Macrolide treatment for Mycobacterium abscessus and Mycobacterium massiliense infection and inducible resistance

Limited predictive power of known resistance genes for phenotypic drug resistance in clinical Mycobacterium abscessus complex from Beijing in China

Mycobacterium abscessus complex (MABC) is an emerging pathogen with intrinsic multidrug resistance. Genomic sequencing technology has been widely applied to predict bacterial resistance in other bacteria, but the catalog of known resistance-determining genes to explain phenotypic resistance in the MABC is incomplete for many antibiotics. Eighty-one MABC strains were isolated from sputum samples of patients with pulmonary disease in the Beijing Chest Hospital. All isolates were tested for minimum inhibitory concentrations (MICs) to eight antibiotics and underwent whole-genome sequencing (WGS). Of the total 81 MABC isolates, six strains exhibited clarithromycin (CLM) resistance by day 3 in culture, but only one (16.7%, 1/6) contained a mutation in the rrl gene. All M. abscessus strains contained the erm (41)28T (100.0%, 49/49) polymorphism and exhibited CLM-induced resistance after 14 days in culture. Of the 61 imipenem-resistant strains, 12 (19.7%, 12/61) had mutations in the bla gene. Although there were four (4.9%) amikacin-resistant, nine (11.1%) linezolid-resistant, eight (9.9%) clofazimine-resistant, 23 (28.4%) bedaquiline-resistant, and 27 (33.3%) cefoxitin-resistant strains, no known mutations associated with resistance to these antibiotics were found. These results suggest that the explanatory power of known resistance genes for clinical MABC resistance is limited and that other unidentified genes or novel resistance mechanisms may be involved.

Macrolide resistance in Mycobacterium abscessus: current insights and future perspectives

Mycobacterium abscessus (MAB) is a rapidly growing, non-tuberculous mycobacterium that has emerged as a significant pathogen in both pulmonary and extrapulmonary infections. It is rising in prevalence, especially among individuals with underlying lung conditions such as cystic fibrosis and chronic obstructive pulmonary disease, highlighting its growing clinical importance. The treatment of MAB infections is notoriously challenging due to intrinsic resistance to many antibiotics and low cure rates, typically <50%. Macrolides are a cornerstone in the treatment of MAB infections because regimens that include effective macrolide therapy are associated with higher cure rates. However, MAB possesses intrinsic and acquired drug resistance mechanisms against macrolides, complicating drug susceptibility testing and selection of highly effective treatment regimens. This review aims to provide a summary of the current understanding of macrolide resistance mechanisms in MAB. We explored the epidemiology of resistance in different countries and the molecular mechanisms involved. We have highlighted the variability in sensitivity of existing markers to predict phenotypic macrolide drug resistance across different countries, suggesting the involvement of unknown resistance mechanisms. By synthesizing current knowledge and identifying gaps in the literature, this review seeks to inform clinical practice and guide future research efforts in the fight against MAB drug resistance.

Cyclophostin and Cyclipostins analogues counteract macrolide-induced resistance mediated by erm(41) in Mycobacterium abscessus

BACKGROUND

Mycobacterium abscessus is an emerging pathogen causing severe pulmonary infections, particularly in individuals with underlying conditions, such as cystic fibrosis or chronic obstructive pulmonary disease. Macrolides, such as clarithromycin (CLR) or azithromycin (AZM), represent the cornerstone of antibiotherapy against the M. abscessus species. However, prolonged exposure to these macrolides can induce of Erm(41)-mediated resistance, limiting their spectrum of activity and leading to therapeutic failure. Therefore, inhibiting Erm(41) could thwart this resistance mechanism to maintain macrolide susceptibility, thus increasing the rate of treatment success. In our previous study, the Erm(41) methyltransferase was identified as a possible target enzyme of Cyclipostins and Cyclophostin compounds (CyC).

METHODS

Herein, we exploited this feature to evaluate the in vitro activity of CLR and AZM in combination with different CyC via the checkerboard assay on macrolide-susceptible and induced macrolide-resistant M. abscessus strains selected in vitro following exposure CLR and AZM.

RESULTS

Our results emphasize the use of the CyC to prevent/overcome Erm(41)‑induced resistance and to restore macrolide susceptibility.

CONCLUSION

This work should expand our therapeutic arsenal in the fight against a antibioticresistant mycobacterial species and could provide the opportunity to revisit the therapeutic regimen for combating M. abscessus pulmonary infections in patients, and particularly in erm(41)-positive strains.

Current challenges in pulmonary nontuberculous mycobacterial infection: a case series with literature review

BACKGROUND

The prevalence of nontuberculous mycobacteria pulmonary disease (NTM-PD), particularly caused by Mycobacterium avium complex (MAC), is rising due to improved diagnostics, increased awareness, and more susceptible populations. NTM-PD significantly affects quality of life and imposes substantial economic costs. Understanding its clinical features, risk factors, and treatment challenges is vital for enhancing patient outcomes.

PATIENTS AND METHODS

A convenience sample from the University of Connecticut Health Center and Wayne State University involving patients with NTM-PD from 2021 to 2024 was studied retrospectively. Cases were selected to demonstrate typical diagnostic and treatment challenges, followed by a multidisciplinary roundtable discussion to examine patient-centered care strategies.

RESULTS

Analysis of six cases pinpointed chronic lung conditions and immunomodulatory therapy as key risk factors. Standard treatment, involving extensive multi-drug regimens, frequently results in poor adherence due to side effects and complex management requirements. The discussions underlined the importance of a customized, interdisciplinary approach to improve treatment effectiveness and patient quality of life.

CONCLUSIONS

NTM-PD is an escalating public health issue with notable clinical and economic consequences. Managing this disease effectively demands a comprehensive, patient-centered strategy that includes precise diagnosis, flexible treatment plans, and collaborative care.

Mycobacterium abscessus extracellular vesicles increase mycobacterial resistance to clarithromycin in vitro

Nontuberculous Mycobacteria (NTM) are a group of emerging bacterial pathogens that have been identified in cystic fibrosis (CF) patients with microbial lung infections. The treatment of NTM infection in CF patients is challenging due to the natural resistance of NTM species to many antibiotics. Mycobacterium abscessus is one of the most common NTM species found in the airways of CF patients. In this study, we characterized the extracellular vesicles (EVs) released by drug-sensitive M. abscessus untreated or treated with clarithromycin (CLR), one of the frontline anti-NTM drugs. Our data show that exposure to CLR increases mycobacterial protein trafficking into EVs as well as the secretion of EVs in culture. Additionally, EVs released by CLR-treated M. abscessus increase M. abscessus resistance to CLR when compared to EVs from untreated M. abscessus. Proteomic analysis further indicates that EVs released by CLR-treated M. abscessus carry an increased level of 50S ribosomal subunits, the target of CLR. Taken together, our results suggest that EVs play an important role in M. abscessus resistance to CLR treatment.

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.

[A pharmacologic approach to treatment of Mycobacterium abscessus pulmonary disease]

Mycobacterium abscessus is a fast-growing non-tuberculous mycobacteria complex causing pulmonary infections, comprising the subspecies abscessus, massiliense and bolletii. Differences are based predominantly on natural inducible macrolide resistance, active in most Mycobacterium abscessus spp abscessus species and in Mycobacterium abscessus spp bolletii but inactive in Mycobacterium abscessus spp massiliense. Therapy consists in long-term treatment, combining multiple antibiotics. Prognosis is poor, as only 40% of patients experience cure. Pharmacodynamic and pharmacokinetic data on M. abscessus have recently been published, showing that therapy ineffectiveness might be explained by intrinsic bacterial resistance (macrolides…) and by the unfavorable pharmacokinetics of the recommended antibiotics. Other molecules and inhaled antibiotics are promising.

Catheter-associated Mycobacterium intracellulare biofilm infection in C3HeB/FeJ mice

Non-tuberculosis mycobacterial (NTM) diseases are steadily increasing in prevalence and mortality worldwide. Mycobacterium avium and M. intracellulare, the two major pathogens of NTM diseases, are resistant to antibiotics, and chlorine, necessitating their capacity to survive in natural environments (e.g. soil and rivers) and disinfected municipal water. They can also form biofilms on artificial surfaces to provide a protective barrier and habitat for bacilli, which can cause refractory systemic disseminated NTM disease. Therefore, preventing biofilm formation by these pathogens is crucial; however, not many in vivo experimental systems and studies on NTM biofilm infection are available. This study develops a mouse model of catheter-associated systemic disseminated disease caused by M. intracellulare that reproduces the pathophysiology of catheter-associated infections observed in patients undergoing peritoneal dialysis. In addition, the bioluminescence system enabled noninvasive visualization of the amount and distribution of bacilli in vivo and conveniently examine the efficacy of antimicrobials. Furthermore, the cellulose-based biofilms, which were extensively formed in the tissue surrounding the catheter insertion site, reduced drug therapy effectiveness. Overall, this study provides insights into the cause of the drug resistance of NTM and may guide the development of new therapies for NTM diseases.

Additive Effects of Cyclic Peptide [R4W4] When Added Alongside Azithromycin and Rifampicin against Mycobacterium avium Infection

Mycobacterium avium (M. avium), a type of nontuberculous mycobacteria (NTM), poses a risk for pulmonary infections and disseminated infections in immunocompromised individuals. Conventional treatment consists of a 12-month regimen of the first-line antibiotics rifampicin and azithromycin. However, the treatment duration and low antibiotic tolerability present challenges in the treatment of M. avium infection. Furthermore, the emergence of multidrug-resistant mycobacterium strains prompts a need for novel treatments against M. avium infection. This study aims to test the efficacy of a novel antimicrobial peptide, cyclic [R4W4], alongside the first-line antibiotics azithromycin and rifampicin in reducing M. avium survival. Colony-forming unit (CFU) counts were assessed after treating M. avium cultures with varying concentrations of cyclic [R4W4] alone or in conjunction with azithromycin or rifampicin 3 h and 4 days post-treatment. M. avium growth was significantly reduced 4 days after cyclic [R4W4] single treatment. Additionally, cyclic [R4W4]-azithromycin and cyclic [R4W4]-rifampicin combination treatments at specific concentrations significantly reduced M. avium survival 3 h and 4 days post-treatment compared with single antibiotic treatment alone. These findings demonstrate cyclic [R4W4] as a potent treatment method against M. avium and provide insight into novel therapeutic approaches against mycobacterium infections.

Antibacterial activity of the novel compound Sudapyridine (WX-081) against Mycobacterium abscessus

Objective

This study aimed to investigate sudapyridine (WX-081) antibacterial activity against Mycobacterium abscessus in vitro and its effect on in vivo bacterial growth and host survival using a zebrafish model of M. abscessus infection.

Methods

WX-081 in vitro antibacterial activity was assessed based on growth inhibition of M. abscessus standard strain ATCC19977 and 36 clinical isolates. Maximum tolerated concentrations (MTCs) of WX-081, bedaquiline, and azithromycin and inhibition of M. abscessus growth were assessed in vivo after fluorescently labelled bacilli and drugs were injected into zebrafish. Bacterial counts were analysed using one-way ANOVA and fluorescence intensities of zebrafish tissues were analysed and expressed as the mean ± SE. Moreover, Kaplan-Meier survival analysis was conducted to assess intergroup differences in survival of M. abscessus-infected zebrafish treated with different drug concentrations using a log-rank test, with a p value <0.05 indicating a difference was statistically significant.

Results

Drug sensitivity testing of M. abscessus standard strain ATCC19977 and 36 clinical isolates revealed MICs ranging from 0.12-0.96 µg/mL and MIC50 and MIC90 values of 0.48 µg/mL and 0.96 µg/mL, respectively. Fluorescence intensities of M. abscessus-infected zebrafish tissues was lower after treatment with the WX-081 MTC (62.5 µg/mL) than after treatment with the azithromycin MTC (62.5 µg/mL) and the bedaquiline MTC (15.6 µg/mL). When the concentration of WX-081 increased from 1.95µg/mL to 1/8 MTC(7.81µg/mL), the survival rate of zebrafish at 4-9 dpf decreased from 90.00% to 81.67%.

Conclusion

WX-081 effectively inhibited M. abscessus growth in vitro and in vivo and prolonged survival of M. abscessus-infected zebrafish, thus indicating that WX-081 holds promise as a clinical treatment for M. abscessus infection.

Antibacterial activity of the novel oxazolidinone contezolid (MRX-I) against Mycobacterium abscessus

Objective

To evaluate contezolid (MRX-I) antibacterial activity against Mycobacterium abscessus in vitro and in vivo and to assess whether MRX-I treatment can prolong survival of infected zebrafish.

Methods

MRX-I inhibitory activity against M. abscessus in vitro was assessed by injecting MRX-I into zebrafish infected with green fluorescent protein-labelled M. abscessus. Thereafter, infected zebrafish were treated with azithromycin (AZM), linezolid (LZD) or MRX-I then maximum tolerated concentrations (MTCs) of drugs were determined based on M. abscessus growth inhibition using one-way ANOVA. Linear trend analysis of CFU counts and fluorescence intensities (mean ± SE values) was performed to detect linear relationships between MRX-I, AZM and LZD concentrations and these parameters.

Results

MRX-I anti-M. abscessus minimum inhibitory concentration (MIC) and MTC were 16 μg/mL and 15.6 μg/mL, respectively. MRX-I MTC-treated zebrafish fluorescence intensities were significantly lower than respective LZD group intensities (whole-body: 439040 ± 3647 vs. 509184 ± 23064, p < 0.01); head: 74147 ± 2175 vs. 95996 ± 8054, p < 0.05). As MRX-I concentration was increased from 0.488 μg/mL to 15.6 μg/mL, zebrafish whole-body, head and heart fluorescence intensities decreased. Statistically insignificant differences between the MRX-I MTC group survival rate (78.33%) vs. corresponding rates of the 62.5 μg/mL-treated AZM MTC group (88.33%, p > 0.05) and the 15.6 μg/mL-treated LZD MTC group (76.67%, p > 0.05) were observed.

Conclusion

MRX-I effectively inhibited M. abscessus growth and prolonged zebrafish survival when administered to M. abscessus-infected zebrafish, thus demonstrating that MRX-I holds promise as a clinical treatment for human M. abscessus infections.

A narrative review of nontuberculous mycobacterial pulmonary disease: microbiology, epidemiology, diagnosis, and management challenges

INTRODUCTION

Nontuberculous mycobacteria (NTM) are a diverse group of mycobacterial species that are ubiquitous in the environment. They are opportunistic pathogens that can cause a range of diseases, especially in individuals with underlying structural lung disease or compromised immune systems.

AREAS COVERED

This paper provides an in-depth analysis of NTM infections, including microbiology, environmental sources and transmission pathways, risk factors for disease, epidemiology, clinical manifestations and diagnostic approaches, guideline-based treatment recommendations, drugs under development, and management challenges.

EXPERT OPINION

Future approaches to the management of NTM pulmonary disease will require therapies that are well tolerated, can be taken for a shorter time period and perhaps less frequently, have few drug-drug interactions, and are active against the various strains of pathogens. As the numbers of infections increase, such therapies will be welcomed by clinicians and patients.

Mycobacterium abscessus Causes Highly Resistant Infection as a Breast Abscess

Mycobacterium abscessus is an increasing threat to public health due to its multi-drug resistance and increasing prevalence. The pathogen most commonly causes chronic respiratory infections, but it may also invade locally through the skin and soft tissue damage caused by trauma, piercings, or tattoos. A 58-year-old African American female presented with a five-month history of recurrent abscesses in the right breast. She had previously been treated with doxycycline and ceftriaxone injections at an outside clinic with minimal improvement. Following incision and drainage, cultures and susceptibilities showed M. abscessus infection with a high level of drug resistance. Due to financial barriers, the patient received a suboptimal antibiotic regimen and required multiple surgical procedures, resulting in only temporary wound healing. At the time of this report, the patient is recovering from her fourth incision and drainage, with cultures and susceptibilities pending and discussions of a total mastectomy. M. abscessus is a highly resistant bacteria capable of causing skin and soft tissue infections of the breast. Such infections may occur without an inciting event and require extensive surgical and antimicrobial management.

Peptidyl tRNA Hydrolase Is Required for Robust Prolyl-tRNA Turnover in Mycobacterium tuberculosis

Enzymes involved in rescuing stalled ribosomes and recycling translation machinery are ubiquitous in bacteria and required for growth. Peptidyl tRNA drop-off is a type of abortive translation that results in the release of a truncated peptide that is still bound to tRNA (peptidyl tRNA) into the cytoplasm. Peptidyl tRNA hydrolase (Pth) recycles the released tRNA by cleaving off the unfinished peptide and is essential in most bacteria. We developed a sequencing-based strategy called copper sulfate-based tRNA sequencing (Cu-tRNAseq) to study the physiological role of Pth in Mycobacterium tuberculosis (Mtb). While most peptidyl tRNA species accumulated in a strain with impaired Pth expression, peptidyl prolyl-tRNA was particularly enriched, suggesting that Pth is required for robust peptidyl prolyl-tRNA turnover. Reducing Pth levels increased Mtb's susceptibility to tRNA synthetase inhibitors that are in development to treat tuberculosis (TB) and rendered this pathogen highly susceptible to macrolides, drugs that are ordinarily ineffective against Mtb. Collectively, our findings reveal the potency of Cu-tRNAseq for profiling peptidyl tRNAs and suggest that targeting Pth would open new therapeutic approaches for TB. IMPORTANCE Peptidyl tRNA hydrolase (Pth) is an enzyme that cuts unfinished peptides off tRNA that has been prematurely released from a stalled ribosome. Pth is essential in nearly all bacteria, including the pathogen Mycobacterium tuberculosis (Mtb), but it has not been clear why. We have used genetic and novel biochemical approaches to show that when Pth levels decline in Mtb, peptidyl tRNA accumulates to such an extent that usable tRNA pools drop. Thus, Pth is needed to maintain normal tRNA levels, most strikingly for prolyl-tRNAs. Many antibiotics act on protein synthesis and could be affected by altering the availability of tRNA. This is certainly true for tRNA synthetase inhibitors, several of which are drug candidates for tuberculosis. We find that their action is potentiated by Pth depletion. Furthermore, Pth depletion results in hypersensitivity to macrolides, drugs that are not active enough under ordinary circumstances to be useful for tuberculosis.

In Vitro Antimicrobial Activities of Tigecycline, Eravacycline, Omadacycline, and Sarecycline against Rapidly Growing Mycobacteria

Infections caused by rapidly growing mycobacteria (RGM) have increased globally. Chemotherapy against these infections is challenging due to the minimal antimicrobial choices available. The main aim of this study was to evaluate the in vitro susceptibilities of four tetracyclines against different RGM species. The MICs of eravacycline (ERC), omadacycline (OMC), sarecycline (SAC), and tigecycline (TGC) against the reference strains of 27 RGM species and 121 RGM clinical isolates were determined by microtiter plate assay. The minimum bactericidal concentrations (MBCs) and cytotoxicities of these antibiotics were also tested. Except for SAC, the other three tetracyclines had MICs of ≤0.5 μg/mL against all 27 RGM reference strains. ERC generally presented the lowest MICs, with MIC₉₀s against the clinical isolates of Mycobacterium abscessus subsp. abscessus, Mycobacterium abscessus subsp. massiliense, and Mycobacterium fortuitum of 0.25 μg/mL, 0.25 μg/mL, and 0.06 μg/mL, respectively. TGC and OMC also showed equivalent in vitro inhibitory activities against the isolates, while the TGC MIC₉₀s for M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. fortuitum were lower than or equal to the OMC MIC₉₀s (1, 1, and 0.25 μg/mL versus 1, 2, and 2 μg/mL). In addition, the MIC₅₀s of three of the antibiotics for each species were always 2-fold lower than the corresponding MIC₉₀s. MBC and cytotoxicity assays indicated that all four tetracycline antibiotics tested were bacteriostatic agents with low toxicity to the THP-1 cell line. Tetracycline antibiotics are efficacious in RGM infection treatment, with omadacycline showing the best promise for clinical application due to its potent antimicrobial activity, safety, and convenient administration route. IMPORTANCE The global rise in antibiotic-resistant nontuberculous mycobacteria has prompted the urgent need for new antimicrobials, especially oral antibiotics. Currently, adverse effects have limited the use of tetracycline-class antibiotics, particularly tigecycline (TGC), in the treatment of rapidly growing mycobacteria (RGM). However, several new tetracycline-class antibiotics might overcome the limitations of TGC. We assessed the in vitro antibiotic susceptibilities of four tetracyclines (eravacycline, omadacycline, sarecycline, and tigecycline) against reference RGM strains and clinical isolates of different RGM species. We showed that three of these antibiotics (tigecycline, eravacycline, and omadacycline) might be efficacious in M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. fortuitum treatment. Furthermore, omadacycline was more promising for clinical application for M. abscessus infections as an oral drug, whereas sarecycline, which had the best safety parameters, should be considered a potential antibiotic for M. abscessus infections caused by susceptible strains. Our work underscores the possible clinical applications of tetracycline-class antibiotics in the treatment of RGM infections.

Rapid and Accurate Discrimination of Mycobacterium abscessus Subspecies Based on Matrix-Assisted Laser Desorption Ionization-Time of Flight Spectrum and Machine Learning Algorithms

Mycobacterium abscessus complex (MABC) has been reported to cause complicated infections. Subspecies identification of MABC is crucial for adequate treatment due to different antimicrobial resistance properties amid subspecies. However, long incubation days are needed for the traditional antibiotic susceptibility testing (AST). Delayed effective antibiotics administration often causes unfavorable outcomes. Thus, we proposed a novel approach to identify subspecies and potential antibiotic resistance, guiding early and accurate treatment. Subspecies of MABC isolates were determined by secA1, rpoB, and hsp65. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) spectra were analyzed, and informative peaks were detected by random forest (RF) importance. Machine learning (ML) algorithms were used to build models for classifying MABC subspecies based on spectrum. The models were validated by repeated five-fold cross-validation to avoid over-fitting. In total, 102 MABC isolates (52 subspecies abscessus and 50 subspecies massiliense) were analyzed. Top informative peaks including m/z 6715, 4739, etc. were identified. RF model attained AUROC of 0.9166 (95% CI: 0.9072-0.9196) and outperformed other algorithms in discriminating abscessus from massiliense. We developed a MALDI-TOF based ML model for rapid and accurate MABC subspecies identification. Due to the significant correlation between subspecies and corresponding antibiotics resistance, this diagnostic tool guides a more precise and timelier MABC subspecies-specific treatment.

Identification of and discrimination between the Mycobacterium abscessus complex and Mycobacterium avium complex directly from sputum using quadruplex real-time PCR

Introduction. Cystic fibrosis (CF) is a serious disease with multisystemic clinical signs that is easily and frequently complicated by bacterial infection. Recently, the prevalence of nontuberculous mycobacteria as secondary contaminants of CF has increased, with the Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MABSC) being the most frequently identified. The MABSC includes subspecies of significant clinical importance, mainly due to their resistance to antibiotics.Gap statement. Sensitive method for early detection and differentiation of MABSC members and MAC complex for use in routine clinical laboratories is lacking. A method based on direct DNA isolation from sputum, using standard equipment in clinical laboratories and allowing uncovering of possible sample inhibition (false negative results) would be required. The availability of such a method would allow accurate and accelerated time detection of MABSC members and their timely and targeted treatment.Aim. To develop a real time multiplex assay for rapid and sensitive identification and discrimination of MABSC members and MAC complex.Methodology. The method of DNA isolation directly from the sputum of patients followed by quadruplex real-time quantitative PCR (qPCR) detection was developed and optimised. The sensitivity and limit of detection (LOD) of the qPCR was determined using human sputum samples artificially spiked with a known amount of M. abscessus subsp. massiliense (MAM).Results. The method can distinguish between MAC and MABSC members and, at the same time, to differentiate between M. abscessus subsp. abscessus/subsp. bolletii (MAAb/MAB) and MAM. The system was verified using 61 culture isolates and sputum samples from CF and non-CF patients showing 29.5 % MAAb/MAB, 14.7 % MAM and 26.2 % MAC. The LOD was determined to be 1 490 MAM cells in the sputum sample with the efficiency of DNA isolation being 95.4 %. Verification of the qPCR results with sequencing showed 100 % homology.Conclusions. The developed quadruplex qPCR assay, which is preceded by DNA extraction directly from patients' sputum without the need for culturing, significantly improves and speeds up the entire process of diagnosing CF patients and is therefore particularly suitable for use in routine laboratories.

Atypical Mycobacteriosis Due to Mycobacterium abscessus subsp. massiliense: Our Experince

BACKGROUND

Members of Micobacterium. abscessus complex comprises three subspecies (M. abscessus subsp. Abscessus, M. abscessus subsp. Bolletii, and M. abscessus subsp. Massiliense) and are a rapid-growing nontuberculous mycobacteria present in different aquatic habitats and soil. It often causes a wide spectrum of infections involving pulmonary infections, surgical wound infections, and infections related to mesotherapy, catheters, hemodialysis devices, endocarditis, and disseminated infections in immunocompromised individuals.

METHODS

In this article we comment on the most relevant aspects of nine patients with skin lesions caused by M. abscessus subsp. massiliense infection. Clinical characteristics, histopathology, and molecular identification were performed.

RESULTS

The patients in the clinical cases presented a history of trauma, tattoos, and physical therapy techniques. The most common treatments were minocycline and clindamycin, doxycycline, ceftriaxone, cephalexin, moxifloxacin, rifampicin, and trimethoprim-sulfamethoxazole. The evolution of the treated patients was acceptable, except for one patient, who showed a partial improvement. M. massiliense were identified in all clinical cases using a species-specific PCR.

CONCLUSION

Our series consisted of nine cases of skin biopsies recorded in different years; for this reason, we do not have all the data necessary for a complete description, in particular in four cases, causing limitations in the manuscript, especially in the therapy used and the evolution of patients due to lack of follow-up.

Omadacycline for management of Mycobacterium abscessus infections: a review of its effectiveness, place in therapy, and considerations for use

The Mycobacterium abscessus complex (MABC) is a group of acid-fast, rapidly dividing non-tuberculous mycobacteria (NTM) that include a number of clinically important subspecies, including M. abscessus, M. bolletii, and M. massiliense. These organisms are prevalent in the environment and are primarily associated with human pulmonary or skin and skin structure infections (SSSI) but may cause more deep-seeded disseminated infections and bacteremia in the immunocompromised. Importantly, these NTM are resistant to most first-line anti-tuberculous agents and, due to intrinsic or acquired resistance, exhibit exceedingly low, variable, and geographically distinct susceptibilities to commonly used antibacterial agents including older tetracyclines, macrolides, aminoglycosides, cephalosporins, carbapenems, and sulfamethoxazole-trimethoprim. Omadacycline is a novel third-generation member of the tetracycline family of antibacterials that has recently been demonstrated to have potent anti-NTM effects and clinical efficacy against MABC, including M. abscessus. The purpose of this review is to present a comprehensive and up-to-date assessment on the body of literature on the role of omadacycline for M. abscessus infections. Specifically, the in vitro and in vivo microbiology, mechanisms of action, mechanisms of resistance, clinical pharmacokinetics, clinical efficacy, adverse effects, dosage and administration, and place in therapy of omadacycline in management of M. abscessus infections will be detailed.

Mycobacterium abscessus pathogenesis identified by phenogenomic analyses

The medical and scientific response to emerging and established pathogens is often severely hampered by ignorance of the genetic determinants of virulence, drug resistance and clinical outcomes that could be used to identify therapeutic drug targets and forecast patient trajectories. Taking the newly emergent multidrug-resistant bacteria Mycobacterium abscessus as an example, we show that combining high-dimensional phenotyping with whole-genome sequencing in a phenogenomic analysis can rapidly reveal actionable systems-level insights into bacterial pathobiology. Through phenotyping of 331 clinical isolates, we discovered three distinct clusters of isolates, each with different virulence traits and associated with a different clinical outcome. We combined genome-wide association studies with proteome-wide computational structural modelling to define likely causal variants, and employed direct coupling analysis to identify co-evolving, and therefore potentially epistatic, gene networks. We then used in vivo CRISPR-based silencing to validate our findings and discover clinically relevant M. abscessus virulence factors including a secretion system, thus illustrating how phenogenomics can reveal critical pathways within emerging pathogenic bacteria.

Mycobacterium abscessus: It's Complex

Mycobacterium abscessus (M. abscessus) is an opportunistic pathogen usually colonizing abnormal lung airways and is often seen in patients with cystic fibrosis. Currently, there is no vaccine available for M. abscessus in clinical development. The treatment of M. abscessus-related pulmonary diseases is peculiar due to intrinsic resistance to several commonly used antibiotics. The development of either prophylactic or therapeutic interventions for M. abscessus pulmonary infections is hindered by the absence of an adequate experimental animal model. In this review, we outline the critical elements related to M. abscessus virulence mechanisms, host-pathogen interactions, and treatment challenges associated with M. abscessus pulmonary infections. The challenges of effectively combating this pathogen include developing appropriate preclinical animal models of infection, developing proper diagnostics, and designing novel strategies for treating drug-resistant M. abscessus.

Management of Mycobacterium avium complex and Mycobacterium abscessus pulmonary disease: therapeutic advances and emerging treatments

Nontuberculous mycobacterial pulmonary disease (NTM-PD) remains a challenging condition to diagnose and treat effectively. Treatment of NTM-PD is prolonged, frequently associated with adverse effects and has variable success. In this review, we consider the factors influencing clinicians when treating NTM-PD and discuss outcomes from key studies on the pharmacological management of Mycobacterium avium complex pulmonary disease and M. abscessus pulmonary disease. We highlight issues relating to treatment-related toxicity and provide an overview of repurposed and emerging therapies for NTM-PD.

Highly Discriminative Genotyping of Mycobacterium abscessus Complex Using a Set of Variable Number Tandem Repeats in China

In this study, our aims were to comparatively analyze the power of variable number tandem repeat (VNTR) typing to discriminate isolates within subspecies and to identify a potential genetic marker for better molecular typing of Mycobacterium abscessus complex (MABC) strains. A total of 103 clinical MABC isolates were collected from a nationwide cross-sectional study in China. Eighteen VNTR loci were chosen to genotype the MABC isolates. Of the 103 clinical MABC isolates, there were 76 (73.8%) M. abscessus subsp. abscessus (MAA) and 27 (26.2%) M. abscessus subsp. massiliense (MAM) isolates. Among the patients with MAA lung diseases, the percentage of patients older than 45 years (67.1%) was significantly higher than that of patients with MAM lung diseases [33.3%, adjusted odds ratio (aOR) = 0.36, 95% CI = 0.13–0.98, p = 0.046]. Fifteen VNTR loci were designated as being “highly discriminant” in our sample, except for TR109. The total of 103 MABC isolates were fully discriminated into 103 unique patterns by an 18-locus VNTR set [Hunter–Gaston Discriminatory Index (HGDI) = 1.000], of which the inclusion of the top 12 loci yielded a comparative HGDI value (HGDI = 0.9998). Remarkably, the order of the diversity of the VNTR loci showed significant difference between the MAA and MAM isolates. TR137 and TR2, two loci with high diversity indices for the MAA isolates, only yielded poor discriminatory power for the MAM isolates; the allelic diversity (h) values were 0.0000 and 0.2621, respectively. A detailed analysis of TR137 in combination with the other 17 VNTR loci showed that the combination of TR137–TR2 could fully distinguish MAA from MAM isolates. In conclusion, our data revealed that MAA is more prone to affect elderly patients. Additionally, the population structure of the MABC isolates circulating in China has high diversity. The combined use of the TR137 and TR2 loci provides a simple criterion for the precise identification of MABC to the subspecies level.

A rabbit model to study antibiotic penetration at the site of infection for non-tuberculous mycobacterial lung disease: macrolide case study

Nontuberculous mycobacterial pulmonary disease (NTM-PD) is a potentially fatal infectious disease requiring long treatment duration with multiple antibiotics and against which there is no reliable cure. Among the factors that have hampered the development of adequate drug regimens is the lack of an animal model that reproduces the NTM lung pathology required for studying antibiotic penetration and efficacy. Given the documented similarities between tuberculosis and NTM immunopathology in patients, we first determined that the rabbit model of active tuberculosis reproduces key features of human NTM-PD and provides an acceptable surrogate model to study lesion penetration. We focused on clarithromycin, a macrolide and pillar of NTM-PD treatment, and explored the underlying causes of the disconnect between its favorable potency and pharmacokinetics, and inconsistent clinical outcome. To quantify pharmacokinetic-pharmacodynamic target attainment at the site of disease, we developed a translational model describing clarithromycin distribution from plasma to lung lesions, including the spatial quantitation of clarithromycin and azithromycin in mycobacterial lesions of two patients on long-term macrolide therapy. Through clinical simulations, we visualized the coverage of clarithromycin in plasma and four disease compartments, revealing heterogeneous bacteriostatic and bactericidal target attainment depending on the compartment and the corresponding potency against nontuberculous mycobacteria in clinically relevant assays. Overall, clarithromycin's favorable tissue penetration and lack of bactericidal activity indicated that its clinical activity is limited by pharmacodynamic rather than pharmacokinetic factors. Our results pave the way towards the simulation of lesion pharmacokinetic-pharmacodynamic coverage by multi-drug combinations, to enable the prioritization of promising regimens for clinical trials.

Sitafloxacin Expresses Potent Anti-Mycobacterium abscessus Activity

Therapeutic options for treating Mycobacterium abscessus infections are extremely limited; quinolones are important. The in vitro anti-M. abscessus activities of nine quinolones, emphasizing sitafloxacin, were investigated. Antimicrobial susceptibility testing was performed on 10 non-tuberculous mycobacterium reference strains and 194 clinical, M. abscessus isolates. The activity of sitafloxacin against intracellular M. abscessus residing within macrophages was also evaluated. A checkerboard assay was conducted to determine synergy between sitafloxacin and 10 clinically important antibiotics. Among the nine quinolones tested, sitafloxacin exhibited the greatest anti-M. abscessus activity with MIC₅₀ and MIC₉₀ of 1 and 2 mg/L, respectively. Sitafloxacin exerted a bacteriostatic effect on M. abscessus and inhibited the intracellular growth of M. abscessus at concentrations equivalent to clarithromycin. No antagonism between sitafloxacin and 10 clinically important anti-M. abscessus antibiotics was evident. In summary, sitafloxacin exhibited a significant advantage relative to other quinolones in inhibiting the growth of M. abscessus in vitro, suggesting the potential inclusion of sitafloxacin in new strategies to treat M. abscessus infections.

Host-Pathogen Interactions Operative during Mycobacteroides abscessus Infection

Mycobacteroides abscessus (previously Mycobacterium abscessus; Mabc), one of rapidly growing nontuberculous mycobacteria (NTM), is an important pathogen of NTM pulmonary diseases (NTM-PDs) in both immunocompetent and immunocompromised individuals. Mabc infection is chronic and often challenging to treat due to drug resistance, motivating the development of new therapeutics. Despite this, there is a lack of understanding of the relationship between Mabc and the immune system. This review highlights recent progress in the molecular architecture of Mabc and host interactions. We discuss several microbial components that take advantage of host immune defenses, host defense pathways that can overcome Mabc pathogenesis, and how host-pathogen interactions determine the outcomes of Mabc infection. Understanding the molecular mechanisms underlying host-pathogen interactions during Mabc infection will enable the identification of biomarkers and/or drugs to control immune pathogenesis and protect against NTM infection.

Varying clinical presentations of nontuberculous mycobacterial disease : Similar to but different from tuberculosis

The incidence rate of pulmonary nontuberculous mycobacterial disease (PNTMD) in Japan is the highest among major industrialized nations. Although the typical clinical course and radiological manifestations of PNTMD are different from those of pulmonary tuberculosis (TB), confusion about these mycobacterial diseases leads to a diagnostic pitfall. Diagnostic challenges include the coexistence of Mycobacterium tuberculosis (MTB) and nontuberculous mycobacteria (NTM), false positives for NTM in MTB nucleic acid amplification tests, microbial substitution, and abnormal radiological manifestations caused by NTM. Features of extrapulmonary NTM diseases, such as pleurisy, vertebral osteomyelitis, and disseminated disease, are different from the corresponding tuberculous diseases. Moreover, the immunological background of the patient (status of human immunodeficiency virus infection with or without antiviral therapy, continuation or discontinuation of immunosuppressive therapy, use of immune checkpoint inhibitor, pregnancy and delivery, etc.) influences the pathophysiology of mycobacterial diseases. This review describes the varying clinical presentations of NTM disease with emphasis on the differences from TB. J. Med. Invest. 68 : 220-227, August, 2021.

Nontuberculous Mycobacteria

Nontuberculous mycobacteria (NTM) are ubiquitous in the environment and 193 species of NTM have been discovered thus far. NTM species vary in virulence from benign environmental organisms to difficult-to-treat human pathogens. Pulmonary infections remain the most common manifestation of NTM disease in humans and bronchiectasis continues to be a major risk factor for NTM pulmonary disease (NTM PD). This article will provide a useful introduction and framework for clinicians involved in the management of bronchiectasis and NTM. It includes an overview of the epidemiology, pathogenesis, diagnosis, and management of NTM PD. We will address the challenges faced in the diagnosis of NTM PD and the importance of subspeciation in guiding treatment and follow-up, especially in Mycobacterium abscessus infections. The treatment of both Mycobacterium avium complex and M. abscessus, the two most common NTM species known to cause disease, will be discussed in detail. Elements of the recent ATS/ERS/ESCMID/IDSA NTM guidelines published in 2020 will also be reviewed.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Drug Treatment of Non-Tuberculous Mycobacteria in Cystic Fibrosis

Non-tuberculous mycobacteria (NTM) are an emerging group of pulmonary infectious pathogens of increasing importance to the management of patients with cystic fibrosis (CF). NTM include slow-growing mycobacteria such as Mycobacterium avium complex (MAC) and rapidly growing mycobacteria such as Mycobacterium abscessus. The incidence of NTM in the CF population is increasing and infection contributes to significant morbidity to the patient and costs to the health system. Treating M. abscessus requires the combination of multiple costly antibiotics for months, with potentially significant toxicity associated with treatment. Although international guidelines for the treatment of NTM infection in CF are available, there are a lack of robust pharmacokinetic studies in CF patients to inform dosing and drug choice. This paper aims to outline the pharmacokinetic and pharmacodynamic factors informing the optimal treatment of NTM infections in CF.

Invasive Mycobacterium abscessus Complex Infection After Cardiac Surgery: Epidemiology, Management, and Clinical Outcomes

BACKGROUND

We recently mitigated a clonal outbreak of hospital-acquired Mycobacterium abscessus complex (MABC), which included a large cluster of adult patients who developed invasive infection after exposure to heater-cooler units during cardiac surgery. Recent studies have detailed Mycobacterium chimaera infections acquired during cardiac surgery; however, little is known about the epidemiology and clinical courses of cardiac surgery patients with invasive MABC infection.

METHODS

We retrospectively collected clinical data on all patients who underwent cardiac surgery at our hospital and subsequently had positive cultures for MABC from 2013 through 2016. Patients with ventricular assist devices or heart transplants were excluded. We analyzed patient characteristics, antimicrobial therapy, surgical interventions, and clinical outcomes.

RESULTS

Ten cardiac surgery patients developed invasive, extrapulmonary infection from M. abscessus subspecies abscessus in an outbreak setting. Median time from presumed inoculation in the operating room to first positive culture was 53 days (interquartile range [IQR], 38-139 days). Disseminated infection was common, and the most frequent culture-positive sites were mediastinum (n = 7) and blood (n = 7). Patients received a median of 24 weeks (IQR, 5-33 weeks) of combination antimicrobial therapy that included multiple intravenous agents. Six patients required antibiotic changes due to adverse events attributed to amikacin, linezolid, or tigecycline. Eight patients underwent surgical management, and 6 patients required multiple sternal debridements. Eight patients died within 2 years of diagnosis, including 4 deaths directly attributable to MABC infection.

CONCLUSIONS

Despite aggressive medical and surgical management, invasive MABC infection after cardiac surgery caused substantial morbidity and mortality. New treatment strategies are needed, and compliance with infection prevention guidelines remains critical.

Antimicrobial susceptibility profiles of Mycobacterium abscessus complex isolates from respiratory specimens in Shanghai, China

OBJECTIVES

The aim of this study was to compare the antibiotic susceptibility profiles of Mycobacterium abscessus complex (MABC) isolates and to investigate the relationship between susceptibility profiles and genetic mechanisms of macrolide resistance.

METHODS

More than 200 isolates collected from respiratory specimens between 2014 and 2018 were randomly analysed in this study. Minimum inhibitory concentrations (Mics) of ten potential antimicrobial agents were determined by the microplate alamarBlue assay.

RESULTS

We identified 43 MABC isolates, including 32 M. abscessus subsp. abscessus (M. abscessus) (6 from immunocompromised patients) and 11 M. abscessus subsp. massiliense (M. massiliense). The majority of MABC isolates were susceptible to amikacin (96.9% and 100.0% for M. abscessus and M. massiliense, respectively), linezolid (96.9% and 100.0%, respectively), cefoxitin (100.0% and 100.0%, respectively), imipenem (90.6% and 72.7%, respectively) and tobramycin (90.6% and 72.7%, respectively). The resistance rates to clarithromycin and doxycycline in isolates of M. abscessus (68.8% and 100.0%) were significantly higher than those in isolates of M. massiliense (18.2% and 63.6%) (P < 0.05), whereas the percentage of tobramycin-resistant isolates among M. abscessus (9.4%) was significantly lower than among M. massiliense (27.3%) (P = 0.007). Sequencing analyses showed significant differences between erm(41) of M. abscessus and M. massiliense.

CONCLUSION

Mycobacterium abscessus is the dominant pathogen of pulmonary MABC infections in our hospital. Aminoglycosides (amikacin and tobramycin), β-lactams (cefoxitin and imipenem) and linezolid exhibited potent inhibitory activity against MABC in vitro. The erm(41) gene may be a promising marker to predict macrolide susceptibility for M. abscessus.

Comparison of drug-susceptibility patterns and gene sequences associated with clarithromycin and azithromycin resistance in Mycobacterium abscessus complex isolates and evaluation of the accumulation of intrinsic macrolide resistance

Introduction. Mycobacterium abscessus complex (MABC) is an infectious agent associated with macrolide resistance and treatment failure.Hypothesis/Gap Statement. Despite drug-susceptibility testing for MABC isolates including clarithromycin (CAM), long-term treatment with azithromycin (AZM) for MABC disease is recommended.Aim. We compared phenotypic and genotypic resistance to AZM and CAM in clinical isolates and evaluated the accumulation of intrinsic macrolide resistance (AIM) and morphological changes by macrolides exposure.Methodology. Forty-nine isolates were characterized regarding erm(41) sequevars. Sequencing data were compared to the nucleotide sequence of rrl and whiB7. The AIM MIC was performed in three reference strains and 15 isolates were randomized [each set of five isolates with M. abscessus subsp. abscessus (MAA) T28, MAA C28 and subsp. massiliense (MAM)].Results. The 49 isolates were distributed as 24 MAA T28, 5 MAA C28 and 20 MAM. The MIC₅₀ values to CAM at day 3 in MAA T28, C28 and MAM were 1, 0.12 and 0.12 µg ml^-1, while those at day 14 were 32, 0.5 and 0.12 µg ml^-1, respectively. The AZM-MIC₅₀ values at day 3 of the above isolates were 4, 0.25 and 0.5 µg ml^-1, while those at day 14 were >64, 0.5 and 0.5 µg ml^-1, respectively. Neither mutations in rrl of MAA T28 with acquired resistance nor deletions in whiB7 of MAA T28 without inducible resistance were observed . For AIM MIC, MAA T28 showed that the time-to-detection of AZM resistance was significantly faster over that of CAM (P<0.05). Morphological changes were not determined in all isolates.Conclusion. Our findings did not support the suggestion for the preferential use of AZM for, at least, MAA T28 disease due to the high-level MIC value and the increased AIM. The long duration of AZM-based treatment eventually may favour the emergence of isolates with a high-level of intrinsic resistance.

A novel DNA chromatography method to discriminate Mycobacterium abscessus subspecies and macrolide susceptibility

Background

The clinical impact of infection with Mycobacterium (M.) abscessus complex (MABC), a group of emerging non-tuberculosis mycobacteria (NTM), is increasing. M. abscessus subsp. abscessus/bolletii frequently shows natural resistance to macrolide antibiotics, whereas M. abscessus subsp. massiliense is generally susceptible. Therefore, rapid and accurate discrimination of macrolide-susceptible MABC subgroups is required for effective clinical decisions about macrolide treatments for MABC infection. We aimed to develop a simple and rapid diagnostic that can identify MABC isolates showing macrolide susceptibility.

Methods

Whole genome sequencing (WGS) was performed for 148 clinical or environmental MABC isolates from Japan to identify genetic markers that can discriminate three MABC subspecies and the macrolide-susceptible erm(41) T28C sequevar. Using the identified genetic markers, we established PCR based- or DNA chromatography-based assays. Validation testing was performed using MABC isolates from Taiwan.

Finding

We identified unique sequence regions that could be used to differentiate the three subspecies. Our WGS-based phylogenetic analysis indicated that M. abscessus carrying the macrolide-susceptible erm(41) T28C sequevar were tightly clustered, and identified 11 genes that were significantly associated with the lineage for use as genetic markers. To detect these genetic markers and the erm(41) locus, we developed a DNA chromatography method that identified three subspecies, the erm(41) T28C sequevar and intact erm(41) for MABC in a single assay within one hour. The agreement rate between the DNA chromatography-based and WGS-based identification was 99·7%.

Interpretation

We developed a novel, rapid and simple DNA chromatography method for identification of MABC macrolide susceptibility with high accuracy.

Funding

AMED, JSPS KAKENHI

Mycobacterium abscessus Gastric Band Infection Complicated by Immune Reconstitution Inflammatory Syndrome and Cured in the Context of Allogeneic Hematopoietic Stem Cell Transplantation

We present a case of abdominal gastric band-associated Mycobacterium abscessus infection, manifesting after the onset of acute myeloid leukemia, complicated by immune reconstitution inflammatory syndrome (IRIS), and cured while receiving an allogeneic hematopoietic stem cell transplant. IRIS should be considered in less classical situations where there is unexplained clinical deterioration.

3-D printed polyvinyl alcohol matrix for detection of airborne pathogens in respiratory bacterial infections

Novel sampling matrices were manufactured using 3D printing for the detection of respiratory pathogens in expired air. A specific configuration of the matrices was designed using Computer-Aided Design software. Polyvinyl alcohol (PVA) was printed using fused deposition modelling to create a multilayer matrix to enhance the capture of bacteria. The performance of these matrices was compared with gelatine filters that have been used for this work to date. PVA matrices (60 mm diameter) were contaminated with bacteria either by direct inoculation, or by aerosol exposure using an Omron A3 nebuliser. Rough and smooth morphotypes of Mycobacterium abscessus, M. smegmatis and M. bovis BCG, were used in this study to contaminate the matrices. PVA matrices and gelatine sampling filters were contaminated to compare recovery rates for quantitative analyses. These were dissolved in water, bacteria pelleted and DNA extracted followed by a Mycobacterium-specific quantitative Polymerase Chain Reaction (qPCR).The results showed that 3D printed PVA matrices are very effective to capture the bacteria. 3D printed PVA matrix and gelatine filters yielded results of the same order of magnitude for mycobacterial analyses, however, PVA matrix offers several advantages over the latter material. 3D printed PVA is considered as an economic and time-effective matrix as it is cheaper than gelatine filters. PVA is sufficiently robust to be handled and loaded into the surgical masks for sampling, compared to the brittle gelatine filters that required supportive frames. PVA is a synthetic material and it is suitable for DNA-based analyses, whilst gelatine is derived from animal collagen, and carries a high bacterial DNA background that interferes with the target DNA analysis. Furthermore, PVA dissolves in distilled water without requiring chemicals or enzymes, such as the case for gelatine hydrolysis. To summarise, 3D printed PVA sampling matrix is considered a promising tool used for microbiological diagnostic purposes.

Treatment of Nontuberculous Mycobacterial Pulmonary Disease: An Official ATS/ERS/ESCMID/IDSA Clinical Practice Guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

Treatment of nontuberculous mycobacterial pulmonary disease: an official ATS/ERS/ESCMID/IDSA clinical practice guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

Antibiotic treatment for nontuberculous mycobacteria lung infection in people with cystic fibrosis

BACKGROUND

Nontuberculous mycobacteria are mycobacteria, other than those in the Mycobacterium tuberculosis complex, and are commonly found in the environment. Nontuberculous mycobacteria species (most commonly Mycobacterium avium complex and Mycobacterium abscessus) are isolated from the respiratory tract of approximately 5% to 40% of individuals with cystic fibrosis; they can cause lung disease in people with cystic fibrosis leading to more a rapid decline in lung function and even death in certain circumstances. Although there are guidelines for the antimicrobial treatment of nontuberculous mycobacteria lung disease, these recommendations are not specific for people with cystic fibrosis and it is not clear which antibiotic regimen may be the most effective in the treatment of these individuals. This is an update of a previous review.

OBJECTIVES

The objective of our review was to compare antibiotic treatment to no antibiotic treatment, or to compare different combinations of antibiotic treatment, for nontuberculous mycobacteria lung infections in people with cystic fibrosis. The primary objective was to assess the effect of treatment on lung function and pulmonary exacerbations and to quantify adverse events. The secondary objectives were to assess treatment effects on the amount of bacteria in the sputum, quality of life, mortality, nutritional parameters, hospitalizations and use of oral antibiotics.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and hand searching of journals and conference abstract books. Date of last search: 24 February 2020. We also searched a register of ongoing trials and the reference lists of relevant articles and reviews. Date of last search: 21 March 2019.

SELECTION CRITERIA

Any randomized controlled trials comparing nontuberculous mycobacteria antibiotics to no antibiotic treatment, as well as one nontuberculous mycobacteria antibiotic regimen compared to another nontuberculous mycobacteria antibiotic regimen, in individuals with cystic fibrosis.   DATA COLLECTION AND ANALYSIS: Data were not collected because in the one trial identified by the search, data specific to individuals with cystic fibrosis could not be obtained from the pharmaceutical company.

MAIN RESULTS

One completed trial was identified by the searches, but data specific to individuals with cystic fibrosis could not be obtained from the pharmaceutical company.

AUTHORS' CONCLUSIONS

This review did not find any evidence for the effectiveness of different antimicrobial treatment for nontuberculous mycobacteria lung disease in people with cystic fibrosis. Until such evidence becomes available, it is reasonable for clinicians to follow published clinical practice guidelines for the diagnosis and treatment of nodular or bronchiectatic pulmonary disease due to Mycobacterium avium complex or Mycobacterium abscessus in patients with cystic fibrosis.

Treatment for Mycobacterium abscessus complex-lung disease

Nontuberculous mycobacterial infections and colonization are becoming more prevalent worldwide. Mycobacterium abscessus complex (MABC) is one of the predominant pathogens capable of a wide spectrum of infections, with 50% of infections involving the lungs. The decision to commence treatment is determined according to the severity of the disease, risk of progressive disease, presence of comorbidities, and goals of treatment. MABC is resistant to standard antituberculous agents and has variable drug susceptibility across different geographical locations, therefore, antibiotic susceptibility testing of all clinically significant isolates is crucial for selecting a treatment strategy. Pulmonary infections due to MABC is difficult to cure using the currently recommended regimens from the American Thoracic Society and British Thoracic Society. Macrolides are the cornerstone of treatment, but the efficacy of macrolide-based chemotherapy may be compromised by resistance. Despite the introduction of new drugs for treatment, treatment outcomes remain unsatisfactory. The combination of surgical resection of limited lung disease regions with a multidrug, macrolide-based therapy offers the optimal chance of achieving clinical cure of the disease. This review focuses on medical treatment of MABC-lung disease and the efficacy of new agents, such as clofazimine, amikacin inhalation therapy, tigecycline and linezolid, for treating MABC-lung disease.

Spontaneous sputum conversion and reversion in Mycobacterium abscessus complex lung disease

Background

We aim to investigate the rate of spontaneous sputum conversion and reversion in patients with Mycobacterium abscessus complex (MABC) lung disease.

Methods

Among 241 patients diagnosed with MABC lung disease between July 2012 and December 2018, 126 patients with persistent sputum positivity for ≥ 6 months without treatment were enrolled at a tertiary referral center in South Korea. Patients were subdivided into two groups, depending on whether or not treatment was initiated within 2 years of diagnosis. The rates of spontaneous sputum culture conversion and reversion was investigated in patients who did not receive treatment within 2 years.

Results

The mean age of 126 patients was 62.9 years. During a mean follow-up duration of 3.2 years, 33 (26.2%) patients received treatment within 2 years of diagnosis. Among the remaining 93 patients not receiving treatment within 2 years, spontaneous sputum conversion occurred in 24 (25.8%) patients during a mean follow-up duration of 3.7 years after diagnosis. No significant differences were observed in time to conversion between Mycobacterium abscessus and Mycobacterium massiliense lung diseases. The Cox regression analysis showed that malignancy as a comorbid disease and the lower number of lobes involved were independent predictors of spontaneous sputum conversion. After spontaneous sputum conversion, reversion occurred in 27.8% patients at a median of 18.2 months after conversion.

Conclusions

Among patients with MABC lung disease who did not receive treatment for at least 2 years after diagnosis, approximately one-fourth experienced spontaneous conversion. However, not a few patients experienced reversion after spontaneous conversion.

Rifabutin Suppresses Inducible Clarithromycin Resistance in Mycobacterium abscessus by Blocking Induction of whiB7 and erm41

Clarithromycin (CLR) is the corner stone in regimens for the treatment of lung disease caused by Mycobacterium abscessus (Mab). However, many strains harbor the CLR-inducible CLR resistance gene erm41, encoding a ribosome methylase. Induction of erm41 is mediated by the transcription factor whiB7. We hypothesized that an inhibitor of RNA synthesis should be able to block the whiB7-erm41 induction response to CLR exposure and thus suppress CLR resistance. Recently, we discovered that the rifampicin analog rifabutin (RFB) shows attractive potency against Mab. To determine whether RFB-CLR combinations are synergistic, a checkerboard analysis against a collection of erm41 positive and negative Mab strains was carried out. This revealed synergy of the two drugs for erm41 positive but not for erm41 negative strains. To determine whether RFB's potentiation effect was due to inhibition of the transcriptional induction of the whiB7-erm41 resistance system, we measured the effect of CLR alone and in combination with RFB on whiB7 and erm41 mRNA levels. CLR alone strongly induced whiB7 and erm41 expression as expected. The synergistic, growth-inhibiting combination of RFB with CLR blocked induction of both genes. These results suggest that RFB suppresses inducible CLR resistance by preventing induction of whiB7 and erm41 expression.

Dissecting erm(41)-Mediated Macrolide-Inducible Resistance in Mycobacterium abscessus

Macrolides are the cornerstone of Mycobacterium abscessus multidrug therapy, despite that most patients respond poorly to this class of antibiotics due to the inducible resistance phenotype that occurs during drug treatment. This mechanism is driven by the macrolide-inducible ribosomal methylase encoded by erm(41), whose expression is activated by the transcriptional regulator WhiB7. However, it has been debated whether clarithromycin and azithromycin differ in the extent to which they induce erm(41)-mediated macrolide resistance. Herein, we show that macrolide resistance is induced more rapidly in various M. abscessus isolates upon exposure to azithromycin than to clarithromycin, based on MIC determination. Macrolide-induced expression of erm(41) was assessed in vivo using a strain carrying tdTomato placed under the control of the erm(41) promoter. Visualization of fluorescent bacilli in infected zebrafish demonstrates that azithromycin and clarithromycin activate erm(41) expression in vivo That azithromycin induces a more rapid expression of erm(41) was confirmed by measuring the β-galactosidase activity of a reporter strain in which lacZ was placed under the control of the erm(41) promoter. Shortening the promoter region in the lacZ reporter plasmid identified DNA elements involved in the regulation of erm(41) expression, particularly an AT-rich motif sharing partial conservation with the WhiB7-binding site. Mutation of this motif abrogated the macrolide-induced and WhiB7-dependent expression of erm(41). This study provides new mechanistic information on the adaptive response to macrolide treatment in M. abscessus.

Thiostrepton: A Novel Therapeutic Drug Candidate for Mycobacterium abscessus Infection

Mycobacterium abscessus is a rapid-growing, multidrug-resistant, non-tuberculous mycobacterial species responsible for a variety of human infections, such as cutaneous and pulmonary infections. M. abscessus infections are very difficult to eradicate due to the natural and acquired multidrug resistance profiles of M. abscessus. Thus, there is an urgent need for the development of effective drugs or regimens against M. abscessus infections. Here, we report the activity of a US Food and Drug Administration approved drug, thiostrepton, against M. abscessus. We found that thiostrepton significantly inhibited the growth of M. abscessus wild-type strains, subspecies, clinical isolates, and drug-resistant mutants in vitro and in macrophages. In addition, treatment of macrophages with thiostrepton significantly decreased proinflammatory cytokine production in a dose-dependent manner, suggesting an inhibitory effect of thiostrepton on inflammation induced during M. abscessus infection. We further showed that thiostrepton exhibits antimicrobial effects in vivo using a zebrafish model of M. abscessus infection.

Pulmonary Mycobacterium abscessus Subspecies abscessus Disease That Showed a Discrepancy Between the Genotype and Phenotype of Clarithromycin Resistance

Mycobacterium abscessus subspecies abscessus is major subspecies in the M. abscessus complex and is usually refractory to standard antibiotherapy. Genetic tracing of erm (41) T28 is a mechanism for monitoring macrolide resistance. We treated a patient with a pulmonary infection caused by M. abscessus subsp. abscessus with the erm (41) T28 polymorphism, which was susceptible to clarithromycin, and his clinical treatment course was good. The identification of the M. abscessus complex genotype is important, but clinical confirmation of clarithromycin susceptibility is also needed to plan individual treatment strategies.

Pharmacotherapy Approaches in Nontuberculous Mycobacteria Infections

Nontuberculous mycobacteria (NTM) comprise a heterogeneous group of organisms, with only a small subset known to cause disease in humans. Although NTM infection is not a reportable disease, both the increasing clinical recognition and recent advancements in laboratory diagnostic capabilities of NTM infections in immunocompromised and immunocompetent patients are rapidly evolving. We reviewed antimicrobial agents used to treat the most frequently encountered NTM infections and examined optimized drug dosing strategies, toxicity profiles, drug-drug interactions, and the role of therapeutic drug monitoring. Antimicrobial susceptibility testing and patient monitoring on therapy were also examined. We used PubMed to review the published literature on the management of select NTM pathogens, the common syndromes encountered since 2000, and select pharmacokinetic principles of select antimicrobial agents used since 1990. We included select clinical trials, systematic reviews, published guidelines, and observational studies when applicable. The prolonged duration and the necessity for combination therapy for most forms of NTM disease can be problematic for many patients. A multidisciplinary care team that includes pharmacy engagement may help increase rates of optimal patient tolerability and successful treatment completion.

GenoType NTM-DR Performance Evaluation for Identification of Mycobacterium avium Complex and Mycobacterium abscessus and Determination of Clarithromycin and Amikacin Resistance

We evaluated the GenoType NTM-DR (NTM-DR) line probe assay for identifying Mycobacterium avium complex (MAC) species and Mycobacterium abscessus subspecies and for determining clarithromycin and amikacin resistance. Thirty-eight reference strains and 145 clinical isolates (58 MAC and 87 M. abscessus isolates), including 54 clarithromycin- and/or amikacin-resistant strains, were involved. The performance of the NTM-DR assay in rapid identification was evaluated by comparison with results of multigene sequence-based typing, whereas performance in rapid detection of clarithromycin and amikacin resistance was evaluated by comparison with sequencing of the erm(41), rrl, and rrs genes and drug susceptibility testing (DST). The accuracies of MAC and M. abscessus (sub)species identification were 92.1% (35/38) and 100% (145/145) for the 38 reference strains and 145 clinical isolates, respectively. Three MAC strains other than M. intracellulare were found to cross-react with the M. intracellulare probe in the assay. Regarding clarithromycin resistance, NTM-DR detected rrl mutations in 52 isolates and yielded 99.3% (144/145) and 98.6% (143/145) concordant results with sequencing and DST, respectively. NTM-DR sensitivity and specificity in the detection of clarithromycin resistance were 96.3% (52/54) and 100% (91/91), respectively. The NTM-DR yielded accurate erm(41) genotype results for all 87 M. abscessus isolates. Regarding amikacin resistance, NTM-DR detected rrs mutations in five isolates and yielded 99.3% (144/145) and 97.9% (142/145) concordant results with sequencing and DST, respectively. Our results indicate that the NTM-DR assay is a straightforward and accurate approach for discriminating MAC and M. abscessus (sub)species and for detecting clarithromycin and amikacin resistance mutations and that it is a useful tool in the clinical setting.

Managing antibiotic resistance in nontuberculous mycobacterial pulmonary disease: challenges and new approaches

Introduction: The incidence and prevalence rates of nontuberculous mycobacterial (NTM) pulmonary disease have been continuously increasing worldwide. However, the rate of successful treatment of this disease greatly needs improving, particularly when intrinsic (natural) drug resistance and acquired drug resistance in NTM pulmonary disease are associated with poor outcomes for patients. Areas covered: This review covers the major pathogens that cause NTM pulmonary disease caused by Mycobacterium avium complex, Mycobacterium abscessus, and Mycobacterium kansasii; the key drugs and recommended regimens used in the treatment of NTM pulmonary disease; the factors that contribute to resistance to the key drugs, including genetic factors and monotherapy; and the treatment strategies, including revised antibiotic regimens and surgery, that can be used to treat drug-resistant NTM pulmonary disease. Expert opinion: To avoid and overcome drug resistance in NTM pulmonary disease, the appropriate guideline-based treatments are essential, and clinical studies to evaluate new or repurposed drugs are urgently needed.

The differential effect of clarithromycin and azithromycin on induction of macrolide resistance in Mycobacterium abscessus

Aim: Antibiotic resistance in Mycobacterium abscessus renders treatment poorly effective. Despite erm(41)-gene-mediated macrolide resistance, treatment with azithromycin or clarithromycin is recommended. It is contested whether macrolides differ in erm(41) induction. We determine whether this is the case. Methods: M. abscessus CIP104536 was used. Minimum inhibitory concentrations of clarithromycin and azithromycin were determined. Time-kill kinetics of M. abscessus exposed to azithromycin or clarithromycin were performed and RNA was isolated at predetermined intervals for erm(41) quantification. Results: Minimum inhibitory concentrations increased >30-fold. Time-kill kinetics showed a temporary bacteriostatic effect, abrogated by induced resistance. Erm(41) expression was increased following exposure to either macrolide for 7 days. Conclusion: Both macrolides induce resistance similarly, and this should not be an argument in choosing either macrolide for therapy.

Top Questions in the Diagnosis and Treatment of Pulmonary M. abscessus Disease

Mycobacterium abscessus disease is particularly challenging to treat, given the intrinsic drug resistance of this species and the limited data on which recommendations are based, resulting in a greater reliance on expert opinion. We address several commonly encountered questions and management considerations regarding pulmonary Mycobacterium abscessus disease, including the role of subspecies identification, diagnostic criteria for determining disease, interpretation of drug susceptibility test results, approach to therapy including the need for parenteral antibiotics and the role for new and repurposed drugs, and the use of adjunctive strategies such as airway clearance and surgical resection.