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PubMed2026

Prospective outcomes of adults with speciated Mycobacterium avium complex lung disease, 2021-2026.

RATIONALE: Mycobacterium avium complex lung disease (MAC-LD) is clinically heterogeneous and carries diverse outcomes. OBJECTIVES: To describe predictors of clinical progression of MAC-LD in a state-wide cohort. METHODS: We enrolled adults with MAC-LD from across Virginia, USA starting in 2021. Every 6 months we performed respiratory quality of life questionnaire, scored CT scans, and recorded respiratory mycobacterial cultures including MAC speciation. Outcomes were classified using NTM-NET consensus definitions, factors predicting clinical progression analyzed by Poisson regression, and hierarchical clustering on principal components derived from Factorial Analysis of Mixed Data. MEASUREMENTS AND MAIN RESULTS: Of 105 participants the median follow-up was 917 days. Mean age was 69.8 years, 79 (75%) were women, and 70 (67%) had nodular bronchiectasis. M. intracellulare was the most common species, present in 48 (46%) participants at enrollment, followed by M. avium (29, 28%), and M. intracellulare subspecies chimaera (11, 10%). Only 2 (9%) of 22 evaluable participants met the NTM-NET definition of cure. In all participants after multivariable adjustment, older baseline age (incidence rate ratio 1.03 [1, 1.06], p = 0.04) and fibrocavitary CT scan pattern (2.57 [1.33, 4.96], p = 0.005), were associated with unfavorable 12-month clinical progression. Species type and species persistence contributed to characteristics of three distinct phenotypes of MAC-LD of varying severity and clinical progression. CONCLUSIONS: The majority of participants were not assessable for MAC-LD treatment outcomes using strict NTM-NET definitions. Species informed phenotypes of MAC lung disease are prognostically useful and can inform routine management and trial design.

M. intracellulare↗
PubMed2025

Understanding recurrence in Mycobacterium avium complex pulmonary disease: genotypic strategies to support clinical decision-making.

Pulmonary disease caused by Mycobacterium avium complex (MAC-PD) is a chronic, recurrent disease, and its high recurrence rate after treatment makes clinical management difficult. Distinguishing whether recurrence is due to persistence of existing strains or reinfection with new strains is essential for establishing treatment strategies, preventing overuse of antimicrobials, and establishing infection control measures. According to reports, 54%-74% of MAC-PD recurrence is due to reinfection, which may be mainly related to environmental reservoirs such as household water supply. In this review, we present various clinical scenarios in which MAC-PD recurrence may occur and examine genotyping techniques as a strategy to distinguish and respond to them. From traditional methods such as IS1245-based restriction fragment length polymorphism, pulsed-field gel electrophoresis, and hsp65 and rpoB gene sequencing to high-resolution analysis techniques such as multilocus sequence testing and whole-genome sequencing, the latest molecular typing methods are comprehensively summarized. Integrating these genotype data into clinical settings, standardizing single-nucleotide polymorphism-based interpretation thresholds, and promoting the establishment of a global MAC strain database will make a substantial contribution to more accurately distinguishing the recurrence mechanisms of MAC-PD and establishing personalized treatment strategies.IMPORTANCEThe global burden of nontuberculous mycobacterial pulmonary disease (PD) is increasing, with Mycobacterium avium (MAC)-PD being the most prevalent and clinically challenging form. Its low treatment success rates, high frequency of recurrence, and persistent environmental exposure complicate both diagnosis and management. A critical clinical issue is determining whether recurrence represents true relapse, due to persistence of the original strain, or reinfection with a new strain, as this guides treatment and prevents overtreatment. Genotypic strategies capable of resolving strain-level differences can improve diagnostic accuracy, prevent misclassification, and ultimately support more informed treatment decisions. Therefore, integrating genotyping data into clinical workflows, standardizing single-nucleotide polymorphism thresholds, and establishing a global MAC strain database will not only support personalized treatment but also enhance the broader public health response to this disease.

Humans↗
PubMed1979

Comparison of four culture media for isolation of Mycobacterium avium complex from porcine tissues.

The efficiency of four culture media was compared for the isolation of Mycobacterium avium complex from 197 procine tissues. In 82 tissues with microscopic granulomas and acid-fast bacilli, a significantly greater number of isolates were obtained on Middlebrook 7H10 medium with sodium pyruvate than on Stonebrink medium, Herrold egg yolk agar medium, or Lowenstein-Jensen medium (P=0.01). In 46 tissues in which no microscopic granulomas or acid-fast bacilli were observed, a significantly greater number of isolates were made on Middlebrook 7H10 medium or Herrold egg yolk agar medium than on Stonebrink medium or on Lowenstein-Jensen medium (P=0.01). The time required to grow M. avium complex on Lowenstein-Jensen medium was significantly greater than the time required to observe growth on Stonebrink, Middlebrook 7H10, or Herrold egg yolk agar medium (p=0.001).

Animals↗
PubMed2025

Genomic characterisation of recurrent Mycobacterium avium isolates from chronically infected patients reveals patterns of within-host evolution.

BACKGROUND: Mycobacterium avium complex causes chronic and difficult-to-treat infection in vulnerable patient groups, and incidence is increasing worldwide. Whole genome sequencing has the potential to reveal new information about how M. avium persists over time in the human lung. METHODS: We analysed the genomes of 287 isolates of M. avium that were sampled longitudinally from 56 patients. Our dataset included 50 newly sequenced genomes from a cohort of 20 patients from Ireland who were sampled for up to 10 years, and we compared these to 237 published genomes from 2 pre-existing cohorts from Europe to evaluate strains from Ireland in a wider context. Additionally, we performed a combined analysis across the 3 cohorts to examine the changes that occurred over the course of infection. RESULTS: We identified 2 instances where strains from Ireland clustered with strains from Europe within a 13-SNP threshold, supporting previous observations that dominant circulating clones of M. avium are present internationally. Across the 3 cohorts, we found that the communities of M. avium evolved over time within individual hosts, and we report that acquisition of new strains is frequent. Importantly, our findings suggest that M. avium may adapt to the conditions that it faces in the host, with evidence of positive selection of 13 distinct mycobacterial genes. Notably, multiple virulence-associated genes were under selection, including genes that could confer resistance to antibiotics and host defence mechanisms. CONCLUSIONS: Whole genome sequencing provides novel insights into within-host evolution of M. avium and highlights potentially important mycobacterial strategies to enhance persistence that may provide new targets for therapeutic investigation.

Humans↗
PubMed2026

Th2 bias and T-cell exhaustion characterize the immunopathology of non-tuberculous mycobacterial pulmonary disease.

Non-tuberculous mycobacterial pulmonary disease (NTM-PD) is an escalating global health concern with poorly defined immunological mechanisms, necessitating comprehensive profiling to guide therapeutic advances. We analyzed peripheral blood from 28 treatment-naïve NTM-PD patients (19 Mycobacterium avium complex, 9 Mycobacterium abscessus) and 27 matched controls using 42-marker mass cytometry (CyTOF) and Luminex multiplex assays. A random forest model identified predictive markers, while an in vitro murine macrophage model evaluated chemokine production. NTM-PD patients displayed significant immune shifts, including increased classical monocytes (CD14+ CD16-), reduced NKT-like cells (CD3+ CD56+), and elevated T-cell exhaustion markers (PD-1, TOX). This coincided with a Th1/Th2 balance shift characterized by heightened IL-13. Elevated IFN-γ-inducible chemokines CXCL9 and CXCL10 coexisted with this Th2-biased signature, indicating a complex, dysregulated inflammatory state. A model integrating immune-cell frequencies and cytokine profiles achieved robust diagnostic accuracy (AUC = 0.922) with prognostic potential. In vitro, NTM-infected macrophages produced substantial CXCL9 and CXCL10 levels relative to the LPS maximal activation benchmark, identifying them as a major cellular source. These findings propose an immunological framework wherein T-cell exhaustion and a Th2-biased microenvironment strongly correlate with NTM-PD pathogenesis. CXCL9, CXCL10, and IL-13 emerge as candidate therapeutic targets, while our predictive model offers a foundational approach for risk stratification.

Humans↗
PubMed1979

Heat inactivation of Mycobacterium avium-Mycobacterium intracellulare complex organisms in aqueous suspension.

Isolants from swine and from humans representing serotypes 1, 2, 4, 8, and 10 of the Mycobacterium avium-Mycobacterium intracellulare complex were compared for heat tolerance in aqueous suspension. The most heat-resistant isolant found was a serovar 10 isolated from a human. This isolant was examined further to determine the rate of kill at various temperatures and pH's, the effect of meat protein and fat, and the effect of nitrite. Kill rates were not significant at 60 degrees C or below. Decimal reduction values were 4 min or less at 65 degrees C and 1.5 min or less at 70 degrees C. Kill rates were slightly higher at pH values of 6.5 and 7.0 than at 5.5 or 6.0. the water-soluble fraction of wiener emulsion did not alter kill rates, but the saline-soluble fraction protected the organism somewhat. Fat did not affect the survival of the organisms except to eliminate the protective effect of saline extract when the suspension contained 50% fat. The addition of sodium nitrite to the suspension did not alter the heat sensitivity of the organisms.

Animals↗
PubMed1979

Gas chromatographic characterization of porcine and human strains belonging to the Mycobacterium avium-intracellulare complex.

Trifluoroacetylated whole-cell methanolysates of 23 strains designated as belonging to the Mycobacterium avium-intracellulare complex by biochemical, growth chromogenicity and chicken pathogenicity tests, were analysed by gas chromatography. Twenty of the strains were isolated from pigs and the remainder from human beings. Serological typing showed that 13 of the porcine strains, but none of the human strains, belonged to M. avium. The remaining strains, except one which showed autoagglutination, did not react with antisera to M. avium (serotypes 1-3), thus suggesting that they belonged to M. intracellulare. Five different, highly reproducible chromatographic patterns, the main peaks of which were considered as representing bacterial carbohydrates and fatty acids, could be distinguished by visual examination and by cluster analysis. The chromatographic results could not be correlated with those obtained from serotyping of the strains studied. Mycobacteria recovered from different organs of one and the same pig gave virtually identical chromatograms. The strains isolated from three human beings had a chromatographic pattern which was identical with one of those produced by the porcine strains. The present investigation indicates that the gas chromatographic analytic technique used differentiates bacteria within the M. avium-intracellulare complex, without assigning the organisms to species.

Animals↗
PubMed1979

[Mycobacteria in arthropodes of different biotopes (author's transl)].

Many arthropodes are found in close contact with soil and other material contaminated by mycobacteria. In order to clear up their importance as potential carriers of germs of the MAIS complex (Mycobacterium avium, intracellulare, scrofulaceum), we investigated 835 samples of arthropodes taken from different biotopes. Following a treatment according to the cultural method developed by us (Beerwerth, 1967), we isolated 606 strains of mycobacteria from 302 (36.0%) out of 835 samples. Incubation at room temperature was more effective than incubation at 37 degrees C. 96 (15.8%) in 606 strains did not grow at 37 degrees C. In arthropodes taken from pasture-ground we mainly found mycobacteria of group II according to Runyon, while in arthropodes from arable land, stables and saw mills mycobacteria of group III predominated. Samples of arthropodes taken from forests, moorland and waters showed a comparatively similar spectrum of species. Strains of the MAIS complex - M. avium, intracellulare, scrofulaceum - were frequent in areas of saw mills (80 = 20.5% in 356 strains), but rarely found amongst the remaining biotopes (11 = 4.4% in 250 species). Mycobacteria were chiefly isolated from larvae and imagines living in permanent contact with soil and less from winged shapes. The epidemiological importance of arthropodes spreading pathogenic mycobacteria should not be overvalued.

Animals↗
PubMed2026

Effectiveness of mass spectrometry and genomic analysis in the surveillance of nontuberculous Mycobacterium in Taiwan.

Nontuberculous mycobacteria (NTM) are diverse, and species-level identification remains challenging in routine diagnostics. We analyzed NTM isolates collected at three regional centers of the National Taiwan University Hospital (NTUH) from 2019 to 2024 to assess geographic variation and identification performance after implementation of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Among 3,188 cases meeting the microbiological criteria for probable pulmonary NTM disease, the species distribution differed by region: Mycobacterium avium complex predominated in central Taiwan (Yunlin, 47.3%), whereas M. abscessus complex (Taipei, 26.5%) and M. kansasii (Hsinchu, 12.4%) were more common in northern Taiwan. In 2019, 14.5% of isolates were reported to be unidentified by MALDI-TOF MS; with workflow optimization and database updates, this percentage decreased but plateaued at 4.5-4.8%. Whole-genome sequencing (WGS) of 61 randomly selected persistently unidentified isolates revealed eight average nucleotide identity (ANI)-defined clusters; 55 isolates (90.2%) could not be assigned to known species using current reference databases. Two clusters detected only in Hsinchu were phylogenetically closest to M. kyorinense, with ANI values below the species demarcation threshold. Overall, we observed marked regional heterogeneity of NTM in Taiwan and a persistent identification gap that remained after MALDI-TOF MS optimization and follow-up WGS.IMPORTANCEThis study characterized regional differences in the NTM species distribution across Taiwan, and the results highlight the limitations of current identification approaches. MALDI-TOF MS identifies most isolates, but locally circulating lineages represent a persistent gap in global reference libraries. Even with whole-genome sequencing (WGS), 90.2% (55/61) of persistently unresolved isolates could not be assigned to known species in the current reference databases despite the formation of clear ANI- and phylogeny-defined clusters. These findings show that both proteomic and genomic reference resources for clinical NTM remain incomplete. Expanding regionally representative databases and performing WGS for isolates that remain unresolved by MALDI-TOF MS will be necessary to improve species-level resolution for surveillance and clinical interpretation.

Taiwan↗
PubMed1979

Pulmonary mycobacterial infections due to Mycobacterium intracellulare-avium complex. Clinical features and course in 100 consecutive cases.

One hundred consecutive cases of pulmonary infection due to Mycobacterium intracellulare-avium seen during a 3 1/2-year period qualified for review on the basis of a compatible chest x-ray film, repeated isolations from cultures of sputum, and follow-up of three to eight years. Infections with M intracellulare-avium represented 27 percent of all mycobacterial infections seen during this period, including those due to M tuberculosis. The cases of disease due to M intracellulare-avium were predominantly in men with preexisting pulmonary disease, with a peak incidence in the sixth decade, but nearly one-third of the cases were in younger persons free of coexisting disease. The disease was chronic and indolent in most cases, and only a few showed a progressive course. A stable course was frequently observed despite prolonged persistently positive cultures of sputum. A favorable prognosis was most often found in those with previously treated tuberculosis. Poor prognosis was often due to a serious associated disease, such as cancer, rather than to advancing mycobacterial infection itself. Age, sex, or race was unrelated to prognosis. Conversion to negative status on culture was attained in one-half of the cases. Those with extensive radiographic involvement or cavitation were more likely to have treatment fail bacteriologically. No combination of chemotherapy appeared to be particularly effective, including the use of five or more drugs in eight cases demonstrating progressive disease. Surgery, too, was ultimately disappointing in that recurrence appeared in six of 18 carefully selected cases.

Adult↗
PubMed2025

Novel mutations associated with clofazimine resistance in Mycobacterium intracellulare.

BACKGROUND: Clofazimine is a promising repurposed drug for treating Mycobacterium avium-intracellulare complex pulmonary disease, but its resistance mechanisms in Mycobacterium intracellulare remain poorly understood. OBJECTIVE: This study aims to elucidate the resistance mechanisms of M. intracellulare to clofazimine. METHODS: We isolated 36 clofazimine-resistant M. intracellulare mutants in vitro and performed whole-genome sequencing to identify resistance-associated mutations. Gene complementation was used to validate the role of the identified mutations. RESULTS: We identified various mutations in the marR gene (WP_009952290.1) in 61% of clofazimine-resistant mutants by whole-genome sequencing. Mutations were identified in additional genes encoding ssuD (flavin-dependent oxidoreductase, C67A), lppI (membrane lipoprotein, C207 deletion), GMC oxidoreductase (glucose-methanol-choline oxidoreductase, G157 deletion), MASE1 domain-containing protein (C62G) and PPE family protein (222C deletion). Gene complementation experiments demonstrated that introducing the wild-type marR in clofazimine-resistant strain (L72) with marR mutations reduced clofazimine MIC from 1 mg/L to susceptible baseline (0.25 mg/L), confirming its critical role in clofazimine resistance. Notably, the M. intracellulare MarR lacks homology to Mycobacterium tuberculosis MarR family protein Rv0678 (MmpR) involved in clofazimine and bedaquiline resistance but is flanked by non-efflux pump genes (dhmA and doxX), and unlike M. tuberculosis, its mutation does not cause bedaquiline cross-resistance, indicating a different MarR and distinct regulatory mechanism for clofazimine resistance in M. intracellulare. CONCLUSIONS: This work highlights marR as a key determinant of clofazimine resistance in M. intracellulare and underscores the need for further mechanistic studies with implications for rapid molecular detection and effective treatment.

Clofazimine↗
PubMedDate not supplied

[Relationships between "Mycobacterium simiae" and the "M. avium-intracellulare-scrofulaceum" complex (author's transl)].

The 24 strains of Mycobacterium simiae described in this report were isolated from 12 black Africans, 6 from white Europeans, 5 from primates and 1 from a leprosy infected Armadillo. These strains form 3 groups having the similar morphologic and cultural properties as M. intracellulare. Two groups were similar with respect to pigmentation, urease activity and niacin production but differed serologically, the second group being of M. intracellulare serotype 18. The third group was less homogenous and was intermediate to M. simiae and M. intracellulare. Thus M. simiae belong to the M. avium-intracellulare-simiae-scrofulaceum (MAISS) complex. Two cases of well characterized pulmonary disease progressed like M. avium mycobacteriosis.

Animals↗
PubMed1979

Influence of pork consumption on human infection with Mycobacterium avian-intracellulare.

The hypothesis that eating pork from animals infected with organisms of the Mycobacterium avium-intracellular complex is a significant cause of human mycobacteriosis was examined by skin testing students with purified protein derivative from M. intracellulare to determine their sensitivity to M. avium-intracellulare. No significant differences in sensitivity could be demonstrated between those individuals who had never eaten pork and those who ate pork routinely. It was concluded that sensitivity to purified protein derivative from M. intracellulare in this population did not involve eating pork.

Animals↗
PubMed1979

Laboratory diagnosis of bovine tuberculosis.

Lesions of suspected bovine tuberculosis were examined by culture, histopathology and auramine-O (AO) stained smears and the findings correlated with field aspects of the disease. Of 642 lesions considered to be tuberculous, 62.0% yielded M. bovis and 4.5% other mycobacteria (OM). M. bovis and OM were recovered also from 0.6% and 3.6% respectively of 165 cattle which gave tuberculin reactions but had no visible lesions at slaughter. Of 262 lesions in which a histopathological diagnosis other than tuberculosis was made, 1.5% and 3.0% yielded M. bovis and OM respectively. All OM isolates tested belonged to the Mycobacterium-avium-intracellulare-scrofulaceum (MAIS) complex with a predominance of serotype 2. A good relationship was found between the recovery of mycobacteria and histopathology but examination of smears revealed 22.0% apparent false negatives. Apparent false negative culture results were also reported for 35.8% of lesions positive on histopathology and smear examination. The majority of herds yielding M. bovis contained reactors to the tuberculin test and many of these had lesions of tuberculosis. In contrast, herds yielding OM seldom contained reactors to the tuberculin test and rarely reactors with tuberculous lesions. The thoracic cavity was the main site of lesions from infections by M. bovis and OM.

Animals↗
PubMed1979

Reliable urease test for identification of mycobacteria.

A simple, modified formation for urea broth gave consistent, reliable results to aid in the differentiation of Mycobacterium species. In a study of 1,346 isolates representing 17 different species, tests read after 7 days were distinct and reproducible. The use of this test facilitates the identification of Mycobacterium species, such as M. scrofulaceum, the M. avium complex, the M. terrae complex, and M. triviale.

Bacteriological Techniques↗
PubMed1979

Identification of clinical isolates of mycobacteria with gas-liquid chromatography alone.

Identification of 18 mycobacterial species was performed by analysis of profiles obtained by using gas-liquid chromatography. Organisms were saponified in methanolic NaOH, and the reaction mixture was treated with BF(3) in methanol and extracted with a hexane-chloroform mixture. An identification scheme was developed from 128 stock strains and tested against a collection of 79 clinical isolates. By using gas-liquid chromatographic profiles alone, 58% of specimens were correctly identified to species level, and an additional 41% were correctly identified to a group of two or three organisms. Use in a clinical laboratory over a 2-month period proved chromatography to be as accurate as and more rapid than concurrent biochemical testing. Of 81 isolates tested, 64% were identified to species level by chromatography alone. An additional 35% were differentiated to the same groups of two or three organisms as found in our analysis of stock strains. These groups consisted of: Mycobacterium tuberculosis, M. bovis, and M. xenopi; M. avium complex, M. gastri, and M. scrofulaceum; or M. fortuitum and M. chelonei. Identification to species level from these groups could usually be done by colonial morphology alone and could always be done by the addition of one selected biochemical test. This study demonstrated the practical application of gas-liquid chromatography in the identification of mycobacteria in a clinical laboratory. In particular, all strains of M. gordonae and M. kansasii were identified to species level. M. tuberculosis was definitively identified in 85% of cases. When it could not be definitely identified, the only alternatives were M. bovis and M. xenopi, both of which are rare causes of infection.

Chromatography, Gas↗