Extrapulmonary Mycobacterium abscessus Infections, France, 2012-20201.

Mycobacterium abscessus infection is challenging to treat. Extrapulmonary M. abscessus infections (EP-MAB) are less common than pulmonary M. abscessus infections. To evaluate treatment regimens, we retrospectively analyzed consecutive microbiologically confirmed EP-MAB cases diagnosed in France during 2012-2020. We studied 45 patients with EP-MAB, including 14 bone and joint infections, 10 skin and soft tissue infections, and 8 lymph node infections. Most (62%) patients had no reported immunodeficiency. In 27 patients, EP-MAB followed healthcare-associated (44%) or environmental (16%) injuries. Of the 45 isolates, 25 were subspecies abscessus, 10 bolletii, and 9 massiliense; 1 was unidentified. Cure was achieved for 36 (80%) patients who received a median antimicrobial regimen of 6 months; 22 (55%) also underwent surgery. Four patients died, and 5 were unavailable for follow-up. EP-MAB predominantly affects immunocompetent patients after an injury; outcomes are favorable. We propose a >6-month regimen of antimicrobial therapy with consideration for surgery and regular patient reassessment.

Atypical Mycobacterium abscessus BlaRI Ortholog Mediates Regulation of Energy Metabolism but Not ß-Lactam Resistance.

Mycobacterium abscessus (Mab) is highly drug resistant, and understanding regulation of antibiotic resistance is critical to future antibiotic development. Regulatory mechanisms controlling Mab's ß-lactamase (BlaMab) that mediates ß-lactam resistance remain unknown. S. aureus encodes a prototypical protease-mediated two-component system BlaRI regulating the ß-lactamase BlaZ. BlaR binds extracellular ß-lactams, activating an intracellular peptidase domain which cleaves BlaI to derepress blaZ. Mycobacterium tuberculosis (Mtb) encodes homologs of BlaRI (which we will denote as BlaIR to reflect the inverted gene order in mycobacteria) that regulate not only the Mtb ß-lactamase, blaC, but also additional genes related to respiration. We identified orthologs of blaIRMtb in Mab and hypothesized that they regulate blaMab. Surprisingly, neither deletion of blaIRMab nor overexpression of only blaIMab altered blaMab expression or ß-lactam susceptibility. However, BlaIMab did bind to conserved motifs upstream of several Mab genes involved in respiration, yielding a putative regulon that partially overlapped with BlaIMtb. Prompted by evidence that respiration inhibitors including clofazimine induce the BlaI regulon in Mtb, we found that clofazimine triggers induction of blaIRMab and its downstream regulon. Highlighting an important role for BlaIRMab in adapting to disruptions in energy metabolism, constitutive repression of the BlaIMab regulon rendered Mab highly susceptible to clofazimine. In addition to our unexpected findings that BlaIRMab does not regulate ß-lactam resistance, this study highlights the novel role of mycobacterial BlaRI-type regulators in regulating electron transport and respiration.

Evolution toward extremely high imipenem resistance in Mycobacterium abscessus outbreak strains.

Treatment of Mycobacterium abscessus pulmonary disease requires multiple antibiotics including intravenous ß-lactams (e.g., imipenem). M. abscessus produces a ß-lactamase (BlaMab) that inactivates ß-lactam drugs but less efficiently carbapenems. Due to intrinsic and acquired resistance in M. abscessus and poor clinical outcomes, it is critical to understand the development of antibiotic resistance both within the host and in the setting of outbreaks. We compared serial longitudinally collected M. abscessus subsp. massiliense isolates from the index case of a cystic fibrosis center outbreak and four outbreak-related strains. We found strikingly high imipenem resistance in the later patient isolates, including the outbreak strain (MIC > 512 µg/mL). The phenomenon was recapitulated upon exposure of intracellular bacteria to imipenem. Addition of the ß-lactamase inhibitor avibactam abrogated the resistant phenotype. Imipenem resistance was caused by an increase in ß-lactamase activity and increased blaMab mRNA level. Concurrent increase in transcription of the preceding ppiA gene indicated upregulation of the entire operon in the resistant strains. Deletion of the porin mspA coincided with the first increase in MIC (from 8 to 32 µg/mL). A frameshift mutation in msp2 responsible for the rough colony morphology and a SNP in ATP-dependent helicase hrpA cooccurred with the second increase in MIC (from 32 to 256 µg/mL). Increased BlaMab expression and enzymatic activity may have been due to altered regulation of the ppiA-blaMab operon by the mutated HrpA alone or in combination with other genes described above. This work supports using carbapenem/ß-lactamase inhibitor combinations for treating M. abscessus, particularly imipenem-resistant strains.

Phosphatidylserine liposomes induce a phagosome acidification-dependent and ROS-mediated intracellular killing of Mycobacterium abscessus in human macrophages.

Mycobacterium abscessus (Mab) is an opportunistic nontuberculous mycobacterium responsible of difficult-to-treat pulmonary infections in vulnerable patients, such as those suffering from Cystic Fibrosis (CF), where it represents a major cause of morbidity and mortality. Additionally, due to the intrinsic extensive antimicrobial resistance spectrum displayed by this species and the side effects reported for some available antibiotics, the therapeutic management of such infections remains extremely difficult. In the present study, we show that phosphatidylserine liposomes (PS-L) enhance intracellular mycobacterial killing of Mab infected human macrophages with functional or pharmacologically inhibited cystic fibrosis conductance regulator (CFTR), by a mechanism involving phagosome acidification and reactive oxygen species (ROS) production. Additionally, PS-L significantly reduce proinflammatory response of Mab infected macrophages in terms of NF-kB activation and TNF-α production, irrespective of CFTR inhibition. Altogether, these results represent the proof of concept for a possible future development of PS-L as a therapeutic strategy against difficult-to-treat Mab infection.

Prevalence of resistance to macrolides and aminoglycosides in Mycobacterium avium, M. abscessus, and M. chelonae identified in the Laboratorio Nacional de Referencia of Colombia from 2018 to 2022 / Prevalencia de la resistencia a macrólidos y aminoglucósidos en los complejos Mycobacterium avium y M. abscessus y en Mycobacterium chelonae identificados en el Laboratorio Nacional de Referencia de Colombia entre el 2018 y el 2022.

Introduction: The Mycobacterium chelonae species and the M. avium and M. abscessus complexes are emerging pathogens that cause mycobacteriosis. Treatment depends on the species and subspecies identified. The drugs of choice are macrolides and aminoglycosides. However, due to the resistance identified to these drugs, determining the microbe's sensitivity profile will allow clinicians to improve the understanding of the prognosis and evolution of these pathologies. Objective: To describe the macrolide and aminoglycoside susceptibility profile of cultures identified by Colombia's Laboratorio Nacional de Referencia de Mycobacteria from 2018 to 2022, as Mycobacterium avium complex, M. abscessus complex, and M. chelonae. Materials and methods. This descriptive study exposes the susceptibility profile to macrolides and aminoglycosides of cultures identified as M. avium complex, M. abscessus complex, and M. chelonae using the GenoType® NTM-DR method. Materials and methods: This descriptive study exposes the susceptibility profile to macrolides and aminoglycosides of cultures identified as M. avium complex, M. abscessus complex, and M. chelonae using the GenoType® NTM-DR method. Results: We identified 159 (47.3 %) cultures as M. avium complex, of which 154 (96.9 %) were sensitive to macrolides, and 5 (3.1 %) were resistant; all were sensitive to aminoglycosides. From the 125 (37.2 %) cultures identified as M. abscessus complex, 68 (54.4 %) were sensitive to macrolides, 57 (45.6 %) were resistant to aminoglycosides, and just one (0.8 %) showed resistance to aminoglycosides. The 52 cultures (15.5 %) identified as M. chelonae were sensitive to macrolides and aminoglycosides. Conclusions: The three studied species of mycobacteria have the least resistance to Amikacin. Subspecies identification and their susceptibility profiles allow the establishment of appropriate treatment schemes, especially against M. abscessus.

Introducción. Mycobacterium chelonae y los complejos Mycobacterium avium y M. abscessus, son agentes patógenos emergentes causantes de micobacteriosis. El tratamiento de esta infección depende de la especie y la subespecie identificadas. Los fármacos de elección son los macrólidos y aminoglucósidos, contra los cuales se ha reportado resistencia; por esta razón, el determinar el perfil de sensibilidad le permite al médico tratante comprender mejor el pronóstico y la evolución de estas infecciones. Objetivo. Describir los perfiles de sensibilidad ante macrólidos y aminoglucósidos, de los cultivos identificados como complejo Mycobacterium avium, complejo M. abscessus o especie M. chelonae, en el Laboratorio Nacional de Referencia de Micobacterias durante los años 2018 a 2022. Materiales y métodos. Se llevó a cabo un estudio descriptivo del perfil de sensibilidad a macrólidos y aminoglucósidos, de los cultivos identificados como complejo M. avium, complejo M. abscessus o M. chelonae, mediante la metodología GenoType® NTM-DR. Resultados. Los cultivos del complejo M. avium fueron 159 (47,3 %), de los cuales, 154 (96,9 %) fueron sensibles y 5 (3,1 %) resistentes a los macrólidos; todos fueron sensibles a los aminoglucósidos. Del complejo M. abscessus se estudiaron 125 (37,2 %) cultivos, 68 (54,4 %) resultaron sensibles y 57 (45,6 %) resistentes a los macrólidos; solo un cultivo (0,8 %) fue resistente a los aminoglucósidos. De M. chelonae se analizaron 52 cultivos (15,5 %), todos sensibles a los macrólidos y aminoglucósidos. Conclusiones. En las tres especies de micobacterias estudiadas, la resistencia contra la amikacina fue la menos frecuente. La identificación de las subespecies y los perfiles de sensibilidad permiten instaurar esquemas de tratamiento adecuados, especialmente en las micobacteriosis causadas por M. abscessus.

The autophagy-targeting compound V46 enhances antimicrobial responses to Mycobacteroides abscessus by activating transcription factor EB.

Mycobacteroides abscessus (Mabc) is a rapidly growing nontuberculous mycobacterium that poses a considerable challenge as a multidrug-resistant pathogen causing chronic human infection. Effective therapeutics that enhance protective immune responses to Mabc are urgently needed. This study introduces trans-3,5,4'-trimethoxystilbene (V46), a novel resveratrol analogue with autophagy-activating properties and antimicrobial activity against Mabc infection, including multidrug-resistant strains. Among the resveratrol analogues tested, V46 significantly inhibited the growth of both rough and smooth Mabc strains, including multidrug-resistant strains, in macrophages and in the lungs of mice infected with Mabc. Additionally, V46 substantially reduced Mabc-induced levels of pro-inflammatory cytokines and chemokines in both macrophages and during in vivo infection. Mechanistic analysis showed that V46 suppressed the activation of the protein kinase B/Akt-mammalian target of rapamycin signaling pathway and enhanced adenosine monophosphate-activated protein kinase signaling in Mabc-infected cells. Notably, V46 activated autophagy and the nuclear translocation of transcription factor EB, which is crucial for antimicrobial host defenses against Mabc. Furthermore, V46 upregulated genes associated with autophagy and lysosomal biogenesis in Mabc-infected bone marrow-derived macrophages. The combination of V46 and rifabutin exerted a synergistic antimicrobial effect. These findings identify V46 as a candidate host-directed therapeutic for Mabc infection that activates autophagy and lysosomal function via transcription factor EB.

Investigating the role of MAB_1915 in intrinsic resistance to multiple drugs in Mycobacterium abscessus.

The increasing clinical significance of Mycobacterium abscessus is owed to its innate high-level, broad-spectrum resistance to antibiotics and therefore rapidly evolves as an important human pathogen. This warrants the identification of novel targets for aiding the discovery of new drugs or drug combinations to treat M. abscessus infections. This study is inspired by the drug-hypersensitive profile of a mutant M. abscessus (U14) with transposon insertion in MAB_1915. We validated the role of MAB_1915 in intrinsic drug resistance in M. abscessus by constructing a selectable marker-free in-frame deletion in MAB_1915 and complementing the mutant with the same or extended version of the gene and then followed by drug susceptibility testing. Judging by the putative function of MAB_1915, cell envelope permeability was studied by ethidium bromide accumulation assay and susceptibility testing against dyes and detergents. In this study, we established genetic evidence of the role of MAB_1915 in intrinsic resistance to rifampicin, rifabutin, linezolid, clarithromycin, vancomycin, and bedaquiline. Disruption of MAB_1915 has also been observed to cause a significant increase in cell envelope permeability in M. abscessus. Restoration of resistance is observed to depend on at least 27 base pairs upstream of the coding DNA sequence of MAB_1915. MAB_1915 could therefore be associated with cell envelope permeability, and hence its role in intrinsic resistance to multiple drugs in M. abscessus, which presents it as a novel target for future development of effective antimicrobials to overcome intrinsic drug resistance in M. abscessus. IMPORTANCE: This study reports the role of a putative fadD (MAB_1915) in innate resistance to multiple drugs by M. abscessus, hence identifying MAB_1915 as a valuable target and providing a baseline for further mechanistic studies and development of effective antimicrobials to check the high level of intrinsic resistance in this pathogen.

Characterization of novel double-reporter strains of Mycobacterium abscessus for drug discovery: a study in mScarlet.

Mycobacterium abscessus (Mab) is an emerging pathogen that poses a severe health threat, especially in people with cystic fibrosis and other chronic lung diseases. Available drugs are largely ineffective due to an exquisite intrinsic resistance, making Mab infections only comparable to multidrug-resistant tuberculosis. Current treatment is based on lengthy multidrug therapy, complicated by poor outcomes and high rates of treatment failure, recurrence, and mortality. Thus, finding new and more efficient drugs to combat this pathogen is urgent. However, drug discovery efforts targeting Mab have been limited, and traditional drug screening methods are labor-intensive, low-throughput, and do not reflect clinical effectiveness. Therefore, this work aimed to develop a new, efficient, and reliable tool for drug screening against Mab that can be used in vitro for identifying hits in a high-throughput manner and in vivo to select drug candidates for future clinical trials. We engineered two stable double-reporter strains of Mab capable of emitting strong fluorescent and luminescent signals. This is due to the expression of mScarlet protein and luciferase enzyme or the entire lux operon. Importantly, these strains maintain the same ground characteristics as the non-transformed Mab strain. We show that these new strains can be applied to various setups, from MIC determination in broth cultures and macrophage infection assays to in vivo infection (using the Galleria mellonella model). Using these strains enhances the potential for high-throughput screening of thousands of compounds in a fast and reliable way. IMPORTANCE: Mycobacterium abscessus (Mab) is currently considered an "incurable nightmare." Its intrinsic resistance, high toxicity, long duration, and low cure rates of available therapies often lead to the clinical decision not to treat. Moreover, one of the significant drawbacks of anti-Mab drug development is the lack of correlation between in vitro susceptibility and clinical efficacy. Most drug screening assays are performed on Mab growing in liquid cultures. But being an intracellular pathogen, inducing granulomas and biofilm formation, the broth culture is far from ideal as in vitro drug-testing setup. This study presents new double-reporter Mab strains that allow direct real-time bacterial detection and quantification in a non-invasive way. These strains can be applied to an extensive range of experimental settings, far surpassing the utility of single-reporter bacteria. They can be used in all steps of the pre-clinical anti-Mab drug development pipeline, constituting a highly valuable tool to increase its success.

Efficacies of omadacycline + amikacin + imipenem and an all-oral regimen omadacycline + clofazimine + linezolid in a mouse model of M. abscessus lung disease.

Treatment outcomes for Mycobacteroides abscessus (Mab, also known as Mycobacterium abscessus) disease are still unsatisfactory, mainly due to issues with drug toxicity, tolerability, and efficacy. Treating Mab disease is challenging due to its high baseline antibiotic resistance, initial requirement for intravenous therapy, and poor medication tolerance. Omadacycline, a new tetracycline, is active against Mab. Since any new antibiotic effective against Mab is expected to be used in combination with other antibiotics, we evaluated the efficacy of two triple-drug combinations comprising omadacycline, omadacycline + amikacin + imipenem, and omadacycline + clofazimine + linezolid against two contemporary Mab clinical isolates in a mouse model of Mab lung disease. Antibiotic administration was initiated 1-week post-infection and was given daily, with Mab burden in the lungs at treatment completion serving as the endpoint. Omadacycline alone moderately reduced Mab levels and maintained better health in mice compared to untreated ones, which typically suffered from the infection. The omadacycline + clofazimine + linezolid combination showed immediate bactericidal activity and enhanced efficacy over 6 weeks, particularly against the more resistant strain (M9507). However, the clofazimine + linezolid combination lacked early bactericidal activity. When combined with amikacin and imipenem, omadacycline did not improve the regimen's effectiveness over 4 weeks of treatment. Our study showed that omadacycline + clofazimine + linezolid exhibited significant bactericidal activity over an extended treatment duration. However, adding omadacycline to amikacin and imipenem did not improve regimen effectiveness against the evaluated clinical isolates within 4 weeks. Further research in Mab disease patients is needed to determine the most effective omadacycline-containing regimen.IMPORTANCEMycobacteroides abscessus is a common environmental bacterium that causes infections in people with compromised lung function, including those with bronchiectasis, cystic fibrosis, chronic obstructive pulmonary disease, and weakened immune systems, especially among older individuals. Treating M. abscessus disease is challenging due to the limited effectiveness and toxicity of current antibiotics, which often require prolonged use. Omadacycline, a new antibiotic, shows promise against M. abscessus. Using a mouse model that mimics M. abscessus disease in humans, we studied the effectiveness of including omadacycline with recommended antibiotics. Adding omadacycline to clofazimine and linezolid significantly improved treatment outcomes, rapidly clearing the bacteria from the lungs and maintaining effectiveness throughout. This oral combination is convenient for patients. However, adding omadacycline to amikacin and imipenem did not improve treatment effectiveness within 4 weeks. Further study with M. abscessus patients is necessary to optimize omadacycline-based treatment strategies for this disease.

The novel drug candidate VOMG kills Mycobacterium abscessus and other pathogens by inhibiting cell division.

AIMS: The incidence of lung infections is increasing worldwide in individuals suffering from cystic fibrosis and chronic obstructive pulmonary disease. Mycobacterium abscessus is associated with chronic lung deterioration in these populations. The intrinsic resistance of M. abscessus to most conventional antibiotics jeopardizes treatment success rates. To date, no single drug has been developed targeting M. abscessus specifically. The objective of this study was to characterize VOMG, a pyrithione-core drug-like small molecule, as a new compound active against M. abscessus and other pathogens. METHODS: A multi-disciplinary approach including microbiological, chemical, biochemical and transcriptomics procedures was used to validate VOMG as a promising anti-M. abscessus drug candidate. RESULTS: To the authors' knowledge, this is the first study to report the in-vitro and in-vivo bactericidal activity of VOMG against M. abscessus and other pathogens. Besides being active against M. abscessus biofilm, the compound showed a favourable pharmacological (ADME-Tox) profile. Frequency of resistance studies were unable to isolate resistant mutants. VOMG inhibits cell division, particularly the FtsZ enzyme. CONCLUSIONS: VOMG is a new drug-like molecule active against M. abscessus, inhibiting cell division with broad-spectrum activity against other microbial pathogens.

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.

Efficacy of epetraborole against Mycobacteroides abscessus in a mouse model of lung infection.

Mycobacteroides abscessus (Mab or Mycobacterium abscessus) is a fast-growing mycobacterium that is ubiquitous in the environment and can cause opportunistic disease in people with lung comorbidity and immunodeficiency. There are no Food and Drug Administration-approved drugs for this disease, and repurposed antibiotics have a poor microbiological response. To address the need for effective new antibiotics, we determined the efficacy of epetraborole (EBO) against three Mab clinical isolates in a mouse model of lung Mab infection. Reduction in lung Mab burden over 4 weeks of treatment was the study end point. EBO was administered orally once daily at doses of 25 and 50 mg/kg, which achieved exposures approximating the once-daily dosing of 250 mg and 500 mg, respectively, in humans. EBO administration led to a gradual reduction in the lung Mab burden. After 4 weeks of treatment, the efficacies of 25 and 50 mg/kg EBO against isolates ATCC 19977 and M9501 were comparable. However, against isolate M9530, 50 mg/kg EBO was more efficacious than 25 mg/kg and comparable with parenteral imipenem, one of the most efficacious antibiotics against Mab. We also undertook a dose-ranging study by evaluating the efficacies of once-daily oral administration of 0.5, 5, 10, 25, and 100 mg/kg EBO against M9501 over 4 weeks. Once-daily oral 100 mg/kg EBO was as effective as twice-daily 100 mg/kg imipenem injection. Our study suggests that EBO could address the unmet need for effective oral treatment options for Mab lung disease, given the high rates of Mab drug resistance and limited tolerable intravenous options.

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.

An optimized cyclophosphamide-treated mouse model of Mycobacterium abscessus pulmonary infection.

Mycobacterium abscessus pulmonary infections are increasingly problematic, especially for immunocompromised individuals and those with underlying lung conditions. Currently, there is no reliable standardized treatment, underscoring the need for improved preclinical drug testing. We present a simplified immunosuppressed mouse model using only four injections of cyclophosphamide, which allows for sustained M. abscessus lung burden for up to 16 days. This model proved effective for antibiotic efficacy evaluation, as demonstrated with imipenem or amikacin.

Zafirlukast induces DNA condensation and has bactericidal effect on replicating Mycobacterium abscessus.

Mycobacterium abscessus infections are emerging in cystic fibrosis patients, and treatment success rate in these patients is only 33% due to extreme antibiotic resistance. Thus, new treatment options are essential. An interesting target could be Lsr2, a nucleoid-associated protein involved in mycobacterial virulence. Zafirlukast is a Food and Drug Administration (FDA)-approved drug against asthma that was shown to bind Lsr2. In this study, zafirlukast treatment is shown to reduce M. abscessus growth, with a minimal inhibitory concentration of 16 µM and a bactericidal concentration of 64 µM in replicating bacteria only. As an initial response, DNA condensation, a known stress response of mycobacteria, occurs after 1 h of treatment with zafirlukast. During continued zafirlukast treatment, the morphology of the bacteria alters and the structural integrity of the bacteria is lost. After 4 days of treatment, reduced viability is measured in different culture media, and growth of M. abscessus is reduced in a dose-dependent manner. Using transmission electron microscopy, we demonstrated that the hydrophobic multilayered cell wall and periplasm are disorganized and ribosomes are reduced in size and relocalized. In summary, our data demonstrate that zafirlukast alters the morphology of M. abscessus and is bactericidal at 64 µM. The bactericidal concentration of zafirlukast is relatively high, and it is only effective on replicating bacteria but as zafirlukast is an FDA-approved drug, and currently used as an anti-asthma treatment, it could be an interesting drug to further study in in vivo experiments to determine whether it could be used as an antibiotic for M. abscessus infections.

In vitro effects of the new oral ß-lactamase inhibitor xeruborbactam in combination with oral ß-lactams against clinical Mycobacterium abscessus isolates.

Non-tuberculosis mycobacteria (NTM), particularly Mycobacterium abscessus subsp. abscessus (M. abscessus), are increasingly being recognized as etiological agents of NTM pulmonary disease. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics, including ß-lactams. M. abscessus produces a class A ß-lactamase, whose activity is inhibited by cyclic boronic acid ß-lactamase inhibitors. We aimed to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid ß-lactamase inhibitor, against M. abscessus when combined with five ß-lactams (amoxicillin, tebipenem, cefdinir, cefuroxime, and cefoxitin). The drug susceptibilities of 43 M. abscessus clinical isolates obtained from 43 patients between August 2005 and May 2014 were tested. The MIC results for each ß-lactam with or without 4 µg/mL xeruborbactam were examined. Xeruborbactam lowered the MIC90 values of tebipenem, amoxicillin, cefuroxime, and cefdinir by 5, ≥4, 3, and 3 dilutions, respectively. The MIC90 values of cefoxitin without xeruborbactam were 32 µg/mL and did not change upon the addition of xeruborbactam. The lowest MIC90 value was obtained for tebipenem with xeruborbactam. Almost all isolates had an MIC of 4 µg/mL; one isolate had an MIC of 2 µg/mL. With respect to the susceptibility to the same family drug, the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%) for tebipenem with xeruborbactam. Combining tebipenem and xeruborbactam could be considered an effective all-oral regimen that benefits outpatient treatment of M. abscessus pulmonary disease. IMPORTANCE: Mycobacterium abscessus subsp. abscessus (M. abscessus) disease is treated in two phases; injectable drugs for initial followed by others for continuation. There is a need to develop all-oral treatment methods for M. abscessus infection, especially in the continuation phase. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics. This is the first report to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid ß-lactamase inhibitor capable of inhibiting the class A ß-lactamase produced by M. abscessus, against 43 M. abscessus clinical isolates when combined with five ß-lactam antibiotics. Xeruborbactam lowered the MIC90 values of tebipenem by five dilutions, and the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%). We showed that the tebipenem-xeruborbactam combination might be of interest to explore further as a potentially effective oral regimen for outpatient treatment of M. abscessus pulmonary disease.

Cu-promoted synthesis of triclosan-Mannich and Glaser adducts: anti-mycobacterial evaluation with in silico validations.

Aim: The WHO, Global tuberculosis report 2022 estimated number of tuberculosis (TB) cases reached 10.6 million in 2021, reflecting a 4.5% increase compared with the 10.1 million reported in 2020. The incidence rate of TB showed 3.6% rise from 2020 to 2021. Results/methodology: This manuscript discloses Cu-promoted single pot A3-coupling between triclosan (TCS)-based alkyne, formaldehyde and secondary amines to yield TCS-based Mannich adducts. Additionally, the coupling of TCS-alkynes in the presence of Cu(OAc)2 afforded the corresponding homodimers. Among tested compounds, the most potent one in the series 11 exhibited fourfold higher potency than rifabutin against drug-resistant Mycobacterium abscessus. The selectivity index was also substantially improved, being 26 (day 1) and 15 (day 3), which is four-times better than TCS.

[Box: see text].

In vitro and intracellular activity of vaborbactam combined with ß-lactams against Mycobacterium abscessus.

OBJECTIVES: Mycobacterium abscessus has emerged as an opportunistic pathogen responsible for lung infections, especially in cystic fibrosis patients. In spite of the production of the broad-spectrum ß-lactamase BlaMab, the carbapenem imipenem is recommended in the initial phase of the treatment of pulmonary infections. Here, we determine whether the addition of vaborbactam, a second-generation ß-lactamase inhibitor belonging to the boronate family, improves the activity of ß-lactams against M. abscessus. METHODS: The activity of ß-lactams, alone or in combination with vaborbactam, was evaluated against M. abscessus CIP104536 by determining MICs, time-killing and intramacrophage activity. Kinetic parameters for the inhibition of BlaMab by vaborbactam were determined by spectrophotometry. RESULTS: The combination of vaborbactam (8 mg/L) with ß-lactams decreased more than 8 times the MIC of amoxicillin (from >1024 to 128 mg/L) and 2 times the MICs of meropenem (from 16 to 8 mg/L) and imipenem (from 4 to 2 mg/L). The reduction of the MICs was less than that obtained with avibactam at 4 mg/L for amoxicillin (from >1024 to 16 mg/L, more than 64 times less) and for meropenem (from 16 to 4 mg/L, 4 times less). In vitro and intracellularly, M. abscessus was not killed by the meropenem/vaborbactam combination, in spite of significant in vitro inhibition of BlaMab by vaborbactam. CONCLUSIONS: Inhibition of BlaMab by vaborbactam decreases the MIC of ß-lactams, including that of meropenem. As meropenem/vaborbactam is clinically available, this combination offers an alternative therapeutic option that should be evaluated for the treatment of pulmonary infections due to M. abscessus.

Case Commentary: Dual ß-lactam as part of regimen to treat Mycobacterium abscessus lung disease.

Individuals with compromised lung function and immunity are susceptible to developing chronic Mycobacterium abscessus infection. Current treatment recommendations typically involve using one ß-lactam antibiotic in combination with non-ß-lactam antibiotics. However, a recent case study (B. Becken, K. M. Dousa, J. L. Johnson, S. M. Holland, and R. A. Bonomo, Antimicrob Agents Chemother 68:e00319-24, 2024, https://doi.org/10.1128/aac.00319-24) demonstrated successful treatment of chronic M. abscessus lung disease in a child using two ß-lactam antibiotics simultaneously. This commentary reviews the emerging evidence and outstanding questions regarding dual ß-lactam therapy for M. abscessus infections.

Clofazimine serum concentration and safety/efficacy in nontuberculous mycobacterial pulmonary disease treatment.

BACKGROUND: Clofazimine (CFZ) has shown promising effects against Mycobacterium avium-intracellulare complex pulmonary disease (MAC-PD) and Mycobacterium abscessus species pulmonary disease (MABS-PD). However, the optimal CFZ dose remains unknown. We aimed to explore the relationship between steady-state CFZ concentration and its safety and efficacy in MAC-PD and MABS-PD. METHODS: This prospective observational study focused on patients with MAC-PD and MABS-PD treated with CFZ (UMIN 000041053). To understand the safety and efficacy profile of CFZ and elucidate its optimal concentration, we analyzed CFZ-induced pigmentation grade, QTc interval, and culture conversion outcomes in relation to serum CFZ concentration using Student's t-test, a concentration-QTc model, and multivariable logistic regression analysis, respectively. In total, 64 patients (34 with MAC-PD; 30 with MABS-PD) were included. RESULTS: The steady-state concentration of CFZ was higher in the moderate-to-severe pigmentation group than in the none-to-light pigmentation group (P < 0.001). At a CFZ concentration of 1 mg/L, the QTc interval was prolonged by 17.3 ms (95 % confidence interval [CI], 3.9-25.4) from baseline. Culture conversion was achieved in 33 (51.6 %) patients. The only significant predictor of culture conversion was surgery (adjusted odds ratio, 5.4; 95 % CI, 1.3-38.0). CFZ concentration and MIC of CFZ less than 0.25 mg/L were not associated with culture conversion in this study. CONCLUSION: CFZ-induced pigmentation and QT interval prolongation are associated with serum CFZ concentrations. CFZ dosage may be optimized by monitoring serum CFZ concentration.