AR-12 Exhibits Direct and Host-Targeted Antibacterial Activity toward Mycobacterium abscessus

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.

[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.

Repurposing miconazole and tamoxifen for the treatment of Mycobacterium abscessus complex infections through in silico chemogenomics approach

Drug repositioning is an alternative to overcome the complexity of the drug discovery and approval procedures for the treatment of Mycobacterium abscessus Complex (MABSC) infections that are increasing globally due to the emergency of antimicrobial resistance mechanisms. Here, an in silico chemogenomics approach was performed to compare the sequences from 4942 M. abscessus subsp. abscessus (M. abscessus) proteins with 5258 or 3473 therapeutic targets registered in the DrugBank or Therapeutic Target Database, respectively. This comparison identified 446 drugs or drug candidates whose targets were homologous to M. abscessus proteins. These identified drugs were considered potential inhibitors of MABSC (anti-MABSC activity). Further screening and inspection resulted in the selection of ezetimibe, furosemide, itraconazole, miconazole (MCZ), tamoxifen (TAM), and thiabendazole (THI) for experimental validation. Among them, MCZ and TAM showed minimum inhibitory concentrations (MIC) of 32 and 24 µg mL-1 against M. abscessus, respectively. For M. bolletii and M. massiliense strains, MCZ and TAM showed MICs of 16 and 24 µg mL-1, in this order. Subsequently, the antibacterial activity of MCZ was confirmed in vivo, indicating its potential to reduce the bacterial load in the lungs of infected mice. These results show that MCZ and TAM can serve as molecular scaffolds for the prospective hit-2-lead optimization of new analogs with greater potency, selectivity, and permeability.

Nosiheptide Harbors Potent In Vitro and Intracellular Inhbitory Activities against Mycobacterium tuberculosis

Multidrug-resistant tuberculosis (MDR-TB) is often associated with poor clinical outcomes. In this study, we evaluated the potential of nosiheptide (NOS) as a new drug candidate for treating Mycobacterium tuberculosis infections, including MDR-TB. The antimicrobial susceptibility testing was performed to determine the MICs of NOS against 18 reference strains of slowly growing mycobacteria (SGM) and 128 clinical isolates of M. tuberculosis. The postantibiotic effects (PAE) and interaction with other antituberculosis drugs of NOS were also evaluated using M. tuberculosis H37Rv. Fifteen out of the 18 tested reference strains of SGM had MICs far below 1 μg/mL. From the 128 M. tuberculosis clinical isolates, the MIC₅₀ and MIC₉₀ were 0.25 μg/mL and 1 μg/mL, respectively; the tentative epidemiological cutoff (ECOFF) was defined at 1 μg/mL. Furthermore, a Lys89Thr mutation was found in one M. tuberculosis isolate with a MIC of NOS >8 μg/mL. After 24 h of incubation, NOS at 1 μg/mL inhibited 25.79 ± 1.22% of intracellular bacterial growth, which was comparable with the inhibitory rate of 25.71 ± 3.67% achieved by rifampin at 2 μg/mL. Compared to rifampicin and isoniazid (INH), NOS had a much longer PAE, i.e., a value of about 16 days. In addition, a partial synergy between NOS and INH was observed. NOS has potent inhibitory activities against M. tuberculosis in vitro as well as in macrophages. Furthermore, the long PAE and partial synergistic effect with INH, in addition to the added safety of long-term use as a feed additive in husbandry, provide support for NOS being a promising drug candidate for tuberculosis treatment. IMPORTANCE This study is aimed at chemotherapy for MDR-TB, mainly to explore the anti-TB activity of the existing chemotherapeutic reagent. We found that NOS has potent inhibitory activities against M. tuberculosis in vitro regardless of the drug-resistant profile. Furthermore, NOS also showed the long PAE and partial synergistic effect with INH and is nontoxic, providing support for its promise as a drug candidate for drug-resistant tuberculosis treatment.

In vitro and intracellular inhibitory activities of nosiheptide against Mycobacterium abscessus

The high level of inherent drug resistance of Mycobacterium abscessus makes the infection caused by it very difficult to be treated. The objective of this study was to evaluate the potential of nosiheptide (NOS) as a new drug candidate for treating M. abscessus infections. The microplate AlamarBlue assay was performed to determine the minimum inhibitory concentrations (MICs) of NOS for 28 reference strains of rapidly growing mycobacteria (RGM) and 77 clinical isolates of M. abscessus. Time-kill kinetic and post-antibiotic effect (PAE) of NOS against M. abscessus was evaluated. Its bactericidal activity against M. abscessus in macrophages was determined by an intracellular colony numerating assay. NOS manifested good activity against the reference strains of RGM and M. abscessus clinical isolates in vitro. The MICs of NOS against M. abscessus clinical isolates ranged from 0.0078 to 1 μg/ml, and the MIC₅₀ and MIC₉₀ were 0.125 μg/ml and 0.25 μg/ml, respectively. The pattern of growth and kill by NOS against M. abscessus was moderate with apparent concentration-dependent characteristics, and the PAE value of NOS was found to be ~6 h. Furthermore, NOS had low cell toxicity against the THP-1 cell line after 48 h of exposure (IC₅₀ = 106.9 μM). At 4 μg/ml, NOS exhibited high intracellular bactericidal activity against M. abscessus reference strains with an inhibitory rate of 66.52% ± 1.51%, comparable with that of clarithromycin at 2 μg/ml. NOS showed suitable inhibitory activities against M. abscessus in vitro and in macrophages and could be a potential drug candidate to treat M. abscessus infection.

Treatment of infection-induced vascular pathologies is protective against persistent rough morphotype Mycobacterium abscessus infection in zebrafish

Mycobacterium abscessus infections are of increasing global prevalence and are often difficult to treat due to complex antibiotic resistance profiles. While there are similarities between the pathogenesis of M. abscessus and tuberculous mycobacteria, including granuloma formation and stromal remodelling, there are distinct molecular differences at the host-pathogen interface. Here we have used a zebrafish-M. abscessus model and host-directed therapies that were previously identified in the zebrafish-M. marinum model to identify potential host-directed therapies against M. abscessus infection. We find efficacy of anti-angiogenic and vascular normalizing therapies against rough M. abscessus infection, but no effect of anti-platelet drugs.

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.

AR-12 Has a Bactericidal Activity and a Synergistic Effect with Gentamicin against Group A Streptococcus

Streptococcus pyogenes (group A Streptococcus (GAS) is an important human pathogen that can cause severe invasive infection, such as necrotizing fasciitis and streptococcal toxic shock syndrome. The mortality rate of streptococcal toxic shock syndrome ranges from 20% to 50% in spite of antibiotics administration. AR-12, a pyrazole derivative, has been reported to inhibit the infection of viruses, intracellular bacteria, and fungi. In this report, we evaluated the bactericidal activities and mechanisms of AR-12 on GAS infection. Our in vitro results showed that AR-12 dose-dependently reduced the GAS growth, and 2.5 μg/mL of AR-12 significantly killed GAS within 2 h. AR-12 caused a remarkable reduction in nucleic acid and protein content of GAS. The expression of heat shock protein DnaK and streptococcal exotoxins was also inhibited by AR-12. Surveys of the GAS architecture by scanning electron microscopy revealed that AR-12-treated GAS displayed incomplete septa and micro-spherical structures protruding out of cell walls. Moreover, the combination of AR-12 and gentamicin had a synergistic antibacterial activity against GAS replication for both in vitro and in vivo infection. Taken together, these novel findings obtained in this study may provide a new therapeutic strategy for invasive GAS infection.

A Novel Oxazolidinone, Contezolid (MRX-I), Expresses Anti-Mycobacterium abscessus Activity In Vitro

An evaluation of the anti-Mycobacterium abscessus activity expressed by a novel oxazolidinone, contezolid (MRX-I), toward 12 reference strains and 194 clinical isolates was conducted. Contezolid was active against M. abscessusin vitro, with effects comparable to the anti-M. abscessus effects of linezolid both extracellularly and intracellularly. Contezolid did not antagonize the most frequently used anti-M. abscessus drugs, and preexposure to contezolid did not induce drug resistance. These results provide a novel approach to treating M. abscessus infections.

Current Molecular Therapeutic Agents and Drug Candidates for Mycobacterium abscessus

Mycobacterium abscessus has been recognised as a dreadful respiratory pathogen among the non-tuberculous mycobacteria (NTM) because of misdiagnosis, prolonged therapy with poor treatment outcomes and a high cost. This pathogen also shows extremely high antimicrobial resistance against current antibiotics, including the anti-tuberculosis agents. Therefore, current chemotherapies require a long curative period and the clinical outcomes are not satisfactory. Thus, there is an urgent need for discovering and developing novel, more effective anti-M. abscessus drugs. In this review, we sum the effectiveness of the current anti-M. abscessus drugs and drug candidates. Furthermore, we describe the shortcomings and difficulties associated with M. abscessus drug discovery and development.

Carbonyl Cyanide 3-Chlorophenylhydrazone (CCCP) Exhibits Direct Antibacterial Activity Against Mycobacterium abscessus

Objective

Treatment choices for Mycobacterium abscessus (M. abscessus) infections are very limited, and the prognosis is generally poor. Effective new antibiotics or repurposing existing antibiotics against M. abscessus infection are urgently needed. Carbonyl cyanide 3-chlorophenylhydrazone (CCCP), a member of the lipophilic weak acid class, is known as an efflux pump inhibitor for Mycobacterium tuberculosis. The aim of this study was to determine the inhibitory activity of CCCP as a potential novel antibiotic against M. abscessus.

Methods

A total of 47 reference strains of different mycobacterial species and 60 clinical isolates of M. abscessus were enrolled. In vitro inhibitory activity of CCCP was accessed using microplates alamar blue method with the reference and clinical isolates. The activity of CCCP against intracellular M. abscessus residing within macrophage was also evaluated by intracellular colony numerating assay.

Results

CCCP exhibited good activity against M. abscessus clinical isolates in vitro, the minimum inhibitory concentration (MIC) ranged from 0.47 μg/mL to 3.75 μg/mL, with a MIC₅₀ of 1.875 μg/mL and MIC₉₀ of 3.75 μg/mL. At concentrations safe for the cells, CCCP exhibited highly intracellular bactericidal activities against M. abscessus and M. massiliense reference strains, with inhibitory rates of 84.8%±8.8% and 72.5%±13.7%, respectively. CCCP demonstrated bactericidal activity against intracellular M. abscessus that was comparable to clarithromycin, and concentration-dependent antimicrobial activity against M. abscessus in macrophages was observed. In addition, CCCP also exhibited good activities against most reference strains of rapidly growing mycobacterial species.

Conclusion

CCCP could be a potential candidate of novel antimicrobiological agent to treat M. abscessus infection.

Pipeline of anti-Mycobacterium abscessus small molecules: Repurposable drugs and promising novel chemical entities

The Mycobacterium abscessus complex is a group of emerging pathogens that are difficult to treat. There are no effective drugs for successful M. abscessus pulmonary infection therapy, and existing drug regimens recommended by the British or the American Thoracic Societies are associated with poor clinical outcomes. Therefore, novel antibacterial drugs are urgently needed to contain this global threat. The current anti-M. abscessus small-molecule drug development process can be enhanced by two parallel strategies-discovery of compounds from new chemical classes and commercial drug repurposing. This review focuses on recent advances in the finding of novel small-molecule agents, and more particularly focuses on the activity, mode of action and structure-activity relationship of promising inhibitors from five different chemical classes-benzimidazoles, indole-2-carboxamides, benzothiazoles, 4-piperidinoles, and oxazolidionones. We further discuss some other interesting small molecules, such as thiacetazone derivatives and benzoboroxoles, that are in the early stages of drug development, and summarize current knowledge about the efficacy of repurposable drugs, such as rifabutin, tedizolid, bedaquiline, and others. We finally review targets of therapeutic interest in M. abscessus that may be worthy of future drug and adjunct therapeutic development.

Gallium Porphyrin and Gallium Nitrate Synergistically Inhibit Mycobacterial Species by Targeting Different Aspects of Iron/Heme Metabolism

There is an urgent need for new effective and safe antibiotics active against pathogenic mycobacterial species. Gallium (Ga) nitrate (Ga(NO₃)₃) and Ga porphyrin (GaPP) have each been shown to inhibit the growth of a variety of mycobacterial species. The Ga(III) ion derived from Ga(NO₃)₃ has the potential to disrupt the mycobacterial Fe(III) uptake mechanisms and utilization, including replacing iron (Fe) in the active site of enzymes, resulting in the disruption of function. Similarly, noniron metalloporphyrins such as heme mimetics, which can be transported across the bacterial membrane via heme-uptake pathways, would potentially block the acquisition of iron-containing heme and bind to heme-utilizing proteins, making them nonfunctional. Given that they likely act on different aspects of mycobacterial Fe metabolism, the efficacy of combining Ga(NO₃)₃ and GaPP was studied in vitro against Mycobacterium avium, Mycobacterium abscessus, and Mycobacterium tuberculosis (M. tb). The combination was then assessed in vivo in a murine pulmonary infection model of M. abscessus. We observed that Ga(NO₃)₃ in combination with GaPP exhibited synergistic inhibitory activity against the growth of M. avium, M. tb, and M. abscessus, being most active against M. abscessus. Activity assays indicated that Ga(NO₃)₃ and GaPP inhibited both catalase and aconitase at high concentrations. However, the combination showed a synergistic effect on the aconitase activity of M. abscessus. The Ga(NO₃)₃/GaPP combination via intranasal administration showed significant antimicrobial activity in mice infected with M. abscessus. M. abscessus CFU from the lungs of the Ga(NO₃)₃/GaPP-treated mice was significantly less compared to that of nontreated or single Ga(III)-treated mice. These findings suggest that combinations of different Ga(III) compounds can synergistically target multiple iron/heme-utilizing mycobacterial enzymes. The results support the potential of combination Ga therapy for development against mycobacterial pathogens.