Search Results (26)

Nontuberculous mycobacteria are opportunistic pathogens increasingly associated with human disease. Within this group, the Mycobacterium avium complex (MAC), which includes M. avium, M. intracellulare and M. intracellulare subsp. chimaera, is the most frequent cause of infection. The increase in MAC cases worldwide has made it crucial to understand their population structure, clinical relevance and resistance mechanisms. Recent advances in whole-genome sequencing (WGS) and molecular approaches have improved the knowledge of taxonomy, population structure and genetic diversity, while also enabling the investigation of transmission and epidemiology. Clinically, MAC most often causes chronic pulmonary disease, but extrapulmonary forms, including disseminated disease, also occur. Presentation can vary by infecting species, while host factors such as pre-existing lung disease or immunosuppression further increase the risk. Treatment outcomes remain less favourable than desired, in part due to antimicrobial resistance involving de novo-acquired mutations. Pathogenesis is also influenced by interactions between MAC and host cells, including mechanisms of immune evasion and inflammatory modulation. In addition, emerging evidence suggests that gut–lung axis dysbiosis may influence susceptibility to MAC infection. This review outlines current knowledge on the population structure, clinical significance, resistance and host–pathogen interactions of MAC. Full article

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. Full article

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. Full article

Background/Objectives: In this study, the efficacy of benzo[h]chromene derivatives as antiprotozoal and antimycobacterial agents was explored. Methods: A total of twenty compounds, including benzo[h]chromene alkyl diesters and benzo[h]chromene-triazole derivatives, were synthesized and tested against Trypanosoma cruzi, Leishmania braziliensis, L. infantum, and strains of Mycobacterium abscessus and Mycobacterium intracellulare LIID-01. Notably, compounds 1a, 1b, 2a, and 3f exhibited superior activity against Trypanosoma cruzi, with IC₅₀ values of 19.2, 37.3, 68.7, and 24.7 µM, respectively, outperforming the reference drug benznidazole (IC₅₀: 54.7 µM). Results: Compounds 1b and 3f showed excellent selectivity indices against Leishmania braziliensis, with SI values of 19 and 18, respectively, suggesting they could be potential alternatives to the commonly used, but more selective, miltefosine (IC₅₀: 64.0 µM, SI: 43.0). Additionally, compounds 1a, 1b, and 3f were most effective against Leishmania infantum, with IC₅₀ values of 24.9, 30.5, and 46.6 µM, respectively. Compounds 3f and 3h were particularly potent against various Mycobacterium abscessus strains, highlighting their significance given the inherent resistance of these bacteria to standard antimicrobials. Conclusions: The sensitivity of Mycobacterium intracellulare LIID-01 to these compounds also underscored their potential in managing infections by the Mycobacterium avium–intracellulare complex. Full article

Background: The Mycobacterium avium complex includes the commonest non-tuberculous mycobacteria associated with human infections. These infections have been associated with the production of biofilms in many cases, but there are only a few studies about biofilms produced by the species included in this group. Methods: Three collection strains (M. avium ATCC25291, M. intracellulare ATCC13950, and M. chimaera DSM756), three clinically significant strains (647, 657, and 655), and three clinically non-significant ones (717, 505, and 575) of each species were included. The clinical significance of the clinical isolates was established according to the internationally accepted criteria. The biofilm ultrastructure was studied by Confocal-Laser Scanning Microscopy by using BacLight Live–Dead and Nile Red stains. The viability, covered surface, height, and relative autofluorescence were measured in several images/strain. The effect of clarithromycin was studied by using the technique described by Muñoz-Egea et al. with modifications regarding incubation time. The study included clarithromycin in the culture medium at a concentration achievable in the lungs (11.3 mg/L), using one row of wells as the control without antibiotics. The bacterial viability inside the biofilm is expressed as a percentage of viable cells. The differences between the different parameters of the biofilm ultrastructure were analyzed by using the Kruskal–Wallis test. The correlation between bacterial viability in the biofilm and treatment time was evaluated by using Spearman’s rank correlation coefficient (ρ). Results: The strains showed differences between them with all the studied parameters, but neither a species-specific pattern nor a clinical-significance-specific pattern were detected. For the effect of clarithromycin, the viability of the bacteria contained in the biofilm was inversely proportional to the exposure time of the biofilm (ρ > −0.3; p-value < 0.05), excluding two M. chimaera strains (M. chimaera DSM756 and 575), which showed a weak positive correlation with treatment time (0.2 < ρ < 0.39; p-value < 0.05). Curiously, despite a clarithromycin treatment of 216 h, the percentage of the biofilm viability of the strains evaluated here was not less than 40% at best (M. avium 717). Conclusions: All the M. avium complex strains studied can form biofilm in vitro, but the ultrastructural characteristics between them suggest that these are strain-specific characteristics unrelated to the species or the clinical significance. The clarithromycin effect on MAC species is biofilm-age/time-of-treatment-dependent and appears to be strain-specific while being independent of the clinical significance of the strain. Full article

Glutathione (GSH) is an important intracellular antioxidant responsible for neutralizing reactive oxygen species (ROS). Our laboratory previously demonstrated that the oral administration of liposomal GSH improves immune function against mycobacterium infections in healthy patients along with patients with HIV and Type 2 diabetes. We aim to determine if the topical application of a glutathione–cyclodextrin nanoparticle complex (GSH-CD) confers a therapeutic effect against mycobacterium infections. In our study, healthy participants received either topical GSH-CD (n = 15) or placebo (n = 15) treatment. Subjects were sprayed four times twice a day for three days topically on the abdomen. Blood draws were collected prior to application, and at 1, 4, and 72 h post-initial topical application. GSH, malondialdehyde (MDA), and cytokine levels were assessed in the processed blood samples of study participants. Additionally, whole blood cultures from study participants were challenged with Mycobacterium avium (M. avium) infection in vitro to assess mycobacterium survival post-treatment. Topical GSH-CD treatment was observed to elevate GSH levels in peripheral blood mononuclear cells (PBMCs) and red blood cells and decrease MDA levels in PBMCs 72 h post-treatment. An increase in plasma IL-2, IFN-γ, IL-12p70, and TNF-α was observed at 72 h post-topical GSH-CD treatment. Enhanced mycobacterium clearance was observed at 4 h and 72 h post-topical GSH-CD treatment. Overall, topical GSH-CD treatment was associated with improved immune function against M. avium infection. The findings of this pilot study suggest GSH–cyclodextrin complex formulation can be used topically as a safe alternative mode of GSH delivery in the peripheral blood. Full article

Background: It has been suggested that Mycobacterium avium, Mycobacterium intracellulare, and M. chimaera have differential drug susceptibility patterns. We prospectively analyzed and compared the drug susceptibility patterns among these species over an 8.5-year period. Methods: A microdilution method (Slomyco^®) was performed for drug susceptibility testing of 402 M. avium, 273 M. intracellulare, and 139 M. chimaera clinical isolates. Results: M. avium showed significantly higher resistance to moxifloxacin, ciprofloxacin, rifampicin, ethambutol, streptomycin, linezolid, cotrimoxazole, and clarithromycin. M. avium also showed higher minimum inhibitory concentrations (MIC) than M. intracellulare and M. chimaera against all drugs except ethionamide, to which M. intracellulare and M. chimaera showed greater resistance. Conclusions: Our series demonstrated differential drug resistance patterns among the most frequent M. avium complex species. M. avium was more resistant than M. intracellulare and M. chimaera versus eight antibiotics and showed greater MIC values to most of the antibiotics studied. These data suggest that knowledge of the local distribution and susceptibility profiles of these pathogens is essential for adequate clinical management. Full article

Non-tuberculous mycobacteria are widely distributed in environments and are capable of infecting humans, particularly those with a compromised immune system. The most prevalent species that cause nontuberculous mycobacterial lung diseases are slow-growing bacteria from the Mycobacterium avium complex (MAC), mainly M. avium or M. intracellulare. The key treatment of MAC infections includes macrolides, ethambutol, and rifampicin; however, the therapy outcomes are unsatisfactory. Phenotypic drug susceptibility testing is a conditional recommendation prior to treatment, and critical concentrations for clarithromycin, amikacin, moxifloxacin, and linezolid have been established. In this review, data from studies on the determination of MIC of clinical isolates using the broth microdilution method were summarized. A significant variation in the MIC distributions from different studies was found. The main reasons could impact the findings: insufficient reproducibility of the phenotypic testing and variation in species lineages identified in different laboratories, which could have various intrinsic susceptibility to drugs. For most of the drugs analyzed, the MICs are too high, which could undermine the treatment efficiency. Further improvement of treatment outcomes demands the validation of microbiological resistance criteria together with the identification of molecular mechanisms of resistance. Full article

Nontuberculous mycobacterial (NTM) infections present a treatment challenge for clinicians and patients. There are limited data about current susceptibility patterns and treatment outcomes in U.S. adults. This was a 10-year, single-center, retrospective, observational cohort study of adults with a positive NTM culture and clinical suspicion of infection between 1 January 2010 and 30 June 2020. The primary objective was to identify predictors for favorable treatment outcomes. Key secondary objectives were characterization of NTM epidemiology, susceptibility profiles, and safety and tolerability of treatment, including the proportion of subjects with an antimicrobial change and the reasons for the change. Of 250 subjects diagnosed with NTM infection, the most prevalent NTM isolates were Mycobacterium avium intracellulare complex (66.8%) followed by Mycobacterium abscessus (17.6%). Antimicrobial susceptibility data were available for 52.4% of the cohort (45.8% slow growers; 54.2% rapid growers). Only 88 (35%) subjects received treatment with evaluable clinical outcomes. The proportion of subjects with a favorable outcome was 61.4%. More subjects in the unfavorable outcome group experienced a change in antimicrobial therapy (73.5% vs. 51.9%, p = 0.043). The most common reason for antimicrobial change was adverse drug events (n = 36, 67.9%). In the regression model, private insurance was associated with a favorable outcome, whereas having multiple antimicrobial changes was associated with an unfavorable outcome. The complexity of NTM treatment and high incidence of medication-related issues suggest the necessity of interdisciplinary collaboration to improve overall treatment outcomes in NTM infections. Full article

Mycobacterial infections are a group of life-threatening conditions triggered by fast- or slow-growing mycobacteria. Some mycobacteria, such as Mycobacterium tuberculosis, promote the deaths of millions of lives throughout the world annually. The control of mycobacterial infections is influenced by the challenges faced in the diagnosis of these bacteria and the capability of these pathogens to develop resistance against common antibiotics. Detection of mycobacterial infections is always demanding due to the intracellular nature of these pathogens that, along with the lipid-enriched structure of the cell wall, complicates the access to the internal contents of mycobacterial cells. Moreover, recent studies depicted that more than 20% of M. tuberculosis (Mtb) infections are multi-drug resistant (MDR), and only 50% of positive MDR-Mtb cases are responsive to standard treatments. Similarly, the susceptibility of nontuberculosis mycobacteria (NTM) to first-line tuberculosis antibiotics has also declined in recent years. Exploiting mycobacteriophages as viruses that infect mycobacteria has significantly accelerated the diagnosis and treatment of mycobacterial infections. This is because mycobacteriophages, regardless of their cycle type (temperate/lytic), can tackle barriers in the mycobacterial cell wall and make the infected bacteria replicate phage DNA along with their DNA. Although the infectivity of the majority of discovered mycobacteriophages has been evaluated in non-pathogenic M. smegmatis, more research is still ongoing to find mycobacteriophages specific to pathogenic mycobacteria, such as phage DS6A, which has been shown to be able to infect members of the M. tuberculosis complex. Accordingly, this review aimed to introduce some potential mycobacteriophages in the research, specifically those that are infective to the three troublesome mycobacteria, M. tuberculosis, M. avium subsp. paratuberculosis (MAP), and M. abscessus, highlighting their theranostic applications in medicine. Full article

Mycobacterium chimaera (MC) is an environmental, slowly growing, non-tuberculous mycobacterium (NTM) belonging to Mycobacterium avium complex (MAC), which recently has been linked to severe cardiovascular infections following open heart and vascular surgery. The majority of the diagnostic laboratory tests used in routine are not able to distinguish MC from M. intracellulare (MI), because of the great genetic similarity existing between these two species. The Genotype Mycobacterium NTM-DR™ represents a valid method to differentiate between these species, but it is expensive, requiring also specialized personnel. Recently, MALDI-TOF MS has been proposed to identify relevant NTM. However, a software implementation is required to distinguish between MC and MI, presenting the two microorganisms’ overlapping spectra. The present study evaluates the feasibility of applying a MALDI-TOF logarithmic-based analysis in the routine of a clinical microbiology laboratory, and proposes an easy-to-use template spreadsheet to make the results quickly interpretable. The protocol was previously validated through the identification of 87 strains of MC/MI collected from clinical and environmental samples, and it was identified using the GenoType Mycobacterium NTM-DR™ and/or WGS. The proposed protocol provides accurate identification for the isolates tested; moreover, it is less expensive and more rapid than sequencing methods and can be implemented with minimum effort. Full article

Nontuberculous mycobacteria (NTM) cause lung infections in patients with underlying pulmonary diseases (PD). The Mycobacteriumavium-intracellulare complex (MAC) is the most frequently involved NTM. The MAC-PD treatment is based on the administration of several antibiotics for long periods of time. Nonetheless, treatment outcomes remain very poor. Among the factors involved is the ability of MAC isolates to form biofilm. The aim of the study was to assess the in vitro activity of different antibiotics and potential antibiofilm agents (PAAs) against MAC biofilm. Four antibiotics and six PAAs, alone and/or in combination, were tested against planktonic forms of 11 MAC clinical isolates. Biofilm was produced after 4 weeks of incubation and analyzed with the crystal violet assay. The antibiotics and PAAs were tested by measuring the absorbance (minimum biofilm inhibition concentrations, MBICs) and by performing subcultures (minimum biofilm eradication concentrations, MBECs). The clarithromycin/amikacin and clarithromycin/ethambutol combinations were synergistic, decreasing the MBECs values compared to the individual antibiotics. The amikacin/moxifloxacin combination showed indifference. The MBIC values decreased significantly when PAAs were added to the antibiotic combinations. These results suggest that antibiotic combinations should be further studied to establish their antibiofilm activity. Moreover, PAAs could act against the biofilm matrix, facilitating the activity of antibiotics. Full article

Mycobacteriosis is mainly caused by two groups of species: Mycobacterium tuberculosis and non-tuberculosis mycobacteria (NTM). The pathogens cause not only respiratory infections, but also general diseases. The common problem in these pathogens as of today is drug resistance. Tuberculosis (TB) is a major public health concern. A major challenge in the treatment of TB is anti-mycobacterial drug resistance (AMR), including multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis. Recently, the success rate of the treatment of drug-resistant tuberculosis (DR-TB) has improved significantly with the introduction of new and repurposed drugs, especially in industrialized countries such as Japan. However, long-term treatment and the adverse events associated with the treatment of DR-TB are still problematic. To solve these problems, optimal treatment regimens designed/tailor-made for each patient are necessary, regardless of the location in the world. In contrast to TB, NTM infections are environmentally oriented. Mycobacterium avium-intracellulare complex (MAC) and Mycobacterium abscessus species (MABS) are the major causes of NTM infections in Japan. These bacteria are naturally resistant to a wide variation of antimicrobial agents. Macrolides, represented by clarithromycin (CLR) and amikacin (AMK), show relatively good correlation with treatment success. However, the efficacies of potential drugs for the treatment of macrolide-resistant MAC and MABS are currently under evaluation. Thus, it is particularly difficult to construct an effective treatment regimen for macrolide-resistant MAC and MABS. AMR in NTM infections are rather serious in Japan, even when compared with challenges associated with DR-TB. Given the AMR problems in TB and NTM, the appropriate use of drugs based on accurate drug susceptibility testing and the development of new compounds/regimens that are strongly bactericidal in a short-time course will be highly expected. Full article

A total of 152 aerosol and spider web samples were collected: 96 spider’s webs in karst areas in 4 European countries (Czech Republic, France, Italy, and Slovakia), specifically from the surface environment (n = 44), photic zones of caves (n = 26), and inside (aphotic zones) of caves (n = 26), 56 Particulate Matter (PM) samples from the Sloupsko-Sosuvsky Cave System (speleotherapy facility; n = 21) and from aerosol collected from the nearby city of Brno (n = 35) in the Czech Republic. Nontuberculous mycobacteria (NTM) were isolated from 13 (13.5%) spider’s webs: 5 isolates of saprophytic NTM (Mycobacterium gordonae, M. kumamotonense, M. terrae, and M. terrae complex) and 6 isolates of potentially pathogenic NTM (M. avium ssp. hominissuis, M. fortuitum, M. intracellulare, M. peregrinum and M. triplex). NTM were not isolated from PM collected from cave with the speleotherapy facility although mycobacterial DNA was detected in 8 (14.3%) samples. Temperature (8.2 °C, range 8.0–8.4 °C) and relative humidity (94.7%, range 93.6–96.6%) of air in this cave were relatively constant. The average PM_2.5 and PM₁₀ mass concentration was 5.49 µg m⁻³ and 11.1 µg m⁻³. Analysed anions (i.e., F⁻, Cl⁻, NO₂⁻, SO₄²⁻, PO₄³⁻ and NO₃⁻) originating largely from the burning of wood and coal for residential heating in nearby villages in the surrounding area. The air in the caves with speleotherapy facilities should be monitored with respect to NTM, PM and anions to ensure a safe environment. Full article

Non-tuberculous mycobacteria (NTM) have been recognized as a causative agent of various human diseases, including severe infections in immunocompromised patients, such as people living with HIV. The most common species identified is the Mycobacterium avium-intracellulare complex (MAI/MAC), accounting for a majority of infections. Despite abundant information detailing the clinical significance of NTM, little is known about host–pathogen interactions in NTM infection. MicroRNAs (miRs) serve as important post-transcriptional regulators of gene expression. Using a microarray profile, we found that the expression of miR-155 and cyclo-oxygenase 2 (COX-2) is significantly increased in bone-marrow-derived macrophages from mice and human monocyte-derived macrophages from healthy volunteers that are infected with NTM. Antagomir against miR-155 effectively suppressed expression of COX-2 and reduced Prostaglandin E₂(PGE2) secretion, suggesting that COX-2/PGE2 expression is dependent on miR-155. Mechanistically, we found that inhibition of NF-κB activity significantly reduced miR-155/COX-2 expression in infected macrophages. Most importantly, blockade of COX-2, E-prostanoid receptors (EP2 and EP4) enhanced killing of MAI in macrophages. These findings provide novel mechanistic insights into the role of miR-155/COX-2/PGE2 signalling and suggest that induction of these pathways enhances survival of mycobacteria in macrophages. Defining host–pathogen interactions can lead to novel immunomodulatory therapies for NTM infections which are difficult to treat. Full article