A novel class of antimicrobial drugs selectively targets a Mycobacterium tuberculosis PE-PGRS protein.

The continued spread of drug-resistant tuberculosis is one of the most pressing and complex challenges facing tuberculosis management worldwide. Therefore, developing a new class of drugs is necessary and urgently needed to cope with the increasing threat of drug-resistant tuberculosis. This study aims to discover a potential new class of tuberculosis drug candidates different from existing tuberculosis drugs. By screening a library of compounds, methyl (S)-1-((3-alkoxy-6,7-dimethoxyphenanthren-9-yl)methyl)-5-oxopyrrolidine-2-carboxylate (PP) derivatives with antitubercular activity were discovered. MIC ranges for PP1S, PP2S, and PP3S against clinically isolated drug-resistant Mycobacterium tuberculosis strains were 0.78 to 3.13, 0.19 to 1.56, and 0.78 to 6.25 µg/ml, respectively. PPs demonstrated antitubercular activities in macrophage and tuberculosis mouse models, showing no detectable toxicity in all assays tested. PPs specifically inhibited M. tuberculosis without significantly changing the intestinal microbiome in mice. Mutants selected in vitro suggest that the drug targets the PE-PGRS57, which has been found only in the genomes of the M. tuberculosis complex, highlighting the specificity and safety potency of this compound. As PPs show an excellent safety profile and highly selective toxicity specific to M. tuberculosis, PPs are considered a promising new candidate for the treatment of drug-resistant tuberculosis while maintaining microbiome homeostasis.

In vitro activity of alpha-viniferin isolated from the roots of Carex humilis against Mycobacterium tuberculosis.

This study explores the antitubercular activity of α-viniferin, a bioactive phytochemical compound obtained from Carex humilis. α-Viniferin was active against both drug-susceptible and -resistant strains of Mycobacterium tuberculosis at MIC50s of 4.6 µM in culture broth medium and MIC50s of 2.3-4.6 µM inside macrophages and pneumocytes. In combination with streptomycin and ethambutol, α-viniferin exhibited an additive effect and partial synergy, respectively, against M. tuberculosis H37Rv. α-Viniferin also did not show cytotoxicity in any of the cell lines tested up to a concentration of 147 µM, which gives this compound a selectivity index of >32. Moreover, α-viniferin was active against 3 Staphylococcus species, including methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), and methicillin-resistant Staphylococcus epidermidis (MRSE).

Thymoquinone (TQ) inhibits the replication of intracellular Mycobacterium tuberculosis in macrophages and modulates nitric oxide production.

BACKGROUND: Human tuberculosis, which is caused by the pathogen Mycobacterium tuberculosis, remains a major public health concern. Increasing drug resistance poses a threat of disease resurgence and continues to cause considerable mortality worldwide, which necessitates the development of new drugs with improved efficacy. Thymoquinone (TQ), an essential compound of Nigella sativa, was previously reported as an active anti-tuberculosis agent. METHODS: In this study, the effects of TQ on intracellular mycobacterial replication are examined in macrophages. In addition, its effect on mycobacteria-induced NO production and pro-inflammatory responses were investigated in Mycobacterium tuberculosis (MTB)-infected Type II human alveolar and human myeloid cell lines. RESULTS: TQ at concentrations ranging from 12.5 to 25 µg/mL and 6.25 to 12.5 µg/mL reduced intracellular M. tuberculosis H37Rv and extensively drug-resistant tuberculosis (XDR-TB) 72 h post-infection in RAW 264.7 cells. TQ treatment also produced a concentration-dependent reduction in nitric oxide production in both H37Rv and XDR-TB infected RAW 264.7 cells. Furthermore, TQ reduced the expression of inducible nitric oxide synthase (iNOS) and pro-inflammatory molecules such as tumor necrosis factor-alpha (TNF-α) and interlukin-6 (IL-6) in H37Rv-infected cells and eventually reduced pathogen-derived stress in host cells. CONCLUSIONS: TQ inhibits intracellular H37Rv and XDR-TB replication and MTB-induced production of NO and pro-inflammatory molecules. Therefore, along with its anti-inflammatory effects, TQ represents a prospective treatment option to combat Mycobacterium tuberculosis infection.

In vitro Antitubercular Activity of 3-Deoxysappanchalcone Isolated From the Heartwood of Caesalpinia sappan Linn.

Responsible for nearly 1.5 million deaths every year, the infectious disease tuberculosis remains one of the most serious challenges to global health. The emergence of multidrug-resistant tuberculosis and, more recently, extensively drug-resistant tuberculosis poses a significant threat in our effort to control this epidemic. New drugs are urgently needed to combat the growing threat of antimicrobial resistance. To achieve this goal, we screened approximately 500 species of medicinal plant methanol extracts and their solvent partitioned fractions for potential inhibitors of Mycobacterium tuberculosis growth. Using microdilution screening, the ethyl acetate solvent partitioned fraction from the heartwood of Caesalpinia sappan exhibited strong antitubercular activity. We isolated the active compound and identified it as 3-deoxysappanchalcone. The extracted 3-deoxysappanchalcone possessed activity against both drug-susceptible and drug-resistant strains of M. tuberculosis at MIC50 s of 3.125-12.5 µg/mL in culture broth and MIC50 s of 6.25-12.5 µg/mL inside macrophages and pneumocytes. 3-Deoxysappanchalcone was also found to act in partial synergy with streptomycin/ethambutol against M. tuberculosis H37Rv. 3-Deoxysappanchalcone had no cytotoxicity against the A549 cell line up to a concentration of 100 µg/mL (selectivity index > 8-32). Further studies are warranted to establish the in vivo effect and therapeutic potential of 3-deoxysappanchalcone. Copyright © 2017 John Wiley & Sons, Ltd.

Rescue of pyrimidine-defective Pseudomonas aeruginosa through metabolic complementation.

Chronic infections harbor multiple pathogens where dynamic interactions between members of the polymicrobial community play a major role in determining the infection outcome. For example, in a nutrient-rich polymicrobial infection, bacteria have the potential to undergo evolutionary changes that impair their ability to synthesize essential metabolites. This adaptation may facilitate metabolic interdependencies between neighboring pathogens and lead to difficult-to-treat chronic infections. Our research group previously demonstrated that Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA), typically considered classical competitors, can adopt a cooperative lifestyle through bi-directional purine exchange medicated by exogenous DNA (eDNA) release. To further validate our initial findings, in this study, we investigated the potential exchange of pyrimidine between PA and other pathogens, which is another constituent of DNA. In our findings, we observed that a pyrimidine-deficient transposon mutant strain of PA showed improved growth when co-cultured with wild-type PA, SA, Acinetobacter baumannii (AB), and Enterococcus faecalis (EF). Additionally, improved fitness of pyrimidine-deficient PA was further observed in chemical complementation with eDNA and uridine-5'-monophosphate. Interestingly, the rescue of PA growth through eDNA complementation is not as effective as in intact cells, such as SA, AB, EF, and wild-type PA, implying that eDNA is a lesser contributor to this metabolic complementation. Also, the exchange mechanism between pathogens involves more active mechanisms beyond simple eDNA or metabolite release. Our data further highlights the importance of cell-to-cell contact for effective and increased metabolic complementation. IMPORTANCE: This research holds crucial implications for combating chronic infections, where multiple pathogens coexist and interact within the same environment. By uncovering the dynamic exchange of pyrimidines between Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA), our study reveals a previously unrecognized aspect of interspecies cooperation. The observed enhanced growth of a pyrimidine-deficient PA strain when co-cultured with SA suggests potential avenues for understanding and disrupting bacterial metabolic interdependencies in chronic infection settings. Furthermore, our findings highlight the mechanisms involved in metabolic exchange, emphasizing the importance of cell-to-cell contact. This research explored essential metabolic interactions to address the challenges posed by difficult-to-treat chronic infections.

Increased Susceptibility of Mycobacterium tuberculosis to Ethionamide by Expressing PPs-Induced Rv0560c.

Tuberculosis, an infectious disease, is one of the leading causes of death worldwide. Drug-resistant tuberculosis exacerbates its threat. Despite long-term and costly treatment with second-line drugs, treatment failure rates and mortality remain high. Therefore, new strategies for developing new drugs and improving the efficiency of existing drug treatments are urgently needed. Our research team reported that PPs, a new class of potential anti-tuberculosis drug candidates, can inhibit the growth of drug-resistant Mycobacterium tuberculosis. Here, we report a synergistic effect of PPs with ethionamide (ETH), one of the second-line drugs, as a result of further research on PPs. While investigating gene expression changes based on microarray and 2DE (two-dimensional gel electrophoresis), it was found that PPs induced the greatest overexpression of Rv0560c in M. tuberculosis. Based on this result, a protein microarray using Rv0560c protein was performed, and it was confirmed that Rv0560c had the highest interaction with EthR, a repressor for EthA involved in activating ETH. Accordingly, a synergistic experiment was conducted under the hypothesis of increased susceptibility of ETH to M. tuberculosis by PPs. As a result, in the presence of 0.5× MIC PPs, ETH showed a growth inhibitory effect on drug-sensitive and -resistant M. tuberculosis even at a much lower concentration of about 10-fold than the original MIC of ETH. It is also suggested that the effect was due to the interaction between PPs and Rv2887, the repressor of Rv0560c. This effect was also confirmed in a mouse model of pulmonary tuberculosis, confirming the potential of PPs as a booster to enhance the susceptibility of M. tuberculosis to ETH in treating drug-resistant tuberculosis. However, more in-depth mechanistic studies and extensive animal and clinical trials are needed in the future.

Biodegradation and Removal of PAHs by Bacillus velezensis Isolated from Fermented Food.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment. They are highly toxigenic and carcinogenic. Probiotic bacteria isolated from fermented foods were tested to check their ability to degrade and/or detoxify PAHs. Five probiotic bacteria with distinct morphologies were isolated from a mixture of 26 fermented foods co-cultured with benzo(a)pyrene (BaP) containing Bushnell Haas minimal broth. Among them, B. velezensis (PMC10) significantly reduced the abundance of BaP in the broth. PMC10 completely degraded BaP presented at a lower concentration in broth culture. B. velezensis also showed a clear zone of degradation on a BaP-coated Bushnell Haas agar plate. Gene expression profiling showed significant increases of PAH ringhydroxylating dioxygenases and 4-hydroxybenzoate 3-monooxygenase genes in B. velezensis in response to BaP treatment. In addtion, both live and heat-killed B. velezensis removed BaP and naphthalene (Nap) from phosphate buffer solution. Live B. velezensis did not show any cytotoxicity to macrophage or human dermal fibroblast cells. Live-cell and cell-free supernatant of B. velezensis showed potential anti-inflammatory effects. Cell-free supernatant and extract of B. velezensis also showed free radical scavenging effects. These results highlight the prospective ability of B. velezensis to biodegrade and remove toxic PAHs from the human body and suggest that the biodegradation of BaP might be regulated by ring-hydroxylating dioxygenase-initiated metabolic pathway.

Synthesis and activity of BNF15 against drug-resistant Mycobacterium tuberculosis.

Aim: Tuberculosis is the leading cause of mortality among infectious diseases worldwide. Finding a new competent anti tubercular therapy is essential. Materials & methods: We screened thousands of compounds and evaluated their efficacy against Mycobacterium tuberculosis. Results: Initially, 2-nitronaphtho[2,3-b]benzofuran-6,11-dione was active against M. tuberculosis. Next, among 15 newly synthesized derivatives, BNF15 showed promising effect against all drug-sensitive and drug-resistant M. tuberculosis (MIC: 0.02-0.78 µg/ml). BNF15 effectively killed intracellular M. tuberculosis and nontuberculous mycobacteria. BNF15 exhibited a prolonged post antibiotic effect superior to isoniazid, streptomycin, and ethambutol and synergistic interaction with rifampicin. In acute oral toxicity test, BNF15 did not show toxic effect at a concentration up to 2000 mg/kg. Conclusion: These results highlight the perspective of BNF15 to treat drug-resistant M. tuberculosis.

Melanin Bleaching and Melanogenesis Inhibition Effects of Pediococcus acidilactici PMC48 Isolated from Korean Perilla Leaf Kimchi.

Overproduction and accumulation of melanin in the skin will darken the skin and cause skin disorders. So far, components that can inhibit tyrosinase, a melanin synthase of melanocytes, have been developed and used as ingredients of cosmetics or pharmaceutical products. However, most of existing substances can only inhibit the biosynthesis of melanin while melanin that is already synthesized and deposited is not directly decomposed. Thus, their effects in decreasing melanin concentration in the skin are weak. To overcome the limitation of existing therapeutic agents, we started to develop a substance that could directly biodegrade melanin. We screened traditional fermented food microorganisms for their abilities to direct biodegrade melanin. As a result, we found that a kimchi-derived Pediococcus acidilactici PMC48 had a direct melanin-degrading effect. This PMC48 strain is a new strain, different from P. acidilactici strains reported so far. It not only directly degrades melanin, but also has tyrosinase-inhibiting effect. It has a direct melanindecomposition effect. It exceeds existing melanin synthesis-inhibiting technology. It is expected to be of high value as a raw material for melanin degradation drugs and cosmetics.

In vitro activity of DNF-3 against drug-resistant Mycobacterium tuberculosis.

Due to the emergence of multidrug-resistant and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis, new antituberculosis drugs are urgently required to improve the efficacy of current tuberculosis (TB) treatment. To achieve this goal, ca. 1000 chemical compounds were screened for potential antimycobacterial activity, among which methyl 5-(2-diethylaminoethoxy)-7,12-dioxo-7,12 dihydrodinaphtho[1,2-b;2',3'-d]furan-6-carboxylate (DNF-3) showed strong activity against all of the tested drug-susceptible and -resistant M. tuberculosis strains, with 50% minimum inhibitory concentrations (MIC50 values) of 0.02-0.39 µg/mL both in culture broth and within murine RAW 264.7 macrophage cells. When DNF-3 was used in combination with rifampicin or streptomycin, it exhibited direct synergy against XDR-TB and an additive effect against M. tuberculosis H37Rv. DNF-3 displayed a long post-antibiotic effect (PAE) that was comparable with rifampicin but was superior to isoniazid, streptomycin and ethambutol. Importantly, DNF-3 showed no cytotoxicity to any cell line tested, with a selectivity index (SI) of >32. DNF-3 was also active against 27 nontuberculous mycobacteria (NTM) strains, Staphylococcus spp. and Streptococcus spp. Taken together, these results indicate that DNF-3 is a promising new candidate drug for treating TB. Further studies are warranted to establish the in vivo effect and therapeutic potential of DNF-3.

In vitro activity of collinin isolated from the leaves of Zanthoxylum schinifolium against multidrug- and extensively drug-resistant Mycobacterium tuberculosis.

BACKGROUND: Tuberculosis is a very serious infectious disease that threatens humanity, and the emergence of multidrug-resistant (MDR), extensively drug-resistant (XDR) strains resistant to drugs suggests that new drug development is urgent. In order to develop new tuberculosis drug, we have conducted in vitro anti-tubercular tests on thousands of plant-derived substances and finally found collinin extracted from the leaves of Zanthoxylum schinifolium, which has an excellent anti-tuberculosis effect. PURPOSE: To isolate an anti-tubercular bioactive compound from the leaves of Z. schinifolium and evaluate whether this agent demonstrates any potential in vitro characteristics suitable for the development of future anti-tubercular drugs to treat MDR and XDR Mycobacterium tuberculosis. METHODS: The methanolic extracts of the leaves of Z. schinifolium were subjected to bioassay-guided fractionation against M. tuberculosis using a microbial cell viability assay. In addition, following cell cytotoxicity assay, an intracellular anti-mycobacterial activity of the most active anti-tubercular compound was investigated after it was purified. RESULTS: The active compound with anti-tubercular activity isolated from leaves of Z. schinifolium was identified as a collinin. The extracted collinin showed anti-tubercular activity against both drug-susceptible and -resistant strains of M. tuberculosis at 50% minimum inhibitory concentrations (MIC50s) of 3.13-6.25 µg/ml in culture broth and MIC50s of 6.25-12.50 µg/ml inside Raw264.7 and A549 cells. Collinin had no cytotoxicity against human lung pneumocytes up to a concentration of 100 µg/ml (selectivity index > 16-32). CONCLUSIONS: Collinin extracted from the leaves of Z. schinifolium significantly inhibits the growth of MDR and XDR M. tuberculosis in the culture broth. In addition, it also inhibits the growth of intracellular drug-susceptible and drug-resistant tuberculosis in Raw264.7 and A549 cells. To our knowledge, this is the first report on the in vitro anti-tubercular activity of collinin, and our data suggest collinin as a potential drug to treat drug-resistant tuberculosis. Further studies are warranted to assess the in vivo efficacy and therapeutic potential of collinin.

In Vitro Effect of DFC-2 on Mycolic Acid Biosynthesis in Mycobacterium tuberculosis.

DFC-2, a methyl 5-[2-(dimethylamino)ethoxy]-7,12-dioxo-7,12-dihydrodinaphtho[1,2-b:2',3'-d]furan-6-carboxylate, is reported to have antitubercular effects against Mycobacterium tuberculosis. At concentrations ranging from 0.19 to 0.39 µg/ml, DFC-2 inhibited both drug-susceptible and -resistant strains of M. tuberculosis. Microarray analyses were employed to gain insights into the molecular mechanisms of DFC-2's action in M. tuberculosis. The most affected functional gene category was "lipid biosynthesis," which is involved in mycolic acid synthesis. The decrease in transcription of genes related to mycolic acid synthesis was confirmed by RT-PCR. Furthermore, we found that DFC-2 triggered a reduction in mycolic acid levels, showing a similar pattern to that of mycolic acid synthesis inhibitor isoniazid. These results may explain how this compound kills mycobacteria efficiently by inhibiting mycolic acid synthesis.