Mycobacterium tuberculosis is wrapped in complex waxes, impermeable to most antibiotics. Comparing Mycobacterium bovis BCG and M. tuberculosis mutants that lack phthiocerol dimycocerosates (PDIM) and/or phenolic glycolipids with wild-type strains, we observed that glycopeptides strongly inhibited PDIM-deprived mycobacteria. Vancomycin together with a drug targeting lipid synthesis inhibited multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical isolates. Our study puts glycopeptides in the pipeline of potential antituberculosis (TB) agents and might provide a new antimycobacterial drugscreening strategy. Mycobacterium tuberculosis remains a leading cause of morbidity, tuberculosis (TB), and mortality in the world. M. tuberculosis is intrinsically resistant to most classical antibiotics, partly because of its impermeable cell wall (1-6). Due to selective mutations in M. tuberculosis, almost one-third of new TB patients are now infected with first-line drug-resistant strains, monoresistant strains, or multidrug-resistant (MDR) strains. Consequently, second-line therapies are often implemented, leading to the appearance of extensively drug-resistant (XDR) strains (7,8). There is therefore a growing urgency in the need for new antimycobacterial therapies.The mycobacterial cell wall is composed of peptidoglycan covalently attached to arabinogalactan, which are in turn esterified by very-long-chain mycolic acids. Various noncovalently attached lipids are embedded at the outer surface and necessary for capsule formation. Among these lipids, two related waxes, phthiocerol dimycocerosates (PDIM) and phenolic glycolipids (PGL), are involved in virulence (9-11). PDIM and PGL are only or mostly, respectively, found in pathogenic mycobacteria, but their roles in antibiotic resistance remain unclear (12-16). In Mycobacterium marinum, a mild (2-to 10-fold) increase in antibiotic susceptibility was observed in PDIM-and PGL-deficient strains (14, 15). In contrast, in PDIM-and PGL-deficient M. tuberculosis, no change was detected (13).The present study aimed to understand how mycobacteria can become susceptible to glycopeptides. Using PDIM-negative and/or PGL-negative strains of Mycobacterium bovis BCG and M. tuberculosis, we investigated the correlation between the absence of PDIM and the glycopeptide susceptibility. Subsequently, we investigated whether vancomycin could synergistically inhibit MDR and XDR strains with a mycobacterial lipids synthesis inhibitor.We recently reported that the chaperonin Cpn60.1/GroEL-1/ Hsp60-1 of M. bovis BCG was necessary for the integrity of the cell wall as the ⌬cpn60.1 strain showed an abnormal mycobacterial cell wall with a lack of PDIM and mycolates with two more carbon atoms (17). We investigated the susceptibility of the wild-type (WT), ⌬cpn60.1, and complemented ⌬cpn60.1 M. bovis BCG (GL2 strain) strains to several antituberculosis drugs. We used the NCCLS agar proportion method (18) to determine the MIC scale range of each antibiotic. We inoculated equal quantities of s...

Tuberculosis is still a cause of major concern, partly due to the emergence of multidrug-resistant strains. New drugs are therefore needed. Vancomycin can target mycobacteria with cell envelope deficiency. In this study, we used a vancomycin susceptibility assay to detect drugs hampering lipid synthesis in Mycobacterium bovis BCG and in Mycobacterium tuberculosis. We tested three drugs already used to treat human obesity: tetrahydrolipstatin (THL), simvastatin, and fenofibrate. Only vancomycin and THL were able to synergize on M. bovis BCG and on M. tuberculosis, although mycobacteria could also be inhibited by simvastatin alone. Lipid analysis allowed us to identify several lipid modifications in M. tuberculosis H37Rv treated with those drugs. THL treatment mainly reduced the phthiocerol dimycocerosate (PDIM) content in the mycobacterial cell wall, providing an explanation for the synergy, since PDIM deficiency has been related to vancomycin susceptibility. Proteomic analysis suggested that bacteria treated with THL, in contrast to bacteria treated with simvastatin, tried to recover, inducing, among other reactions, lipid synthesis. The combination of THL and vancomycin should be considered a promising solution in developing new strategies to treat multidrug-resistant tuberculosis.

The success of Mycobacterium tuberculosis as a pathogen is well established: tuberculosis is the leading cause of death by a single infectious agent worldwide. The threat of multi- and extensively drug-resistant bacteria has renewed global concerns about this pathogen and understanding its virulence strategies will be essential in the fight against tuberculosis. The current review will focus on phthiocerol dimycocerosates (PDIMs), a long-known and well-studied group of complex lipids found in the M. tuberculosis cell envelope. Numerous studies show a role for PDIMs in several key steps of M. tuberculosis pathogenesis, with recent studies highlighting its involvement in bacterial virulence, in association with the ESX-1 secretion system. Yet, the mechanisms by which PDIMs help M. tuberculosis to control macrophage phagocytosis, inhibit phagosome acidification and modulate host innate immunity, remain to be fully elucidated.

4-N,N-Dimethylamino-1,8-naphthalimide conjugate of trehalose (DMN-Tre) is a fluorogenic dye recently developed as a diagnostic tool for tuberculosis. DMN-Tre selectively labels the mycobacterial cell wall through the Ag85 enzymes. In this work, we disclose a protocol describing the total synthesis of DMN-Tre with more than 99% purity. We further developed a protocol for in vitro and intercellular labeling of various mycobacterial strains. DMN-Tre labeling was found to be a useful tool to study in vitro and intracellular Mycobacterium tuberculosis (Mtb) physiology and as an end-point readout system in high-content image-based screening (HCS) of drug molecules. Such uses of DMN-Tre labeling provide a simple, fast, and cheap alternative to the existing, time-consuming approach that requires Mtb strains to be genetically transformed with fluorescent reporter genes.

Carbapenem-resistant Enterobacterales , such as KPC-producing Klebsiella pneumoniae , represent a major threat to public health. Novel drug combinations including imipenem-relebactam (IPM-REL) have recently been introduced and have been shown to exhibit excellent activity toward such strains.