Tuberculosis (TB), an infectious disease, has been a leading cause of morbidity and mortality for decades. The causative agent of TB is the Mycobacterium tuberculosis (Mtb) which can infects various parts of the body, mainly the lungs in pulmonary TB cases. Mycobacterium bovis Bacillus Calmette–Guerin (BCG) is the only approved vaccine for TB, but its efficiency to combat pulmonary TB is limited. Multidrug-resistant (MDR) TB and extensive drug-resistant (XDR) TB requires the evolution of more potent vaccines. Therefore, this research aims to generate a universal TB subunit vaccine using advanced immunoinformatics techniques. In generating a novel multiepitope subunit vaccine, we selected the conserved and experimentally confirmed antigens Rv0058, Rv0101, and Rv3343. After a rigorous evaluation, the top candidates from predicted Helper T-lymphocytes (HTL), Cytotoxic T-lymphocytes (CTL), and B-cell epitopes were considered potential vaccine candidates. Immunogenicity was enhanced by the addition of an adjuvant to the ultimate construct of the vaccine. B-cell epitopes predictions guaranteed the eventual induction of a humoral response. Thereafter, dynamics simulations and molecular docking validated the vaccine-receptor complex’s stability and high affinity for the immune receptor TLR-3. Also, immune simulations revealed the significantly elevated levels of immunoglobulins such as IgM, cytokines such as interleukin-2, helper T (Th) cells, and cytotoxic T-cell populations. These results agreed with the actual inflammatory response and showed rapid antigen clearance after manifold exposure. Finally, the E. coli K12 strain was confirmed via in-silico cloning for quality expression. Nevertheless, in vivo experiments should be performed to validate the safety of the proposed vaccine and its inherent ability to prevent TB infection.

The polymorphism at amino acid 17 of quinolone resistance-determining region of GyrA has been stated with a potential role in fluoroquinolone susceptibility in different mycobacterial species. However, no study has provided dependable evidence so far. Here, we verified that gene-edited Mycobacterium abscessus mutants bearing Ser/Gly at this position were more susceptible to fluoroquinolones than their parent strain and the revertant that supports mycobacteria containing Ser/Gly at this position were more susceptible to fluoroquinolones than those containing Ala. IMPORTANCE: Fluoroquinolones (FQs) play a key role in the treatment regimens against tuberculosis and non-tuberculous mycobacterial infections. However, there are significant differences in the sensitivities of different mycobacteria to FQs. In this study, we proved that this is associated with the polymorphism at amino acid 17 of quinolone resistance-determining region of Gyrase A by gene editing. This is the first study using CRISPR-associated recombination for gene editing in Mycobacterium abscessus to underscore the contribution of the amino acid substitutions in GyrA to FQ susceptibilities in mycobacteria.

Mycobacterium abscessus, a fast‐growing, non‐tuberculous mycobacterium resistant to most antimicrobial drugs, causes a wide range of serious infections in humans, posing a significant public health challenge. The development of effective genetic manipulation tools for M. abscessus is still in progress, limiting both research and therapeutic advancements. However, the clustered regularly interspaced short palindromic repeats (CRISPR)‐associated protein (Cas) systems have emerged as promising tools for generating highly specific double‐strand breaks (DSBs) in its genome. One of the mechanisms that repair these DSBs is the error‐prone nonhomologous end‐joining (NHEJ) pathway, which facilitates targeted gene editing. In this study, we introduced a novel application of the CRISPR‐NHEJ approach in M. abscessus. We demonstrated that NrgA from M. marinum plays a crucial role in repairing DSBs induced by the CRISPR‐Cas system in M. abscessus. Contrary to previous findings, our study also revealed that inhibiting or overexpressing components of homologous recombination/single‐strand annealing significantly reduces the efficiency of NHEJ repair in M. abscessus. This discovery challenges current perspectives and suggests that NHEJ repair in M. abscessus may involve components from both homologous recombination and single‐strand annealing pathways, highlighting the complex interactions among the three DSB repair mechanisms in M. abscessus.

Introduction: Infections caused by non-tuberculosis mycobacteria are significantly worsening across the globe. M. fortuitum complex is a rapidly growing pathogenic species that is of clinical relevance to both humans and animals. This pathogen has the potential to create adverse effects on human healthcare.Methods: The MF GZ001 clinical strain was collected from the sputum of a 45-year-old male patient with a pulmonary infection. The morphological studies, comparative genomic analysis, and drug resistance profiles along with variants detection were performed in this study. In addition, comparative analysis of virulence genes led us to understand the pathogenicity of this organism.Results: Bacterial growth kinetics and morphology confirmed that MF GZ001 is a rapidly growing species with a rough morphotype. The MF GZ001 contains 6413573 bp genome size with 66.18 % high G+C content. MF GZ001 possesses a larger genome than other related mycobacteria and included 6156 protein-coding genes. Molecular phylogenetic tree, collinearity, and comparative genomic analysis suggested that MF GZ001 is a novel member of the M. fortuitum complex. We carried out the drug resistance profile analysis and found single nucleotide polymorphism (SNP) mutations in key drug resistance genes such as rpoB, katG, AAC(2')-Ib, gyrA, gyrB, embB, pncA, blaF, thyA, embC, embR, and iniA. In addition, the MF GZ001strain contains mutations in iniA, iniC, pncA, and ribD which conferred resistance to isoniazid, ethambutol, pyrazinamide, and para-aminosalicylic acid respectively, which are not frequently observed in rapidly growing mycobacteria. A wide variety of predicted putative potential virulence genes were found in MF GZ001, most of which are shared with well-recognized mycobacterial species with high pathogenic profiles such as M. tuberculosis and M. abscessus.Discussion: Our identified novel features of a pathogenic member of the M. fortuitum complex will provide the foundation for further investigation of mycobacterial pathogenicity and effective treatment.

Treatment of Mycobacterium abscessus (Mab) infections is very challenging due to its intrinsic resistance to most available drugs. Therefore, it is crucial to discover novel anti‐Mab drugs. In this study, we explored an intrinsic resistance mechanism through which Mab resists echinomycin (ECH). ECH showed activity against Mab at a minimum inhibitory concentration (MIC) of 2 µg/ml. A ΔembC strain in which the embC gene was knocked out showed hypersensitivity to ECH (MIC: 0.0078–0.0156 µg/ml). The MICs of ECH‐resistant strains screened with reference to ΔembC ranged from 0.25 to 1 µg/ml. Mutations in EmbB, including D306A, D306N, R350G, V555I, and G581S, increased the Mab's resistance to ECH when overexpressed in ΔembC individually (MIC: 0.25–0.5 µg/ml). These EmbB mutants, edited using the CRISPR/Cpf1 system, showed heightened resistance to ECH (MIC: 0.25–0.5 µg/ml). The permeability of these Mab strains with edited genes and overexpression was reduced, as evidenced by an ethidium bromide accumulation assay, but it remained significantly higher than that of the parent Mab. In summary, our study demonstrates that ECH exerts potent anti‐Mab activity and confirms that EmbB and EmbC are implicated in Mab's sensitivity to ECH. Mutation in EmbB may partially compensate for a loss of EmbC function.