Rough Variants Research Articles

Trehalose polyphleates participate in Mycobacterium abscessus fitness and pathogenesis.

Mycobacteria produce a large repertoire of surface-exposed lipids with major biological functions. Among these lipids, trehalose polyphleates (TPPs) are instrumental in the infection of Mycobacterium abscessus by the therapeutic phage BPs. However, while the biosynthesis and transport of TPPs across the membrane by MmpL10 have been reported, the role of TPPs in host infection remains enigmatic. Here, we addressed whether the loss of TPPs influences interactions with macrophages and the virulence of M. abscessus. As anticipated, the deletion of mmpL10 in smooth (S) and rough (R) variants of M. abscessus abrogated TPP production, which was rescued upon gene complementation. Importantly, infection of human THP-1 cells with the mmpL10 mutants was associated with decreased intramacrophage survival and a reduced proportion of infected cells. The rough mmpL10 mutant showed an impaired capacity to block phagosomal acidification and was unable to co-localize with Galectin-3, a marker of phagosomal membrane damage. This suggests that TPPs participate, directly or indirectly, in phagolysosomal fusion and in phagosomal membrane damage to establish cytosolic communication. The TPP defect that affects the fitness and virulence of M. abscessus was further demonstrated in zebrafish embryos using a rough clinical strain resistant to phage BPs and harboring a frameshift mutation in mmpL10. Infection with this strain was correlated with a slight decrease in embryo survival and a reduced bacterial burden as compared to the corresponding parental and complemented derivatives. Together, these results indicate that TPPs are important surface lipids contributing to the pathogenicity of M. abscessus.IMPORTANCETrehalose polyphleates (TPPs) are complex lipids associated with the mycobacterial cell surface and were identified 50 years ago. While the TPP biosynthetic pathway has been described recently, the role of these lipids in the biology of mycobacteria remains yet to be established. The wide distribution of TPPs across mycobacterial species suggests that they may exhibit important functions in these actinobacteria. Here, we demonstrate that Mycobacterium abscessus, an emerging multidrug-resistant pathogen that causes severe lung diseases in cystic fibrosis patients, requires TPPs for survival in macrophages and virulence in a zebrafish model of infection. These findings support the importance of this underexplored family of lipids in mycobacterial pathogenesis.

Characterization of a Salmonella enterica serovar Typhimurium lineage with rough colony morphology and multidrug resistance

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a major cause of salmonellosis, and the emergence of multidrug-resistant pathovariants has become a growing concern. Here, we investigate a distinct rough colony variant exhibiting a strong biofilm-forming ability isolated in China. Whole-genome sequencing on 2,212 Chinese isolates and 1,739 publicly available genomes reveals the population structure and evolutionary history of the rough colony variants. Characterized by macro, red, dry, and rough (mrdar) colonies, these variants demonstrate enhanced biofilm formation at 28 °C and 37 °C compared to typical rdar colonies. The mrdar variants exhibit extensive multidrug resistance, with significantly higher resistance to at least five classes of antimicrobial agents compared to non-mrdar variants. This resistance is primarily conferred by an IncHI2 plasmid harboring 19 antimicrobial resistance genes. Phylogenomic analysis divides the global collections into six lineages. The majority of mrdar variants belong to sublineage L6.5, which originated from Chinese smooth colony strains and possibly emerged circa 1977. Among the mrdar variants, upregulation of the csgDEFG operons is observed, probably due to a distinct point mutation (−44G > T) in the csgD gene promoter. Pangenome and genome-wide association analyses identify 87 specific accessory genes and 72 distinct single nucleotide polymorphisms associated with the mrdar morphotype.

A Case-Based Review of LVAD Infection by MABC

Abstract We present a review of literature and report a case of left ventricular assist device (LVAD) infection and postsurgical wound infection with Mycobacterium abscessus complex (MABC) following exposure to sewage and tap water, respectively. The initial infectious process involved the driveline and the deep pocket and progressed to involve LVAD. Prior to availability of culture results, the patient was started on linezolid followed by surgical debridement of driveline site and change of exit site. The debrided tissue grew a smooth and a rough colony variant of MABC. After 2 weeks of imipenem intravenous (IV), tigecycline IV, azithromycin oral (PO), and tedizolid PO, the patient presented to us with worsening of wound status. Antimicrobial therapy was changed to amikacin IV, imipenem IV, and cefoxitin IV along with bedside debridement, removal of 3 sutures, and placement of wound vacuum device. Amikacin IV, imipenem IV, and cefoxitin IV were then replaced with Recarbio (imipenem/cilastatin/relebactam) IV plus amoxicillin PO with significant improvement. The patient underwent LVAD removal and heart transplantation after 5 weeks and was discharged 15 days later. Following showering at home, the patient developed signs of extensive infection involving the surgical wound (chest and abdominal walls). Tigecycline IV and azithromycin IV were started. Imipenem/cilastatin/ relebactam IV plus amoxicillin PO were replaced by bedaquiline PO because of the continued financial burden to the patient. The patent was discharged on bedaquiline PO and azithromycin PO to complete 18 months of antimicrobial therapy at which time he was enjoying a very active lifestyle as he did prior to the diagnosis of advanced heart failure. He continues to do well 2 years 9 months after heart transplantation and more than a year after stopping all antimycobacterial therapy.

Transcriptome profiles of macrophages upon infection by morphotypic smooth and rough variants of Mycobacterium abscessus

Mycobacterium abscessus (Mab) infection can be deadly in patients with chronic lung diseases like cystic fibrosis (CF). In vitro and in vivo, Mab may adopt a smooth (S) or rough (R) morphotype, the latter linked to more severe disease conditions. In vitro studies revealed differences in pathogenicity and immune response to S and R morphotypes. We propose that in vivo both morphotypes exist and may transiently switch depending on the environment, having important pathogenic and immunologic consequences. This can be modeled by morphotypic S and R variants of Mab selected based on in vitro growth conditions. Here, we report the first analysis of early transcriptional events in mouse bone marrow derived macrophages (BMDMs) upon infection with media-selected interchangeable Mab-S and Mab-R morphotypes.The early transcriptional events after infection with both morphotypes showed considerable overlap of the pro-inflammatory genes that were differentially regulated compared to the uninfected macrophages. We also observed signature genes significantly differentially regulated in macrophages during infection of media-selected morphotypic Mab-S and Mab-R variants. In conclusion, media-selected Mab-S and Mab-R behave in a similar fashion to stable S and R types with respect to pathogenesis and immune response, serving as a useful model for environmentally influenced morphotype selection.

Evaluation and activity of new porphyrin-peptide cage-type conjugates for the photoinactivation of Mycobacterium abscessus.

Mycobacterium abscessus is increasingly recognized as an emerging opportunistic pathogen causing severe lung diseases and cutaneous infections. However, treatment of M. abscessus infections remains particularly challenging, largely due to intrinsic resistance to a wide panel of antimicrobial agents. New therapeutic alternatives are urgently needed. Herein, we show that, upon limited irradiation with a blue-light source, newly developed porphyrin-peptide cage-type photosensitizers exert a strong bactericidal activity against smooth and rough variants of M. abscessus in planktonic cultures and in biofilms, at low concentrations. Atomic force microscopy unraveled important morphological alterations that include a wrinkled and irregular bacterial surface. The potential of these compounds for a photo-therapeutic use to treat M. abscessus skin infections requires further evaluations.IMPORTANCEMycobacterium abscessus causes persistent infections and is extremely difficult to eradicate. Despite intensive chemotherapy, treatment success rates remain very low. Thus, given the unsatisfactory performances of the current regimens, more effective therapeutic alternatives are needed. In this study, we evaluated the activity of newly described porphyrin-peptide cage-type conjugates in the context of photodynamic therapy. We show that upon light irradiation, these compounds were highly bactericidal against M. abscessus in vitro, thus qualifying these compounds for future studies dedicated to photo-therapeutic applications against M. abscessus skin infections.

Differential Immune Responses and Underlying Mechanisms of Metabolic Reprogramming in Smooth and Rough Variants of Mycobacterium peregrinum Infections.

Mycobacterium peregrinum (Mpgm) is a rapidly growing mycobacteria that is classified as a nontuberculous mycobacterium (NTM) and is commonly found in environmental sources such as soil, water, and animals. Mpgm is considered an opportunistic pathogen that causes infection in immunocompromised individuals or those with underlying medical conditions. Although there have been clinical reports on Mpgm, reports of the immune response and metabolic reprogramming have not been published. Thus, we studied standard Mpgm-ATCC and two clinical strains (Mpgm-S and Mpgm-R) using macrophages and mouse bone marrow-derived cells. Mpgm has two types of colony morphologies: smooth and rough. We grew all strains on the 7H10 agar medium to visually validate the morphology. Cytokine levels were measured via ELISA and real-time PCR. The changes in mitochondrial function and glycolysis in Mpgm-infected macrophages were measured using an extracellular flux analyzer. Mpgm-S-infected macrophages showed elevated levels of inflammatory cytokines, including interleukin (IL)-6, IL-12p40, and tumor necrosis factor (TNF)-α, compared to Mpgm-ATCC- and Mpgm-R-infected macrophages. Additionally, our findings revealed metabolic changes in Mpgm-ATCC and two clinical strains (Mpgm-S and Mpgm-R) during infection; significant changes were observed in the mitochondrial respiration, extracellular acidification, and the oxygen consumption of BMDMs upon Mpgm-S infection. In summary, within the strains examined, Mpgm-S displayed greater virulence, triggered a heightened immune response, and induced more profound shifts in bioenergetic metabolism than Mpgm-ATCC and Mpgm-R. This study is the first to document distinct immune responses and metabolic reorganization following Mpgm infection. These findings lay a crucial foundation for further investigations into the pathogenesis of Mpgm.

Immobilization of rough morphotype Mycolicibacterium neoaurum R for androstadienedione production.

Enhance the androstadienedione (Androst-1,4-diene-3,17-dione, ADD) production of rough morphotype Mycolicibacterium neoaurum R by repeated-batch fermentation of immobilized cells. M. neoaurum R was a rough colony morphotype variant, obtained from the routine plating of smooth M. neoaurum strain CICC 21097. M. neoaurum R showed rougher cell surface and aggregated in broth. The ADD production of M. neoaurum R was notably lower than that of M. neoaurum CICC 21097 during the free cell fermentation, but the yield gap could be erased after proper cell immobilization. Subsequently, repeated-batch fermentation of immobilized M. neoaurum R was performed to shorten the production cycle and enhance the bio-production efficiency of ADD. Through the optimization of the immobilization carriers and the co-solvents for phytosterols, the ADD productivity of M. neoaurum R immobilized by semi-expanded perlite reached 0.075g/L/h during the repeated-batch fermentation for 40days. The ADD production of the rough-type M. neoaurum R was notably enhanced by the immobilization onto semi-expanded perlite. Moreover, the ADD batch yields of M. neoaurum R immobilized by semi-expanded perlite were maintained at high levels during the repeated-batch fermentation.

Silencing essential gene expression in Mycobacterium abscessus during infection.

Mycobacterium abscessus is a multi-drug-resistant non-tuberculous mycobacterial species causing tuberculosis-like lung infections. The functional characterization of the extensive repertoire of genes encoding virulence factors and drug targets has been largely restricted by the lack of powerful genetic tools. In this study, we evaluated the performances of a Tet-OFF system, previously optimized for M. tuberculosis and M. smegmatis. Fluorescence reporter M. abscessus strains were developed where mCherry was under the control of the Tet-OFF regulatory system on an integrative plasmid. The addition of anhydrotetracycline (ATc) correlated with a decrease in fluorescence intensity not only in solid and broth medium but also in colony biofilms, for both smooth and rough variants of M. abscessus. Next, unmarked mmpL3 conditional knockdown mutants were engineered in both smooth and rough M. abscessus. Biochemical studies indicated that the addition of ATc was associated with a dose-dependent decrease in (i) the production of the MmpL3 protein, (ii) the biosynthesis of trehalose dimycolate and mycolylated arabinogalactan, (iii) bacterial viability on agar and liquid medium as well as in biofilms. Importantly, intravenous injection of ATc in zebrafish embryos infected with the rough mmpL3 conditional mutant impeded bacterial growth and correlated with a significant gain in embryo survival. These results suggest that mmpL3 is essential for M. abscessus growth in vitro and in the infected host, thus validating MmpL3 as an attractive drug target. Together, this study demonstrates the potential of ATc-dependent repression to modulate the expression of M. abscessus genes in the infected host. IMPORTANCE Mycobacterium abscessus represents the most common rapidly growing mycobacterial pathogen in cystic fibrosis and is extremely difficult to eradicate. Essential genes are required for growth, often participate in pathogenesis, and encode valid drug targets for further chemotherapeutic developments. However, assessing the function of essential genes in M. abscessus remains challenging due to the limited spectrum of efficient genetic tools. Herein, we generated a Tet-OFF-based system allowing to knock down the expression of mmpL3, encoding the mycolic acid transporter in mycobacteria. Using this conditional mutant, we confirm the essentiality of mmpL3 in planktonic cultures, in biofilms, and during infection in zebrafish embryos. Thus, in this study, we developed a robust and reliable method to silence the expression of any M. abscessus gene during host infection.

Characterization of Mycobacterium abscessus colony-biofilms based on bi-dimensional images.

Mycobacterium abscessus biofilm aggregates have been shown in the lungs of cystic fibrosis patients and are often tolerant to drugs. Herein, we analyzed bi-dimensional images of either fluorescent or Congo red-stained M. abscessus colony-biofilms grown on a membrane to monitor growth and shape of M. abscessus smooth and rough variants. These colony-biofilms responded differently to rifabutin and bedaquiline, thus highlighting the importance of the morphotype to properly address antibiotic treatment in patients with biofilm-related infections.

Altered phagocytosis and morphogenesis of phenotypic switching-derived strains of the pathogenic Candida tropicalis co-cultured with phagocytic cells

Background and objectiveCandida tropicalis is among the most prevalent human pathogenic yeast species. Switch states of C. tropicalis differ in virulence traits. Here, we evaluate the effect of phenotypic switching on phagocytosis and yeast-hyphae transition in C. tropicalis. MethodsC. tropicalis morphotypes included a clinical strain and two switch strains (rough variant and rough revertant). In vitro, phagocytosis assay was performed using peritoneal macrophages and hemocytes. The proportion of hyphal cells was ascertained by scoring morphology using optical microscopy. Expression of the WOR1 (White-opaque regulator 1) and EFG1 (Enhanced filamentous growth protein 1) was determined by quantitative PCR. ResultsThe rough variant was more resistant to in vitro phagocytosis by peritoneal macrophages than that observed for the clinical strain, while hemocytes phagocytosed clinical and rough variant to the same extent. The rough revertant was more phagocytosed than the clinical strain by both phagocytes. During co-incubation with phagocytic cells, the clinical strain of C. tropicalis exists mainly as blastoconidia. The co-culture of the rough variant with macrophages resulted in a higher percentage of hyphae than blastoconidia cells, while in co-culture with hemocytes, no differences were observed between the percentage of hyphae and blastoconidia. The expression levels of WOR1 in the rough variant co-cultured with phagocytes were significantly higher than they were in the clinical strain. ConclusionsDifferences on phagocytosis and hyphal growth between switch states cells of C. tropicalis co-cultured with phagocytic cells were observed. The pronounced hyphal growth may affect the complex host-pathogen relationship and favor the pathogen to escape phagocytosis. The pleiotropic effects of phenotypic switching suggest that this event may contribute to the success of infection associated with C. tropicalis.

Study of the Plastic Behavior of Rough Bearing Surfaces Using a Half-Space Contact Model and the Fatigue Life Estimation According to the Fatemi–Socie Model

A multiscale approach for the fatigue life estimation of rolling bearings is presented in this paper and applied to inner rings of cylindrical roller bearings of the type NU208. The forces acting in the rolling contact are determined from system-oriented modeling at the macro level. The microscale contact simulations are carried out in a half-space contact model. The stresses on the inner ring are determined and used in the local fatigue approach, according to Fatemi–Socie, for fatigue life estimation. Four surface variants were investigated, one ideally smooth surface and three real (rough) surfaces. The three rough surface variants used different finishing processes: fine ground, hard turned, and rough ground were produced. A load case with a maximum pressure of 2.4 GPa in the roller-inner ring contact was investigated. In addition to the fatigue life estimation, the plasticity behavior (surface topography, resulting contact pressure, and residual stress) of the three manufactured surfaces stood in the focus of the work. As the comparison between experimental and simulated results confirms, good predictions can be made with the simulation model.

Cysteamine/Cystamine Exert Anti-Mycobacterium abscessus Activity Alone or in Combination with Amikacin.

Host-directed therapies are emerging as a promising tool in the curing of difficult-to-treat infections, such as those caused by drug-resistant bacteria. In this study, we aim to test the potential activity of the FDA- and EMA-approved drugs cysteamine and cystamine against Mycobacterium abscessus. In human macrophages (differentiated THP-1 cells), these drugs restricted M. abscessus growth similar to that achieved by amikacin. Here, we use the human ex vivo granuloma-like structures (GLS) model of infection with the M. abscessus rough (MAB-R) and smooth (MAB-S) variants to study the activity of new therapies against M. abscessus. We demonstrate that cysteamine and cystamine show a decrease in the number of total GLSs per well in the MAB-S and MAB-R infected human peripheral blood mononuclear cells (PBMCs). Furthermore, combined administration of cysteamine or cystamine with amikacin resulted in enhanced activity against the two M. abscessus morpho variants compared to treatment with amikacin only. Treatment with cysteamine and cystamine was more effective in reducing GLS size and bacterial load during MAB-S infection compared with MAB-R infection. Moreover, treatment with these two drugs drastically quenched the exuberant proinflammatory response triggered by the MAB-R variant. These findings showing the activity of cysteamine and cystamine against the R and S M. abscessus morphotypes support the use of these drugs as novel host-directed therapies against M. abscessus infections.

Rough and smooth variants of Mycobacterium abscessus are differentially controlled by host immunity during chronic infection of adult zebrafish

Prevalence of Mycobacterium abscessus infections is increasing in patients with respiratory comorbidities. After initial colonisation, M. abscessus smooth colony (S) variants can undergo an irreversible genetic switch into highly inflammatory, rough colony (R) variants, often associated with a decline in pulmonary function. Here, we use an adult zebrafish model of chronic infection with R and S variants to study M. abscessus pathogenesis in the context of fully functioning host immunity. We show that infection with an R variant causes an inflammatory immune response that drives necrotic granuloma formation through host TNF signalling, mediated by the tnfa, tnfr1 and tnfr2 gene products. T cell-dependent immunity is stronger against the R variant early in infection, and regulatory T cells associate with R variant granulomas and limit bacterial growth. In comparison, an S variant proliferates to high burdens but appears to be controlled by TNF-dependent innate immunity early during infection, resulting in delayed granuloma formation. Thus, our work demonstrates the applicability of adult zebrafish to model persistent M. abscessus infection, and illustrates differences in the immunopathogenesis induced by R and S variants during granulomatous infection.

Barriers for adoption of Industry 4.0 in sustainable food supply chain: a circular economy perspective

PurposeFood supply chains (FSCs) are fast becoming more and more complex. Sustainability is a necessary strategy in FSCs to meet the environmental, economic and societal requirements. Industry 4.0 (I4.0) applications for a circular economy (CE) will play a significant role in sustainable food supply chains (SFSCs). I4.0 applications can be used in for traceability, tracking, inspection and quality monitoring, environmental monitoring, precision agriculture, farm input optimization, process automation, etc. to improve circularity and sustainability of FSCs. However, the factors integrating I4.0 and CE adoption in SFSC are not yet very well understood. Furthermore, despite such high potential I4.0 adoption is also met with several barriers. The present study identifies and analyzes twelve barriers for the adoption of I4.0 in SFSC from an CE context.Design/methodology/approachA cause-effect analysis and prominence ranking of the barriers are done using Rough-DEMATEL technique. DEMATEL is a widely used technique that is applied for a structured analysis of a complex problems. The rough variant of DEMATEL helps include the uncertainty and vagueness of decision maker related to the I4.0 technologies.Findings“Technological immaturity,” “High investment,” “Lack of awareness and customer acceptance” and “technological limitations and lack of eco-innovation” are identified as the most prominent barriers for adoption of I4.0 in SFSC.Originality/valueSuccessful mitigation of these barriers will improve the sustainability of FSCs through accelerated adoption of I4.0 solutions. The findings of the study will help managers, practitioners and planners to understand and successfully mitigate these barriers.

A Screening of the MMV Pandemic Response Box Reveals Epetraborole as a New Potent Inhibitor against Mycobacterium abscessus.

Mycobacterium abscessus is the one of the most feared bacterial respiratory pathogens in the world. Unfortunately, there are many problems with the current M. abscessus therapies available. These problems include misdiagnoses, high drug resistance, poor long-term treatment outcomes, and high costs. Until now, there have only been a few new compounds or drug formulations which are active against M. abscessus, and these are present in preclinical and clinical development only. With that in mind, new and more powerful anti-M. abscessus medicines need to be discovered and developed. In this study, we conducted an in vitro-dual screen against M. abscessus rough (R) and smooth (S) variants using a Pandemic Response Box and identified epetraborole as a new effective candidate for M. abscessus therapy. For further validation, epetraborole showed significant activity against the growth of the M. abscessus wild-type strain, three subspecies, drug-resistant strains and clinical isolates in vitro, while also inhibiting the growth of M. abscessus that reside in macrophages without cytotoxicity. Furthermore, the in vivo efficacy of epetraborole in the zebrafish infection model was greater than that of tigecycline. Thus, we concluded that epetraborole is a potential anti-M. abscessus candidate in the M. abscessus drug search.

Droplet microarrays for cell culture: effect of surface properties and nanoliter culture volume on global transcriptomic landscape.

The development of novel chemically developed and physically defined surfaces and environments for cell culture and screening is important for various biological applications. The Droplet microarray (DMA) platform based on hydrophilic-superhydrophobic patterning enables high-throughput cellular screening in nanoliter volumes and on various biocompatible surfaces. Here we performed phenotypic and transcriptomic analysis of HeLa-CCL2 cells cultured on DMA, with a goal to analyze cellular response on different surfaces and culture volumes down to 3 nL, compared with conventional cell culture platforms. Our results indicate that cells cultured on four tested substrates: nanostructured nonpolymer, rough and smooth variants of poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) polymer and poly(thioether) dendrimer are compatible with cells grown in Petri dish. Cells cultured on nanostructured nonpolymer coating exhibited the closet transcriptomic resemblance to that of cells grown in Petri dish. Analysis of cells cultured in 100, 9, and 3 nL media droplets on DMA indicated that all but cells grown in 3 nL volumes had unperturbed viability with minimal alterations in the transcriptome compared with 96-well plate. Our findings demonstrate the applicability of DMA for cell-based assays and highlight the possibility of establishing regular cell culture on various biomaterial-coated substrates and in nanoliter volumes, along with routinely used cell culture platforms.

Beyond phenotype: The genomic heterogeneity of co-infecting Mycobacterium abscessus smooth and rough colony variants in cystic fibrosis patients

Two unrelated cystic fibrosis patients were co-infected with Mycobacterium abscessus smooth and rough phenotypes. Smooth M. abscessus is proposed as the infecting form, and the subsequent loss of glycopeptidolipids in the host leads to a rough phenotype. Whole-genome sequencing (WGS) diagnosed two different M. abscessus strains in patient N°1 but only one strain in patient N°2. In patient N°1, rough isolate had novel mutations potentially involved in smooth-to-rough morphology changes. In patient N°2, four genes were present in only the smooth isolate. In addition, we obtained different susceptibility profiles in the four clinical isolates. We revealed a new paradigm describing a cystic fibrosis patient infected with two different clones, including a rough isolate, and identifying a rough M. abscessus clone that did not lose glycopeptidolipids. We propose WGS for the identification of heterogenic isolates and genetic determinants of antimicrobial resistance, which we believe will positively influence treatment prognosis.

Maillard reaction products inhibit the periodontal pathogen Aggregatibacter actinomycetemcomitans by chelating iron

ObjectiveTo determine the mechanism of growth inhibition of Aggregatibacter actinomycetemcomitans by Maillard reaction products (MRP). DesignGrowth and cell viabilities in the presence or absence of MRP were measured for both the rough and smooth variants of the bacteria. Effects of addition of ferrous and ferric ions on the inhibition of the bacteria by MRP were determined. ResultsMRPs decreased the extent of complex formation of Chrome Azurol S with iron suggesting that MRPs can chelate iron effectively. The chelation causes growth inhibition of both the rough and smooth strains. At low concentrations of the inhibitor, lag time was extended by approximately 12 h while at high concentrations, cells were killed, decreasing cell viability by up to 8 orders of magnitude. Growth of both the rough and smooth strains could be restored to original level by addition of iron. For the rough strain, both ferrous and ferric ions could relieve the inhibition by MRP while for the smooth strain only ferrous ion was effective. ConclusionMRPs inhibit the growth of A. actinomycetemcomitans by chelating iron and the inhibition can be relieved by addition of iron.

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.

Alternative Treatment to Remove Resistant Strains of Vibrio cholerae in Water

AbstractResistant strains of Vibrio cholerae have the potential to reemerge in aquatic reservoirs where they remain in a viable but not cultivable (VBNC) state, or as a rough variant embedded in an...