OPC-167832, a Novel Carbostyril Derivative with Potent Antituberculosis Activity as a DprE1 Inhibitor.

There is an urgent need for new, potent antituberculosis (anti-TB) drugs with novel mechanisms of action that can be included in new regimens to shorten the treatment period for TB. After screening a library of carbostyrils, we optimized 3,4-dihydrocarbostyril derivatives and identified OPC-167832 as having potent antituberculosis activity. The MICs of the compound for Mycobacterium tuberculosis ranged from 0.00024 to 0.002 µg/ml. It had bactericidal activity against both growing and intracellular bacilli, and the frequency of spontaneous resistance for M. tuberculosis H37Rv was less than 1.91 × 10-7 It did not show antagonistic effects with other anti-TB agents in an in vitro checkerboard assay. Whole-genome and targeted sequencing of isolates resistant to OPC-167832 identified decaprenylphosphoryl-ß-d-ribose 2'-oxidase (DprE1), an essential enzyme for cell wall biosynthesis, as the target of the compound, and further studies demonstrated inhibition of DprE1 enzymatic activity by OPC-167832. In a mouse model of chronic TB, OPC-167832 showed potent bactericidal activities starting at a dose of 0.625 mg/kg of body weight. Further, it exhibited significant combination effects in 2-drug combinations with delamanid, bedaquiline, or levofloxacin. Finally, 3- or 4-drug regimens comprised of delamanid and OPC-167832 as the core along with bedaquiline, moxifloxacin, or linezolid showed efficacy in reducing the bacterial burden and preventing relapse superior to that of the standard treatment regimen. In summary, these results suggest that OPC-167832 is a novel and potent anti-TB agent, and regimens containing OPC-167832 and new or repurposed anti-TB drugs may have the potential to shorten the duration of treatment for TB.

Adduct Formation of Delamanid with NAD in Mycobacteria.

Delamanid (DLM), a nitro-dihydroimidazooxazole derivative currently approved for pulmonary multidrug-resistant tuberculosis (TB) therapy, is a prodrug activated by mycobacterial 7,8-didemethyl-8-hydroxy 5-deazaflavin electron transfer coenzyme (F420)-dependent nitroreductase (Ddn). Despite inhibiting the biosynthesis of a subclass of mycolic acids, the active DLM metabolite remained unknown. Comparative liquid chromatography-mass spectrometry (LC-MS) analysis of DLM metabolites revealed covalent binding of reduced DLM with a nicotinamide ring of NAD derivatives (oxidized form) in DLM-treated Mycobacterium tuberculosis var. Bacille de Calmette et Guérin. Isoniazid-resistant mutations in the type II NADH dehydrogenase gene (ndh) showed a higher intracellular NADH/NAD ratio and cross-resistance to DLM, which were restored by complementation of the mutants with wild-type ndh Our data demonstrated for the first time the adduct formation of reduced DLM with NAD in mycobacterial cells and its importance in the action of DLM.

Delamanid Kills Dormant Mycobacteria In Vitro and in a Guinea Pig Model of Tuberculosis.

Tuberculosis (TB) treatment is long and requires multiple drugs, likely due to various phenotypes of TB bacilli with variable drug susceptibilities. Drugs with broad activity are urgently needed. This study aimed to evaluate delamanid's activity against growing or dormant bacilli in vitro as well as in vivo Cultures of Mycobacterium bovis BCG Tokyo under aerobic and anaerobic conditions were used to study the activity of delamanid against growing and dormant bacilli, respectively. Delamanid exhibited significant bactericidal activity against replicating and dormant bacilli at or above concentrations of 0.016 and 0.4 mg/liter, respectively. To evaluate delamanid's antituberculosis activity in vivo, we used a guinea pig model of chronic TB infection in which the lung lesions were similar to those in human TB disease. In the guinea pig TB model, a daily dose of 100 mg delamanid/kg of body weight for 4 or 8 weeks demonstrated strong bactericidal activity against Mycobacterium tuberculosis Importantly, histological examination revealed that delamanid killed TB bacilli within hypoxic lesions of the lung. The combination regimens containing delamanid with rifampin and pyrazinamide or delamanid with levofloxacin, ethionamide, pyrazinamide, and amikacin were more effective than the standard regimen (rifampin, isoniazid, and pyrazinamide). Our data show that delamanid is effective in killing both growing and dormant bacilli in vitro and in the guinea pig TB model. Adding delamanid to current TB regimens may improve treatment outcomes, as demonstrated in recent clinical trials with pulmonary multidrug-resistant (MDR) TB patients. Delamanid may be an important drug for consideration in the construction of new regimens to shorten TB treatment duration.

Preparation and properties of O-chitosan quaternary ammonium salt/polyvinyl alcohol/graphene oxide dual self-healing hydrogel.

A simple method had been developed through O-chitosan quaternary ammonium salt (O-HACC), polyvinyl alcohol (PVA) and graphene oxide (GO) to prepare O-HACC/PVA/GO dual self-healing bacteriostatic hydrogels. Then the hydrogels and materials were characterized by FT-IR, X-RD, 1H NMR, SEM and TG. The hydrogel's compressive strength, equilibrium swelling and bacteriostatic efficiency were systematically studied. The research results showed that the maximum equilibrium swelling rate of hydrogel was 720%, the maximum compressive strength was 1500 Pa, and could self-heal within 12 h. In addition, the hydrogel could effectively inhibit E. coli and S. aureus, and also showed a good release behavior for bovine serum albumin (BSA). The CCK-8 method proved that the hydrogel was non-toxic to murine fibroblasts and could promote cell proliferation and growth to a certain extent. This research has potential significance for the application of self-healing hydrogel materials in the field of biomedicine.

Translocation of VP1686 upregulates RhoB and accelerates phagocytic activity of macrophage through actin remodeling.

Here, we report that Vibrio parahaemolyticus induces a rapid remodeling of macrophage actin and activates RhoB GTPase. Mutational analysis revealed that the effects depend on type III secretion system 1 regulated translocation of a V. parahaemolyticus effector protein, VP1686, into the macrophages. Remodeling of actin is shown to be necessary for increased bacterial uptake followed by initiation of apoptosis in macrophages. This provides evidence for functional association of the VP1686 in triggering an eat-me-and-die signal to the host.

Polyclonality of Staphylococcus epidermidis residing on the healthy ocular surface.

Staphylococcus epidermidis is part of the normal bacterial flora on the ocular surface. The chromosomal DNA of bacterial isolates obtained from the conjunctival sac, upper and lower lid margins, and upper and lower Meibomian glands of healthy volunteers was subjected to SmaI digestion and PFGE to study the genetic diversity of the organisms. Multiple colonies were also examined of S. epidermidis derived from the conjunctival sac of the same subjects. Lastly, commensal bacteria were harvested from the ocular surfaces of four healthy subjects once a month for 6 months, and the genetic background of the S. epidermidis isolates was analysed. It was found that bacterial strains not only from different subjects but also from multiple ocular surface sites of the same subject exhibited different PFGE patterns. In five of 42 subjects multiple colonies of S. epidermidis were isolated from the conjunctival sac; three harboured multiple colonies with different PFGE patterns, and two manifested multiple colonies with identical PFGE patterns. S. epidermidis isolated from the conjunctival sac of the same subjects over a 6-month period exhibited varying PFGE patterns. The data demonstrate the polyclonality of S. epidermidis on the healthy ocular surface.

A targeting approach for delivery of polymer microparticle-antibody conjugate against Vibrio parahaemolyticus-induced cytotoxicity to human intestinal epithelial cells.

A major traditional of antibacterial drugs is antibiotic which promotes more rapid release of the toxins from bacteria cells in human body, which causes severe infection. The thermostable direct hemolysin (TDH) has been proposed as a major virulence factor of Vibrio parahaemolyticus (Vp). This study covers the preparation of polymer microparticle-antibody conjugate for the development of a drug targeting approach for antibacterial drug delivery. The chemical binding of antibodies (ab) to latex bead of 0.2 mum diameter was performed by using a water-soluble carbodiimide technique. Confocal microscopy revealed that the bacteria were strongly absorbed by the latex beads with bound anti-Vp polyclonal antibody (pAb). Treatment with a latex bead bound both anti-Vp pAb and anti-TDH monoclonal antibody (mAb) significantly inhibited bacterial adherence to the Caco-2 cells (p < 0.01), and reduced TDH-induced cytotoxicity in histology. These preliminary results suggest that it may be possible to effectively protect against Vp infection by using this microparticle-antibody conjugate delivery system.

Demonstration and characterization of manganese superoxide dismutase of Providencia alcalifaciens.

Superoxide dismutases convert superoxide anions to molecular oxygen and hydrogen peroxide. These enzymes constitute one of the major defense mechanisms of cells against oxidative stress and play a role in the pathogenesis of certain invasive bacteria. In this study, we reported for the first time here that Providencia alcalifaciens, a member of the family Enterobacteriaceae, produces a superoxide dismutase (SOD) as a major protein in culture supernatants. This protein was purified by a series of column chromatographic separations. The N-terminal amino acid sequence of the protein was determined to be highly homologous to manganese superoxide dismutase of Escherichia coli or Salmonella reported. The gene (sodA) encoding for SOD of P. alcalifaciens was cloned and sequenced. The sodA-encoded protein has a molecular weight of about 23.5 kDa, and the DNA sequence of P. alcalifaciens sodA gene (627 bp) has about 83% identity to the E. coli SOD gene. We constructed a sodA deletion mutant and its complemented strain of P. alcalifaciens. In J774, a macrophage cell line, the sodA deletion mutant was more susceptible to killing by macrophages than the wildtype strain and its complemented strain. When we injected the mutant strain, its complemented strain and wildtype strain intraperitoneally into DDY strain mice, we found that the sodA deletion mutant proved significantly less virulent while the complemented strain recovered the virulence to the same level of wildtype strain of P. alcalifaciens. These results suggested that manganese superoxide dismutase plays an important role in intracellular survival of P. alcalifaciens.