Antimicrobial discovery from natural and unusual sources

Venom: A Promising Avenue for Antimicrobial Therapeutics

Venom in medicine is well documented in the chronicles of ancient Greece and the Roman Empire and persisted into the Renaissance and even into the modern era. Venoms were not always associated with detrimental consequences. Since ancient times, the curative capacity of venom has been recognized, portraying venom as a metaphor for pharmacy and medicine. Venom proteins and peptides' antimicrobial potential has not undergone systematic exploration despite the huge literature on natural antimicrobials. In light of the escalating challenge of antimicrobial resistance and the diminishing effectiveness of antibiotics, there is a pressing need for innovative antimicrobials capable of effectively addressing illnesses caused by multidrug-resistant microorganisms. This review adds to our understanding of the effectiveness of different venom components against a host of pathogenic microorganisms. The aim is to illuminate the various antimicrobials present in venom and venom peptides, thereby emphasizing the unexplored medicinal potential for antimicrobial properties. We have presented a concise summary of the molecular examination of the venom peptides' functioning processes, as well as the current clinical and preclinical progress of venom antimicrobial peptides.

A Mini-Review of Anti-Listerial Compounds from Marine Actinobacteria (1990-2023)

Among the foodborne illnesses, listeriosis has the third highest case mortality rate (20-30% or higher). Emerging drug-resistant strains of Listeria monocytogenes, a causative bacterium of listeriosis, exacerbate the seriousness of this public health concern. Novel anti-Listerial compounds are therefore needed to combat this challenge. In recent years, marine actinobacteria have come to be regarded as a promising source of novel antimicrobials. Hence, our aim was to provide a narrative of the available literature and discuss trends regarding bioprospecting marine actinobacteria for new anti-Listerial compounds. Four databases were searched for the review: Academic Search Ultimate, Google Scholar, ScienceDirect, and South African Thesis and Dissertations. The search was restricted to peer-reviewed full-text manuscripts that discussed marine actinobacteria as a source of antimicrobials and were written in English from 1990 to December 2023. In total, for the past three decades (1990-December 2023), only 23 compounds from marine actinobacteria have been tested for their anti-Listerial potential. Out of the 23 reported compounds, only 2-allyoxyphenol, adipostatins E-G, 4-bromophenol, and ansamycins (seco-geldanamycin B, 4.5-dihydro-17-O-demethylgeldanamycin, and seco-geldanamycin) have been found to possess anti-Listerial activity. Thus, our literature survey reveals the scarcity of published assays testing the anti-Listerial capacity of bioactive compounds sourced from marine actinobacteria during this period.

Bacterial community and culturable actinomycetes of Phyllostachys viridiglaucescens rhizosphere

During the course of development plants form tight interactions with microorganisms inhabiting their root zone. In turn, rhizosphere bacteria, in particular members of the phylum Actinomycetota, positively influence the host plant by increasing access to essential nutrients and controlling the pathogenic microorganism's population. Herein, we report the characterisation of the rhizosphere associated actinobacteria community of Phyllostachys viridiglaucescens growing in the Nikitsky Botanical Garden (Crimean Peninsula, Ukraine). The overall composition of the bacterial community was elucidated by 16S rRNA gene amplicon sequencing followed by isolation of culturable microorganisms with the focus on actinomycetes. The metagenomic approach revealed that the representatives of phylum Actinomycetota (57.1%), Pseudomonadota (20.0%), and Acidobacteriota (12.2%) were dominating in the studied microbiome with Ilumatobacter (phylum Actinomycetota) (13.1%) being the dominant genus. Furthermore, a total of 159 actinomycete isolates, belonging to eight genera of Streptomyces, Micromonospora, Nonomuraea, Arthrobacter, Actinomadura, Kribbella, Cellulosimicrobium, and Mumia, were recovered from P. viridiglaucescens rhizosphere. The isolated species were tested for antimicrobial activity. 64% of isolates were active against at least one bacterial test-culture and 7.5% against fungal test culture. In overall, the rhizosphere bacterial communities act as a great source of actinobacterial diversity with the high potential for production of new bioactive compounds.

Genomic and phenotypic characterization of Pseudomonas sp. GOM7, a novel marine bacterial species with antimicrobial activity against multidrug-resistant Staphylococcus aureus

Antimicrobial resistance (AMR) represents a serious threat to global health. The development of new drugs to combat infections caused by bacteria resistant to multiple or even all available antibiotics is urgent. Most antibiotics used up to date have been identified from soil microorganisms. The marine environment represents an alternative source with great potential for the identification of microorganisms that produce bioactive molecules, including antibiotics. In this study, we analyzed the antibacterial activity of a collection of 82 bacterial strains isolated from marine water and sediment samples collected from the Southwestern Gulf of Mexico. Eight of the marine isolates inhibited the growth of different pathogenic bacteria, seven of which were identified as presumptive Pseudomonas aeruginosa. Interestingly, genome sequencing and phylogenetic analysis revealed that the remaining marine isolate showing antibacterial activity is a novel Pseudomonas species that we denominated Pseudomonas sp. GOM7, which was not pathogenic in the Galleria mellonella infection model in the conditions tested. Notably, Pseudomonas sp. GOM7 inhibited the growth of multidrug and methicillin-resistant strains of the priority pathogen Staphylococcus aureus. Our results show that the anti-S. aureus compound(s) produced by Pseudomonas sp. GOM7 can be extracted from the culture supernatant of this bacterium with the organic solvent ethyl acetate. Annotation of the Pseudomonas sp. GOM7 genome revealed the presence of several biosynthetic gene clusters predicted to code for possible antimicrobial compounds. Our results further highlight the potential of bacteria from the Gulf of Mexico as a source of novel antimicrobials.

Synergistic Activity of Thymol with Commercial Antibiotics against Critical and High WHO Priority Pathogenic Bacteria

The use of synergistic combinations between natural compounds and commercial antibiotics may be a good strategy to fight against microbial resistance, with fewer side effects on human, animal and environmental, health. The antimicrobial capacity of four compounds of plant origin (thymol and gallic, salicylic and gentisic acids) was analysed against 14 pathogenic bacteria. Thymol showed the best antimicrobial activity, with MICs ranging from 125 µg/mL (for Acinetobacter baumannii, Pasteurella aerogenes, and Salmonella typhimurium) to 250 µg/mL (for Bacillus subtilis, Klebsiella aerogenes, Klebsiella pneumoniae, Serratia marcescens, Staphylococcus aureus, and Streptococcus agalactiae). Combinations of thymol with eight widely used antibiotics were studied to identify combinations with synergistic effects. Thymol showed synergistic activity with chloramphenicol against A. baumannii (critical priority by the WHO), with streptomycin and gentamicin against Staphylococcus aureus (high priority by the WHO), and with streptomycin against Streptococcus agalactiae, decreasing the MICs of these antibiotics by 75% to 87.5%. The kinetics of these synergies indicated that thymol alone at the synergy concentration had almost no effect on the maximum achievable population density and very little effect on the growth rate. However, in combination with antibiotics at the same concentration, it completely inhibited growth, confirming its role in facilitating the action of the antibiotic. The time-kill curves indicated that all the combinations with synergistic effects were mainly bactericidal.

Biological Activity of Cyclic Peptide Extracted from Sphaeranthus amaranthoides Using De Novo Sequencing Strategy by Mass Spectrometry for Cancer

Though there are several advancements and developments in cancer therapy, the treatment remains challenging. In recent years, the antimicrobial peptides (AMPs) from traditional herbs are focused for identifying and developing potential anticancer molecules. In this study, AMPs are identified from Sphaeranthus amaranthoides, a natural medicinal herb widely used as a crucial immune stimulant in Indian medicine. A total of 86 peptide traces were identified using liquid-chromatography–electrospray-ionisation mass spectrometry (LC-ESI-MS). Among them, three peptides were sequenced using the manual de novo sequencing technique. The in-silico prediction revealed that SA923 is a cyclic peptide with C-N terminal interaction of the carbon atom of ASP7 with the nitrogen atom of GLU1 (1ELVFYRD7). Thus, SA923 is presented under the orbitides class of peptides, which lack the disulfide bonds for cyclization. In addition, SA923, steered with the physicochemical properties and support vector machine (SVM) algorithm mentioned for the segment, has the highest in silico anticancer potential. Further, the in vitro cytotoxicity assay revealed the peptide has anti-proliferative activity, and toxicity studies were demonstrated in Danio rerio (zebrafish) embryos.

Prospecting in silico antibacterial activity of a peptide from trypsin inhibitor isolated from tamarind seed

Bacterial infections have become a global concern, stimulating the growing demand for natural and biologically safe therapeutic agents with antibacterial action. This study was evaluated the genotoxicity of the trypsin inhibitor isolated from tamarind seeds (TTI) and the antibacterial effect of TTI theoric model, number 56, and conformation number 287 (TTIp 56/287) and derived peptides in silico. TTI (0.3 and 0.6 mg.mL⁻¹) did not cause genotoxicity in cells (p > 0.05). In silico, a greater interaction of TTIp 56/287 with the Gram-positive membrane (GP) was observed, with an interaction potential energy (IPE) of −1094.97 kcal.mol⁻¹. In the TTIp 56/287-GP interaction, the Arginine, Threonine (Thr), and Lysine residues presented lower IPE. In molecular dynamics (MD), Peptidotrychyme59 (TVSQTPIDIPIGLPVR) showed an IPE of −518.08 kcal.mol⁻¹ with the membrane of GP bacteria, and the Thr and Arginine residues showed the greater IPE. The results highlight new perspectives on TTI and its derived peptides antibacterial activity.

A Review of the Antimicrobial Potential of Musca domestica as a Natural Approach with Promising Prospects to Countermeasure Antibiotic Resistance

Drug-resistant pathogens have become a serious public health concern worldwide considering the rapid emergence and distribution of new strains, which outpace the development of antimicrobial drugs. It is a complex and serious clinical problem that can cause an epidemic of a disease; consequently, numerous research studies are conducted to determine the solution to these problems, including the development of new antibiotics derived from natural sources such as insects. The housefly (Musca domestica L.), an insect known as a cosmopolitan pest, possesses several qualities that can ameliorate diseases; consequently, they can be used as a bioactive component in the development of medicines. These qualities include its potential as a source of antibacterial agents. The external surface components, wings, internal organs, and whole body extract of M. domestica can all contribute antimicrobial potential due to bioactive compounds they produce. This article discusses several antimicrobial properties of M. domestica that could be utilized for healthcare benefits.

Anti-Inflammatory, Antipyretic, and Analgesic Properties of Potamogeton perfoliatus Extract: In Vitro and In Vivo Study

Natural antioxidants, especially those of plant origins, have shown a plethora of biological activities with substantial economic value, as they can be extracted from agro-wastes and/or under exploited plant species. The perennial hydrophyte, Potamogeton perfoliatus, has been used traditionally to treat several health disorders; however, little is known about its biological and its medicinal effects. Here, we used an integrated in vitro and in vivo framework to examine the potential effect of P. perfoliatus on oxidative stress, nociception, inflammatory models, and brewer’s yeast-induced pyrexia in mice. Our results suggested a consistent in vitro inhibition of three enzymes, namely 5-lipoxygenase, cyclooxygenases 1 and 2 (COX-1 and COX-2), as well as a potent antioxidant effect. These results were confirmed in vivo where the studied extract attenuated carrageenan-induced paw edema, carrageenan-induced leukocyte migration into the peritoneal cavity by 25, 44 and 64% at 200, 400 and 600 mg/kg, p.o., respectively. Moreover, the extract decreased acetic acid-induced vascular permeability by 45% at 600 mg/kg, p.o., and chemical hyperalgesia in mice by 86% by 400 mg/kg, p.o., in acetic acid-induced writhing assay. The extract (400 mg/kg) showed a longer response latency at the 3 h time point (2.5 fold of the control) similar to the nalbuphine, the standard opioid analgesic. Additionally, pronounced antipyretic effects were observed at 600 mg/kg, comparable to paracetamol. Using LC-MS/MS, we identified 15 secondary metabolites that most likely contributed to the obtained biological activities. Altogether, our findings indicate that P. perfoliatus has anti-inflammatory, antioxidant, analgesic and antipyretic effects, thus supporting its traditional use and promoting its valorization as a potential candidate in treating oxidative stress-associated diseases.