Nontuberculous Mycobacteria Infection Research Articles

Challenges in Diagnosis and Management of Non- Tuberculous Mycobacterial infection: Report of three cases

Non-tuberculous mycobacteria (NTM) can cause a wide range of infections, from affecting the lungs (pulmonary) to the other parts of the body (extrapulmonary) like skin, soft tissue, surgical wounds, and areas around catheters and implants. A significant challenge is that NTM infections are often misdiagnosed as tuberculosis. This case series highlights these difficulties by exploring three patient experiences. The first case involves a 48-year-old man who developed a prolonged fever following coronary artery bypass grafting (CABG) surgery. He also presented with enlarged liver and spleen (hepatosplenomegaly). Imaging studies revealed a large saccular aortic ascending aneurysm. While surgery (ascending aortic and proximal arch replacement) addressed the aneurysm, the definitive diagnosis came later. Histopathological and microbiological examinations ultimately revealed the culprit to be NTM. In second case, a 56-year-old male underwent a laparoscopic bilateral total extraperitoneal inguinal hernia repair. However, he experienced persistent serous drainage from the incision site post-surgery. To investigate the cause, discharge was collected and subjected to various tests. Therefore, a PCR test for Non-tuberculous Mycobacteria (NTM) was performed. This test returned positive, confirming the diagnosis of NTM infection rather than tuberculosis. And our third case was post operative endophthalmitis following cataract surgery due to NMT. Through these case reports, our Aim is to raise awareness among healthcare professionals. Bangladesh J Medicine 2025; 36: 66-70

Host Long Noncoding RNAs as Key Players in Mycobacteria-Host Interactions.

Mycobacterial infections, caused by various species within the Mycobacterium genus, remain one of the main challenges to global health across the world. Understanding the complex interplay between the host and mycobacterial pathogens is essential for developing effective diagnostic and therapeutic strategies. Host long noncoding RNAs (lncRNAs) have emerged as key regulators in cellular response to bacterial infections within host cells. This review provides an overview of the intricate relationship between mycobacterial infections and host lncRNAs in the context of Mycobacterium tuberculosis and non-tuberculous mycobacterium (NTM) infections. Accumulation of evidence indicates that host lncRNAs play a critical role in regulating cellular response to mycobacterial infection within host cells, such as macrophages, the primary host cells for mycobacterial intracellular survival. The expression of specific host lncRNAs has been implicated in the pathogenesis of mycobacterial infections, providing potential targets for the development of novel host-directed therapies and biomarkers for TB diagnosis. In summary, this review aims to highlight the current state of knowledge regarding the involvement of host lncRNAs in mycobacterial infections. It also emphasizes their potential application as novel diagnostic biomarkers and therapeutic targets.

Inhibitors of acetohydroxyacid synthase as promising agents against non-tuberculous mycobacterial diseases.

Acetohydroxyacid synthase (AHAS), exclusively present in microorganisms and plants, is a promising target for several herbicides due to its catalytic role in the branched-chain amino acid biosynthetic pathway. Previous studies have shown that K13787, a pyrazolopyrimidine sulfonamide AHAS inhibitor, was moderately effective against pulmonary infection caused by M. tuberculosis and nontuberculous mycobacteria (NTM). In this study, we synthesized various structural derivatives of K13787 based on the molecular docking studies and assessed their MICs against mycobacteria species. Among the synthetic compounds screened, K13787, along with KNT2077 and KNT2099, exhibited inhibitory efficacy against M. avium and M. abscessus, including CLR-resistant NTM species. Notably, these compounds displayed a synergistic effect (FIC ≤ 0.5) when combined with CLR against M. avium and M. abscessus. Our findings suggest that these newly identified AHAS-targeted compounds hold promise as lead candidates for novel antimycobacterial agents against NTM infections. Considering the structure-activity relationship, K13787, KNT2077, and KTN2099 emerge as potential treatments for NTM species.

Promoting the Efficacy of Deferiprone-Gallium-Protoporphyrin (IX) against Mycobacterium abscessus Intracellular Infection with Lipid Liquid Crystalline Nanoparticles.

Nontuberculous mycobacteria (NTM) are among the recalcitrant bacterial strains that cause difficult-to-treat infections for patients with chronic underlying pulmonary conditions. The bacteria's intrinsic resistance to various antibiotics and their ability to infect macrophages enable them to overcome both the host immune response and standard antibiotics. Unconventional approaches to treating NTM-mediated infections are required. Using the heme mimic agent gallium protoporphyrin (GaPP) and the iron chelator deferiprone (DEF) in combination has been proven as an effective strategy against different bacteria including NTM in vitro. To enable more effective delivery and promote the activity of DEF/GaPP against intracellular NTM infections, both compounds are loaded in lipid liquid crystalline nanoparticles (LCNP). GaPP and DEF are sufficiently entrapped in LCNP with entrapment efficiency of 98% ± 2.1 and 39.4% ± 4.2, respectively. DEF/GaPP LCNP has an average diameter of 171 nm ± 10.2 with a uniform size distribution. DEF/GaPP LCNP reduces the viability of Mycobacterium abscessus intracellular infection by 3.34 log10 in comparison to the control group and is significantly more efficacious than nonformulated DEF/GaPP. Furthermore, DEF/GaPP LCNP is nontoxic to human bronchial epithelial cells in vitro. These findings are envisaged to pave the way for future progress in eradicating NTM-mediated infections.

Use of epigenetically modified bacteriophage and dual beta-lactams to treat a Mycobacterium abscessus sternal wound infection

Nontuberculous mycobacterium (NTM) infections are challenging to manage and are frequently non-responsive to aggressive but poorly-tolerated antibiotic therapies. Immunosuppressed lung transplant patients are susceptible to NTM infections and poor patient outcomes are common. Bacteriophages present an alternative treatment option and are associated with favorable clinical outcomes. Similarly, dual beta-lactam combinations show promise in vitro, but clinical use is sparse. We report here a patient with an uncontrolled Mycobacterium abscessus infection following a bilateral lung transplant and failed antibiotic therapy. Both smooth and rough colony morphotype strains were initially present, but treatment with two phages that kill the rough strain – including epigenetic-modification to overcome restriction – resulted in isolation of only the smooth strain. The rough and smooth strains have similar antibiotic susceptibilities suggesting that the phages specifically eliminated the rough strain. Dual beta-lactam therapy with meropenem and ceftazidime-avibactam provided further clinical improvement, and the phages act synergistically with meropenem in vitro.

Systematic literature review of the diagnosis, prognosis, and treatment of peritoneal dialysis-related infection caused by nontuberculous mycobacteria

The number of peritoneal dialysis (PD) catheter-related infections and peritonitis caused by nontuberculous mycobacteria (NTM) has been increasing. Nonetheless, the optimal timing for the relocation of the exit site, removal and reinsertion of the PD catheter, prognosis, and duration of antibiotic treatment remain unclear. This literature review aimed to investigate the epidemiology of patient characteristics and evaluate the most effective diagnostic and treatment strategies for PD catheter-related infections and peritonitis caused by NTM. The systematic literature review was conducted on published cases of PD catheter-related infection and peritonitis caused by NTM in PubMed, Embase, and Ichushi databases up to August 2022. A total of 335 cases (64.1%, male; mean age, 53.4 years; mean dialysis duration, 25.4 months) were analyzed. The most common causative agent of infection was Mycobacterium abscessus (40.1%), followed by Mycobacterium fortuitum (24.8%) and Mycobacterium chelonae (16.6%). With respect to diagnosis, 42.9%, 28.1%, and 29.0% of cases were diagnosed as PD catheter-related infection only, peritonitis only, and both, respectively. The initial cultures were positive for NTM only, positive for any other bacteria, and negative for NTM only in 56.5%, 19.8%, and 23.7% of cases, respectively. Ultimately, more than 80% of cases were treated with multiple antibiotics. PD catheter removal was performed in 55.4% of patients with PD catheter-related infections only and 85.5% of those with PD peritonitis. PD continuation or resumption was possible in 62.2% and 16.0% of patients, respectively. In conclusion, our findings indicate that it is advisable to perform acid-fast bacilli stain and culture in order to promptly identify NTM. PD catheter removal may be an essential management strategy during the early stages of NTM infection.

Skin and Soft Tissue Nontuberculous Mycobacteria Infection: A Retrospective Case Series of 49 Patients.

The incidence of skin and soft tissue nontuberculous mycobacteria infection (SSTNI) is increasing. But it may be challenging to diagnose and treat SSTNI. To summarize course, clinical features, diagnosis and treatment of SSTNI and discuss the association between SSTNI and procedures. A retrospective case series study was conducted among patients diagnosed with SSTNI after surgical procedures. Medical history was collected, disease course and characteristics were analyzed. 49 patients were collected. Among them, 39 (80%) patients were infected with Mycobacterium abscesses. 40 (82%) patients had a history of fat-related procedures. The median and interquartile range of onset time were 15 and 43 days (1-100). Time from first visit to diagnosis was 82±57 days (23-308). Wound healing time was 161±92 days (30-545). The most common symptom were redness (96%), followed by swelling (96%), abscess (84%), pain (80%) and induration (76%). The most common infected site were head and neck (56%), followed by breasts (20%). 6 (12.5%) patients were diagnosed clearly before admission to our department. 10 (28%) patients showed positive acid-fast bacilli (AFB) smears among 36 patients. Treatment included debridement surgeries, drainage and antibiotics. Patient with the above symptoms should be considered as SSTNI. Results of AFB smears are frequently negative after empirical antibiotic treatment so that molecular diagnostic techniques are required for rapid and accurate identification. Debridement surgeries, drainage and sensitive antibiotics are effective. Drug safety and psychological status should be paid attention. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Multiple pathogen infections accompanied with ocular pathologies in a patient with high-titer Anti-IFN-γ autoantibodies: a case report

The typical clinical characteristic of patients with anti-IFN-γ autoantibodies (AIGAs) is primarily associated with infection caused by intracellular pathogens. With continued research, additional clinical characteristics have been gradually uncovered. Here, we present a case of multiple pathogen infections accompanied by ocular pathologies in a patient with high titers of AIGAs. The patient, a 53-year-old female patient, was admitted to our hospital after finding a mass in the right supraclavicular fossa. She was successively diagnosed with Talaromyces marneffei, Aspergillus flavus and Nontuberculous mycobacteria (NTM) infections. Then, she received a complete course of antifungal agents for nearly 3.5 years and anti-NTM treatment for nearly 3 years, with discontinuation upon symptom improvement. However, there was a rapid recurrence of the infection upon cessation of the drug despite improvement in the patient’s symptoms. Moreover, when the recurrent infection stabilized, the patient exhibited immune conjunctivitis and dry eye, which was successfully treated by tacrolimus eye drops and lubricant. Patients with high-titer AIGAs are more prone to experiencing recurrence and/or persistent infection, as well as immune disorders.

JIB-04, an inhibitor of Jumonji histone demethylase as a potent antitubercular agent against Mycobacterium tuberculosis.

The increasing drug resistance of Mycobacterium tuberculosis (Mtb), coupled with the limited availability of effective anti-tuberculosis medications, poses significant challenges for the management and treatment of tuberculosis (TB). Globally, non-tuberculous mycobacteria (NTM) infections are increasing, with Mycobacterium avium complex and Mycobacterium abscessus (Mab) being the most common in labs and having few treatment options. There's an urgent need for innovative therapies against Mtb and NTM that are effective and have minimal side effects. The study evaluated the in vitro efficacy of JIB-04, a Jumonji histone demethylase inhibitor, against Mtb, Mab, and multidrug-resistant (MDR) clinical isolates using the minimum inhibitory concentration (MIC) assay. We also determined the minimum bactericidal concentrations (MBCs) of JIB-04 against the H37Rv and H37Ra strains. A time-kill assay was performed to assess the comparative efficacy of JIB-04 and rifampicin against H37Ra. Additionally, the study investigated the impact of JIB-04 on biofilm formation and the persistence of H37Ra over extended periods. Our findings demonstrated a substantial inhibitory effect of JIB-04 on the growth of Mab, Mtb, and MDR clinical isolates. JIB-04 showed bactericidal effects at twice the MIC, outperforming rifampicin in reducing viable cell counts over 8 days. It showed moderate cytotoxicity to mammalian cells but effectively inhibited biofilm formation. In our anoxia model, JIB-04 induced a significant, concentration-dependent reduction in bacterial load. JIB-04 is a promising candidate for the treatment of MDR tuberculosis.

Nontuberculous Mycobacterial Infective Endocarditis: A Systematic Review of Clinical Characteristics and Outcomes.

Infective endocarditis (IE) due to nontuberculous mycobacteria (NTM) is a rare infection, and several outbreaks have been reported in the last 2 decades. However, the clinical spectrum is still poorly understood. This systematic review aimed to evaluate the clinical characteristics and outcomes in NTM IE. We searched the major electronic databases (PubMed, Scopus, and Google Scholar) with appropriate keywords to December 2023. We included studies based on predefined diagnostic criteria, and relevant data were collected on clinical presentation and treatment outcomes. The study was registered with PROSPERO (CRD42023492577). A total of 97 studies were reviewed, encompassing 167 patients with NTM IE. The earliest cases were reported in 1975, involving M chelonae and M fortuitum. M chimaera was the most prevalent species (38.9%), though rapidly growing NTM (RGM) were more common than slow-growing NTM (SGM; 59.3% vs 40.7%). Disseminated NTM infection occurred in 84% of cases, with bone marrow infiltration and osteomyelitis as frequent manifestations. Prosthetic valves were the main risk factor, present in 63.5% of cases. In native valve IE, nearly all cases (n = 27, 96%) were attributed to RGM. The overall mortality rate was 44.9%, with conservative management without surgery associated with poorer outcomes (66.7% vs 30.6%). Mortality was comparable between SGM and RGM IE, although relapses were more common in SGM IE (17.6% vs 1.9%). This review highlights the changing epidemiology of NTM IE with the emergence of RGM IE. Disseminated infections in the setting of prosthetic valves warrant NTM evaluation. The high mortality rate necessitates the role of early surgery.

Comparison of molecular testing methods for diagnosing non-tuberculous mycobacterial infections.

Rapid and accurate identification of non-tuberculous mycobacteria (NTM) is crucial yet challenging, promoting the development of novel molecular techniques such as amplification-based targeted high-throughput sequencing and metagenomic unbiased high-throughput sequencing. We aimed to evaluate the diagnostic value of these molecular techniques for NTM infection. A total of 115 clinical specimens from patients with confirmed NTM infection were subjected to multiplex polymerase chain reaction detection techniques (multi-PCR), metagenomic Next-Generation Sequencing (mNGS), targeted Next-Generation Sequencing (tNGS), and targeted Nanopore sequencing (tNanopore). Positivity rates and species identification were compared among these techniques. The sensitivity of mNGS, tNGS, and multi-PCR in NTM-infection diagnosis was 44.3%, 42.6%, and 36.5%, respectively, while the sensitivity of the three methods in combination increased to 54.8%. The pathogen identification results of mNGS, tNGS and multi-PCR were matched in 80.6% (25/31) samples at the species level, among which 14 samples (45.2%) was completely matched at the subspecies level. The results of tNanopore, tNGS and mNGS at the species level were completely matched in 73.3% (22/30) samples. These molecular assays demonstrated comparable performance in precisely identifying NTM species in clinical specimens, showing their promising potential as efficient and alternative tools for the rapid diagnosis of NTM disease.

Mycobacteroides abscessus outbreak and mitigation in a cardiothoracic transplant population: the problem with tap water

Hospital outbreaks caused by Mycobacteroides abscessus complex are a major cause for concern in vulnerable patients such as the cardiothoracic transplant population. To describe the outbreak investigation and mitigation steps undertaken to address an increase in healthcare-associated M. abscessus complex cases in an inpatient cardiothoracic transplant population. We extracted clinical characteristics from patients with M.abscessus pre-outbreak (March 2018 to December 2020) and during the outbreak (January 2021 to June 2022) from the electronic medical record. A multi-disciplinary team conducted the outbreak investigation and devised a mitigation strategy to implement at our institution. The baseline incidence of healthcare-associated M.abscessus was 0.11 cases per 10,000 patient-days; this increased to 0.24 cases per 10,000 patient-days during the outbreak. There were 1/9 (11%) cardiothoracic transplant patients in the pre-outbreak group compared with 7/12 (58%) during the outbreak, and respiratory specimen types compromised 6/9 (67%) of M.abscessus results in the pre-outbreak group compared with 10/12 (83%) during the outbreak. Among the clinical care activities involving water, a variety of water sources were utilized, including filtered and tap water. The incidence of healthcare-associated M.abscessus subsequently decreased to 0.06 cases per 10,000 patient-days after implementing an outbreak-mitigation strategy of sterile water precautions. Robust educational efforts from a multi-disciplinary team on eliminating exposure to tap water were effective measures to reduce healthcare-associated M.abscessus incidence at our institution. Non-tuberculous mycobacteria infection surveillance, targeted education, and water mitigation strategies may be beneficial preventative strategies for other lung transplant centres facing similar issues.

Differentiation complex sputum microbiome in patients suspected TB pulmonary

<b>Purpose: </b>This is the first study to attempt microbiome diversity using metagenomic full-length 16S rRNA from respiratory specimens suspected of chronic pulmonary TB patients.<br /> <b>Materials and methods:</b> A 33 patients with suspected chronic pulmonary TB were included. Sputum specimens were cultured to detect <i>mycobacterium sp.</i> and extracted using QiAmp DNA mini kit modification and 16S rRNA metagenomic sequencing by nanopore grid ion sequencer. Microbiome analysis was performed using Pavian and Krona tools.<br /> <b>Results: </b>9 patients were diagnosed with TB based on GeneXpert MTB/RIF assay, and 3 patients were detected with NTM pulmonary infection.The common genera identified from TB culture positive patients were <i>streptococcus sp.</i>, <i>prevotella sp., </i>and <i>veilonella sp. </i>However, less was detected in two NTM infection patients<i>. </i>Metagenomic analysis revealed community bacteria species, including mycobacterium tuberculosis and NTM species, with the lowest number of unique reads. The abundance of <i>streptococcus sp.</i> were less than 30% in 4 patient with comorbid diabetes mellitus.<br /> <b>Conclusions:</b> Metagenomic targeted 16SrRNA full-length sequencing in the clinical respiratory specimen can provide diagnostic insight beyond standard microbiologic cultures and detailed profiling of microbial communities at the species level.

SQ31f is a potent non-tuberculous mycobacteria antibiotic by specifically targeting the mycobacterial F-ATP synthase.

Non-tuberculous mycobacteria (NTM) infection presents a growing global health problem and requires new antibiotics targeting enzymes that are essential for the pathogens under various metabolic conditions, with high target specificity, good solubility and with attractive combinatory potency. SQ31f was synthesized by a simplified synthesis protocol, and its effect on growth inhibition of fast- and slow-growing NTM and clinical isolates, whole-cell ATP depletion, ex vivo macrophages and its potency in combination with other antibiotics were evaluated. Molecular docking studies were employed to assess SQ31f's binding mode. We present- squaramide SQ31f as a novel anti-NTM inhibitor targeting the NTM F1FO-ATP synthase, essential for ATP formation, regulation of ATP homeostasis and proton motive force under multiple growth conditions. The potency of SQ31f in growth inhibition of fast- and slow-growing NTM and clinical isolates correlates with whole-cell ATP depletion, which is not caused by altered oxygen consumption. SQ31f's high aqueous solubility enables binding to the waterfilled cytosolic proton half channel in the subunits a-c interface of the FO domain. As presented for the fast-growing Mycobacterium abscessus, the compound is active against intracellular-residing M. abscessus. Importantly, SQ31f shows an additive effect of the anti-M. abscessus drugs clofazimine, rifabutin or amikacin, and an attractive potentiation of linezolid, clarithromycin, or the oral pair tebipenem and avibactam. SQ31f represents an attractive inhibitor to tackle the issues associated with NTM drug tolerance and toxicity. Its combinatory potency with anti-M. abscessus drugs holds potential for overcoming resistance, while also reducing intensive compound synthesis and associated costs.

Primary cutaneous infections with non-tuberculous mycobacteria: a report of 6 cases

BackgroundThe incidence of non-tuberculous mycobacterium infection has shown a gradual increasing trend in recent years, among which cutaneous manifestations as an important aspect. This study aimed to describe the clinical features and microbiological findings in 6 cases of primary cutaneous nontuberculous mycobacterium infection.MethodsIn this retrospective study from June 2021 to June 2022, the clinical data and microbiological results of six cases diagnosed with primary cutaneous non-tuberculous mycobacterium infection in department of dermatology, Hangzhou Third People’s Hospital were analyzed.ResultsAll six cases were primary cutaneous non-tuberculous mycobacterium infections, four of which had a history of trauma or exposure, and two had an underlying disease that could lead to compromised immunity. All patients presented with erythema nodular skin lesions, four on the upper or lower extremities, one on the face, and one on the right hip. The histopathological findings of five patients who underwent biopsy were granulomatous inflammatory changes with mixed infiltration. Laboratory cultures using tissue or tissue fluid were all successful, including four Mycobacterium marinum, one Mycobacterium abscessus, and one Mycobacterium avium. Metagenomics next-generation sequencing detected results consistent with culture colonies in only two cases. With the exception of case 4, all patients responded well to oral medication, with a course of treatment ranging from 4 months to 1 year, and the prognosis was good.ConclusionsThe clinical features of primary cutaneous non-tuberculous mycobacterium infection are often lacking in specificity, and the identification of related strains is difficult for a variety of reasons. Although the results of metagenomics next-generation sequencing are useful for pathogen spectrum identification, its diagnostic value should be carefully reevaluated under certain circumstances. Patients with suspected triggers who do not respond well to conventional treatments should be suspected as atypical infection and potential immunosuppression. If diagnosed and treated promptly, the prognosis of primary cutaneous non-tuberculous mycobacterium infection is generally good.

Mycobacterium paragordonae pulmonary disease with rapidly growing solitary lesions: a case report and literature review.

Mycobacterium paragordonae (MPG) is a novel and uncommon nontuberculous mycobacterium (NTM). We describe a case of MPG pulmonary disease (MPGPD) with a single, rapidly growing, pulmonary mass, which has rarely been reported. A chest CT scan of a 66-year-old woman revealed a rapidly growing solitary mass-like lesion in the upper lobe of the right lung, which was not seen in the previous chest CT scan six months ago. H&E-stained section of the CT-guided percutaneous lung tissue biopsy specimen showed chronic inflammatory changes with epithelioid granulomas. Metagenomic next-generation sequencing (mNGS) of lung tissue biopsy specimen identified MPG with a sequence number of 1617 and a confidence level of 99%. Because the subsequent MPG droplet digital PCR (MPG-ddPCR) test of the lung tissue biopsy was positive, she was eventually diagnosed with MPGPD. She was administered a quadruple oral regimen comprising clarithromycin, levofloxacin, rifampicin, and ethambutol according to the ATS/IDSA protocol for Mycobacterium gordonae (MG) infection. The chest CT scans showed a significant reduction in the lesion one month after the treatment and almost complete resolution four months later. MPGPD is a rare NTM infection. The imaging manifestations of MPGPD are diverse and may even show rapid development. mNGS of tissue biopsy can enable prompt diagnosis of MPG infection and is a good alternative to routine NTM microbial testing. The ATS/IDSA protocol for MG infection is an effective treatment for MPG infection.

TBAJ-587, a novel diarylquinoline, is active against Mycobacterium abscessus.

Nontuberculous mycobacteria (NTM) infections are extremely difficult to treat due to a natural resistance to many antimicrobials. TBAJ-587 is a novel diarylquinoline, which shows higher anti-tuberculosis activity, lower lipophilicity, and weaker inhibition of hERG channels than bedaquiline (BDQ). The susceptibilities of 11 NTM reference strains and 194 clinical Mycobacterium abscessus isolates to TBAJ-587 were determined by the broth microdilution assay. The activity of TBAJ-587 toward the growth of M. abscessus in macrophages was also evaluated. Minimum bactericidal concentration and time-kill kinetic assays were conducted to distinguish between the bactericidal and bacteriostatic activities of TBAJ-587. The synergy between TBAJ-587 and eight clinically important antibiotics was determined using a checkerboard assay. TBAJ-587 was highly effective against M. abscessus by targeting its F-ATP synthase c chain. The antimicrobial activities of TBAJ-587 and BDQ toward intracellular M. abscessus were comparable. The in vivo activities of TBAJ-587 and BDQ in an immunocompromised mouse model were also comparable. TBAJ-587 expressed bactericidal activity and was compatible with eight anti-NTM drugs commonly used in clinical practice; no antagonism was discovered. As such, TBAJ-587 represents a potential candidate for the treatment of NTM infections.

Rational Exploration of 2,4-Diaminopyrimidines as DHFR Inhibitors Active against Mycobacterium abscessus and Mycobacterium avium, Two Emerging Human Pathogens.

Nontuberculous mycobacteria (NTM) are emerging human pathogens linked to severe pulmonary diseases. Current treatments involve the prolonged use of multiple drugs and are often ineffective. Bacterial dihydrofolate reductase (DHFR) is a key enzyme targeted by antibiotics in Gram-negative bacterial infections. However, existing DHFR inhibitors designed for Gram-negative bacteria often fail against mycobacterial DHFRs. Here, we detail the rational design of NTM DHFR inhibitors based on P218, a malarial DHFR inhibitor. We identified compound 8, a 2,4-diaminopyrimidine exhibiting improved pharmacological properties and activity against purified DHFR, and whole cell cultures of two predominant NTM species: Mycobacterium avium and Mycobacterium abscessus. This study underscores the potential of compound 8 as a promising candidate for the in vivo validation of DHFR as an effective treatment against NTM infections.

Epidemiology of bronchiectasis at a single center in Japan: a retrospective cohort study

BackgroundThe characteristics of bronchiectasis (BE) in Asia, including Japan, remain largely unknown. We aimed to provide insights into the clinical characteristics and treatment outcomes of BE, especially regarding nontuberculous mycobacteria (NTM) infection and its poorly understood impact on prognosis. We also aimed to clarify the effect of long-term macrolide antibiotic use in patients with BE, who had no history of exacerbations.MethodsIn this single-center, retrospective study, the medical records of patients who satisfied the BE criteria between January 1, 2012, and August 31, 2023, were reviewed. Severe exacerbations and mortality during the observation period were recorded. Baseline characteristics and overall survival of patients with and without NTM infection, and factors influencing the time to the first exacerbation and death were analyzed. Additionally, the effects of long-term macrolide antibiotic use in patients without a history of severe exacerbations were estimated.ResultsIn a cohort of 1044 patients with BE, the rate of severe exacerbation was 22.3%, with mortality rates of 3.2% over 3 years. Notably, the high prevalence of NTM infection (n = 410, 39.3%) in this cohort was distinctive. NTM infection was not associated with either the time to first severe exacerbation (p = 0.5676, adjusted hazard ratio = 1.11) or mortality (p = 0.4139, adjusted hazard ratio = 0.78). Compared with the NTM group, the non-NTM group had a higher proportion of elevated inflammatory markers, with significant differences in C-reactive protein levels (p = 0.0301) and blood neutrophil counts (p = 0.0273). Pseudomonas aeruginosa colonization was more frequent in the non-NTM group (p = 0.0003). Among patients with non-NTM infection and without a history of exacerbation in the past 2 years, 38.2% received long-term macrolide antibiotics that did not invariably prolong the time to first severe exacerbation (p = 0.4517, IPW p = 0.3555).ConclusionsThis study highlights BE epidemiology in Japan, noting that the presence of NTM infection may not necessarily worsen the prognostic outcomes and advising caution in the casual use of macrolides for milder cases without a history of exacerbations.Clinical trial registrationUMIN Clinical Trials Registry Number: UMIN000054726 (Registered on 21 June 2024).

Non-tuberculous mycobacteria enhance the tryptophan-kynurenine pathway to induce immunosuppression and facilitate pulmonary colonization.

The increasing prevalence of non-tuberculous mycobacterium (NTM) infections alongside tuberculosis (TB) underscores a pressing public health challenge. Yet, the mechanisms governing their infection within the lung remain poorly understood. Here, we integrate metagenomic sequencing, metabolomic sequencing, machine learning classifiers, SparCC, and MetOrigin methods to profile bronchoalveolar lavage fluid (BALF) samples from NTM/TB patients. Our aim is to unravel the intricate interplay between lung microbial communities and NTM/Mycobacterium tuberculosis infections. Our investigation reveals a discernible reduction in the compositional diversity of the lung microbiota and a diminished degree of mutual interaction concomitant with NTM/TB infections. Notably, NTM patients exhibit a distinct microbial community characterized by marked specialization and notable enrichment of Pseudomonas aeruginosa and Staphylococcus aureus, driving pronounced niche specialization for NTM infection. Simultaneously, these microbial shifts significantly disrupt tryptophan metabolism in NTM infection, leading to an elevation of kynurenine. Mycobacterium intracellulare, Mycobacterium paraintracellulare, Mycobacterium abscessus, and Pseudomonas aeruginosa have been implicated in the metabolic pathways associated with the conversion of indole to tryptophan via tryptophan synthase within NTM patients. Additionally, indoleamine-2,3-dioxygenase converts tryptophan into kynurenine, fostering an immunosuppressive milieu during NTM infection. This strategic modulation supports microbial persistence, enabling evasion from immune surveillance and perpetuating a protracted state of NTM infection. The elucidation of these nuanced microbial and metabolic dynamics provides a profound understanding of the intricate processes underlying NTM and TB infections, offering potential avenues for therapeutic intervention and management.