The complexities and challenges of preventing and treating nontuberculous mycobacterial diseases

Replicon RNA vaccines: design, delivery, and immunogenicity in infectious diseases and cancer

Replicon RNA (RepRNA) represents a cutting-edge technology in the field of vaccinology, fundamentally transforming vaccine design and development. This innovative approach facilitates the induction of robust immune responses against a range of infectious diseases and cancers. RepRNA vaccines leverage the inherent capabilities of RNA-dependent RNA polymerase associated with self-replicating repRNA, allowing for extreme replication within host cells. This process enhances antigen production and subsequently stimulates adaptive immunity. Additionally, the generation of double-stranded RNA during RNA replication can activate innate immune responses. Numerous studies have demonstrated that repRNA vaccines elicit potent humoral and cellular immune responses that are broader and more durable than those generated by conventional mRNA vaccines. These significant immune responses have been shown to provide protection in various models for infectious diseases and cancers. This article will explore the design and delivery of RepRNA vaccines, the mechanisms of immune activation, preclinical studies addressing infectious diseases and tumors, and related clinical trials that focus on safety and immunogenicity.

Multicenter, retrospective cohort study of antimycobacterial treatment-related harms among patients with non-tuberculosis Mycobacterium infections in the United States

Non-tuberculosis mycobacteria (NTM) are extensively drug-resistant organisms that require long-term therapy. The study purpose was to quantify the incidence of and risk factors for antimycobacterial-associated adverse drug events (ADEs) in persons with NTM infections receiving outpatient therapy. A multicenter, retrospective cohort was performed of persons with NTM infections who received antimycobacterial treatment from 2013 to 2024. Inclusion criteria were age ≥18 years, ≥1 month of outpatient treatment, and ≥1 follow-up outpatient visit within 3 months of index encounter. Mycobacterium avium complex and Mycobacterium tuberculosis complex were excluded. The primary outcome was development of pre-specified treatment-related ADE or acute kidney injury (AKI), thrombocytopenia, and/or Clostridioides difficile infection (CDI) through 12 months of therapy. Secondary outcomes included therapy discontinuation due to any treatment-related ADEs. Two hundred patients were included: 14% developed a pre-specified ADE. Mycobacterium abscessus (29%) was the most common pathogen; most initial regimens included a macrolide (54%), systemic aminoglycoside (24%), β-lactam (24%), or tetracycline derivative (22%). The most common pre-specified ADEs were thrombocytopenia (9%), AKI (8%), and CDI (<1%). The median (IQR) time-to-ADE was 25 (18-38) days from initial outpatient regimen; patients who received aminoglycoside- or oxazolidinone-based therapies were more likely to develop a pre-specified ADE (adjOR, 3.9; 95% CI, 1.7-9.2). Therapy discontinuation due to any ADE occurred in 35% of patients; the median (IQR) time-to-any ADE was 32 (21-58) days. ADEs in persons with NTM infections are common and occur near the first month of outpatient treatment. Intensified monitoring and/or use of more tolerable antimycobacterial regimens early in treatment may be an appropriate approach to avoid harms.Treatment of non-tuberculosis mycobacteria is complicated by adverse drug events (ADEs). This work quantified the incidence and time course of pre-determined, clinically relevant ADEs (acute kidney injury, thrombocytopenia, and C. difficile infection), which occurred in 14% of patients within 30 days of outpatient treatment.

Interpreting diagnosis outcomes for tuberculosis to timely and reliably predict non-tuberculosis mycobacteria isolation

Introduction. Timely distinguishing non-tuberculous mycobacteria (NTM) from Mycobacterium tuberculosis is needed, but it is challenging.Hypothesis. Smear-positive and tuberculosis (TB) molecular-test-negative outcomes could timely and accurately predict NTM existence in the clinical specimen.Methodology. Laboratory outcomes of the smear test and TB molecular test outcomes were evaluated in a high TB and NTM prevalence setting. Additionally, the interferon-gamma release assay (IGRA) outcome was scrutinized to assess its supplementary value to the above strategy.Results. The smear-positive/Xpert MTB/RIF (Cepheid, USA) outcomes accurately predicted 91.67% (198/216) of the NTM isolation, while that of smear-positive/Simultaneous Amplification and Testing method (SAT-TB) (Rendu Biotechnology, China) negative outcomes was 84.5% (169/200). Applying these indicators to rule out TB could achieve an accuracy of up to 99.49% (3435/3453). Combining smear-positive, Xpert-negative and SAT-TB-negative outcomes increased the accuracy up to 95%. Adding a negative IGRA outcome to the indicators further increased the accuracy to over 96%, albeit at the cost of losing prediction sensitivity. When evaluating the strategy in NTM isolates, the indicators successfully predicted about 40% of these isolations with over 92% accuracy.Conclusion. A smear-positive/molecular TB test-negative outcome could timely and accurately predict NTM isolation in the given setting. This strategy could predict ~40% of the NTM isolations of the patients on their first day of hospital visit.

Application value of nucleic acid MALDI-TOF MS in mycobacterial species identification and drug resistance detection in Mycobacterium tuberculosis

Tuberculosis (TB) and non-tuberculous mycobacteria (NTM) infections pose global health threats, requiring swift and accurate identification for effective treatment. This study aims to assess the ability of nucleic acid matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) to rapidly identify Mycobacterium tuberculosis (MTB), NTM, and the drug resistance of MTB. A comparative analysis of 133 clinical samples was performed using acid-fast bacilli (AFB) staining, Lowenstein-Jensen (LJ) culture, GeneXpert, real-time PCR, and nucleic acid MALDI-TOF MS. The study focused on the diagnostic performance of nucleic acid MALDI-TOF MS in detecting MTB and NTM, as well as its accuracy in identifying the drug resistance profiles of MTB. The positive detection rate of nucleic acid MALDI-TOF MS for mycobacterium was 84.96%, which was significantly higher than that of AFB staining (29.32%). For NTM, nucleic acid MALDI-TOF MS had 89.29% sensitivity and 97.14% specificity, with an area under the curve (AUC) of 0.932, which was superior to other methods. The nucleic acid MALDI-TOF MS identified 28 NTM species, while real-time PCR identified only 12. Drug resistance detection showed concordance rates of 80% to 95% compared with drug sensitivity tests of LJ culture. Nucleic acid MALDI-TOF identified mutations, like KatG315 AGC-ACC for low-level isoniazid resistance, rpoB 531 TCG-TTG for high-level rifampicin resistance, and the InhA-15 C-T mutations, were also found in six isoniazid resistance cases and prothionamide resistance cases. Nucleic acid MALDI-TOF MS is a valuable diagnostic tool for the rapid and precise identification of mycobacterial species and the drug resistance profiles of MTB. With high sensitivity and specificity, it can guide the early initiation of effective anti-tuberculosis treatment in clinical settings.IMPORTANCETuberculosis (TB) remains a critical global health challenge, exacerbated by the emergence of drug-resistant strains. Accurate, rapid diagnosis is imperative for effective treatment and control of TB. The ability to discern MTB from NTM is equally vital, as they demand distinct therapeutic approaches. This study underscores the significance of nucleic acid matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) technology in providing a swift and precise diagnostic tool. Its high sensitivity and specificity in identifying mycobacterial species and their resistance profiles are paramount for guiding targeted anti-tuberculosis therapy. By potentially reducing the time to diagnosis and enabling personalized treatment plans, this technology could revolutionize TB management, ultimately mitigating its impact on public health.

Genomic insights into the plasmidome of non-tuberculous mycobacteria

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Genetic variations underlying aminoglycoside resistance in antibiotic-induced Mycobacterium intracellulare mutants

Mycobacterium avium complex (MAC) is an emerging pathogen leading to public health concerns in developing and developed countries, particularly among immunocompromised individuals and patients with structural lung diseases. Current clinical guidelines recommend combination antibiotic therapy for treating MAC pulmonary disease (MAC-PD). However, the rising prevalence of antibiotic resistance poses significant challenges, including treatment failure and clinical recurrence. A deeper understanding of the mechanisms underlying MAC antibiotic resistance is essential to improve treatment outcomes. This study investigates the genetic variations associated with aminoglycoside resistance in an antibiotic-induced Mycobacterium intracellulare mutant derived from a clinical strain. Whole-genome analysis identified seven mutations in the aminoglycoside-resistant mutant, including single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels). Key genetic alterations included a frameshift variant in a gene encoding a secreted protein antigen, missense mutations in rpsL and rsmG, and synonymous and in-frame deletion variants in srfAB and mtrB, respectively. These findings highlight the complex genetic landscape of aminoglycoside resistance in M. intracellulare. Understanding these resistance determinants provides valuable insights for developing diagnostic tools to detect drug-resistant MAC strains and optimizing therapeutic strategies for managing MAC infections in clinical practice.

In vitro activity of omadacycline against geographically diverse rapidly growing nontuberculous mycobacteria (NTM) clinical isolates

Nontuberculous mycobacteria (NTM) are emerging opportunistic pathogens with limited treatment options due to resistance to multiple antibiotic classes. This study aimed to evaluate the in vitro activity of omadacycline and comparator antibiotics against rapidly growing mycobacteria (RGM) clinical isolates. Minimum inhibitory concentration (MIC) evaluation of RGM clinical isolates was performed by two independent laboratories (EU and Japan). A total of 383 isolates (211 EU, 172 Japan) were evaluated. Omadacycline was active against all RGM species tested. For Mycobacterium abscessus subsp. abscessus, MIC50 and MIC90 values (read at 100 % inhibition) were 1 and 4 µg/mL (EU) and 0.5 and 1 µg/mL (Japan), respectively. Mycobacterium fortuitum and Mycobacterium chelonae both had MIC90 values of 0.5 µg/mL (Japan). Omadacycline has consistent, potent in vitro activity against RGM clinical isolates from 15 geographically diverse countries, and thus warrants additional studies and continued development of omadacycline as a potential treatment option for NTM-related disease.

Extrapulmonary Nontuberculous Mycobacteria Infection: The New-Age Neglected Infectious Disease

Nontuberculous mycobacteria (NTM), otherwise known as atypical mycobacteria, primarily cause pulmonary disease. However, with the increase in the immunocompromised population, infections caused by NTM at extrapulmonary (EP) sites have been on the rise in the past decade. Clinical presentations can commonly include lymphadenitis and skin and soft tissue infections. The diagnosis is challenging due to the invasive nature of the sample collection and the low degree of suspicion. Furthermore, detection up to the speciation level is important as management is species-specific. With limited data and studies regarding extrapulmonary nontuberculous mycobacteria (EP-NTM) disease, a multidisciplinary approach with awareness is required to recognize the pathogen early for appropriate and timely institution of therapy.

A novel in silico molecular tool for comprehensive differentiation of Mycobacterium species

The Identification of various mycobacterial species is critical for understanding their pathogenicity and epidemiology. Despite the existence of several established methods for identifying mycobacterial species, each of these methods has several significant limitations, including high costs, substantial time demands, and a restricted ability to detect a wide range of recoverable species. This study presents an in silico method using restriction fragment length polymorphism (RFLP) to differentially identify 75 clinically important mycobacterial species.The present investigation employed specific primer combinations to identify and generate a distinct hypervariable sequence across the ribosomal RNA gene. This unique sequence using appropriate restriction enzyme digestion followed by gel electrophoresis enabled the creation of highly precise and distinct patterns or profiles for each of the 75 medically relevant Mycobacterium species, including members of closely related Mycobacterium complex groups. This approach can quickly and reliably identify mycobacterial species, allowing for more timely treatment decisions and contributing to beneficial epidemiological investigations.

Transposon-sequencing across multiple Mycobacterium abscessus isolates reveals significant functional genomic diversity among strains

Mycobacterium abscessus (Mab) is a clinically significant pathogen and a highly genetically diverse species due to its large accessory genome. The functional consequence of this diversity remains unknown mainly because, to date, functional genomic studies in Mab have been primarily performed on reference strains. Given the growing public health threat of Mab infections, understanding the functional genomic differences among Mab clinical isolates can provide more insight into how its genetic diversity influences gene essentiality, clinically relevant phenotypes, and importantly, potential drug targets. To determine the functional genomic diversity among Mab strains, we conducted transposon-sequencing (TnSeq) on 21 genetically diverse clinical isolates, including 15 M. abscessus subsp. abscessus isolates and 6 M. abscessus subsp. massiliense isolates, cataloging all the essential and non-essential genes in each strain. Pan-genome analysis revealed a core set of 3,845 genes and a large accessory genome of 11,507. We identified 259 core essential genes across the 21 clinical isolates and 425 differentially required genes, representing ~10% of the Mab core genome. We also identified genes whose requirements were subspecies, lineage, and isolate-specific. Finally, by correlating TnSeq profiles, we identified 19 previously uncharacterized genetic networks in Mab. Altogether, we find that Mab clinical isolates are not only genetically diverse but functionally diverse as well.

IMPORTANCE

This study investigates the genetic diversity of Mycobacterium abscessus (Mab), a bacteria known for causing difficult-to-treat infections. Researchers performed transposon-sequencing (TnSeq) on 21 different clinical isolates of Mab to identify essential and non-essential genes in each strain. Through this analysis, they identified core genes required for growth across all strains. Interestingly, they also identified genes whose requirement for growth or "essentiality" were subspecies, lineage, and isolate-specific. This study reveals that Mab's genetic diversity translates into significant functional differences among clinical isolates. Insights from this paper lay essential groundwork for future studies exploring the biological and clinical implications of genetic diversity in Mab clinical isolates. Understanding this diversity could guide targeted therapies and offer new insights into managing infections caused by Mab, a growing public health concern.

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

PURPOSES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Not the Silver Bullet: Uncovering the Unexpected Limited Impacts of Silver-Containing Showerheads on the Drinking Water Microbiome

The incidence of waterborne disease outbreaks in the United States attributed to drinking water-associated pathogens that can cause infections in the immunocompromised DWPIs (e.g., Legionella pneumophila, nontuberculous mycobacteria (NTM), and Pseudomonas aeruginosa, among others) appears to be increasing. An emerging technology adopted to reduce DWPIs are point-of-use devices, such as showerheads that contain silver, a known antimicrobial material. In this study, we evaluate the effect of silver-containing showerheads on DWPI density and the broader microbiome in shower water under real-use conditions in a full-scale shower system, considering three different silver-modified showerhead designs: (i) silver mesh within the showerhead, (ii) silver-coated copper mesh in the head and hose, and (iii) silver-embedded polymer composite compared to conventional plastic and metal showerheads. We found no significant difference in targeted DWPI transcriptional activity in collected water across silver and nonsilver shower head designs. Yet, the presence of silver and how it was incorporated in the showerhead influenced the metal concentrations, microbial rare taxa, and microbiome functionality. Microbial dynamics were also influenced by the showerhead age (i.e., time after installation). The results of this study provide valuable information for consumers and building managers to consider when choosing a showerhead meant to reduce microorganisms in shower water.

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

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

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.

Novel Synthetic Peptide Agelaia-12 Has Improved Activity Against Mycobacterium abscessus Complex

Fast-growing mycobacteria cause difficult-to-treat infections due to their high intrinsic resistance to antibiotics as well as disinfectant agents. Mycobacterium abscessus complex (MAC) is the main cause of nontuberculous mycobacteria diseases. In this work, we evaluated the activity of the novel synthetic antimicrobial peptide, Agelaia-12, against Mycobacterium abscessus and M. massiliense. Agelaia-12 showed a minimum inhibitory concentration (MIC) of 25 μM detected against M. abscessus and M. massiliense with no cytotoxicity. The scanning electronic microscopy analysis of mycobacterial treated with Agelaia-12 demonstrated the presence of filamentous structures and aggregation of the cells. Congo red binding assay of M. abscessus exhibited altered dye accumulation after treatment with Agelaia-12. Treatment of M. abscessus- or M. massiliense-infected murine macrophages with Agelaia-12 decreased the mycobacterial load by 92% for the tested strains. Additionally, IFN-y KO mice infected with M. abscessus or M. massiliense and treated with Agelaia-12 showed a 98% reduction in lung bacterial load. Thus, the synthetic peptide Agelaia-12 may be a promising biomolecule for the treatment of mycobacteriosis, and its structural properties may serve as a foundational model for the design and development of novel pharmaceutical agents aimed at combating this disease.

Intrapulmonary pharmacokinetics of SPR719 following oral administration of SPR720 to healthy volunteers

SPR720 is a phosphate ester prodrug that is converted rapidly in vivo to SPR719, the active moiety, which exhibits potent in vitro activity against clinically relevant mycobacterial species including Mycobacterium avium complex (MAC) and Mycobacterium abscessus. SPR720 is in clinical development for the treatment of nontuberculous mycobacterial pulmonary disease (NTM-PD) due to MAC. This study evaluated the safety and the intrapulmonary pharmacokinetics of SPR719 in healthy volunteers. A total of 30 subjects received oral SPR720 1,000 mg once daily for 7 days followed by bronchoscopy and bronchoalveolar lavage, with blood samples collected for plasma pharmacokinetic assessments. Mean SPR719 area under the concentration-time curve from time 0 to 24 hours (AUC0-24) and maximum concentration (Cmax) for plasma, epithelial lining fluid (ELF), and alveolar macrophages (AM) were 52,418 ng·h/mL and 4,315 ng/mL, 59,880 ng·h/mL and 5,429 ng/mL, and 128,105 ng·h/mL and 13,033 ng/mL, respectively. The ratios of ELF to total plasma concentrations of SPR719 based on AUC0-24 and Cmax were 1.14 and 1.26, and the ratios of AM to total plasma concentrations of SPR719 based on AUC0-24 and Cmax were 2.44 and 3.02, respectively. When corrected for protein binding, the ratios of ELF to unbound plasma concentrations of SPR719 for AUC0-24 and Cmax were 19.87 and 21.88, and the ratios of AM to unbound plasma concentrations of SPR719 for AUC0-24 and Cmax were 42.50 and 52.53, respectively. No unexpected safety findings were observed. Results from this study of the intrapulmonary disposition of SPR719 support further investigation of SPR720 as a potential oral agent for the treatment of patients with NTM-PD.This study is registered with Clinicaltrials.gov as NCT05955586.

Olink proteomics and lipidomics analysis of serum from patients infected with non-tuberculous mycobacteria and Mycobacterium tuberculosis

BACKGROUND

Non-tuberculous mycobacterial (NTM) and Mycobacterium tuberculosis (MTB) infections are difficult to diagnose and treat, significantly burdening global health. The host immune status is generally believed to be associated with the onset and progression of NTM and MTB infections, but its specific impact remains unclear.

METHODS

In the present study, proteomics and lipidomics analysis of serum from normal controls (n = 26) and patients with MTB (n = 26), rapidly growing NTM (RGM, n = 15), and slowly growing NTM (SGM, n = 21) were conducted using the Olink technique based on a highly sensitive and specific neighborhood extension assay and the lipidomics technique.

RESULTS

IFN-γ, CXCL9, CXCL10, CXCL11, and CXCL13, etc. were simultaneously upregulated in MTB, RGM, and SGM, while lipids FAHFA 22:3, FAHFA 26:4, FAHFA 24:4, FAHFA 20:5, FAHFA 18:2 simultaneously downregulated. IL8, CCL3, CXCL5, and MCP-2, etc. were simultaneously upregulated in RGM and SGM compared to MTB, as well as PCs, LPCs, PEs, and LPEs. Compared with RGM, IL7, CD27, CCL17, CXCL12, and LPC 28:7-SN2 were downregulated in SGM. Pathway analyses revealed that tuberculosis, sphingolipid signaling pathway, and adipocytokine signaling pathway were regulated at the protein level and metabolite level. Diagnostic panels comprising immune-associated proteins and lipids greatly enhance diagnostic specificity and sensitivity.

CONCLUSION

This integrated multi-omics analysis provides a more comprehensive understanding of the molecular landscape of NTM and MTB, which may provide molecular targets for specialized therapies.

In vitro antimicrobial activity of doxycycline, minocycline, and tigecycline against Mycobacterium abscessus complex: A meta-analysis study

PURPOSE

Mycobacterium abscessus complex (MABC) infections are increasing worldwide. Furthermore, these infections have a low treatment success rate due to their resistance to many current antibiotics. This study aimed to determine the overall in vitro activity of the tetracyclines doxycycline (DOX), minocycline (MIN), and tigecycline (TGC) against MABC clinical isolates.

PATIENTS AND METHODS

A systematic review of PubMed/MEDLINE, Web of Science, and Embase was conducted up to August 28, 2023. Studies applying the drug susceptibility testing standards of the Clinical and Laboratory Standards Institute were considered. A random effects model was used to assess the total in vitro resistance rates of the MABC clinical isolates to DOX, MIN, and TGC. The I2 and Cochran's Q statistics were employed to evaluate the origins of heterogeneity. All analyses were conducted using CMA V.3 software.

RESULTS

Twenty-six publications (22, 12, and 11 studies on DOX, MIN, and TGC, respectively) were included. The pooled in vitro resistance rates of the MABC clinical isolates to DOX and MIN at the breakpoint of 8 μg/mL were 93.0 % (95 % CI, 89.2 %-95.5 %) and 87.2 % (95 % CI, 76.5 %-93.4 %), respectively. In the case of TGC, the breakpoints of 2, 4, and 8 μg/mL were associated with pooled resistance rates of 2.5 % (95 % CI, 0.5 %-11.6 %), 7.2 % (95 % CI, 4.0 %-12.5 %), and 16.8 % (95 % CI, 4.7 %-45.0 %), respectively.

CONCLUSION

Among the three examined tetracyclines, MABC exhibited extremely high resistance rates to DOX and MIN, thereby limiting their use in treating MABC infections. Conversely, MABC showed an increased susceptibility rate to TGC, highlighting TGC administration as a viable treatment option for patients with MABC infections.

Determination of bactericidal activity against 3HC-2-Tre-labelled Mycobacterium abscessus (Mycobacteroides abscessus) by automated fluorescence microscopy

The minimum bactericidal concentration (MBC) of antibiotics is an important parameter for the potency of a drug in eradicating a bacterium as well as an important measure of the potential of a drug candidate in research and development. We have established a fluorescence-based microscopy method for the determination of MBCs against the non-tuberculous mycobacterium Mycobacterium abscessus (Mycobacteroides abscessus) to simplify and accelerate the performance of MBC determination compared to counting colony forming units on agar. Bacteria are labelled with the trehalose-coupled dye 3HC-2-Tre and analysed in a 96-well plate. The results of the new method are consistent with MBC determination by plating on agar. The method was used to evaluate the bactericidality of the antibiotics rifabutin, moxifloxacin, amikacin, clarithromycin and bedaquiline. Bactericidal effects against M. abscessus were observed, which are consistent with literature data.

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.

Investigating cutaneous tuberculosis and nontuberculous mycobacterial infections a Department of Dermatology, Beijing, China: a comprehensive clinicopathological analysis

Background

Cutaneous tuberculosis (CTB) and nontuberculous mycobacteria (NTM) infections present considerable diagnostic and therapeutic challenges. This study aims to provide a comprehensive clinicopathological analysis of CTB and NTM infections.

Methods

We conducted a retrospective analysis of 103 patients diagnosed with cutaneous tuberculosis (CTB) and nontuberculous mycobacteria (NTM) infections at a Beijing dermatology department from January 2000 to January 2024. Demographic, clinical, histological, and laboratory finding data were collected. Diagnostic methods and histopathological examination were recorded. Treatment regimens and outcomes were reviewed. Descriptive statistics were used to summarize demographic and clinical data, and continuous variables expressed as means and standard deviations (SD), and categorical variables as frequencies and percentages. Statistical analyses were conducted using SPSS version 25.0.

Results

The cohort included 103 patients (40.8% males and 59.2% females), with a mean age of 51.86 years. Common clinical manifestations included nodules (97.1%), erythema (74.8%), and plaques (68.9%). Histological examination revealed hyperkeratosis (68.9%), parakeratosis (23.3%), and extensive neutrophil infiltration (95.1%) were observed. Acid fast bacteria (AFB) stains and nucleic acid tests exhibited respective positivity rates of 39.6% and 52.3%, respectively. Most patients were treated with a combination of three drugs; 77.1% of patients showed improvement, with the cure rate for CTB being 20.0%.

Discussion

This study highlights the diverse clinical and histological presentations of CTB and NTM infections, emphasizing the need for comprehensive diagnostic approaches. The variability in treatment regimens reflects the complex management of these infections.

Conclusion

The implementation of advanced molecular techniques and standardized treatment protocols is imperative for enhancing diagnostic precision and therapeutic outcomes.

Noncanonical mutations in ribosome nascent peptide exit tunnel confer clarithromycin resistance in Mycobacterium abscessus complex

OBJECTIVES

Mycobacterium abscessus is a non-tuberculous mycobacterial pathogen that causes pulmonary and skin infections globally. Clarithromycin plays a pivotal role in treating M. abscessus infections, with resistance often leading to treatment failure. While canonical mutations in the 23S rRNA residue 2270/2271 are recognized as the primary mechanism for acquired clarithromycin resistance, resistant isolates lacking these mutations have been widely reported. This study aims to identify new mechanisms of clarithromycin resistance in M. abscessus.

METHODS

We selected spontaneous resistant mutants derived from two parental strains characterized by erm(41) T28 and C28 sequevars, respectively. Whole-genome sequencing was performed on mutants lacking the 23S rRNA 2270/2271 mutations. Site-directed mutagenesis was used to confirm the resistance phenotypes of newly identified mutations. Bioinformatic analysis of publicly available genomes was conducted to evaluate the presence of these mutations in clinical isolates. The spatial localization of these mutations in the ribosome was analyzed to investigate potential mechanisms of resistance.

RESULTS

A total of 135 resistant mutants were selected from the parental strains. Sequencing of the 78 mutants lacking the 23S rRNA 2270/2271 mutations identified mutations within the peptidyl-transferase center and hairpin loops 35, 49, and 74 of the 23S rRNA. These noncanonical mutations were identified in 57 of 1875 genomes of clinical isolates. Thirteen representative mutations were introduced into the bacterial genome, and their contributions to macrolide resistance were confirmed. The newly identified mutations all localized at the entrance of the nascent peptide exit tunnel, potentially contributing to resistance by disrupting the macrolide binding pocket.

CONCLUSION

Several noncanonical 23S rRNA mutations conferring clarithromycin resistance were identified. These mutations enhance our understanding of macrolide resistance in M. abscessus and could serve as important markers for diagnosing clarithromycin resistance.

Effects of non-tuberculous mycobacteria on BCG vaccine efficacy: A narrative review

The Mycobacterium tuberculosis bacterial pathogen is responsible for the ongoing global tuberculosis (TB) epidemic. Bacille Calmette-Guérin (BCG), the only currently approved TB vaccine, is successful in preventing disseminated disease in newborns. However, it has a variable efficacy against pulmonary TB in adults. This protective effect of the vaccine varies greatly among different populations and geographical areas, which the increased exposure of particular populations to non-tuberculous mycobacteria (NTM) is considered as one of the reasons for this issue. Numerous studies have shown that exposure to NTM species causes the host immune system to be improperly primed. It has also been suggested that NTM species may be blamed for reduction in BCG vaccine effectiveness against M. tuberculosis. The increased exposure of certain populations to NTM has diverse effects on BCG efficacy. Moreover, the exposure to NTM can induce opposite effects on BCG efficacy depending on the NTM exposure route and survivability. A detailed understanding of the impact of NTM exposure on the efficacy of the BCG vaccine is essential for ongoing efforts to develop new TB vaccines as it may ultimately be a crucial success factor. The aim of this study was to review the findings of the studies focusing on the effects of NTM on BCG vaccine efficacy in animal models.

Modeling nontuberculous mycobacterial infections in zebrafish

The incidence of infections due to nontuberculous mycobacteria (NTM) has increased rapidly in recent years, surpassing tuberculosis in developed countries. Due to inherent antimicrobial resistance, NTM infections are particularly difficult to treat with low cure rates. There is an urgent need to understand NTM pathogenesis and to develop novel therapeutic approaches for the treatment of NTM diseases. Zebrafish have emerged as an excellent animal model due to genetic amenability and optical transparency during embryonic development, allowing spatiotemporal visualization of host-pathogen interactions. Furthermore, adult zebrafish possess fully functional innate and adaptive immunity and recapitulate important pathophysiological hallmarks of mycobacterial infection. Here, we report recent breakthroughs in understanding the hallmarks of NTM infections using the zebrafish model.

Treatment for non-tuberculous mycobacteria: challenges and prospects

Non-Tuberculous mycobacteria (NTM) are opportunistic environmental bacteria. Globally, NTM incidence is increasing and modeling suggests that, without new interventions, numbers will continue to rise. Effective treatments for NTM infections remain suboptimal. Standard therapy for Mycobacterium avium complex, the most commonly isolated NTM, requires a 3-drug regime taken for approximately 18 months, with rates of culture conversion reported between 45 and 70%, and high rates of relapse or reinfection at up to 60%. New therapeutic options for NTM treatment are urgently required. A survey of ongoing clinical trials for new NTM therapy listed on ClinicalTrials.Gov using the terms 'Mycobacterium avium', 'Mycobacterium abscessus', 'Mycobacterium intracellulare', 'Non tuberculous Mycobacteria' and 'Nontuberculous Mycobacteria' and a selection criterion of interventional studies using antibiotics demonstrates that most trials involve dose and combination therapy of the guideline based therapy or including one or more of; Amikacin, Clofazimine, Azithromycin and the anti-TB drugs Bedaquiline and Linezolid. The propensity of NTMs to form biofilms, their unique cell wall and expression of both acquired and intrinsic resistance, are all hampering the development of new anti-NTM therapy. Increased investment in developing targeted treatments, specifically for NTM infections is urgently required.

Itaconic acid inhibits nontuberculous mycobacterial growth in pH dependent manner while 4-octyl-itaconic acid enhances THP-1 clearance of nontuberculous mycobacteria in vitro

Increasingly prevalent, nontuberculous mycobacteria (NTM) infections affect approximately 20% of people with cystic fibrosis (CF). Previous studies of CF sputum identified lower levels of the host metabolite itaconate in those infected with NTM. Itaconate can inhibit the growth of M. tuberculosis (MTB) in vitro via the inhibition of the glyoxylate cycle enzyme (ICL), but its impact on NTM is unclear. To test itaconic acid's (IA) effect on NTM growth, laboratory and CF clinical strains of Mycobacterium abscessus and Mycobacterium avium were cultured in 7H9 minimal media supplemented with 1-10 mM of IA and short-chain fatty acids (SCFA). M. avium and M. abscessus grew when supplemented with SCFAs, whereas the addition of IA (≥ 10 mM) completely inhibited NTM growth. NTM supplemented with acetate or propionate and 5 mM IA displayed slower growth than NTM cultured with SCFA and ≤ 1 mM of IA. However, IA's inhibition of NTM was pH dependent; as similar and higher quantities (100 mM) of pH adjusted IA (pH 7) did not inhibit growth in vitro, while in an acidic minimal media (pH 6.1), 1 to 5 mM of non-pH adjusted IA inhibited growth. None of the examined isolates displayed the ability to utilize IA as a carbon source, and IA added to M. abscessus isocitrate lyase (ICL) decreased enzymatic activity. Lastly, the addition of cell-permeable 4-octyl itaconate (4-OI) to THP-1 cells enhanced NTM clearance, demonstrating a potential role for IA/itaconate in host defense against NTM infections.

An early and trustable indicator suggestive of non-tuberculosis mycobacteria isolation in a high tuberculosis burden setting

BACKGROUND

Distinguishing between nontuberculous mycobacterial (NTM) lung infections and pulmonary tuberculosis becomes challenging due to their similar clinical manifestations and radiological images. Consequently, instances of delayed diagnosis or misdiagnosis are highly frequent. A feasible and reliable indicator of the existence of NTM in the early stages of the disease would help to solve this dilemma.

METHODS

In this study, we evaluated the potential of smear-positive and Xpert assay (Cepheid, USA) negative outcomes as an early indicator of possible NTM infection in a high TB-burden setting retrospectively and prospectively.

RESULTS

During the study period, 12·77% (138/1081) of the smear-positive cases yielded negative outcomes with the simultaneous Xpert assay. From the 110 patients who yielded smear-positive/Xpert-negative outcomes and cultivated strain as well, 105 (95·45%) were proved to have NTM isolated. By incorporating an additional criterion of a negative result from the Interferon-gamma release assay, the accuracy of the screening method reached 100%. Regarding the NTM presence prediction value, smear-positive/Xpert-negative has a sensitivity of 24·86% (45/181) in all NTM isolated cases but 93·75-96·55% accuracy in retrospective study or 93·75% accuracy in prospective study in smear-positive NTM isolated cases. In addition, the specificity was ∼99·47% (943/948) in smear-positive tuberculosis cases.

CONCLUSION

The clue of the presence of NTM could be obtained on the first day of the hospital visit due to the point of care (POC) feature of smear testing and Xpert assay. About one-fourth of the NTM-isolated patients would benefit from this rapid, convenient, and reliable screening strategy in the given circumstance. Smear-positive/Xpert-negative outcome is an early, trustable indicator that is indicative of NTM isolation.

Multiparameter immunoprofiling for the diagnosis and differentiation of progressive versus nonprogressive nontuberculous mycobacterial lung disease-A pilot study

Clinical prediction of nontuberculous mycobacteria lung disease (NTM-LD) progression remains challenging. We aimed to evaluate antigen-specific immunoprofiling utilizing flow cytometry (FC) of activation-induced markers (AIM) and IFN-γ enzyme-linked immune absorbent spot assay (ELISpot) accurately identifies patients with NTM-LD, and differentiate those with progressive from nonprogressive NTM-LD. A Prospective, single-center, and laboratory technician-blinded pilot study was conducted to evaluate the FC and ELISpot based immunoprofiling in patients with NTM-LD (n = 18) and controls (n = 22). Among 18 NTM-LD patients, 10 NTM-LD patients were classified into nonprogressive, and 8 as progressive NTM-LD based on clinical and radiological features. Peripheral blood mononuclear cells were collected from patients with NTM-LD and control subjects with negative QuantiFERON results. After stimulation with purified protein derivative (PPD), mycobacteria-specific peptide pools (MTB300, RD1-peptides), and control antigens, we performed IFN-γ ELISpot and FC AIM assays to access their diagnostic accuracies by receiver operating curve (ROC) analysis across study groups. Patients with NTM-LD had significantly higher percentage of CD4+/CD8+ T-cells co-expressing CD25+CD134+ in response to PPD stimulation, differentiating between NTM-LD and controls. Among patients with NTM-LD, there was a significant difference in CD25+CD134+ co-expression in MTB300-stimulated CD8+ T-cells (p <0.05; AUC-ROC = 0.831; Sensitivity = 75% [95% CI: 34.9-96.8]; Specificity = 90% [95% CI: 55.5-99.7]) between progressors and nonprogressors. Significant differences in the ratios of antigen-specific IFN-γ ELISpot responses were also seen for RD1-nil/PPD-nil and RD1-nil/anti-CD3-nil between patients with nonprogressive vs. progressive NTM-LD. Our results suggest that multiparameter immunoprofiling can accurately identify patients with NTM-LD and may identify patients at risk of disease progression. A larger longitudinal study is needed to further evaluate this novel immunoprofiling approach.

Rapid and accurate identification and differentiation of Mycobacterium tuberculosis and non-tuberculous mycobacteria using PCR kits available in a high-burden setting

Infections caused by mycobacteria, including Mycobacterium tuberculosis complex (MTBC) and non-tuberculous mycobacteria (NTM), are a major public health issue worldwide. An accurate diagnosis of mycobacterial species is a challenge for surveillance and treatment, particularly in high-burden settings usually associated with low- and middle-income countries. In this study, we analyzed the clinical performance of two commercial PCR kits designed for the identification and differentiation of MTBC and NTM, available in a high-burden setting such as Ecuador. A total of 109 mycobacteria isolates were included in the study, 59 of which were previously characterized as M. tuberculosis and the other 59 as NTM. Both kits displayed great clinical performance for the identification of M. tuberculosis, with 100% sensitivity. On the other hand, for NTM, one of the kits displayed a good clinical performance with a sensitivity of 94.9% (CI 95%: 89-100%), while the second kit had a reduced sensitivity of 77.1% (CI 95%: 65-89%). In conclusion, one of the kits is a fast and reliable tool for the identification and discrimination of MTBC and NTM from clinical isolates.

Rapid detection of clarithromycin resistance in clinical samples of nontuberculous mycobacteria by nucleotide MALDI-TOF MS

The multidrug resistance of nontuberculous mycobacteria (NTM) poses a significant therapeutic challenge. Rapid and reliable drug susceptibility testing is urgently needed for evidence-based treatment decision, especially for macrolides. This study evaluated the utility of nucleotide matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (NMTMS) in detecting clarithromycin resistance. Sixty-four clinical isolates were identified to species by NMTMS, and mutations associated with clarithromycin resistance were detected. Twenty-three M. abscessus (MAB) isolates and 30 M. intracellulare isolates (including M. intracellulare alone and M. intracellulare in combination with other SGM species) were included for analysis. The predictive sensitivity of NMTMS in detecting clarithromycin resistance was 82.35% (95% CI, 56.57% to 96.20%), with an AUC of 0.89 (95% CI, 0.77 to 0.96) in all MAB and M. intracellulare (n = 53), and up to 93.33% (95% CI, 68.05% to 99.83%) in MAB alone (n = 23). The assay provides a rapid, high-throughput, and highly sensitive tool for detecting clarithromycin resistance in NTM, especially in MAB. Optimization of the panel is necessary to enhance diagnostic accuracy.

Nitric oxide-releasing prodrug for the treatment of complex Mycobacterium abscessus infections

Non-tuberculosis mycobacteria (NTM) can cause severe respiratory infection in patients with underlying pulmonary conditions, and these infections are extremely difficult to treat. In this report, we evaluate a nitric oxide (NO)-releasing prodrug [methyl tris diazeniumdiolate (MD3)] against a panel of NTM clinical isolates and as a treatment for acute and chronic NTM infections in vivo. Its efficacy in inhibiting growth or killing mycobacteria was explored in vitro alongside evaluation of the impact to primary human airway epithelial tissue. Airway epithelial tissues remained viable after exposure at concentrations of MD3 needed to kill mycobacteria, with no inherent toxic effect from drug scaffold after NO liberation. Resistance studies conducted via serial passage with representative Mycobacterium abscessus isolates demonstrated no resistance to MD3. When administered directly into the lung via intra-tracheal administration in mice, MD3 demonstrated significant reduction in M. abscessus bacterial load in both acute and chronic models of M. abscessus lung infection. In summary, MD3 is a promising treatment for complex NTM pulmonary infection, specifically those caused by M. abscessus, and warrants further exploration as a therapeutic.

Evaluation of nucleotide MALDI-TOF-MS for the identification of Mycobacterium species

Background

The accurate identification of the Mycobacterium tuberculosis complex (MTBC) and different nontuberculous mycobacteria (NTM) species is crucial for the timely diagnosis of NTM infections and for reducing poor prognoses. Nucleotide matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has been extensively used for microbial identification with high accuracy and throughput. However, its efficacy for Mycobacterium species identification has been less studied. The objective of this study was to evaluate the performance of nucleotide MALDI-TOF-MS for Mycobacterium species identification.

Methods

A total of 933 clinical Mycobacterium isolates were preliminarily identified as NTM by the MPB64 test. These isolates were identified by nucleotide MALDI-TOF-MS and Sanger sequencing. The performance of nucleotide MALDI-TOF MS for identifying various Mycobacterium species was analyzed based on Sanger sequencing as the gold standard.

Results

The total correct detection rate of all 933 clinical Mycobacterium isolates using nucleotide MALDI-TOF-MS was 91.64% (855/933), and mixed infections were detected in 18.65% (174/933) of the samples. The correct detection rates for Mycobacterium intracellulare, Mycobacterium abscessus, Mycobacterium kansasii, Mycobacterium avium, MTBC, Mycobacterium gordonae, and Mycobacterium massiliense were 99.32% (585/589), 100% (86/86), 98.46% (64/65), 94.59% (35/37), 100.00% (34/34), 95.65% (22/23), and 100% (19/19), respectively. For the identification of the MTBC, M. intracellulare, M. abscessus, M. kansasii, M. avium, M. gordonae, and M. massiliense, nucleotide MALDI-TOF-MS and Sanger sequencing results were in good agreement (k > 0.7).

Conclusion

In conclusion, nucleotide MALDI-TOF-MS is a promising approach for identifying MTBC and the most common clinical NTM species.

Bedaquiline for treatment of non-tuberculous mycobacteria (NTM): a systematic review and meta-analysis

BACKGROUND

Non-tuberculous mycobacteria (NTM) infections are increasing in incidence and associated mortality. NTM are naturally resistant to a variety of antibiotics, complicating treatment. We conducted a literature assessment on the efficacy of bedaquiline in treating NTM species in vitro and in vivo (animal models and humans); meta-analyses were performed where possible.

METHOD

Four databases were searched using specific terms. Publications were included according to predefined criteria. Bedaquiline's impact on NTM in vitro, MICs and epidemiological cut-off (ECOFF) values were evaluated. A meta-analysis of bedaquiline efficacy against NTM infections in animal models was performed. Culture conversion, cure and/or relapse-free cure were used to evaluate the efficacy of bedaquiline in treating NTM infection in humans.

RESULTS

Fifty studies met the inclusion criteria: 33 assessed bedaquiline's impact on NTM in vitro, 9 in animal models and 8 in humans. Three studies assessed bedaquiline's efficacy both in vitro and in vivo. Due to data paucity, an ECOFF value of 0.5 mg/mL was estimated for Mycobacterium abscessus only. Meta-analysis of animal studies showed a 1.86× reduction in bacterial load in bedaquiline-treated versus no treatment within 30 days. In humans, bedaquiline-including regimens were effective in treating NTM extrapulmonary infection but not pulmonary infection.

CONCLUSIONS

Bedaquiline demonstrated strong antibacterial activity against various NTM species and is a promising drug to treat NTM infections. However, data on the genomic mutations associated with bedaquiline resistance were scarce, preventing statistical analyses for most mutations and NTM species. Further studies are urgently needed to better inform treatment strategies.

Promising antibacterial efficacy of arenicin peptides against the emerging opportunistic pathogen Mycobacterium abscessus

BACKGROUND

Mycobacterium abscessus, a fast-growing non-tuberculous mycobacterium, is an emerging opportunistic pathogen responsible for chronic bronchopulmonary infections in people with respiratory diseases such as cystic fibrosis (CF). Due to its intrinsic polyresistance to a wide range of antibiotics, most treatments for M. abscessus pulmonary infections are poorly effective. In this context, antimicrobial peptides (AMPs) active against bacterial strains and less prompt to cause resistance, represent a good alternative to conventional antibiotics. Herein, we evaluated the effect of three arenicin isoforms, possessing two or four Cysteines involved in one (Ar-1, Ar-2) or two disulfide bonds (Ar-3), on the in vitro growth of M. abscessus.

METHODS

The respective disulfide-free AMPs, were built by replacing the Cysteines with alpha-amino-n-butyric acid (Abu) residue. We evaluated the efficiency of the eight arenicin derivatives through their antimicrobial activity against M. abscessus strains, their cytotoxicity towards human cell lines, and their hemolytic activity on human erythrocytes. The mechanism of action of the Ar-1 peptide was further investigated through membrane permeabilization assay, electron microscopy, lipid insertion assay via surface pressure measurement, and the induction of resistance assay.

RESULTS

Our results demonstrated that Ar-1 was the safest peptide with no toxicity towards human cells and no hemolytic activity, and the most active against M. abscessus growth. Ar-1 acts by insertion into mycobacterial lipids, resulting in a rapid membranolytic effect that kills M. abscessus without induction of resistance.

CONCLUSION

Overall, the present study emphasized Ar-1 as a potential new alternative to conventional antibiotics in the treatment of CF-associated bacterial infection related to M. abscessus.

Recent Development of DNA Gyrase Inhibitors: An Update

Antibiotic or antimicrobial resistance is an urgent global public health threat that occurs when bacterial or fungal infections do not respond to the drug regimen designed to treat these infections. As a result, these microbes are not evaded and continue to grow. Antibiotic resistance against natural and already-known antibiotics like Ciprofloxacin and Novobiocin can be overcome by developing an agent that can act in different ways. The success of agents like Zodiflodacin and Zenoxacin in clinical trials against DNA gyrase inhibitors that act on different sites of DNA gyrase has resulted in further exploration of this target. However, due to the emergence of bacterial resistance against these targets, there is a great need to design agents that can overcome this resistance and act with greater efficacy. This review provides information on the synthetic and natural DNA gyrase inhibitors that have been developed recently and their promising potential for combating antimicrobial resistance. The review also presents information on molecules that are in clinical trials and their current status. It also analysed the SAR studies and mechanisms of action of enlisted agents.

Prevalence and Characteristics of Non-tuberculous Mycobacteria (NTM) Infection in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation: a Systematic Review and Meta-analysis

PURPOSE

Non-tuberculous mycobacteria (NTM) infections in hematopoietic stem cell transplantation (HSCT) recipients represent a diagnostic and therapeutic challenge. Here, we aimed to review and analyze current literature on incidence, clinical presentation, and outcome of NTM infection after allogeneic HSCT.

METHODS

We performed a systematic review and meta-analysis of available literature regarding NTM infection in children and adults receiving allogeneic HSCT.

RESULTS

We identified 56 articles eligible for the analysis. Among 15 studies, describing 15,798 allogeneic HSCT, we estimated a prevalence of 1.26% (95% CI 0.72, 1.93) of NTM after transplant. Analysis of 175 patients with NTM infection showed a median time of diagnosis of 318 days after HSCT, an increased prevalence in adults (82.9%), and a most frequent pulmonary involvement (44%). Comparison between children and adults revealed an earlier post-transplant disease onset (median 130 days vs 287 days) and most frequent non-pulmonary presentation in children. A vast heterogeneity of therapeutic approach reflected the lack of universal recommendations regarding drug combination and duration of therapy. Overall, NTM-related mortality accounted for 33% in this systematic review.

CONCLUSION

Although rare, NTM infections can complicate post-transplant course with a high mortality rate in children and adults. The lack of prospective studies and guidelines prevents identification of risk factors and therapeutic recommendations.

Intracellular and in vivo activities of oxazolidinone drugs against Mycobacterium avium complex infection

The prevalence of Mycobacterium avium complex-pulmonary disease (MAC-PD) has become a growing concern worldwide, and current treatments involving macrolides (clarithromycin [CLR] or azithromycin), ethambutol, and rifampicin have limited success, highlighting the need for better therapeutic strategies. Recently, oxazolidinone drugs have been identified as novel anti-tuberculosis drugs effective against drug-resistant M. tuberculosis. However, the effects of these drugs against MAC are still controversial due to limited data. Here, we first evaluated the intracellular anti-MAC activities of two oxazolidinone drugs, linezolid (LZD) and delpazolid (DZD), against 10 macrolide-susceptible MAC strains and one macrolide-resistant M. avium strain in murine bone marrow-derived macrophages (BMDMs) and found that both drugs demonstrated similar potential. The synergistic efficacies with CLR were then determined in a chronic progressive MAC-PD murine model by initiating a 4-week treatment at 8 weeks post-infection. Upon assessment of bacterial burdens and inflamed lesions, oxazolidinone drugs exhibited no anti-MAC effect, and there was no significant difference in the synergistic effect of CLR between LZD and DZD. These findings suggest that oxazolidinone drugs inhibit intracellular bacterial growth, even against macrolide-resistant MAC, but their clinical application requires further consideration.

Evaluating anti-GPL-core IgA as a diagnostic tool for non-tuberculous mycobacterial infections in Thai patients with high antibody background

Diagnosis of non-tuberculous mycobacterial (NTM) infection is difficult due to low sensitivity and time-consuming laboratory tests. Current serological assays fail in tropical countries due to high antibody background. This study aimed to investigate an appropriate method for detecting anti-glycopeptidolipid (GPL)-core antibodies to diagnose NTM infection in Thailand. Heparinized plasma samples were collected from 20 patients with NTM-pulmonary disease (NTM-PD) and 22 patients with disseminated NTM (dNTM) for antibody detection by ELISA. The results were compared with those from patients with tuberculosis, other bacterial pulmonary infections and healthy controls. Among the different antibody isotypes, anti-GPL-core IgA exhibited the highest suitability. Therefore, anti-GPL-core IgA and its subclass IgA2 were further investigated. A significant increase in antibody levels was observed during the active infection stage, whereas NTM-PD with culture conversion at the 6-month follow-up showed reduced IgA levels. The diagnostic cut-off for IgA and IgA2 was newly defined as 1.4 and 1.0 U/ml, respectively. Using our IgA cut-off, the sensitivity and specificity for diagnosing NTM-PD were 77.3% and 81.4%, respectively. The new IgA cut-off demonstrated significantly improved specificity compared to the manufacturer's cut-off. Thus, serological detection of anti-GPL-core IgA, with a cut-off of 1.4 U/ml, can be a valuable tool for supporting NTM diagnosis in Thailand.

Unveiling the Clinical Diversity in Nontuberculous Mycobacteria (NTM) Infections: A Comprehensive Review

Once considered rare, nontuberculous mycobacterial (NTM) infections have garnered increasing attention in recent years. This comprehensive review provides insights into the epidemiology, clinical diversity, diagnostic methods, treatment strategies, prevention, and emerging research trends in NTM infections. Key findings reveal the global prevalence of NTM infections, their diverse clinical presentations affecting respiratory and extra-pulmonary systems, and the diagnostic challenges addressed by advances in microbiological, radiological, and immunological methods. Treatment complexities, especially drug resistance and patient adherence, are discussed, along with the vulnerability of special populations. The importance of early detection and management is underscored. Prospects in NTM research, including genomics, diagnostics, drug development, and multidisciplinary approaches, promise to enhance our understanding and treatment of these infections. This review encapsulates the multifaceted nature of NTM infections, offering a valuable resource for clinicians, researchers, and public health professionals.

Building a model for the differential diagnosis of non-tuberculous mycobacterial lung disease and pulmonary tuberculosis: A case-control study based on immunological and radiological features

BACKGROUND

Although the incidence of non-tuberculous mycobacterial pulmonary disease (NTM-PD) is increasing annually, it is easily misdiagnosed as pulmonary tuberculosis (PTB). This study aimed to screen and identify the immunological and radiological characteristics that differentiate NTM-PD from PTB and to construct a discriminatory diagnostic model for NTM-PD, providing new tools for its differential diagnosis.

METHODS

Hospitalised patients diagnosed with NTM-PD or PTB between January 2019 and June 2023 were included in the study. Immunological and radiological characteristics were compared between the two groups. Based on the selected differential features, a logistic regression algorithm was used to construct a discriminatory diagnostic model for NTM-PD, and its diagnostic performance was preliminarily analysed.

RESULTS

Patients with NTM-PD were significantly older than those with PTB and the tuberculosis-specific interferon-gamma release assay (TB-IGRA) positivity rate was significantly lower in the NTM-PD group. Moreover, the absolute counts of total T lymphocytes, CD4+ T lymphocytes, CD8+ T lymphocytes, NK cells, and B lymphocytes were significantly lower in patients with NTM-PD and PTB than in healthy controls. Additionally, patients with NTM-PD had a significantly lower absolute count of B lymphocytes than the PTB group. Radiological analysis revealed significant differences between patients with NTM-PD and PTB in terms of cavity wall thickness, bronchial dilation, lung consolidation, pulmonary nodule size, pulmonary emphysema, lung bullae, lymph node calcification, pleural effusion, mediastinal and hilar lymphadenopathy, and the tree-in-bud sign. Bronchial dilation was identified as the predominant risk factor of NTM-PD, whereas TB-IGRA positivity, lymph node calcification, pleural effusion, and mediastinal and hilar lymphadenopathies were protective factors. Based on this, we constructed a discriminatory diagnostic model for NTM-PD. Its receiver operating characteristic curve demonstrated good diagnostic performance, with an area under the curve of 0.938. At the maximum Youden index of 0.746, the sensitivity and specificity were 0.835 and 0.911, respectively.

CONCLUSIONS

Patients with NTM-PD and PTB exhibited impaired humoral and cellular immune functions as well as significant differences in radiological features. The constructed NTM-PD diagnostic model demonstrated good diagnostic performance. This study provides a new tool for the differential diagnosis of NTM-PD.

The Homologous Gene of Chromosomal Virulence D (chvD) Presents High Resolution as a Novel Biomarker in Mycobacterium Species Identification

Objective

To evaluate the resolution of chromosomal virulence D (chvD) as a novel marker for mycobacterial species identification.

Methods

A segment of chvD (652 bp) was amplified by PCR from 63 mycobacterial reference strains, 163 nontuberculous mycobacterial clinical isolates, and 16 M. tuberculosis complex (MTBC) clinical isolates. A phylogenetic tree based on the reference strains was constructed by the neighbor-joining and IQ-tree methods. Comparative sequence analysis of the homologous chvD gene efficiently differentiated the species within the genus Mycobacterium. Slowly growing Mycobacterium (SGM) and rapidly growing Mycobacterium (RGM) were separated in the phylogenetic tree based on the chvD gene.

Results

The sequence discrepancies were obvious between M. kansasii and M. gastri, M. chelonae and M. abscessus, and M. avium and M. intracellulare, none of which could be achieved by 16S ribosomal RNA (rRNA) homologous gene alignment. Furthermore, chvD manifested larger intraspecies diversity among members of M. intracellulare subspecies. A total of 174 of the 179 (97.21%) clinical isolates, consisting of 12 mycobacterial species, were identified correctly by chvD blast. Four M. abscessus subsp. abscessus were identified as M. abscessus subsp. bolletii by chvD. MTBC isolates were indistinguishable, because they showed 99.84%-100% homology.

Conclusion

Homologous chvD is a promising gene marker for identifying mycobacterial species, and could be used for highly accurate species identification among mycobacteria.

Non-Mycobacteria Tuberculosis in Africa: A Literature Review

Background

Non-tuberculous mycobacteria (NTM) have been reported to cause pulmonary and extrapulmonary infections. These NTMs are often misdiagnosed as MTB due to their similar clinical presentations to tuberculosis, leading to inappropriate treatment and increased morbidity and mortality rates. This literature review aims to provide an overview of the prevalence, clinical manifestations, diagnosis, and management of NTM infections in Africa.

Methods

A systematic search was performed using various electronic databases including PubMed, Scopus, and Web of Science. The search was limited to studies published in the English language from 2000 to 2021. The following keywords were used: "non-tuberculous mycobacteria", "NTM", "Africa", and "prevalence". Studies that focused solely on the Mycobacterium tuberculosis complex or those that did not report prevalence rates were excluded. Data extraction was performed on eligible studies. Overall, a total of 32 studies met the inclusion criteria and were included in this review.

Results

In our literature review, we identified a total of 32 studies that reported non-tuberculosis mycobacteria (NTM) in Africa. The majority of these studies were conducted in South Africa, followed by Ethiopia and Nigeria. The most commonly isolated NTM species were Mycobacterium avium complex (MAC), Mycobacterium fortuitum, and Mycobacterium abscessus. Many of the studies reported a high prevalence of NTM infections among HIV-positive individuals. Other risk factors for NTM infection included advanced age, chronic lung disease, and previous tuberculosis infection.

Conclusion

In conclusion, this literature review highlights the significant burden of non-tuberculosis mycobacteria infections in Africa. The prevalence of these infections is high, and they are often misdiagnosed due to their similarity to tuberculosis. The lack of awareness and diagnostic tools for non-tuberculosis mycobacteria infections in Africa is a major concern that needs to be addressed urgently. It is crucial to improve laboratory capacity and develop appropriate diagnostic algorithms for these infections.

A Systematic Review of Nontuberculous Mycobacterium Infection Following Anterior Cruciate Ligament Reconstruction

Although infection following anterior cruciate ligament (ACL) reconstruction is rare, these cases have potentially catastrophic ramifications. Nontuberculous mycobacteria (NTM) are ubiquitous, located in the water supply and soil. Our objective was to review the literature to characterize NTM infection following ACL reconstruction.

Methods

A database search was performed for arthroscopic ACL reconstructions that resulted in a postoperative diagnosis of NTM infection.

Results

The literature search returned 6 case reports that met the inclusion criteria. The initial postoperative presentation occurred after 3 to 52 weeks, which is consistent with reports of postoperative NTM infection.

Conclusions

The common indolent course of NTM infection hinders prompt diagnosis and treatment. Organism susceptibility testing is crucial for effective treatment and limiting unnecessary antibiotic exposure.

Clinical Relevance

The duration of medical treatment for NTM infection is 4 to 6 months, depending on the severity of disease and species. Based on the aggregate literature, we recommend removal of local implants if the infection is localized and without articular involvement. However, in cases of articular involvement, all fixation and graft material should be removed.

Immunogenicity and protection against Mycobacterium avium with a heterologous RNA prime and protein boost vaccine regimen

Prophylactic efficacy of two different delivery platforms for vaccination against Mycobacterium avium (M. avium) were tested in this study; a subunit and an RNA-based vaccine. The vaccine antigen, ID91, includes four mycobacterial antigens: Rv3619, Rv2389, Rv3478, and Rv1886. We have shown that ID91+GLA-SE is effective against a clinical NTM isolate, M. avium 2-151 smt. Here, we extend these results and show that a heterologous prime/boost strategy with a repRNA-ID91 (replicon RNA) followed by protein ID91+GLA-SE boost is superior to the subunit protein vaccine given as a homologous prime/boost regimen. The repRNA-ID91/ID91+GLA-SE heterologous regimen elicited a higher polyfunctional CD4+ TH1 immune response when compared to the homologous protein prime/boost regimen. More significantly, among all the vaccine regimens tested only repRNA-ID91/ID91+GLA-SE induced IFN-γ and TNF-secreting CD8+ T cells. Furthermore, the repRNA-ID91/ID91+GLA-SE vaccine strategy elicited high systemic proinflammatory cytokine responses and induced strong ID91 and an Ag85B-specific humoral antibody response a pre- and post-challenge with M. avium 2-151 smt. Finally, while all prophylactic prime/boost vaccine regimens elicited a degree of protection in beige mice, the heterologous repRNA-ID91/ID91+GLA-SE vaccine regimen provided greater pulmonary protection than the homologous protein prime/boost regimen. These data indicate that a prophylactic heterologous repRNA-ID91/ID91+GLA-SE vaccine regimen augments immunogenicity and confers protection against M. avium.

Potential Use of Mycobacterium paragordonae for Antimycobacterial Drug Screening Systems

Our recent genome-based study indicated that Mycobacterium paragordonae (Mpg) has evolved to become more adapted to an intracellular lifestyle within free-living environmental amoeba and its enhanced intracellular survival within Acanthamoeba castellanii was also proved. Here, we sought to investigate potential use of Mpg for antimycobacterial drug screening systems. Our data showed that Mpg is more susceptible to various antibiotics compared to the close species M. marinum (Mmar) and M. gordonae, further supporting its intracellular lifestyle in environments, which would explain its protection from environmental insults. In addition, we developed two bacterial whole-cell-based drug screening systems using a recombinant Mpg stain harboring a luciferase reporter vector (rMpg-LuxG13): one for direct application to rMpg-LuxG13 and the other for drug screening via the interaction of rMpg-LuxG13 with A. castellanii. Direct application to rMpg-LuxG13 showed lower inhibitory concentration 50 (IC50) values of rifampin, isoniazid, clarithromycin, and ciprofloxacin against Mpg compared to Mmar. Application of drug screening system via the interaction of rMpg-LuxG13 with A. castellanii also exhibited lower IC50 values for rifampin against Mpg compared to Mmar. In conclusion, our data indicate that Mpg is more susceptible to various antibiotics than other strains. In addition, our data also demonstrate the feasibility of two whole cell-based drug screening systems using rMpg-LuxG13 strain for the discovery of novel anti-mycobacterial drugs.

Noncanonical Mismatch Repair Protein NucS Modulates the Emergence of Antibiotic Resistance in Mycobacterium abscessus

NucS/EndoMS-dependent noncanonical mismatch repair (MMR) ensures the stability of genomic DNA in mycobacteria and acts as a guardian of the genome by preventing the accumulation of point mutations. In order to address whether the inactivation of noncanonical MMR could increase the acquisition of drug resistance by mutation, a ΔnucS strain was constructed and explored in the emerging pathogen Mycobacterium abscessus. Deletion of nucS resulted in a mutator phenotype with increased acquisition of resistance to macrolides and aminoglycosides, the two main groups of antimycobacterial agents for M. abscessus treatment, and also to second-line drugs such as fluoroquinolones. Inactivation of the noncanonical MMR in M. abscessus led to increases of 10- to 22-fold in the appearance of spontaneous mutants resistant to the macrolide clarithromycin and the aminoglycosides amikacin, gentamicin, and apramycin, compared with the wild-type strain. Furthermore, emergence of fluoroquinolone (ciprofloxacin) resistance was detected in a nucS-deficient strain but not in a wild-type M. abscessus strain. Acquired drug resistance to macrolides and aminoglycosides was analyzed through sequencing of the 23S rRNA gene rrl and the 16S rRNA gene rrs from independent drug-resistant colonies of both strains. When the acquisition of clarithromycin resistance was examined, a different mutational profile was detected in the M. abscessus ΔnucS strain compared with the wild-type one. To summarize, M. abscessus requires the NucS-dependent noncanonical MMR pathway to prevent the emergence of drug-resistant isolates by mutation. To our knowledge, this is the first report that reveals the role of NucS in a human pathogen, and these findings have potential implications for the treatment of M. abscessus infections. IMPORTANCE Chronic infections caused by M. abscessus are an emerging challenge in public health, posing a substantial health and economic burden, especially in patients with cystic fibrosis. Treatment of M. abscessus infections with antibiotics is particularly challenging, as its complex drug resistance mechanisms, including constitutive resistance through DNA mutation, lead to high rates of treatment failure. To decipher the evolution of antibiotic resistance in M. abscessus, we studied NucS-dependent noncanonical MMR, a unique DNA repair pathway involved in genomic maintenance. Inactivation of NucS is linked to the increase of DNA mutations (hypermutation), which can confer drug resistance. Our analysis detected increased acquisition of mutations conferring resistance to first-line and second-line antibiotics. We believe that this study will improve the knowledge of how this pathogen could evolve into an untreatable infectious agent, and it uncovers a role for hypermutators in chronic infectious diseases under antibiotic pressure.

In Vitro Profiling of the Synthetic RNA Polymerase Inhibitor MMV688845 against Mycobacterium abscessus

In a library screen of tuberculosis-active compounds for anti-Mycobacterium abscessus activity, we previously identified the synthetic phenylalanine amide MMV688845. In Mycobacterium tuberculosis, this class was shown to target the RpoB subunit of RNA polymerase, engaging a binding site distinct from that of the rifamycins. Due to its bactericidal activity, rifampicin is a key drug for the treatment of tuberculosis (TB). However, this natural product shows poor potency against M. abscessus due to enzymatic modification, and its clinical use is limited. Here, we carried out in vitro microbiological profiling of MMV688845 to determine its attractiveness as a substrate for a chemistry optimization project. MMV688845 was broadly active against the M. abscessus complex, displayed bactericidal against M. abscessus in vitro, and in a macrophage infection model showed additivity with commonly used anti-M. abscessus antibiotics and synergy with macrolides. Analyses of spontaneous resistant mutants mapped resistance to RpoB, confirming that MMV688845 has retained its target in M. abscessus. Together with its chemical tractability, the presented microbiological profiling reveals MMV688845 as an attractive starting point for hit-to-lead development to improve potency and to identify a lead compound with demonstrated oral in vivo efficacy. IMPORTANCE Infections with nontuberculous mycobacteria are an increasing health problem, and only a few new drug classes show activity against these multidrug-resistant bacteria. Due to insufficient therapy options, the development of new drug leads is necessary and should be advanced. The lead compound MMV688845, a substance active against M. abscessus complex, was characterized in depth. In various assays, it showed activity against M. abscessus, synergy with other antibiotics, and bactericidal effects.

Vaccination inducing durable and robust antigen-specific Th1/Th17 immune responses contributes to prophylactic protection against Mycobacterium avium infection but is ineffective as an adjunct to antibiotic treatment in chronic disease

Mycobacterium avium complex (MAC) causing pulmonary disease in humanshas emerged worldwide. Thus, effective strategies simultaneously aiming to prevent MAC infection and accelerate therapeutic efficacy are required. To this end, subunit vaccine-induced protection against a well-defined virulent Mycobacterium avium (Mav) isolate was assessed as a preventative and therapeutic modality in murine models. Mav-derived culture filtrate antigen (CFA) was used as a vaccine antigen with glucopyranosyl lipid A stable emulsion (GLA-SE) or GLA-SE plus cyclic-di-GMP (GLA-SE/CDG), and we compared the immunogenicities, protective efficacies and immune correlates. Interestingly, CFA+GLA-SE/CDG immunization induced greater CFA-specific Th1/Th17 responses in both the lung and spleen than among the tested groups. Consequently, protective efficacy was optimally achieved with CFA+GLA-SE/CDG by significantly reducing bacterial loads along with long-lasting maintenance of antigen-specific Th1/Th17 cytokine-producing multifunctional T cell responses and relevant cytokine productions. Thus, we employed this subunit vaccine as an adjunct to antibiotic treatment. However, this vaccine was ineffective in further reducing bacterial loads. Collectively, our study demonstrates that strong Mav CFA-specific Th1/Th17 responses are critical for preventative protection against Mav infection but may be ineffective or even detrimental in an established and progressive chronic disease, indicating that different approaches to combating Mav infection are necessary according to vaccination purposes.

Clinical characteristics of nontuberculous mycobacterial disease in people living with HIV/AIDS in South Korea: A multi-center, retrospective study

With the introduction of combination antiretroviral therapy (cART), the prevalence of human immunodeficiency virus (HIV)-associated nontuberculous mycobacteria (NTM) disease has declined. However, NTM diseases still occur in people living with HIV/acquired immunodeficiency syndrome (AIDS) (PLWHA). We analysed the clinical and microbiological features of NTM diseases in PLWHA in South Korea. PLWHA who were diagnosed with NTM diseases between January 2000 and March 2021 were retrospectively enrolled from five different hospitals in South Korea. Data on baseline demographics, HIV status, CD4+ T cell counts, viral load, past and current cART regimens, isolated NTM species, results of antimicrobial susceptibility tests, treatment regimens, and outcomes were collected by reviewing medical records. A total of 34 cases of NTM in PLWHA were included. Pulmonary and extrapulmonary NTM diseases accounted for 58.8% (n = 20) and 41.2% (n = 14), respectively. The lymph node was the most common site of extrapulmonary NTM disease (64.3%). The age at the time of NTM disease diagnosis was younger in the extrapulmonary NTM group than in the pulmonary NTM group (37.0 vs. 49.0 years). Mean CD4+ T cell counts at the time of NTM disease diagnosis was 186.6 cells/μL (range: 1–1394). Nine patients (26.5%) had fully suppressed viral loads at the time of NTM disease diagnosis. Mycobacterium avium complex (MAC) was the most common species found, followed by M. intracellulare and M. kansasii. MAC isolates were all susceptible to clarithromycin, but the rates of non-susceptibility to moxifloxacin, linezolid, ethambutol, and rifampin were 75%, 37.5%, 12.5%, and 12.5%, respectively. The average duration of treatment was 17 months and the mortality rate was 8.8%. NTM diseases may occur in PLWHA, even with completely suppressed viral loads. The identified clinical features of NTM diseases are essential for its clinical management in South Korea.