New perspectives on antibacterial drug research

Streptomyces coeruleorubidus as a potential biocontrol agent for Newcastle disease virus

Background

Newcastle disease virus (NDV) is a severe disease that affects domestic and wild birds. Controlled antibiotics derived from probiotics have been examined as prospective solutions for preserving seroconversion in NDV-vaccinated fowl. In this study, the secondary metabolite “telomycin” was extracted from Streptomyces coeruleorubidus (S. coeruleorubidus) isolated from Egypt's cultivated soil. The structure of telomycin was determined by the elucidation of spectroscopic analysis, including nuclear magnetic resonance (NMR) and mass spectrometry (MS) spectra, and comparison with the literature. The antiviral activity of the secondary metabolite was tested by checking its effect on NDV hemagglutination activity (HA). Moreover, HA of NDV was tested after inoculation of NDV (control) and a combination of telomycin and NDV in 10- days- specific pathogen-free embryonated chicken eggs (SPF-ECE) daily candling. Histopathological examination was performed for chorioallantoic membranes and liver of SPF-ECE.

Results

S. coeruleorubidus secondary metabolite “telomycin” showed complete hemagglutination inhibition (HI) activity of NDV strain (MN635617) with log10⁶ infectivity titers (EID50/mL). The HA of NDV strain was 8 log² and 9 log² with 0.5% and 0.75% of chicken RBCs, respectively. Preserved structures of chorioallantoic-membranes (CAM) with dilated capillary networks were observed in the treated group inoculated with telomycin and NDV. Histological changes in SPF-ECE liver were examined after inoculation in ova to further characterize the telomycin effect. Telomycin and NDV mixture inoculated group showed preserved cytoarchitecture of hepatocytes with the presence of perivascular foci of lymphocytes. The group that was inoculated with telomycin alone showed normal histology of hepatic acini, central veins, and portal triads.

Conclusion

S. coeruleorubidus telomycin is a promising bioactive agent that might be a biological weapon against a deadly chicken NDV that costs farmers a lot of money.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03349-7.

Switching Bond: Generation of New Antimicrobial Peptides via the Incorporation of an Intramolecular Isopeptide Bond

Antimicrobial peptides (AMPs), which can be modified to kill a broad spectrum of microoganisms or a specific microorganism, are considered as promising alternatives to combat the rapidly widespread, resistant bacterial infections. However, there are still several obstacles to overcome. These include toxicity, stability, and the ability to interfere with the immune response and bacterial resistance. To overcome these challenges, we herein replaced the regular peptide bonds with isopeptide bonds to produce new AMPs based on the well-known synthetic peptides Amp1L and MSI-78 (pexiganan). Two new peptides Amp1EP and MSIEP were generated while retaining properties such as size, sequence, charge, and molecular weight. These new peptides have reduced toxicity toward murine macrophage (RAW 264.7) cells, human monocytic (THP-1) cells, and human red blood cells (hRBCs) and enhanced the stability toward proteolytic degradation. Importantly, the new peptides do not repress the pro-inflammatory cytokine and hence should not modulate the immune response. Structurally, the new peptides, Amp1EP and MSIEP, have a structure of random coils in contrast to the helical structures of the parental peptides as revealed by circular dichroism (CD) analysis. Their mode of action, assessed by flow cytometry, includes permeabilization of the bacterial membrane. Overall, we present here a new approach to modulate AMPs to develop antimicrobial peptides for future therapeutic purposes.

Antimicrobial Nanostructured Coatings: A Gas Phase Deposition and Magnetron Sputtering Perspective

Counteracting the spreading of multi-drug-resistant pathogens, taking place through surface-mediated cross-contamination, is amongst the higher priorities in public health policies. For these reason an appropriate design of antimicrobial nanostructured coatings may allow to exploit different antimicrobial mechanisms pathways, to be specifically activated by tailoring the coatings composition and morphology. Furthermore, their mechanical properties are of the utmost importance in view of the antimicrobial surface durability. Indeed, the coating properties might be tuned differently according to the specific synthesis method. The present review focuses on nanoparticle based bactericidal coatings obtained via magneton-spattering and supersonic cluster beam deposition. The bacteria–NP interaction mechanisms are first reviewed, thus making clear the requirements that a nanoparticle-based film should meet in order to serve as a bactericidal coating. Paradigmatic examples of coatings, obtained by magnetron sputtering and supersonic cluster beam deposition, are discussed. The emphasis is on widening the bactericidal spectrum so as to be effective both against gram-positive and gram-negative bacteria, while ensuring a good adhesion to a variety of substrates and mechanical durability. It is discussed how this goal may be achieved combining different elements into the coating.

Antiviral activities of extremophilic actinomycetes extracts from Kazakhstan's unique ecosystems against influenza viruses and paramyxoviruses

Background

Commercially available antiviral drugs, when used in the treatment of viral infections, do not always result in success. This is an urgent problem currently that needs to be addressed because several viruses including influenza and paramyxoviruses are acquiring multi-drug resistance. A potential solution for this emerging issue is to create new antiviral drugs from available compounds of natural products. It is known that the majority of drugs have been developed using compounds derived from actinomycetes, which are naturally occurring gram-positive bacteria. The purpose of this study was to investigate the antiviral properties of extremophilic actinomycetes extracts from strains that were isolated from extreme environments in Kazakhstan.

Methods

Five strains of extremophilic actinomycetes isolated from the unique ecosystems of Kazakhstan were extracted and tested for antiviral activity against influenza viruses (strains H7N1, H5N3, H1N1 and H3N2) and paramyxoviruses (Sendai Virus and Newcastle Disease Virus). The antiviral activity of these selected extracts was tested by checking their effect on hemagglutination and neuraminidase activities of the studied viruses. Additionally, actinomycetes extracts were compared with commercially available antiviral drugs and some plant preparations that have been shown to exhibit antiviral properties.

Results

The main findings show that extracts from strains K-192, K-340, K-362, K-522 and K525 showed antiviral activities when tested using influenza viruses, Sendai Virus, and Newcastle Disease Virus. These activities were comparable to those shown by Rimantadine and Tamiflu drugs, and “Virospan” and “Flavovir” plant preparations.

Conclusions

We identified several extracts with antiviral activities against several strains of influenza viruses and paramyxoviruses. Our research findings can be applied towards characterization and development of new antiviral drugs from the active actinomycetes extracts.

Secondary Metabolites of Actinomycetes and their Antibacterial, Antifungal and Antiviral Properties

The growing resistance of microorganisms towards antibiotics has become a serious global problem. Therapeutics with novel chemical scaffolds and/or mechanisms of action are urgently needed to combat infections caused by multidrug resistant pathogens, including bacteria, fungi and viruses. Development of novel antimicrobial agents is still highly dependent on the discovery of new natural products. At present, most antimicrobial drugs used in medicine are of natural origin. Among the natural producers of bioactive substances, Actinobacteria continue to be an important source of novel secondary metabolites for drug application. In this review, the authors report on the bioactive antimicrobial secondary metabolites of Actinobacteria that were described between 2011 and April 2018. Special attention is paid to the chemical scaffolds, biological activities and origin of these novel antibacterial, antifungal and antiviral compounds. Arenimycin C, chromopeptide lactone RSP 01, kocurin, macrolactins A1 and B1, chaxamycin D as well as anthracimycin are regarded as the most effective compounds with antibacterial activity. In turn, the highest potency among selected antifungal compounds is exhibited by enduspeptide B, neomaclafungins A-I and kribelloside D, while ahmpatinin i Bu, antimycin A1a, and pentapeptide 4862F are recognized as the strongest antiviral agents.

Fahotyp and Sensitivity to Medications Phage Film-Forming Strains <i>Staphylococcus aureus</i>, Isolated from Respiratory Tract

The study of biological properties of filmforming Staphylococcus aureus strains, including its sensitivity to bacteriophages, is one of the important tasks of laboratory diagnostic service that allows, if it necessary, choose an alternative treatment strategy and to establish the sources of strains. In the study of material from the nose and throat of 26 persons-volunteers the strains of S. aureus were selected. Among them 16 (61.5%) were able to form biofilms. Analysis of resistance to phages drugs of filmformation strains of S. aureus showed that 87.5% strains were sensitive the phages drugs "Piobacteriophage" and "Bacteriophage staphylococcal liquid". Phage type was identified for 9 (56.3%) strains. 64.3% of these strains were sensitive to the 1 phage from set, 21.4% – to 2 and 14.3% – 3 phages. It was determined that 77.8% strains were typed by phages from third group. For 1 strain detected simultaneous sensitivity to phages of 2 and 3 groups. With phage 81 (out of group phage) interacted 4 strains: 2 showed sensitivity only to him and another 2 were also susceptible to phage of third group.

Fahotyp and Sensitivity to Medications Phage Film-Forming Strains <i>Staphylococcus aureus</i>, Isolated from Respiratory Tract

The study of biological properties of filmforming Staphylococcus aureus strains, including its sensitivity to bacteriophages, is one of the important tasks of laboratory diagnostic service that allows, if it necessary, choose an alternative treatment strategy and to establish the sources of strains. In the study of material from the nose and throat of 26 persons-volunteers the strains of S. aureus were selected. Among them 16 (61.5%) were able to form biofilms. Analysis of resistance to phages drugs of filmformation strains of S. aureus showed that 87.5% strains were sensitive the phages drugs "Piobacteriophage" and "Bacteriophage staphylococcal liquid". Phage type was identified for 9 (56.3%) strains. 64.3% of these strains were sensitive to the 1 phage from set, 21.4% – to 2 and 14.3% – 3 phages. It was determined that 77.8% strains were typed by phages from third group. For 1 strain detected simultaneous sensitivity to phages of 2 and 3 groups. With phage 81 (out of group phage) interacted 4 strains: 2 showed sensitivity only to him and another 2 were also susceptible to phage of third group.

Pipeline of Known Chemical Classes of Antibiotics

Many approaches are used to discover new antibiotic compounds, one of the most widespread being the chemical modification of known antibiotics. This type of discovery has been so important in the development of new antibiotics that most antibiotics used today belong to the same chemical classes as antibiotics discovered in the 1950s and 1960s. Even though the discovery of new classes of antibiotics is urgently needed, the chemical modification of antibiotics in known classes is still widely used to discover new antibiotics, resulting in a great number of compounds in the discovery and clinical pipeline that belong to existing classes. In this scenario, the present article presents an overview of the R&D pipeline of new antibiotics in known classes of antibiotics, from discovery to clinical trial, in order to map out the technological trends in this type of antibiotic R&D, aiming to identify the chemical classes attracting most interest, their spectrum of activity, and the new subclasses under development. The result of the study shows that the new antibiotics in the pipeline belong to the following chemical classes: quinolones, aminoglycosides, macrolides, oxazolidinones, tetracyclines, pleuromutilins, beta-lactams, lipoglycopeptides, polymyxins and cyclic lipopeptides.