Identification of the Optimal Cultivation Period Required to Isolate Representatives of Mycobacterium abscessus Complex Isolated from Patients with Cystic Fibrosis.

BACKGROUND: In patients with cystic fibrosis (CF), representatives of the fast-growing Mycobacterium abscessus complex (MABSc) are often distinguished, but the culture of the material taken from such patients increases the growth time. We analyzed the terms of cultivation of MABSc representatives on dense nutrient media and also evaluated the productivity of a modified nutrient medium based on agar for the isolation of Burkholderia cepacia complex (BCC). METHODS: Sixty-four strains of MABSc isolated from patients with CF and suspected tuberculosis were analyzed. The material from the patients was cultured on a universal chromogenic medium, 5% blood agar, yolk-salt agar, selective medium for isolation of BCC, and Löwenstein-Jensen medium. The cultures were incubated for 5 days (37°C, aerobic conditions), after for 23 days (28°C, aerobic conditions). The productivity of the developed nutrient medium was evaluated by the number of cells that gave visible growth after culturing 0.1 mL of a bacterial suspension of 103 CFU/mL. RESULTS: 76.8% of the strains grew in a 2-week period, and 23.2% of the strains were obtained at a later date from 18 to 28 days (average: 21.23 days). The modified medium with a concentration of 240 mg of iron (III) polymaltose hydroxide proved to be the most optimal for the isolation of MABSc. CONCLUSION: When using a chromogenic medium for culture material from patients with CF, it is necessary to extend incubation up to 28 days to increase the probability of MABSc isolation. The modified BCC medium showed a good selectivity result but required further investigation.

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

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

Loss of LpqM proteins in Mycobacterium abscessus is associated with impaired intramacrophage survival.

Mycobacterium abscessus, an emerging pathogen responsible for severe pulmonary infections in cystic fibrosis patients, displays either a smooth (S) or a rough (R) morphotype. Infections with M. abscessus R are associated with increased pathogenicity in animal models and humans. While the S-to-R transition correlating with reduced glycopeptidolipid (GPL) production is well-documented, the recent screening of a transposon library revealed additional gene candidates located outside of the GPL locus involved in this transition. These genes include MAB_1470c, encoding the putative lipoprotein peptidase LpqM. However, experimental confirmation of the implication of this gene in the morphotype switch is lacking. Herein, we re-examined the role of MAB_1470c, and its homolog MAB_1466c, in colonial morphotype changes by generating unmarked deletion mutants in M. abscessus S. Our results indicate that the morphotype of these mutants stayed smooth in different media. Unexpectedly, the intracellular growth of ΔMAB_1470c and ΔMAB_1466c in THP-1 macrophages was significantly reduced as compared to the parental S strain, and these defects were rescued upon complementation with their corresponding genes. Strikingly, the intracellular survival defect was further exacerbated in a mutant lacking both MAB_1470c and MAB_1466c genes. This implies that, despite their primary sequence relatedness, the two proteins are not functionally redundant. Collectively, this suggests that these two LpqM-related lipoproteins are unlikely to be involved in the S-to-R transition but are key players for intramacrophage survival of M. abscessus. IMPORTANCE: Mycobacterium abscessus causes persistent infections in patients with underlying pulmonary diseases, resulting in progressive lung function deterioration. The rough (R) morphotype is well-established as associated with chronic and more aggressive infections in patients. In this study, we individually and simultaneously deleted the MAB_1470c and MAB_1466c genes in M. abscessus S, without observing changes in colony morphotypes. However, these mutants exhibited a severe impairment in their ability to survive within human macrophages, highlighting the critical role of these two lipoproteins in M. abscessus virulence.

In Vitro Resistance against DNA Gyrase Inhibitor SPR719 in Mycobacterium avium and Mycobacterium abscessus.

The aminobenzimidazole SPR719 targets DNA gyrase in Mycobacterium tuberculosis. The molecule acts as inhibitor of the enzyme's ATPase located on the Gyrase B subunit of the tetrameric Gyrase A2B2 protein. SPR719 is also active against non-tuberculous mycobacteria (NTM) and recently entered clinical development for lung disease caused by these bacteria. Resistance against SPR719 in NTM has not been characterized. Here, we determined spontaneous in vitro resistance frequencies in single step resistance development studies, MICs of resistant strains, and resistance associated DNA sequence polymorphisms in two major NTM pathogens Mycobacterium avium and Mycobacterium abscessus. A low-frequency resistance (10-8/CFU) was associated with missense mutations in the ATPase domain of the Gyrase B subunit in both bacteria, consistent with inhibition of DNA gyrase as the mechanism of action of SPR719 against NTM. For M. abscessus, but not for M. avium, a second, high-frequency (10-6/CFU) resistance mechanism was observed. High-frequency SPR719 resistance was associated with frameshift mutations in the transcriptional repressor MAB_4384 previously shown to regulate expression of the drug efflux pump system MmpS5/MmpL5. Our results confirm DNA gyrase as target of SPR719 in NTM and reveal differential resistance development in the two NTM species, with M. abscessus displaying high-frequency indirect resistance possibly involving drug efflux. IMPORTANCE Clinical emergence of resistance to new antibiotics affects their utility. Characterization of in vitro resistance is a first step in the profiling of resistance properties of novel drug candidates. Here, we characterized in vitro resistance against SPR719, a drug candidate for the treatment of lung disease caused by non-tuberculous mycobacteria (NTM). The identified resistance associated mutations and the observed differential resistance behavior of the two characterized NTM species provide a basis for follow-up studies of resistance in vivo to further inform clinical development of SPR719.

Type I Interferons Are Involved in the Intracellular Growth Control of Mycobacterium abscessus by Mediating NOD2-Induced Production of Nitric Oxide in Macrophages.

Mycobacterium abscessus (MAB) is one of the rapidly growing, multidrug-resistant non-tuberculous mycobacteria (NTM) causing various diseases including pulmonary disorder. Although it has been known that type I interferons (IFNs) contribute to host defense against bacterial infections, the role of type I IFNs against MAB infection is still unclear. In the present study, we show that rIFN-ß treatment reduced the intracellular growth of MAB in macrophages. Deficiency of IFN-α/ß receptor (IFNAR) led to the reduction of nitric oxide (NO) production in MAB-infected macrophages. Consistently, rIFN-ß treatment enhanced the expression of iNOS gene and protein, and NO production in response to MAB. We also found that NO is essential for the intracellular growth control of MAB within macrophages in an inhibitor assay using iNOS-deficient cells. In addition, pretreatment of rIFN-ß before MAB infection in mice increased production of NO in the lungs at day 1 after infection and promoted the bacterial clearance at day 5. However, when alveolar macrophages were depleted by treatment of clodronate liposome, rIFN-ß did not promote the bacterial clearance in the lungs. Moreover, we found that a cytosolic receptor nucleotide-binding oligomerization domain 2 (NOD2) is required for MAB-induced TANK binding kinase 1 (TBK1) phosphorylation and IFN-ß gene expression in macrophages. Finally, increase in the bacterial loads caused by reduction of NO levels was reversed by rIFN-ß treatment in the lungs of NOD2-deficient mice. Collectively, our findings suggest that type I IFNs act as an intermediator of NOD2-induced NO production in macrophages and thus contribute to host defense against MAB infection.

Assessment of in vitro activities of novel modified antimicrobial peptides against clarithromycin resistant Mycobacterium abscessus.

Mycobacterium abscessus (Mab) is one of the most drug resistant bacteria with a high treatment failure rate. Antimicrobial peptides (AMPs) are alternative therapeutic agents against this infection. This study was aimed to assess the in vitro activities of thirteen AMPs (S5, S52, S6, S61, S62, S63, KLK, KLK1, KLK2, Pug-1, Pug-2, Pug-3 and Pug-4) that have never been investigated against drug resistant Mab isolates. Only four novel modified AMPs (S61, S62, S63 and KLK1) provided the lowest minimum inhibitory concentration (MIC) values ranging from 200-400 µg/ml against the Mab ATCC19977 strain. These four potential AMPs were further tested with 16 clinical isolates of clarithromycin resistant Mab. The majority of the tested strains (10/16 isolates, 62.5%) showed ~99% kill by all four AMPs within 24 hours with an MIC <50 µg/ml. Only two isolates (12.5%) with acquired clarithromycin resistance, however, exhibited values <50 µg/ml of four potential AMPs, S61, S62, S63 and KLK1 after 3-days-incubation. At the MICs level, S63 showed the lowest toxicity with 1.50% hemolysis and 100% PBMC viability whereas KLK1 showed the highest hemolysis (10.21%) and lowest PBMC viability (93.52%). S61, S62 and S63 were further tested with clarithromycin-AMP interaction assays and found that 5/10 (50%) of selected isolates exhibited a synergistic interaction with 0.02-0.41 FICI values. This present study demonstrated the potential application of novel AMPs as an adjunctive treatment with clarithromycin against drug resistant Mab infection.

A simple, efficient and cost-effective method for medium- to longterm maintenance and storage of Mycobacterium abscessus complex organisms.

Traditional culture of non-tuberculous mycobacteria (NTMs) has involved egg-based formulations (Lowenstein-Jensen medium, Ogawa Egg medium) or defined media (Middlebrook formulations), which have disadvatages of composition complexity, availability and cost. Previously, the commercial agar formulation, Standard Plate Count (SPC) agar [Yeast extract 2.5 g/L, pancreatic digest of casein 5.0 g/L, glucose 1.0 g/L, agar 15.0 g/L, pH 7.0 ± 0.2 at 25 °C] has been shown to be an effective solid medium for the enumeration and laboratory manipulation of Mycobacterium abscessus complex organisms. Given its relative simplicity, commercial availability and inexpensive cost, we wished to evaluate its utility for the medium- to longterm maintenance/storage of these organisms. M. abscessus complex organisms (n = 33), were inoculated onto SPCA slopes and stored undistubed in the dark at ambient temperature for six months. Following this, slopes were broken out and culture of the NTM attempted. All slopes maintained NTM culture viability and were able to initiate growth six months later. We therefore advocate the cost-effective employment of SPCA slopes for the medium- to longterm maintenance of M. abscessus organisms, without the need for complex media, availability of sterile blood and requirements for continuous -80 °C freezing.

Biofilm formation in the lung contributes to virulence and drug tolerance of Mycobacterium tuberculosis.

Tuberculosis is a chronic disease that displays several features commonly associated with biofilm-associated infections: immune system evasion, antibiotic treatment failures, and recurrence of infection. However, although Mycobacterium tuberculosis (Mtb) can form cellulose-containing biofilms in vitro, it remains unclear whether biofilms are formed during infection in vivo. Here, we demonstrate the formation of Mtb biofilms in animal models of infection and in patients, and that biofilm formation can contribute to drug tolerance. First, we show that cellulose is also a structural component of the extracellular matrix of in vitro biofilms of fast and slow-growing nontuberculous mycobacteria. Then, we use cellulose as a biomarker to detect Mtb biofilms in the lungs of experimentally infected mice and non-human primates, as well as in lung tissue sections obtained from patients with tuberculosis. Mtb strains defective in biofilm formation are attenuated for survival in mice, suggesting that biofilms protect bacilli from the host immune system. Furthermore, the administration of nebulized cellulase enhances the antimycobacterial activity of isoniazid and rifampicin in infected mice, supporting a role for biofilms in phenotypic drug tolerance. Our findings thus indicate that Mtb biofilms are relevant to human tuberculosis.

Etamycin as a Novel Mycobacterium abscessus Inhibitor.

The increase in drug-resistant Mycobacterium abscessus, which has become resistant to existing standard-of-care agents, is a major concern, and new antibacterial agents are strongly needed. In this study, we introduced etamycin that showed an excellent activity against M. abscessus. We found that etamycin significantly inhibited the growth of M. abscessus wild-type strain, three subspecies, and clinical isolates in vitro and inhibited the growth of M. abscessus that resides in macrophages without cytotoxicity. Furthermore, the in vivo efficacy of etamycin in the zebrafish (Danio rerio) infection model was greater than that of clarithromycin, which is recommended as the core agent for treating M. abscessus infections. Thus, we concluded that etamycin is a potential anti-M. abscessus candidate for further development as a clinical drug candidate.

Dissecting the antibacterial activity of oxadiazolone-core derivatives against Mycobacterium abscessus.

Mycobacterium abscessus (M. abscessus), a rapidly growing mycobacterium, is an emergent opportunistic pathogen responsible for chronic bronchopulmonary infections in individuals with respiratory diseases such as cystic fibrosis. Most treatments of M. abscessus pulmonary infections are poorly effective due to the intrinsic resistance of this bacteria against a broad range of antibiotics including anti-tuberculosis agents. Consequently, the number of drugs that are efficient against M. abscessus remains limited. In this context, 19 oxadiazolone (OX) derivatives have been investigated for their antibacterial activity against both the rough (R) and smooth (S) variants of M. abscessus. Several OXs impair extracellular M. abscessus growth with moderated minimal inhibitory concentrations (MIC), or act intracellularly by inhibiting M. abscessus growth inside infected macrophages with MIC values similar to those of imipenem. Such promising results prompted us to identify the potential target enzymes of the sole extra and intracellular inhibitor of M. abscessus growth, i.e., compound iBpPPOX, via activity-based protein profiling combined with mass spectrometry. This approach led to the identification of 21 potential protein candidates being mostly involved in M. abscessus lipid metabolism and/or in cell wall biosynthesis. Among them, the Ag85C protein has been confirmed as a vulnerable target of iBpPPOX. This study clearly emphasizes the potential of the OX derivatives to inhibit the extracellular and/or intracellular growth of M. abscessus by targeting various enzymes potentially involved in many physiological processes of this most drug-resistant mycobacterial species.

Sirtuin 3 is essential for host defense against Mycobacterium abscessus infection through regulation of mitochondrial homeostasis.

The global incidence of Mycobacterium abscessus (Mabc), a rapidly growing nontuberculous mycobacterial strain that causes treatment-refractory pulmonary diseases, is increasing. Despite this, the host factors that allow for protection against infection are largely unknown. In this study, we found that sirtuin 3 (SIRT3), a mitochondrial protein deacetylase, plays a critical role in host defense against Mabc infection. Mabc decreased SIRT3 and upregulated mitochondrial oxidative stress in macrophages. SIRT3 deficiency led to increased bacterial loads, histopathological, and mitochondrial damage, and pathological inflammation during Mabc infection. Administration of scavengers of mitochondrial reactive oxygen species significantly decreased the in vivo Mabc burden and excessive inflammation, and induced SIRT3 expression in infected lungs. Notably, SIRT3 agonist (resveratrol) significantly decreased Mabc growth and attenuated inflammation in mice and zebrafishes, indicating the key role for SIRT3 in metazoan host defense. Collectively, these data strongly suggest that SIRT3 is a host-directed therapeutic target against Mabc infection by controlling mitochondrial homeostasis.

Comparison of four agar media for the enumeration of the Mycobacterium abscessus complex.

Background: Traditional culture of nontuberculous mycobacteria (NTMs) has involved egg-based formulations (Lowenstein-Jensen medium) or defined media (Middlebrook formulations), which have disadvantages of composition complexity, availability, and cost. This study quantitatively compared three non-selective, non-blood based basal agars with Columbia blood agar (CBA), to enumerate Mycobacterium abscessus complex organisms in pure culture. Methods: M. abscessus subsp. massiliense, M. abscessus subsp. bolletii, and M. abscessus subsp. abscessus were employed. Inocula of each of these were counted on three basal agar media, including (i) standard plate count agar (SPCA), (ii) tryptone soya agar (TSA), and (iii) Mueller-Hinton agar (MHA) and compared to counts on CBA. Results: All NTM isolates of all subspecies grew successfully on all four media examined. The growth was most profuse on SPCA, with a mean colony diameter of 3 mm, whereas the mean colony diameter on all other media was 1 mm. Statistically, there was no significant difference in counts when comparing CBA with SPCA or MHA (P > 0.05), whereas there was a statistically significant difference between CBA and TSA (P = 0.01). There was no statistically significant difference between SPCA and MHA (P = 0.53). Conclusion: This study indicates that SPCA and MHA are equally effective as CBA, when enumerating of M. abscessus complex organisms. Employment of TSA gave significantly lower counts than CBA (P = 0.01) and therefore should not be employed when enumerating these organisms. SPCA yielded the most profuse growth of all media examined. In addition to these advantages, given that SPCA does (i) not require blood as a medium constituent, (ii) is simple to reconstitute, (iii) is relatively cheap, and (iv) is widely available commercially, this study endorses employment of SPCA for the nonselective culture of M. abscessus complex organisms, including enumeration.

Mycobacterium abscessus subsp. massiliense expressing bacterioferritin have improved resistance to stressful conditions.

AIMS: The importance of bacterioferritin in the virulence and pathogenicity of the genus Mycobacterium is still unclear. The aim of this study was to analyse if the expression of a recombinant bacterioferritin from M. tuberculosis (Mtb) by Mycma could improve the capacity of this bacillus to resist the host defence mechanisms. METHODS AND RESULTS: Recombinant Mycma, expressing bacterioferritin (Rv1876) from Mtb, was developed by transformation with pMIP12_Rv1876. To determine bacterioferritin influence on Mycma physiology and virulence, the mycobacteria growth was analysed in vitro and in vivo. It was observed that the expression of bacterioferritin improved the growth rate of recombinant Mycma_BfrA under iron excess and oxidative stress, as compared to the wild type. Furthermore, in the murine model of infection, it was observed that Mycma_BfrA-infected mice had higher bacillary load and a more pronounced lesion in the lungs when compared with the wild type. CONCLUSION: This study showed that bacterioferritin confers additional resistance to stress conditions, resulting in increased pathogenicity of Mycma during mice infection. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides new insights about the importance of bacterioferritin in the virulence and pathogenicity of the Mycobacterium genus.

PLGA nanocapsules improve the delivery of clarithromycin to kill intracellular Staphylococcus aureus and Mycobacterium abscessus.

Drug delivery systems are promising for targeting antibiotics directly to infected tissues. To reach intracellular Staphylococcus aureus and Mycobacterium abscessus, we encapsulated clarithromycin in PLGA nanocapsules, suitable for aerosol delivery by nebulization of an aqueous dispersion. Compared to the same dose of free clarithromycin, nanoencapsulation reduced 1000 times the number of intracellular S. aureus in vitro. In RAW cells, while untreated S. aureus was located in acidic compartments, the treated ones were mostly situated in non-acidic compartments. Clarithromycin-nanocapsules were also effective against M. abscessus (70-80% killing efficacy). The activity of clarithromycin-nanocapsules against S. aureus was also confirmed in vivo, using a murine wound model as well as in zebrafish. The permeability of clarithromycin-nanocapsules across Calu-3 monolayers increased in comparison to the free drug, suggesting an improved delivery to sub-epithelial tissues. Thus, clarithromycin-nanocapsules are a promising strategy to target intracellular S. aureus and M. abscessus.

Non-pigmented rapidly growing mycobacteria smooth and rough colony phenotypes pathogenicity evaluated using in vitro and experimental models.

Non-pigmented rapidly growing mycobacteria (NPRGM) are widely distributed in water, soil and animals. It has been observed an increasing importance of NPRGM related-infections, particularly due to the high antimicrobial resistance. NPRGM have rough and smooth colony phenotypes, and several studies have showed that rough colony variants are more virulent than smooth ones. However, other studies have failed to validate this observation. In this study, we have performed two models, invitro and in vivo, in order to assess the different pathogenicity of these two phenotypes. We used collection and clinical strains of Mycobacteriumabscessus, Mycobacterium fortuitum and Mycobacteriumchelonae. On the invitro model (macrophages), phagocytosis was higher for M. abscessus and M. fortuitum rough colony variant strains when compared to smooth colony variants. However, we did not find differences with colonial variants of M. chelonae. Survival of Galleriamellonella larvae in the experimental model was lower for M. abscessus and M. fortuitum rough colony variants when compared with larvae infected with smooth colony variants. We did not find differences in larvae infected with M. chelonae.Results of our in vivo study correlated well with the experimental model. This fact could have implications on the interpretation of the clinical significance of the NPRGM isolate colonial variants.

Naturally-Occurring Polymorphisms in QcrB Are Responsible for Resistance to Telacebec in Mycobacterium abscessus.

Mycobacterium abscessus (M. abscessus) is a rapidly growing nontuberculous mycobacteria that is quickly emerging as a global health concern. M. abscessus pulmonary infections are frequently intractable due to the high intrinsic resistance to most antibiotics. Therefore, there is an urgent need to discover effective pharmacological options for M. abscessus infections. In this study, the potency of the antituberculosis drug Telacebec (Q203) was evaluated against M. abscessus. Q203 is a clinical-stage drug candidate targeting the subunit QcrB of the cytochrome bc1:aa3 terminal oxidase. We demonstrated that the presence of four naturally-occurring polymorphisms in the M. abscessus QcrB is responsible for the high resistance of the bacterium to Q203. Genetics reversion of the four polymorphisms sensitized M. abscessus to Q203. While this study highlights the limitation of a direct drug repurposing approach of Q203 and related drugs for M. abscessus infections, it reveals that the M. abscessus cytochrome bc1:aa3 respiratory branch is sensitive to chemical inhibition.

Identification of New MmpL3 Inhibitors by Untargeted and Targeted Mutant Screens Defines MmpL3 Domains with Differential Resistance.

The Mycobacterium tuberculosis mycolate flippase MmpL3 has been the proposed target for multiple inhibitors with diverse chemical scaffolds. This diversity in chemical scaffolds has made it difficult to predict compounds that inhibit MmpL3 without whole-genome sequencing of isolated resistant mutants. Here, we describe the identification of four new inhibitors that select for resistance mutations in mmpL3. Using these resistant mutants, we conducted a targeted whole-cell phenotypic screen of 163 novel M. tuberculosis growth inhibitors for differential growth inhibition of wild-type M. tuberculosis compared to the growth of a pool of 24 unique mmpL3 mutants. The screen successfully identified six additional putative MmpL3 inhibitors. The compounds were bactericidal both in vitro and against intracellular M. tuberculosisM. tuberculosis cells treated with these compounds were shown to accumulate trehalose monomycolates, have reduced levels of trehalose dimycolate, and displace an MmpL3-specific probe, supporting MmpL3 as the target. The inhibitors were mycobacterium specific, with several also showing activity against the nontuberculous mycobacterial species M. abscessus Cluster analysis of cross-resistance profiles generated by dose-response experiments for each combination of 13 MmpL3 inhibitors against each of the 24 mmpL3 mutants defined two clades of inhibitors and two clades of mmpL3 mutants. Pairwise combination studies of the inhibitors revealed interactions that were specific to the clades identified in the cross-resistance profiling. Additionally, modeling of resistance-conferring substitutions to the MmpL3 crystal structure revealed clade-specific localization of the residues to specific domains of MmpL3, with the clades showing differential resistance. Several compounds exhibited high solubility and stability in microsomes and low cytotoxicity in macrophages, supporting their further development. The combined study of multiple mutants and novel compounds provides new insights into structure-function interactions of MmpL3 and small-molecule inhibitors.

Cyclipostins and Cyclophostin Analogues as Multitarget Inhibitors That Impair Growth of Mycobacterium abscessus.

Twelve new Cyclophostin and Cyclipostins analogues (CyC19-30) were synthesized, thus extending our series to 38 CyCs. Their antibacterial activities were evaluated against four pathogenic mycobacteria (Mycobacterium abscessus, Mycobacterium marinum, Mycobacterium bovis BCG, and Mycobacterium tuberculosis) and two Gram negative bacteria. The CyCs displayed very low toxicity toward host cells and were only active against mycobacteria. Importantly, several CyCs were active against extracellular M. abscessus (CyC17/CyC18ß/CyC25/CyC26) or intramacrophage residing mycobacteria (CyC7(α,ß)/CyC8(α,ß)) with minimal inhibitory concentrations (MIC50) values comparable to or better than those of amikacin or imipenem, respectively. An activity-based protein profiling combined with mass spectrometry allowed identification of the potential target enzymes of CyC17/CyC26, mostly being involved in lipid metabolism and/or in cell wall biosynthesis. Overall, these results strengthen the selective activity of the CyCs against mycobacteria, including the most drug-resistant M. abscessus, through the cumulative inhibition of a large number of Ser- and Cys-enzymes participating in key physiological processes.