Rifamycin-mode of action, resistance, and biosynthesis

Investigation of the antimycobacterial activity of African medicinal plants combined with chemometric analysis to identify potential leads

The emergence of drug-resistant Mycobacterium tuberculosis strains is a threat to global health necessitating the discovery of novel chemotherapeutic agents. Natural products drug discovery, which previously led to the discovery of rifamycins, is a valuable approach in this endeavor. Against this backdrop, we set out to investigate the in vitro antimycobacterial properties of medicinal plants from Ghana and South Africa, evaluating 36 extracts and their 252 corresponding solid phase extraction (SPE) generated fractions primarily against the non-pathogenic Mycobacterium smegmatis and Mycobacterium aurum species. The most potent fraction was further evaluated in vitro against infectious M. tuberculosis strain. Crinum asiaticum (bulb) (Amaryllidaceae) emerged as the most potent plant species with specific fractions showing exceptional, near equipotent activity against the non-pathogenic Mycobacterium species (0.39 µg/ml ≤ MIC ≤ 25 µg/ml) with one fraction being moderately active (MIC = 32.6 µg/ml) against M. tuberculosis. Metabolomic analysis led to the identification of eight compounds predicted to be active against M. smegmatis and M. aurum. In conclusion, from our comprehensive study, we generated data which provided an insight into the antimycobacterial properties of Ghanaian and South African plants. Future work will be focused on the isolation and evaluation of the compounds predicted to be active.

Unveiling the Druggable Landscape of Bacterial Peptidyl tRNA Hydrolase: Insights into Structure, Function, and Therapeutic Potential

Bacterial peptidyl tRNA hydrolase (Pth) or Pth1 emerges as a pivotal enzyme involved in the maintenance of cellular homeostasis by catalyzing the release of peptidyl moieties from peptidyl-tRNA molecules and the maintenance of a free pool of specific tRNAs. This enzyme is vital for bacterial cells and an emerging drug target for various bacterial infections. Understanding the enzymatic mechanisms and structural intricacies of bacterial Pth is pivotal in designing novel therapeutics to combat antibiotic resistance. This review provides a comprehensive analysis of the multifaceted roles of Pth in bacterial physiology, shedding light on its significance as a potential drug target. This article delves into the diverse functions of Pth, encompassing its involvement in ribosome rescue, the maintenance of a free tRNA pool in bacterial systems, the regulation of translation fidelity, and stress response pathways within bacterial systems. Moreover, it also explores the druggability of bacterial Pth, emphasizing its promise as a target for antibacterial agents and highlighting the challenges associated with developing specific inhibitors against this enzyme. Structural elucidation represents a cornerstone in unraveling the catalytic mechanisms and substrate recognition of Pth. This review encapsulates the current structural insights of Pth garnered through various biophysical techniques, such as X-ray crystallography and NMR spectroscopy, providing a detailed understanding of the enzyme's architecture and conformational dynamics. Additionally, biophysical aspects, including its interaction with ligands, inhibitors, and substrates, are discussed, elucidating the molecular basis of bacterial Pth's function and its potential use in drug design strategies. Through this review article, we aim to put together all the available information on bacterial Pth and emphasize its potential in advancing innovative therapeutic interventions and combating bacterial infections.

Remapping the Chemical Space and the Pharmacological Space of Drugs: What Can We Expect from the Road Ahead?

This work examines the current landscape of drug discovery and development, with a particular focus on the chemical and pharmacological spaces. It emphasizes the importance of understanding these spaces to anticipate future trends in drug discovery. The use of cheminformatics and data analysis enabled in silico exploration of these spaces, allowing a perspective of drugs, approved drugs after 2020, and clinical candidates, which were extracted from the newly released ChEMBL34 (March 2024). This perspective on chemical and pharmacological spaces enables the identification of trends and areas to be occupied, thereby creating opportunities for more effective and targeted drug discovery and development strategies in the future.

Decoding antimicrobial resistance: unraveling molecular mechanisms and targeted strategies

Antimicrobial resistance poses a significant global health threat, necessitating innovative approaches for combatting it. This review explores various mechanisms of antimicrobial resistance observed in various strains of bacteria. We examine various strategies, including antimicrobial peptides (AMPs), novel antimicrobial materials, drug delivery systems, vaccines, antibody therapies, and non-traditional antibiotic treatments. Through a comprehensive literature review, the efficacy and challenges of these strategies are evaluated. Findings reveal the potential of AMPs in combating resistance due to their unique mechanisms and lower propensity for resistance development. Additionally, novel drug delivery systems, such as nanoparticles, show promise in enhancing antibiotic efficacy and overcoming resistance mechanisms. Vaccines and antibody therapies offer preventive measures, although challenges exist in their development. Non-traditional antibiotic treatments, including CRISPR-Cas systems, present alternative approaches to combat resistance. Overall, this review underscores the importance of multifaceted strategies and coordinated global efforts to address antimicrobial resistance effectively.

Genome-Driven Discovery of Hygrocins in Streptomyces rapamycinicus

Ansamycins, represented by the antituberculosis drug rifamycin, are an important family of natural products. To obtain new ansamycins, Streptomyces rapamycinicus IMET 43975 harboring an ansamycin biosynthetic gene cluster was fermented in a 50 L scale, and subsequent purification work led to the isolation of five known and four new analogues, where hygrocin W (2) belongs to benzoquinonoid ansamycins, and the other three hygrocins, hygrocins X-Z (6-8), are new seco-hygrocins. The structures of ansamycins (1-8) were determined by the analysis of spectroscopic (1D/2D NMR and ECD) and MS spectrometric data. The Baeyer-Villiger enzyme which catalyzed the ester formation in the ansa-ring was confirmed through in vivo CRISPR base editing. The discovery of these compounds further enriches the structural diversity of ansamycins.

The global nitrogen regulator GlnR is a direct transcriptional repressor of the key gluconeogenic gene pckA in actinomycetes

In most actinomycetes, GlnR governs both nitrogen and non-nitrogen metabolisms (e.g., carbon, phosphate, and secondary metabolisms). Although GlnR has been recognized as a global regulator, its regulatory role in central carbon metabolism [e.g., glycolysis, gluconeogenesis, and the tricarboxylic acid (TCA) cycle] is largely unknown. In this study, we characterized GlnR as a direct transcriptional repressor of the pckA gene that encodes phosphoenolpyruvate carboxykinase, catalyzing the conversion of the TCA cycle intermediate oxaloacetate to phosphoenolpyruvate, a key step in gluconeogenesis. Through the transcriptomic and quantitative real-time PCR analyses, we first showed that the pckA transcription was upregulated in the glnR null mutant of Amycolatopsis mediterranei. Next, we proved that the pckA gene was essential for A. mediterranei gluconeogenesis when the TCA cycle intermediate was used as a sole carbon source. Furthermore, with the employment of the electrophoretic mobility shift assay and DNase I footprinting assay, we revealed that GlnR was able to specifically bind to the pckA promoter region from both A. mediterranei and two other representative actinomycetes (Streptomyces coelicolor and Mycobacterium smegmatis). Therefore, our data suggest that GlnR may repress pckA transcription in actinomycetes, which highlights the global regulatory role of GlnR in both nitrogen and central carbon metabolisms in response to environmental nutrient stresses.

IMPORTANCE

The GlnR regulator of actinomycetes controls nitrogen metabolism genes and many other genes involved in carbon, phosphate, and secondary metabolisms. Currently, the known GlnR-regulated genes in carbon metabolism are involved in the transport of carbon sources, the assimilation of short-chain fatty acid, and the 2-methylcitrate cycle, although little is known about the relationship between GlnR and the TCA cycle and gluconeogenesis. Here, based on the biochemical and genetic results, we identified GlnR as a direct transcriptional repressor of pckA, the gene that encodes phosphoenolpyruvate carboxykinase, a key enzyme for gluconeogenesis, thus highlighting that GlnR plays a central and complex role for dynamic orchestration of cellular carbon, nitrogen, and phosphate fluxes and bioactive secondary metabolites in actinomycetes to adapt to changing surroundings.

Proansamycin B derivatives from the post-PKS modification gene deletion mutant of Amycolatopsis mediterranei S699

Ten new proansamycin B congeners (1-10) together with one known (11) were isolated and characterized on the basis of 1D and 2D NMR spectroscopic and HRESIMS data from the Amycolatopsis mediterranei S699 ΔPM::rifR+rif-orf19 mutant. Compounds 8 and 9 featured with six-membered ring and five-membered ring hemiketal, respectively. Compounds 1, 2, and 9 displayed antibacterial activity against MRSA (methicillin-resistant Staphylococcus aureus), with the MIC (minimal inhibitory concentration) values of 64, 8, and 128 µg/mL, respectively. Compound 1 showed significant cytotoxicity against MDA-MB-231, HepG2 and Panc-1 cell lines with IC50 (half maximal inhibitory concentration) values of 2.3 ± 0.2, 2.5 ± 0.3 and 3.8 ± 0.5 μM, respectively.

The shikimate pathway: gateway to metabolic diversity

Covering: 1997 to 2023The shikimate pathway is the metabolic process responsible for the biosynthesis of the aromatic amino acids phenylalanine, tyrosine, and tryptophan. Seven metabolic steps convert phosphoenolpyruvate (PEP) and erythrose 4-phosphate (E4P) into shikimate and ultimately chorismate, which serves as the branch point for dedicated aromatic amino acid biosynthesis. Bacteria, fungi, algae, and plants (yet not animals) biosynthesize chorismate and exploit its intermediates in their specialized metabolism. This review highlights the metabolic diversity derived from intermediates of the shikimate pathway along the seven steps from PEP and E4P to chorismate, as well as additional sections on compounds derived from prephenate, anthranilate and the synonymous aminoshikimate pathway. We discuss the genomic basis and biochemical support leading to shikimate-derived antibiotics, lipids, pigments, cofactors, and other metabolites across the tree of life.

Discovery of olimycin E from Streptomyces sp. 11695

A new natural product olimycin E (1), together with two known compounds of divergolide R (2) and olimycin B (3), were obtained from the marine-derived Streptomyces sp. 11695. The structures of 1-3 were established on the basis of HRESIMS as well as 1D and 2D NMR datasets. The absolute configuration of 1 is identified as 4 R, 6S, 7S, 10 R by comparison the experiment ECD with that of the theoretical ECD. Antibacterial results showed that compound 2 have antibacterial activities against Staphylococcus aureus and MRSA with the MIC values of 32 μg/mL, respectively.

Targeting Iron - Respiratory Reciprocity Promotes Bacterial Death

Discovering new bacterial signaling pathways offers unique antibiotic strategies. Here, through an unbiased resistance screen of 3,884 gene knockout strains, we uncovered a previously unknown non-lytic bactericidal mechanism that sequentially couples three transporters and downstream transcription to lethally suppress respiration of the highly virulent P. aeruginosa strain PA14 - one of three species on the WHO's 'Priority 1: Critical' list. By targeting outer membrane YaiW, cationic lacritin peptide 'N-104' translocates into the periplasm where it ligates outer loops 4 and 2 of the inner membrane transporters FeoB and PotH, respectively, to suppress both ferrous iron and polyamine uptake. This broadly shuts down transcription of many biofilm-associated genes, including ferrous iron-dependent TauD and ExbB1. The mechanism is innate to the surface of the eye and is enhanced by synergistic coupling with thrombin peptide GKY20. This is the first example of an inhibitor of multiple bacterial transporters.

Antitubercular drugs: possible role of natural products acting as antituberculosis medication in overcoming drug resistance and drug-induced hepatotoxicity

Mycobacterium tuberculosis (Mtb) is a pathogenic bacterium which causes tuberculosis (TB). TB control programmes are facing threats from drug resistance. Multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mtb strains need longer and more expensive treatment with many medications resulting in more adverse effects and decreased chances of treatment outcomes. The World Health Organization (WHO) has emphasised the development of not just new individual anti-TB drugs, but also novel medication regimens as an alternative treatment option for the drug-resistant Mtb strains. Many plants, as well as marine creatures (sponge; Haliclona sp.) and fungi, have been continuously used to treat TB in various traditional treatment systems around the world, providing an almost limitless supply of active components. Natural products, in addition to their anti-mycobacterial action, can be used as adjuvant therapy to increase the efficacy of conventional anti-mycobacterial medications, reduce their side effects, and reverse MDR Mtb strain due to Mycobacterium's genetic flexibility and environmental adaptation. Several natural compounds such as quercetin, ursolic acid, berberine, thymoquinone, curcumin, phloretin, and propolis have shown potential anti-mycobacterial efficacy and are still being explored in preclinical and clinical investigations for confirmation of their efficacy and safety as anti-TB medication. However, more high-level randomized clinical trials are desperately required. The current review provides an overview of drug-resistant TB along with the latest anti-TB medications, drug-induced hepatotoxicity and oxidative stress. Further, the role and mechanisms of action of first and second-line anti-TB drugs and new drugs have been highlighted. Finally, the role of natural compounds as anti-TB medication and hepatoprotectants have been described and their mechanisms discussed.

Clostridioides difficile Infection: Diagnosis and Treatment Challenges

Clostridioides difficile is the most important cause of healthcare-associated diarrhea in the United States. The high incidence and recurrence rates of C. difficile infection (CDI), associated with high morbidity and mortality, pose a public health challenge. Although antibiotics targeting C. difficile bacteria are the first treatment choice, antibiotics also disrupt the indigenous gut flora and, therefore, create an environment that is favorable for recurrent CDI. The challenge of treating CDI is further exacerbated by the rise of antibiotic-resistant strains of C. difficile, placing it among the top five most urgent antibiotic resistance threats in the USA. The evolution of antibiotic resistance in C. difficile involves the acquisition of new resistance mechanisms, which can be shared among various bacterial species and different C. difficile strains within clinical and community settings. This review provides a summary of commonly used diagnostic tests and antibiotic treatment strategies for CDI. In addition, it discusses antibiotic treatment and its resistance mechanisms. This review aims to enhance our current understanding and pinpoint knowledge gaps in antimicrobial resistance mechanisms in C. difficile, with an emphasis on CDI therapies.

Genome-wide screen reveals cellular functions that counteract rifampicin lethality in Escherichia coli

IMPORTANCE

Rifamycins are a group of antibiotics with a wide antibacterial spectrum. Although the binding target of rifamycin has been well characterized, the mechanisms underlying the discrepant killing efficacy between gram-negative and gram-positive bacteria remain poorly understood. Using a high-throughput screen combined with targeted gene knockouts in the gram-negative model organism Escherichia coli, we established that rifampicin efficacy is strongly dependent on several cellular pathways, including iron acquisition, DNA repair, aerobic respiration, and carbon metabolism. In addition, we provide evidence that these pathways modulate rifampicin efficacy in a manner distinct from redox-related killing. Our findings provide insights into the mechanism of rifamycin efficacy and may aid in the development of new antimicrobial adjuvants.

An Overview of Various Rifampicin Analogs against Mycobacterium tuberculosis and their Drug Interactions

The success of the TB control program is hampered by the major issue of drug-resistant tuberculosis (DR-TB). The situation has undoubtedly been made more difficult by the widespread and multidrug-resistant (XDR) strains of TB. The modification of existing anti-TB medications to produce derivatives that can function on resistant TB bacilli is one of the potential techniques to overcome drug resistance affordably and straightforwardly. In comparison to novel pharmaceuticals for drug research and progress, these may have a better half-life and greater bioavailability, be more efficient, and serve as inexpensive alternatives. Mycobacterium tuberculosis, which is drugsusceptible or drug-resistant, is effectively treated by several already prescribed medications and their derivatives. Due to this, the current review attempts to give a brief overview of the rifampicin derivatives that can overcome the parent drug's resistance and could, hence, act as useful substitutes. It has been found that one-third of the global population is affected by M. tuberculosis. The most common cause of infection-related death can range from latent TB to TB illness. Antibiotics in the rifamycin class, including rifampicin or rifampin (RIF), rifapentine (RPT), and others, have a special sterilizing effect on M. tuberculosis. We examine research focused on evaluating the safety, effectiveness, pharmacokinetics, pharmacodynamics, risk of medication interactions, and other characteristics of RIF analogs. Drug interactions are especially difficult with RIF because it must be taken every day for four months to treat latent TB infection. RIF continues to be the gold standard of treatment for drug-sensitive TB illness. RIF's safety profile is well known, and the two medicines' adverse reactions have varying degrees of frequency. The authorized once-weekly RPT regimen is insufficient, but greater dosages of either medication may reduce the amount of time needed to treat TB effectively.

Different drug loading methods and antibiotic structure modulate the efficacy of polydopamine nanoparticles as drug nanocarriers

The inefficient delivery of antimicrobials to their target is a significant factor contributing to antibiotic resistance. As such, smart nanomaterials that respond to external stimuli are extensively explored for precise drug delivery. Here, we investigate how drug loading methods and the structure of antibiotics impact the effectiveness of photothermally active polydopamine nanoparticles (PDNPs) as a laser-responsive drug delivery system. We examine two loading methods: in-synthesis and post-synthesis, and evaluate how laser irradiation affects drug release. Density functional theory calculations are also performed to gain deeper insights into the drug-PDNP interactions. Our findings point to the critical role of antibiotic structure and drug loading method in the laser-responsive capabilities of PDNPs as drug nanocarriers. Our study offers valuable insights for optimizing the design and efficiency of PDNP-based drug delivery systems.

Antibiotics from rare actinomycetes, beyond the genus Streptomyces

Throughout the golden age of antibiotic discovery, Streptomyces have been unsurpassed for their ability to produce bioactive metabolites. Yet, this success has been hampered by rediscovery. As we enter a new stage of biodiscovery, omics data and existing scientific repositories can enable informed choices on the biodiversity that may yield novel antibiotics. Here, we focus on the chemical potential of rare actinomycetes, defined as bacteria within the order Actinomycetales, but not belonging to the genus Streptomyces. They are named as such due to their less-frequent isolation under standard laboratory practices, yet there is increasing evidence to suggest these biologically diverse genera harbour considerable biosynthetic and chemical diversity. In this review, we focus on examples of successful isolation and genera that have been the focus of more concentrated biodiscovery efforts, we survey the representation of rare actinomycete taxa, compared with Streptomyces, across natural product data repositories in addition to its biosynthetic potential. This is followed by an overview of clinically useful drugs produced by rare actinomycetes and considerations for future biodiscovery efforts. There is much to learn about these underexplored taxa, and mounting evidence suggests that they are a fruitful avenue for the discovery of novel antimicrobials.

Metal nanoparticles as inhibitors of enzymes and toxins of multidrug-resistant Staphylococcus aureus

Staphylococcus aureus is an aerobic Gram-positive spherical bacterium known to cause a broad range of infections worldwide. It is a major cause of infective skin and soft infections and severe and life-threatening conditions, such as pneumonia, bloodstream infections, and endocarditis. The emergence of drug-resistant strains of S aureus, particularly methicillin-resistant S aureus (MRSA), has become a significant concern in the healthcare community. Antibiotic-resistant S aureus is commonly acquired in hospitals and long-term care facilities. It often affects patients with weakened immune systems, those undergoing invasive medical procedures, or those who have been hospitalized for extended periods. In the US, S aureus is known to cause potentially fatal illnesses, such as toxic shock syndrome (TSS) and acute-onset toxic shock syndrome (TSS), which are characterized by fever and hypotension. It develops resistance to antibiotics through several mechanisms, such as the production of enzymes that inactivate antibiotics, target site modification, efflux pumps, and plasmid-mediated resistance. Therefore, preventing the spread of drug-resistant S aureus is needed, and there is an urgent need to explore novel approaches in the development of anti-staphylococcal agents. This article reviews the principal infections caused by S aureus, major virulence factors, mechanisms of resistance development, and nanotechnology-based solutions for the control of drug-resistant S aureus.

tert-Butylhydroperoxide mediated radical cyanoalkylation/cyanoalkenylation of 2-anilino-1,4-naphthoquinones with vinylarenes/arylalkynes and azobis(alkylcarbonitrile)s

A novel sustainable methodology based on one-pot cyanoalkylation/cyanoalkenylation of 2-anilino-1,4-naphthoquinones with vinylarenes/arylalkynes and azobis(alkylcarbonitrile)s involving a three-component radical cascade pathway has been achieved. Here, tert-butylhydroperoxide (TBHP) acts as an efficient oxidant, and it smoothly drives the reaction, producing the three-component products in very good to excellent yields. This cascade reaction eliminates the use of any base, additive, metal and hazardous cyanating agent. Additionally, this protocol exclusively delivers a stereospecific product in the case of arylalkynes. The involvement of radicals is evidenced through various radical trapping experiments.

Biodegradable and pH-Responsive Amphiphilic Poly(succinimide) Derivatives for Triggered Release of Antibiotics for Management of Infected Wounds

Wound infection has become a healthy economic burden globally. Current wound management mainly relies on the use of antibiotics; however, the misuse and overuse of antibiotics can easily result in antibiotic resistance. This study proposes a biodegradable, biocompatible, and pH-responsive amphiphilic 11-aminoundecanoic acid-grafted polysuccinimide (AUA-PSI) as a nanocarrier for drug encapsulation via nanoprecipitation. The succinimide groups in the backbone of PSI allow facile postfunctionalization via an aminolysis reaction. The degree of substitution of AUA can be modulated to adjust the degradation rate, pH sensitivity, and drug-release profile. Antibiotic rifampicin was incorporated with AUA-PSI to form Rif-AUA-PSI nanoparticles and demonstrated pH-responsiveness and antimicrobial activity. Because of the elevation of the pH value from pH = ∼ 5.5 in healthy skin to pH > 7 in an infected wound, Rif-AUA-PSI nanoparticles begin to decompose and release Rif upon the hydrolysis of succinimide/amide and deprotonation of carboxyl groups. The effective suppression of bacterial growth by Rif-AUA-PSI nanoparticles was demonstrated using a plate count method. More importantly, Rif-AUA-PSI nanoparticles were physically deposited on cotton gauze bandages as an antibiotic wound dressing. The Rif-AUA-PSI-modified gauze was applied to infected wounds on rats for wound management. The results show fast wound healing and inhibition of bacterial growth, which demonstrate that the method promotes modulable amphiphilicity, biodegradability, biocompatibility, pH-responsiveness, and facile modification for nanomedicine and medical devices.

The Combination of Antibiotic and Non-Antibiotic Compounds Improves Antibiotic Efficacy against Multidrug-Resistant Bacteria

Bacterial antibiotic resistance, especially the emergence of multidrug-resistant (MDR) strains, urgently requires the development of effective treatment strategies. It is always of interest to delve into the mechanisms of resistance to current antibiotics and target them to promote the efficacy of existing antibiotics. In recent years, non-antibiotic compounds have played an important auxiliary role in improving the efficacy of antibiotics and promoting the treatment of drug-resistant bacteria. The combination of non-antibiotic compounds with antibiotics is considered a promising strategy against MDR bacteria. In this review, we first briefly summarize the main resistance mechanisms of current antibiotics. In addition, we propose several strategies to enhance antibiotic action based on resistance mechanisms. Then, the research progress of non-antibiotic compounds that can promote antibiotic-resistant bacteria through different mechanisms in recent years is also summarized. Finally, the development prospects and challenges of these non-antibiotic compounds in combination with antibiotics are discussed.

Counteracting antibiotic resistance enzymes and efflux pumps

Bacterial pathogens are constantly evolving new resistance mechanisms against antibiotics; hence, strategies to potentiate existing antibiotics or combat mechanisms of resistance using adjuvants are always in demand. Recently, inhibitors have been identified that counteract enzymatic modification of the drugs isoniazid and rifampin, which have implications in the study of multi-drug-resistant mycobacteria. A wealth of structural studies on efflux pumps from diverse bacteria has also fueled the design of new small-molecule and peptide-based agents to prevent the active transport of antibiotics. We envision that these findings will inspire microbiologists to apply existing adjuvants to clinically relevant resistant strains, or to use described platforms to discover novel antibiotic adjuvant scaffolds.

Rifamycin-Related Polyketides from a Marine-Derived Bacterium Salinispora arenicola and Their Cytotoxic Activity

Eight rifamycin-related polyketides were isolated from the culture broth of a marine-derived bacterium Salinispora arenicola, including five known (2-5 and 8) and three new derivatives (1, 6, and 7). The structures of the new compounds were determined by means of spectroscopic methods (HRESIMS and 1D, 2D NMR) and a comparison of their experimental data with those previously reported in the literature. The isolated compounds were evaluated for their cytotoxicity against one normal, six solid, and seven blood cancer cell lines and 1 showed moderate activity against all the tested cell lines with GI50 values ranging from 2.36 to 9.96 µM.

Deciphering the Timing of Naphthalenic Ring Formation in the Biosynthesis of 8-Deoxyrifamycins

Although the biosynthesis of rifamycin has been studied for three decades, the biosynthetic formation of the naphthalenic ring remains unclear. In this study, by deletion of all post-PKS modification genes, we identified macrolactam precursors released from rif PKS. Isolated prorifamycins (M3 and M4) have a benzenic chromophore and exist in two sets of macrocyclic atropisomers. The transformation from prorifamycins to benzenoid (5) and naphthalenoid (6) was suggested to be a non-enzymatic process, which is an off-PKS assembly.

Biosynthesis of ansamitocin P-3 incurs stress on the producing strain Actinosynnema pretiosum at multiple targets

Microbial bioactive natural products mediate ecologically beneficial functions to the producing strains, and have been widely used in clinic and agriculture with clearly defined targets and underlying mechanisms. However, the physiological effects of their biosynthesis on the producing strains remain largely unknown. The antitumor ansamitocin P-3 (AP-3), produced by Actinosynnema pretiosum ATCC 31280, was found to repress the growth of the producing strain at high concentration and target the FtsZ protein involved in cell division. Previous work suggested the presence of additional cryptic targets of AP-3 in ATCC 31280. Herein we use chemoproteomic approach with an AP-3-derived photoaffinity probe to profile the proteome-wide interactions of AP-3. AP-3 exhibits specific bindings to the seemingly unrelated deoxythymidine diphosphate glucose-4,6-dehydratase, aldehyde dehydrogenase, and flavin-dependent thymidylate synthase, which are involved in cell wall assembly, central carbon metabolism and nucleotide biosynthesis, respectively. AP-3 functions as a non-competitive inhibitor of all three above target proteins, generating physiological stress on the producing strain through interfering diverse metabolic pathways. Overexpression of these target proteins increases strain biomass and markedly boosts AP-3 titers. This finding demonstrates that identification and engineering of cryptic targets of bioactive natural products can lead to in-depth understanding of microbial physiology and improved product titers.

Phytochemicals as Antimicrobials: Prospecting Himalayan Medicinal Plants as Source of Alternate Medicine to Combat Antimicrobial Resistance

Among all available antimicrobials, antibiotics hold a prime position in the treatment of infectious diseases. However, the emergence of antimicrobial resistance (AMR) has posed a serious threat to the effectiveness of antibiotics, resulting in increased morbidity, mortality, and escalation in healthcare costs causing a global health crisis. The overuse and misuse of antibiotics in global healthcare setups have accelerated the development and spread of AMR, leading to the emergence of multidrug-resistant (MDR) pathogens, which further limits treatment options. This creates a critical need to explore alternative approaches to combat bacterial infections. Phytochemicals have gained attention as a potential source of alternative medicine to address the challenge of AMR. Phytochemicals are structurally and functionally diverse and have multitarget antimicrobial effects, disrupting essential cellular activities. Given the promising results of plant-based antimicrobials, coupled with the slow discovery of novel antibiotics, it has become highly imperative to explore the vast repository of phytocompounds to overcome the looming catastrophe of AMR. This review summarizes the emergence of AMR towards existing antibiotics and potent phytochemicals having antimicrobial activities, along with a comprehensive overview of 123 Himalayan medicinal plants reported to possess antimicrobial phytocompounds, thus compiling the existing information that will help researchers in the exploration of phytochemicals to combat AMR.

Broad-Spectrum Inhibitors for Conserved Unique Phosphoethanolamine Methyltransferases in Parasitic Nematodes Possess Anthelmintic Efficacy

In humans, nematode infections are prevalent in developing countries, causing long-term ill health, particularly in children. Worldwide, nematode infections are prevalent in livestock and pets, affecting productivity and health. Anthelmintic drugs are the primary means of controlling nematodes, but there is now high prevalence of anthelmintic resistance, requiring urgent identification of new molecular targets for anthelmintics with novel mechanisms of action. Here, we identified orthologous genes for phosphoethanolamine methyltransferases (PMTs) in nematodes within the families Trichostrongylidae, Dictyocaulidae, Chabertiidae, Ancylostomatoidea, and Ascarididae. We characterized these putative PMTs and found that they possess bona fide PMT catalytic activities. By complementing a mutant yeast strain lacking the ability to synthesize phosphatidylcholine, the PMTs were validated to catalyze the biosynthesis of phosphatidylcholine. Using an in vitro phosphoethanolamine methyltransferase assay with PMTs as enzymes, we identified compounds with cross-inhibitory effects against the PMTs. Corroboratively, treatment of PMT-complemented yeast with the PMT inhibitors blocked growth of the yeast, underscoring the essential role of the PMTs in phosphatidylcholine synthesis. Fifteen of the inhibitors with the highest activity against complemented yeast were tested against Haemonchus contortus using larval development and motility assays. Among them, four were found to possess potent anthelmintic activity against both multiple drug-resistant and susceptible isolates of H. contortus, with IC50 values (95% confidence interval) of 4.30 μM (2.15-8.28), 4.46 μM (3.22-6.16), 28.7 μM (17.3-49.5), and 0.65 μM (0.21-1.88). Taken together, we have validated a molecular target conserved in a broad range of nematodes and identified its inhibitors that possess potent in vitro anthelmintic activity.

Heterologous production of the D-cycloserine intermediate O-acetyl-L-serine in a human type II pulmonary cell model

Tuberculosis (TB) is the second leading cause of death by a single infectious disease behind COVID-19. Despite a century of effort, the current TB vaccine does not effectively prevent pulmonary TB, promote herd immunity, or prevent transmission. Therefore, alternative approaches are needed. We seek to develop a cell therapy that produces an effective antibiotic in response to TB infection. D-cycloserine (D-CS) is a second-line antibiotic for TB that inhibits bacterial cell wall synthesis. We have determined D-CS to be the optimal candidate for anti-TB cell therapy due to its effectiveness against TB, relatively short biosynthetic pathway, and its low-resistance incidence. The first committed step towards D-CS synthesis is catalyzed by the L-serine-O-acetyltransferase (DcsE) which converts L-serine and acetyl-CoA to O-acetyl-L-serine (L-OAS). To test if the D-CS pathway could be an effective prophylaxis for TB, we endeavored to express functional DcsE in A549 cells as a human pulmonary model. We observed DcsE-FLAG-GFP expression using fluorescence microscopy. DcsE purified from A549 cells catalyzed the synthesis of L-OAS as observed by HPLC-MS. Therefore, human cells synthesize functional DcsE capable of converting L-serine and acetyl-CoA to L-OAS demonstrating the first step towards D-CS production in human cells.

Global Epidemiology and Mechanisms of Resistance of Acinetobacter baumannii-calcoaceticus Complex

Acinetobacter baumannii-calcoaceticus complex is the most commonly identified species in the genus Acinetobacter and it accounts for a large percentage of nosocomial infections, including bacteremia, pneumonia, and infections of the skin and urinary tract. A few key clones of A. baumannii-calcoaceticus are currently responsible for the dissemination of these organisms worldwide. Unfortunately, multidrug resistance is a common trait among these clones due to their unrivalled adaptive nature. A. baumannii-calcoaceticus isolates can accumulate resistance traits by a plethora of mechanisms, including horizontal gene transfer, natural transformation, acquisition of mutations, and mobilization of genetic elements that modulate expression of intrinsic and acquired genes.

Molecular mechanisms of antibiotic resistance revisited

Antibiotic resistance is a global health emergency, with resistance detected to all antibiotics currently in clinical use and only a few novel drugs in the pipeline. Understanding the molecular mechanisms that bacteria use to resist the action of antimicrobials is critical to recognize global patterns of resistance and to improve the use of current drugs, as well as for the design of new drugs less susceptible to resistance development and novel strategies to combat resistance. In this Review, we explore recent advances in understanding how resistance genes contribute to the biology of the host, new structural details of relevant molecular events underpinning resistance, the identification of new resistance gene families and the interactions between different resistance mechanisms. Finally, we discuss how we can use this information to develop the next generation of antimicrobial therapies.

Epoxide-Based Synthetic Approaches toward Polypropionates and Related Bioactive Natural Products

Polypropionate units are a common structural feature of many of the natural products in polyketides, some of which have shown a broad range of antimicrobial and therapeutic potential. Polypropionates are composed of a carbon skeleton with alternating methyl and hydroxy groups with a specific configuration. Different approaches have been developed for the synthesis of polypropionates and herein we include, for the first time, all of the epoxide-based methodologies that have been reported over the years by several research groups such as Kishi, Katsuki, Marashall, Miyashita, Prieto, Sarabia, Jung, McDonald, etc. Several syntheses of polypropionate fragments and natural products that employed epoxides as key intermediates have been described and summarized in this review. These synthetic approaches involve enatio- and diastereoselective synthesis of epoxides (epoxy-alcohols, epoxy-amides, and epoxy-esters) and their regioselective cleavage with carbon and/or hydride nucleophiles. In addition, we included a description of the isolation and biological activities of the polypropionates and related natural products that have been synthetized using epoxide-based approaches. In conclusion, the epoxide-based methodologies are a non-aldol alternative approach for the construction of polypropionate.

Antibiotics and Bacterial Resistance-A Short Story of an Endless Arms Race

Despite the undisputed development of medicine, antibiotics still serve as first-choice drugs for patients with infectious disorders. The widespread use of antibiotics results from a wide spectrum of their actions encompassing mechanisms responsible for: the inhibition of bacterial cell wall biosynthesis, the disruption of cell membrane integrity, the suppression of nucleic acids and/or proteins synthesis, as well as disturbances of metabolic processes. However, the widespread availability of antibiotics, accompanied by their overprescription, acts as a double-edged sword, since the overuse and/or misuse of antibiotics leads to a growing number of multidrug-resistant microbes. This, in turn, has recently emerged as a global public health challenge facing both clinicians and their patients. In addition to intrinsic resistance, bacteria can acquire resistance to particular antimicrobial agents through the transfer of genetic material conferring resistance. Amongst the most common bacterial resistance strategies are: drug target site changes, increased cell wall permeability to antibiotics, antibiotic inactivation, and efflux pumps. A better understanding of the interplay between the mechanisms of antibiotic actions and bacterial defense strategies against particular antimicrobial agents is crucial for developing new drugs or drug combinations. Herein, we provide a brief overview of the current nanomedicine-based strategies that aim to improve the efficacy of antibiotics.

Enzymology of assembly line synthesis by modular polyketide synthases

Modular polyketide synthases (PKSs) run catalytic reactions over dozens of steps in a highly orchestrated manner. To accomplish this synthetic feat, they form megadalton multienzyme complexes that are among the most intricate proteins on earth. Polyketide products are of elaborate chemistry with molecular weights of usually several hundred daltons and include clinically important drugs such as erythromycin (antibiotic), rapamycin (immunosuppressant) and epothilone (anticancer drug). The term 'modular' refers to a hierarchical structuring of modules and domains within an overall assembly line arrangement, in which PKS organization is colinearly translated into the polyketide structure. New structural information obtained during the past few years provides substantial direct insight into the orchestration of catalytic events within a PKS module and leads to plausible models for synthetic progress along assembly lines. In light of these structural insights, the PKS engineering field is poised to enter a new era of engineering.

Investigation of protein-ligand binding motions through protein conformational morphing and clustering of cytochrome bc1-aa3 super complex

Cytochrome b (QcrB) is considered an essential subunit in the electron transport chain that coordinates the action of the entire cytochrome bc1 oxidase. It has been identified as an attractive drug target for a new promising clinical candidate Q203 that depletes the intracellular ATP levels in the bacterium, Mycobacterium tuberculosis. However, single point polymorphism (T313A/I) near the quinol oxidation site of QcrB developed resistance to Q203. In the present study, we analyze the structural changes and drug-resistance mechanism of QcrB due to the point mutation in detail through conformational morphing and molecular docking studies. By morphing, we generated conformers between the open and closed state of the electron transporting cytochrome bc1-aa3 super complex. We clustered them to identify four intermediate structures and relevant intra- and intermolecular motions that may be of functional relevance, especially the binding of Q203 in wild and mutant QcrB intermediate structures and their alteration in developing drug resistance. The difference in the binding score and hydrogen bond interactions between Q203 and the wild-type and mutant intermediate structures of QcrB from molecular docking studies showed that the point mutation T313A severely affected the binding affinity of the candidate drug. Together, the findings provide an in-depth understanding of QcrB inhibition in different conformations, including closed, intermediate, and open states of cytochrome bc1-aa3 super complex in Mycobacterium tuberculosis at the atomic level. We also obtain insights for designing QcrB and cytochrome bc1-aa3 inhibitors as potential therapeutics that may combat drug resistance in tuberculosis.

Intercepting biological messages: Antibacterial molecules targeting nucleic acids during interbacterial conflicts

Bacteria live in polymicrobial communities and constantly compete for resources. These organisms have evolved an array of antibacterial weapons to inhibit the growth or kill competitors. The arsenal comprises antibiotics, bacteriocins, and contact-dependent effectors that are either secreted in the medium or directly translocated into target cells. During bacterial antagonistic encounters, several cellular components important for life become a weak spot prone to an attack. Nucleic acids and the machinery responsible for their synthesis are well conserved across the tree of life. These molecules are part of the information flow in the central dogma of molecular biology and mediate long- and short-term storage for genetic information. The aim of this review is to summarize the diversity of antibacterial molecules that target nucleic acids during antagonistic interbacterial encounters and discuss their potential to promote the emergence antibiotic resistance.

Spectroscopic analysis to identify the binding site for Rifampicin on Bovine Serum Albumin

This article reports the interaction of rifampicin, one of the important antituberculosis drugs, with Bovine Serum Albumin (BSA). Herein, we have monitored the fluorescence properties of tryptophan (Trp) residue in BSA to understand the interactions between protein and rifampicin. Fluorescence intensity of BSA was quenched tremendously upon interacting with the drug. Using steady state and time-resolved spectroscopic tools the static and dynamic nature of quenching have been characterised. Time correlated single photon counting technique confirmed that out of two lifetime components ∼6.2 ns and ∼2.8 ns of BSA, the rifampicin has affected only the shorter lifetime component a lot that was assigned to Trp-213 residue. Hence, it was thought that the drug must have been located near to the amino acid residue. Molecular docking studies have revealed the structural information of drug-protein complex which supported the above conjecture, confirming the nearest tryptophan as Trp-213 to the complexing rifampicin molecule.

Merits of Diazirine Photo-Immobilization for Target Profiling of Natural Products and Cofactors

Finding the targets of natural products is of key importance in both chemical biology and drug discovery, and deconvolution of cofactor interactomes contributes to the functional annotation of the proteome. Identifying the proteins that underlie natural compound activity in phenotypic screens helps to validate the respective targets and, potentially, expand the druggable proteome. Here, we present a generally applicable protocol for the photoactivated immobilization of unmodified and microgram quantities of natural products on diazirine-decorated beads and their use for systematic affinity-based proteome profiling. We show that among 31 molecules of very diverse reported activity and biosynthetic origin, 25 could indeed be immobilized. Dose-response competition binding experiments using lysates of human or bacterial cells followed by quantitative mass spectrometry recapitulated targets of 9 molecules with <100 μM affinity. Among them, immobilization of coenzyme A produced a tool to interrogate proteins containing a HotDog domain. Surprisingly, immobilization of the cofactor flavin adenine dinucleotide (FAD) led to the identification of nanomolar interactions with dozens of RNA-binding proteins.

The role of adjuvants in overcoming antibacterial resistance due to enzymatic drug modification

Antibacterial resistance is a prominent issue with monotherapy often leading to treatment failure in serious infections. Many mechanisms can lead to antibacterial resistance including deactivation of antibacterial agents by bacterial enzymes. Enzymatic drug modification confers resistance to β-lactams, aminoglycosides, chloramphenicol, macrolides, isoniazid, rifamycins, fosfomycin and lincosamides. Novel enzyme inhibitor adjuvants have been developed in an attempt to overcome resistance to these agents, only a few of which have so far reached the market. This review discusses the different enzymatic processes that lead to deactivation of antibacterial agents and provides an update on the current and potential enzyme inhibitors that may restore bacterial susceptibility.

The Extent of Antimicrobial Resistance Due to Efflux Pump Regulation

A key mechanism driving antimicrobial resistance (AMR) stems from the ability of bacteria to up-regulate efflux pumps upon exposure to drugs. The resistance gained by this up-regulation is pliable because of the tight regulation of efflux pump levels. This leads to temporary enhancement in survivability of bacteria due to higher efflux pump levels in the presence of antibiotics, which can be reversed when the cells are no longer exposed to the drug. Knowledge of the extent of resistance thus gained would inform intervention strategies aimed at mitigating AMR. Here, we combine mathematical modeling and experiments to quantify the maximum extent of resistance that efflux pump up-regulation can confer via phenotypic induction in the presence of drugs and genotypic abrogation of regulation. Our model describes the dynamics of drug transport in and out of cells coupled with the associated regulation of efflux pump levels and predicts the increase in the minimum inhibitory concentration (MIC) of drugs due to such regulation. To test the model, we measured the uptake and efflux as well as the MIC of the compound ethidium bromide (EtBr), a substrate of the efflux pump LfrA, in wild-type Mycobacterium smegmatis mc²155, as well as in two laboratory-generated strains. Our model captured the observed EtBr levels and MIC fold-changes quantitatively. Further, the model identified key parameters associated with the resulting resistance, variations in which could underlie the extent to which such resistance arises across different drug-bacteria combinations, potentially offering tunable handles to optimize interventions aimed at minimizing AMR.

Functional Studies and Revision of the NFAT-133/TM-123 Biosynthetic Pathway in Streptomyces pactum

The biosynthetic gene cluster of NFAT-133, an inhibitor of the nuclear factor of activated T cells, was recently identified in Streptomyces pactum ATCC 27456. This cluster is conspicuous by its highly disordered noncollinear type I modular polyketide synthase (PKS) genes that encode PKSs with one module more than those expected for the heptaketide NFAT-133 biosynthesis. Thus, the major metabolite NFAT-133 was proposed to derive from an octaketide analogue, TM-123. Here, we report that further bioinformatic analysis and gene inactivation studies suggest that NFAT-133 is not derived from TM-123 but rather a product of programmed KS7 extension skipping of a nascent heptaketide from the PKS assembly line that produces TM-123. Furthermore, identification of NFAT-133/TM-123 analogues from mutants of the ATCC 27456 strain suggests that NftN (a putative dehydrogenase), NftE (a cytochrome P450), and NftG (a putative hydrolase/decarboxylase) function "in trans" during the polyketide chain assembly processes.

Nanobiotics against antimicrobial resistance: harnessing the power of nanoscale materials and technologies

Given the spasmodic increment in antimicrobial resistance (AMR), world is on the verge of “post-antibiotic era”. It is anticipated that current SARS-CoV2 pandemic would worsen the situation in future, mainly due to the lack of new/next generation of antimicrobials. In this context, nanoscale materials with antimicrobial potential have a great promise to treat deadly pathogens. These functional materials are uniquely positioned to effectively interfere with the bacterial systems and augment biofilm penetration. Most importantly, the core substance, surface chemistry, shape, and size of nanomaterials define their efficacy while avoiding the development of AMR. Here, we review the mechanisms of AMR and emerging applications of nanoscale functional materials as an excellent substitute for conventional antibiotics. We discuss the potential, promises, challenges and prospects of nanobiotics to combat AMR.

HelR is a helicase-like protein that protects RNA polymerase from rifamycin antibiotics

Rifamycin antibiotics such as rifampin are potent inhibitors of prokaryotic RNA polymerase (RNAP) used to treat tuberculosis and other bacterial infections. Although resistance arises in the clinic principally through mutations in RNAP, many bacteria possess highly specific enzyme-mediated resistance mechanisms that modify and inactivate rifamycins. The expression of these enzymes is controlled by a 19-bp cis-acting rifamycin-associated element (RAE). Guided by the presence of RAE sequences, we identify a helicase-like protein, HelR, in Streptomyces venezuelae that confers broad-spectrum rifamycin resistance. We show that HelR also promotes tolerance to rifamycins, enabling bacterial evasion of the toxic properties of these antibiotics. HelR forms a complex with RNAP and rescues transcription inhibition by displacing rifamycins from RNAP, thereby providing resistance by target protection . Furthermore, HelRs are broadly distributed in Actinobacteria, including several opportunistic Mycobacterial pathogens, offering yet another challenge for developing new rifamycin antibiotics.

Development of a Mucoadhesive Liquid Crystal System for the Administration of Rifampicin Applicable in Tuberculosis Therapy

Since 1966, rifampicin (RIF) has been considered one of the most potent drugs in the treatment of tuberculosis (TB), which is caused by infection with M. tuberculosis (Mtb). New nanostructured formulations for RIF delivery and alternative routes of administration have been studied as potential forms of treatment. This study evaluates a liquid crystal system for RIF delivery, using alternative drug delivery routes. The systems developed are composed of surfactant, oleylamine, and soy phosphatidylcholine. With the aid of polarized light microscopy, it was possible to determine that the developed systems had a hexagonal mesophase. All systems developed showed non-Newtonian pseudoplasticity and a high degree of thixotropy. Liquid crystal systems with RIF showed an increase in elastic potential, indicating greater mu-coadhesiveness. The evaluation of mucoadhesive forces revealed an increase in the mucoadhesive potential in the presence of mucus, indicating the presence of satisfactory mucoadhesive forces. The 9DR and 10DR liquid crystal systems, when submitted to Differential Scanning Calorimetry analysis, remained structured even at temperatures above 100 °C, showing excellent stability. The developed liquid crystal systems showed a tolerable degree of cytotoxicity and bactericidal potential, for example, the 9DR system demonstrated a reduction in bacterial load after the third day and reached zero CFU on the seventh day of the test. The developed systems were also evaluated in the preclinical model of Mtb-infected mice, using the nasal, sublingual, and cutaneous route for the delivery of RIF associated with a nanostructured liquid crystal system as a possible tool in the treatment of TB.

Micromonospora: A Prolific Source of Bioactive Secondary Metabolites with Therapeutic Potential

Micromonospora, one of the most important actinomycetes genera, is well-known as the treasure trove of bioactive secondary metabolites (SMs). Herein, together with an in-depth genomic analysis of the reported Micromonospora strains, all SMs from this genus are comprehensively summarized, containing structural features, bioactive properties, and mode of actions as well as their biosynthetic and chemical synthesis pathways. The perspective enables a detailed view of Micromonospora-derived SMs, which will enrich the chemical diversity of natural products and inspire new drug discovery in the pharmaceutical industry.

Total Synthesis of Pentaketide Ansamycin Microansamycin H

Herein, we report the first total synthesis of pentaketide ansamycin microansamycin H. Key to our success was the endo-selective epoxide-opening O-alkylation to construct the elusive seven-membered benzoxepane core. Due to the electron-rich disposition of the aromatic substrate, our pivotal transformation was hindered by competing electrophilic aromatic substitution at multiple C-based nucleophilic sites that generated kinetically favored products. Judicious choices of transition metal Lewis acid promoters biased toward the formation of the desired oxepane.

The Use of Antibiotics as Chiral Selectors in Capillary Electrophoresis: A Review

Chirality is becoming an essential issue in modern pharmaceutical research as regulatory agencies emphasize the safety and efficiency of enantiomers in drug development. The development of efficient and reliable chiral separation methods became a necessity in the last 30 years, and capillary electrophoresis (CE), due to its relatively low costs and “green” features, is attracting increased attention. Cyclodextrin (CD) and their derivatives are the most frequently used chiral selectors (CSs) in CE, however, the use of antibiotics as CSs represents an interesting alternative. Various classes of antibiotics (aminoglycosides, ansamycins, glycopeptides, lincosamides, macrolides, tetracyclines) have been used more or less successfully for the enantio-separation of pharmaceuticals. Antibiotics offer the possibility of a multitude of potential interactions (electrostatic, inclusion, hydrogen bonding, etc.) due to their chemical diversity, allowing the enantio-separation of analytes with a wide range of structural characteristics. This article aims to review the application of various classes of antibiotics in the CE enantio-separation of pharmaceuticals. Antibiotic physiochemical characteristics, variables impacting enantio-separation, advantages, and disadvantages when certain antibiotics are used as CSs in CE are also explored.

Phenols in Pharmaceuticals: Analysis of a Recurring Motif

Phenols and phenolic ethers are significant scaffolds recurring both in nature and among approved small-molecule pharmaceuticals. This compendium presents the first comprehensive compilation and analysis of the structures of U.S. FDA-approved molecules containing phenol or phenolic ether fragments. This dataset comprises 371 structures, which are strongly represented by natural products. A total of 55 of the compounds described here are on the World Health Organization's list of essential medicines. Structural analysis reveals significant differences in the physicochemical properties imparted by phenols versus phenol ethers, each having benefits and drawbacks for drug developability. Despite trends over the past decade to increase the fraction of sp³ centers in drug leads, thereby "escaping flatland", phenols and phenolic ethers are represented in 62% of small-molecule drugs approved in 2020, suggesting that this aromatic moiety holds a special place in drugs and natural products.

Role of Antimicrobial Drug in the Development of Potential Therapeutics

Population of the world run into several health-related emergencies among mankind and humans as it creates a challenge for the evolution of novel drug discoveries. One such can be the emergence of multidrug-resistant (MDR) strains in both hospital and community settings, which have been due to an inappropriate use and inadequate control of antibiotics that has led to the foremost human health concerns with a high impact on the global economy. So far, there has been application of two strategies for the development of anti-infective agents either by classical antibiotics that have been derived for their synthetic analogs with increased efficacy or screening natural compounds along with the synthetic compound libraries for the antimicrobial activities. However, need for newer treatment options for infectious diseases has led research to develop new generation of antimicrobial activity to further lessen the spread of antibiotic resistance. Currently, the principles aim to find novel mode of actions or products to target the specific sites and virulence factors in pathogens by a series of better understanding of physiology and molecular aspects of the microbial resistance, mechanism of infection process, and gene-pathogenicity relationship. The design various novel strategies tends to provide us a path for the development of various antimicrobial therapies that intends to have a broader and wider antimicrobial spectrum that helps to combat MDR strains worldwide. The development of antimicrobial peptides, metabolites derived from plants, microbes, phage-based antimicrobial agents, use of metal nanoparticles, and role of CRISPR have led to an exceptional strategies in designing and developing the next-generation antimicrobials. These novel strategies might help to combat the seriousness of the infection rates and control the health crisis system.