial activity of thymoquinone, carvacrol and thymol against multi-drug resistant nontuberculous mycobacteria

Phosphatidylserine liposomes induce a phagosome acidification-dependent and ROS-mediated intracellular killing of Mycobacterium abscessus in human macrophages.

Mycobacterium abscessus (Mab) is an opportunistic nontuberculous mycobacterium responsible of difficult-to-treat pulmonary infections in vulnerable patients, such as those suffering from Cystic Fibrosis (CF), where it represents a major cause of morbidity and mortality. Additionally, due to the intrinsic extensive antimicrobial resistance spectrum displayed by this species and the side effects reported for some available antibiotics, the therapeutic management of such infections remains extremely difficult. In the present study, we show that phosphatidylserine liposomes (PS-L) enhance intracellular mycobacterial killing of Mab infected human macrophages with functional or pharmacologically inhibited cystic fibrosis conductance regulator (CFTR), by a mechanism involving phagosome acidification and reactive oxygen species (ROS) production. Additionally, PS-L significantly reduce proinflammatory response of Mab infected macrophages in terms of NF-kB activation and TNF-α production, irrespective of CFTR inhibition. Altogether, these results represent the proof of concept for a possible future development of PS-L as a therapeutic strategy against difficult-to-treat Mab infection.

Dual β-lactams for the treatment of Mycobacterium abscessus: a review of the evidence and a call to act against an antibiotic nightmare.

Mycobacterium abscessus complex is a group of rapidly growing non-tuberculous mycobacteria (NTM), increasingly emerging as opportunistic pathogens. Current treatment options for these microorganisms are limited and associated with a high rate of treatment failure, toxicity and recurrence. In search of new therapeutic strategies, interest has grown in dual β-lactam (DBL) therapy, as research recently discovered that M. abscessus cell wall synthesis is mainly regulated by two types of enzymes (d,d-transpeptidases and l,d-transpeptidases) differently susceptible to inhibition by distinct β-lactams. In vitro studies testing several DBL combinations have shown synergy in extracellular broth cultures as well as in the intracellular setting: cefoxitin/imipenem, ceftaroline/imipenem, ceftazidime/ceftaroline and ceftazidime/imipenem. The addition of specific β-lactamase inhibitors (BLIs) targeting M. abscessus β-lactamase did not significantly enhance the activity of DBL combinations. However, in vivo data are lacking. We reviewed the literature on DBL/DBL-BLI-based therapies for M. abscessus infections to raise greater attention on this promising yet overlooked treatment option and to guide future preclinical and clinical studies.

Mycobacterium intracellulare mediates macrophage pyroptosis by activating AIM2 and NLRP3 inflammasomes.

Clinically, the incidence of nontuberculous mycobacteria (NTM) lung disease is on the rise, and Mycobacterium intracellulare (M. intracellulare) has attracted much attention as a common opportunistic pathogen in clinical practice. So it is very important to study its immunopathogenic mechanism. In this study, the mechanism of M. intracellulare induced pyroptosis of macrophage was investigated. As shown in Fig.1, the secretion of IL-1β and IL-18 in J774A.1 cells increased with time after M. intracellulare infection and was affected by caspase-1 activation and K + efflux, while caspase-1 was significantly expressed in infected cells. Further from Fig.2, NLRP3,AIM2,ASC proteins were significantly expressed in J774A.1 cells after infection, indicating that the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammasome were involved in the infection process. In addition, when caspase-1 activity and K + efflux were inhibited, the expression of related proteins was significantly reduced. It indicates that the activation of NLRP3 and AIM2 is regulated by caspase-1 and K+. Figure3, the percentage of dead cells with cell membrane damage increases after infection and cleavage of GSDMD proteins occurs. In summary, infection of J774A.1 cells with M. intracellulare induces pyroptosis, and this process is mediated by caspase-1. Our study provides information for further understanding of the molecular mechanism of M. intracellulare infection.

Clinical Characteristics and Outcome of Disseminated Nontuberculous Mycobacteria Infections in Patients With Solid Organ Transplant

Clinical Characteristics and Outcome of Disseminated Nontuberculous Mycobacteria Infections in Patients With Solid Organ Transplant

Incidência de linfadenite granulomatosa suína no ano de 2023 em frigorífico localizado no Triângulo Mineiro, Minas Gerais

Despite the increase in pig production in Brazil, challenges such as the spread of diseases in pig populations and public health concerns, such as the transmission of viruses and bacteria, require constant vigilance during the slaughter of these animals. In this context, granulomatous lymphadenitis (LG) in pigs is a subclinical disease caused mainly by non-tuberculous mycobacteria, with Mycobacterium avium hominissuis being the most prevalent in pigs and humans. The detection of infected animals occurs during slaughter, resulting in losses due to the disposal of viscera and carcasses. This study aimed to report the incidence of LG in a slaughterhouse located in the city of Uberlândia, Minas Gerais, during the year 2023. More than one million slaughtered animals were evaluated, of which more than 100 thousand showed some non-compliance, resulting in 596 cases of LG identified. The data suggest a low incidence of LG in the Triângulo Mineiro region, attributed to advances in disinfection practices and widespread knowledge about the disease. Furthermore, a seasonal pattern was observed in the occurrence of LG, with higher incidences in the coldest months of the year. Factors such as lack of hygiene in facilities, inadequate food supply and the presence of birds can contribute to the spread of the disease. It is concluded that despite the low occurrence in the studied region, LG continues to be a concern due to its economic impact and the need for constant surveillance and improvements in management and hygiene practices.

The Drug Susceptibility of Non-Tuberculous Mycobacteria (NTM) in a Referral Hospital in Rome from 2018 to 2023.

Background: The treatment of non-tuberculous mycobacterial (NTM) infections is challenging because of the difficulty in obtaining phenotypic (pDST) and/or molecular (mDST) drug susceptibility testing and the need of a multi-drug regimen. Objectives: The objective was to describe the in vitro susceptibility patterns of various NTM species through an analysis of susceptibility results obtained on isolates collected between 2018 and 2023. Methods: Species identification and mutations in rrs or rrl genes (mDST) were identified by a line probe assay, while the pDST was performed by broth microdilution and interpreted according to CLSI criteria. Results: We analysed 337 isolates of NTM belonging to 15 species/subspecies. The Mycobacterium avium complex (MAC) was the most common (62%); other species identified included M. gordonae (11%), M. kansasii (5%), the M. abscessus complex (8%), M. chelonae (6%), and M. fortuitum (2%). The results of pDST (claritromycin and amikacin) and mDST (rrl and rrs genes) on 66 NTM strains showed that while wild-type rrl and rrs occurred in 86.3% and 94% strains, respectively, the pDST showed 88% sensitivity for clarithromycin and 57.5% for amikacin. The main incongruity was observed for macrolides. Conclusions: Most NTM are likely to be susceptible to macrolides and aminoglycosides. The molecular identification of resistant genotypes is accurate and strongly recommended for optimal patient management.

Source-to-tap investigation of the occurrence of nontuberculous mycobacteria in a full-scale chloraminated drinking water system.

Nontuberculous mycobacteria (NTM) in drinking water are a significant public health concern. However, an incomplete understanding of the factors that influence the occurrence of NTM in drinking water limits our ability to characterize risk and prevent infection. This study sought to evaluate the influence of season and water treatment, distribution, and stagnation on NTM in drinking water. Samples were collected source-to-tap in a full-scale, chloraminated drinking water system approximately monthly from December 2019 to November 2020. NTM were characterized using culture-dependent (plate culture with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry [MALDI-TOF MS] isolate analysis) and culture-independent methods (quantitative PCR and genome-resolved metagenomics). Sampling locations included source waters, three locations within the treatment plant, and five buildings receiving water from the distribution system. Building plumbing samples consisted of first draw, 5-min flush, and full flush cold-water samples. As the study took place during the COVID-19 pandemic, the influence of reduced water usage in three of the five buildings was also investigated. The highest NTM densities source-to-tap were found in the summer first draw building water samples (107 gene copies/L), which also had the lowest monochloramine concentrations. Flushing was found to be effective for reducing NTM and restoring disinfectant residuals, though flush times necessary to improve water quality varied by building. Clinically relevant NTM species, including Mycobacterium avium, were recovered via plate culture, with increased occurrence observed in buildings with higher water age. Four of five NTM metagenome-assembled genomes were identified to the species level and matched identified isolates.IMPORTANCENTM infections are increasing in prevalence, difficult to treat, and associated with high morbidity and mortality rates. Our lack of understanding of the factors that influence NTM occurrence in drinking water limits our ability to prevent infections, accurately characterize risk, and focus remediation efforts. In this study, we comprehensively evaluated NTM in a full-scale drinking water system, showing that various steps in treatment and distribution influence NTM presence. Stagnant building water contained the highest NTM densities source-to-tap and was associated with low disinfectant residuals. We illustrated the differences in NTM detection and characterization obtained from culture-based and culture-independent methods, highlighting the complementarity between these approaches. We demonstrated that focusing NTM mitigation efforts in building plumbing systems, which have the highest NTM densities source-to-tap, has potential for immediate positive effects. We also identified steps during treatment that increase NTM levels, which provides beneficial information for utilities seeking to reduce NTM in finished water.

Not TB But Not To Be Underestimated: The Challenges of Nontuberculous Mycobacteria Infection in Solid Organ Transplant Recipients.

Not TB But Not To Be Underestimated: The Challenges of Nontuberculous Mycobacteria Infection in Solid Organ Transplant Recipients.