Specific Antimicrobial Activity Research Articles

Bacterial cellulose with CHAPK-mediated specific antimicrobial activity against Staphylococcus aureus

Wound healing represents a complex biological process often hampered by bacterial infections, in particular those caused by Staphylococcus aureus, which is already multiresistant to many antibiotics. In this sense, enzybiotics have additional advantages over conventional antibiotics, since they provide pathogen specificity and do not contribute to antibiotic resistance. However, their soluble administration at the wound site would result in enzyme leakage. On the other hand, bacterial cellulose (BC) pellicles present a very promising dressing and scaffold, given its high purity, water retention capacity, and barrier effect in the wound against possible contaminants. In this study, we present a novel approach that incorporates the enzybiotic CHAPK into BC to develop functionalized membranes that exhibit targeted and controlled antimicrobial activity against S. aureus. The kinetic tests revealed a continuous loading of the enzybiotic into BC until it reaches a maximum and a two-stage release process, characterized by an initial fast release followed by a sustained release. Attenuated total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), and Confocal Laser Scanning Microscopy (CLSM) confirmed the incorporation and the preferential surface localization of CHAPK within the BC membranes. Finally, the BC/CHAPK materials demonstrated the sustained reduction of up to 4 logarithmic units in the viability of S. aureus. Overall, the biomaterials developed here exhibit promising antimicrobial efficacy against S. aureus, offering a potential strategy for wound management and skin infection control while maintaining unharmed the commensal skin microbiota, which impairment could compromise the integrity of the skin barrier function.

Zinc Oxide Nanoparticles in the “Soil–Bacterial Community–Plant” System: Impact on the Stability of Soil Ecosystems

The use of man-made nanoparticles (NPs) has increased exponentially in recent years, many of which accumulate in significant quantities in soil, including through use in agriculture as nanofertilizers and nanopesticides. ZnO NPs are more environmentally friendly but have specific antimicrobial activity, which can affect soil microbiota, thereby influencing key microbial processes such as mineralization, nitrogen fixation and plant growth-promoting activities. Their behavior and persistence in soil depend on their chemical nature and soil characteristics. This review summarizes the applications of ZnO NPs in soil systems and their effects on various plants and soil microorganisms, particularly rhizobacteria that promote plant growth. A stimulating effect of ZnO NPs on the morphometric and biochemical characteristics of plants, as well as on soil microbiota and its activity at relatively low concentrations of up to 500 mg/mL and 250 mg/kg, respectively, is observed. As the concentration of ZnO NPs increases above these limits, toxic effects appear. The different effects of ZnO NPs are related to their size, dose, duration of exposure, solubility in water, as well as soil type, acidity and organic matter content. The review substantiates the need to study the behavior of ZnO NPs in the “soil-plant-microbiota” system for the possibility of using nanotechnologies in the agricultural industry and ensuring the safety of agricultural products.

Potent and specific antibiotic combination therapy against Clostridioides difficile.

Keratinicyclins and keratinimicins are recently discovered glycopeptide antibiotics. Keratinimicins show broad-spectrum activity against Gram-positive bacteria, while keratinicyclins form a new chemotype by virtue of an unusual oxazolidinone moiety and exhibit specific antibiosis against Clostridioides difficile. Here we report the mechanism of action of keratinicyclin B (KCB). We find that steric constraints preclude KCB from binding peptidoglycan termini. Instead, KCB inhibits C. difficile growth by binding wall teichoic acids (WTAs) and interfering with cell wall remodeling. A computational model, guided by biochemical studies, provides an image of the interaction of KCB with C. difficile WTAs and shows that the same H-bonding framework used by glycopeptide antibiotics to bind peptidoglycan termini is used by KCB for interacting with WTAs. Analysis of KCB in combination with vancomycin (VAN) shows highly synergistic and specific antimicrobial activity, and that nanomolar combinations of the two drugs are sufficient for complete growth inhibition of C. difficile, while leaving common commensal strains unaffected.

Exploring the feasibility of bacteriocins EntK1 and EntEJ97s in treatment of systemic vancomycin resistant enterococci infections in mice.

Enterocins K1 and EJ97 have specific antimicrobial activity against Enterococcus faecium and Enterococcus faecalis, respectively. The aim of this study was to investigate the utility of these enterocins for in vivo treatment of systemic enterococcal infections. The antimicrobial effect in blood was analysed and compared against the effect in saline. Colony forming unit counts revealed that the enterocins killed all the bacteria within 1 hour. Additionally, the bactericidal effect against E. faecalis was more rapid in blood, indicating a possible synergy between EntEJ97 and blood. Importantly, no enterocin resistant mutants emerged in these experiments. Injecting the enterocins intraperitoneally in an in vivo mouse model and using fluorescence and minimum inhibitory concentration determination to estimate concentrations of the peptides in plasma, indicate that the enterocins exist in circulation in therapeutic concentrations. Alanine aminotransferase detection, and haemolysis analysis indicates that there is no detectable liver damage or haemolytic effect after injection. The study revealed that EntK1 and EntEJ97 are able to kill all bacteria ex vivo in the presence of blood. In vivo experiments determine that the enterocins exist in circulation in therapeutic concentrations without causing liver damage or haemolysis. Future experiments should test these peptides for treatment of infection in a relevant in vivo model.

Specific Antimicrobial Activities Revealed by Comparative Evaluation of Selected Gemmotherapy Extracts.

Nowadays, unprecedented health challenges are urging novel solutions to address antimicrobial resistance as multidrug-resistant strains of bacteria, yeasts and moulds are emerging. Such microorganisms can cause food and feed spoilage, food poisoning and even more severe diseases, resulting in human death. In order to overcome this phenomenon, it is essential to identify novel antimicrobials that are naturally occurring, biologically effective and increasingly safe for human use. The development of gemmotherapy extracts (GTEs) using plant parts such as buds and young shoots has emerged as a novel approach to treat/prevent human conditions due to their associated antidiabetic, anti-inflammatory and/or antimicrobial properties that all require careful evaluations. Seven GTEs obtained from plant species like the olive (Olea europaea L.), almond (Prunus amygdalus L.), black mulberry (Morus nigra L.), walnut (Juglans regia L.), blackberry (Rubus fruticosus L.), blackcurrant (Ribes nigrum L.) and bilberry (Vaccinium myrtillus L.) were tested for their antimicrobial efficiency via agar diffusion and microbroth dilution methods. The antimicrobial activity was assessed for eight bacterial (Bacillus cereus, Staphylococcus aureus, Salmonella enterica subsp. enterica, Proteus vulgaris, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Listeria monocytogenes), five moulds (Aspergillus flavus, Aspergillus niger, Aspergillus ochraceus, Penicillium citrinum, Penicillium expansum) and one yeast strain (Saccharomyces cerevisiae). The agar diffusion method revealed the blackberry GTE as the most effective since it inhibited the growth of three bacterial, four moulds and one yeast species, having considered the total number of affected microorganism species. Next to the blackberry, the olive GTE appeared to be the second most efficient, suppressing five bacterial strains but no moulds or yeasts. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were then determined for each GTE and the microorganisms tested. Noticeably, the olive GTE appeared to feature the strongest bacteriostatic and bactericidal outcome, displaying specificity for S. aureus, E. faecalis and L. monocytogenes. The other GTEs, such as blueberry, walnut, black mulberry and almond (the list indicates relative strength), were more effective at suppressing microbial growth than inducing microbial death. However, some species specificities were also evident, while the blackcurrant GTE had no significant antimicrobial activity. Having seen the antimicrobial properties of the analysed GTEs, especially the olive and black mulberry GTEs, these could be envisioned as potential antimicrobials that might enhance antibiotic therapies efficiency, while the blackberry GTE would act as an antifungal agent. Some of the GTE mixtures analysed have shown interesting antimicrobial synergies, and all the antimicrobial effects observed argue for extending these studies to include pathological microorganisms.

Study of a combined biological product with antibacterial and probiotic activity

Scientific relevance. The issue of antimicrobial resistance has acquired global significance, urging the search for and use of alternative antibacterial agents to treat infectious diseases. In particular, this situation prompts wider use of biotechnology-derived medicinal products based on bacteriophages and probiotics, including those of the metabolite type. The bacteriotropic (antimicrobial and probiotic) properties of pharmaceutical compositions based on bacteriophages and metabolites of probiotic bacteria suggest a qualitatively new combined antibacterial effect, as well as effectiveness against microorganisms resistant to antibiotics.Aim. The authors aimed to study the properties of a combined biological product with antibacterial and probiotic effects.Materials and methods. The study focused on a combined biological product consisting of a probiotic agent based on Lactobacillus exometabolites and a complex bacteriophage. The antimicrobial activity evaluation involved the Appelmans method, a disc diffusion method using lawn cultures homologous (Staphylococcus spp., Pseudomonas aeruginosa, Escherichia coli, Proteus spp., Enterococcus spp., Salmonella spp., and Shigella spp.) and non-homologous (Acinetobacter baumannii, Klebsiella pneumoniae, and Yersinia enterocolitica) to the complex bacteriophage, and a bioluminescence inhibition test using the genetically modified indicator strain E. coli lum+. The study used bacterial strains isolated from various clinical samples and biotopes in bacteriological laboratories of healthcare institutions in the Perm Territory in 2019–2022. The probiotic activity was assessed by the stimulating effect on model microorganisms of the normal flora.Results. The Appelmans method showed that the combined biological product had high antimicrobial activity against microorganisms homologous to the complex bacteriophage. The titres calculated for the combined biological product and its complex bacteriophage component were comparable and amounted to 10–6.6±0.01 and 10–6.9±0.01, respectively. The disc diffusion method demonstrated that the combined biological product had a more pronounced antibacterial effect on all tested strains than its individual components. The optical density values obtained with the combined biological product were 1.5 and 2 times higher than the values observed with control samples in Bifidobacterium bifidum 1 and Lactobacillus plantarum 8P-А3 cultures, respectively, which demonstrated the stimulating effect of the product on the normal flora. The study results suggest the compatibility of the phage and probiotic components of the combined biological product, as well as its high antimicrobial activity.Conclusions. The novel combined biological product has high specific and non-specific antimicrobial activity, which consists in the inhibition of pathogenic bacteria growth without affecting the normal flora. The combined biological product broadens the range of medicinal products having probiotic and antibacterial effects, particularly on microorganisms resistant to antibiotics.

Salvia officinalis L. and Salvia sclarea Essential Oils: Chemical Composition, Biological Activities and Preservative Effects against Listeria monocytogenes Inoculated into Minced Beef Meat.

In this study, Salvia officinalis L. and Salvia sclarea essential oils (EOs) were investigated using gas chromatography-mass spectrometry (GC-MS) to describe their chemical composition. The obtained results show, for both EOs, a profile rich in terpene metabolites, with monoterpenes predominating sesquiterpenes but with significant qualitative and quantitative differences. The main compound found in the Salvia officinalis EO (SOEO) was camphor (19.0%), while in Salvia sclarea EO (SCEO), it was linalyl acetate (59.3%). Subsequently, the in vitro antimicrobial activity of the EOs against eight pathogenic strains was evaluated. The disc diffusion method showed a significant lysis zone against Gram-positive bacteria. The minimum inhibitory concentrations (MICs) ranged from 3.7 mg/mL to 11.2 mg/mL, indicating that each EO has specific antimicrobial activity. Both EOs also showed significant antiradical activity against DPPH radicals and total antioxidant activity. In addition, the preservative effect of SOEO (9.2%) and SCEO (9.2%), alone or in combination, was tested in ground beef, and the inhibitory effect against Listeria monocytogenes inoculated into the raw ground beef during cold storage was evaluated. Although the effect of each individual EO improved the biochemical, microbiological, and sensory parameters of the samples, their combination was more effective and showed complete inhibition of L. monocytogenes after 7 days of storage at 4 °C. The results show that both EOs could be used as safe and natural preservatives in various food and/or pharmaceutical products.

Evolutionary and in silico guided development of novel peptide analogues for antibacterial activity against ESKAPE pathogens

According to WHO, to combat the resistant strains, new effective anti-microbial agents are needed on an urgent basis and global researchers should focus their efforts and discovery programs on developing them against antibiotic-resistant pathogens or priority pathogens like ESKAPE. In this context, Cationic antimicrobial peptides (AMPs) are being explored extensively as promising next-generation antimicrobials due to their broad range, fast kinetics and multifunctional role. Despite recent advances, it is still a daunting challenge to identify and design a potent AMP with no cytotoxicity, but with broad specific antimicrobial activity, stability and efficacy under in vivo conditions in a cost-effective and robust manner. In this work, as a proof of concept, we designed novel potent AMPs using artificial intelligence based in silico programs. Shortlisted peptide sequences were synthesized using the fmoc chemistry approach, assessed their antimicrobial activity, cell selectivity, mode of action and in vivo efficacy using a series of experiments. The synthesized peptide analogues demonstrated their antimicrobial activity (MIC in the range of 2.5–80 μM) against bacteria. The identified potential lead molecules showed antibacterial activity in physiological conditions with no signs of cytotoxicity. We further tested the antimicrobial activity of peptide analogues for treating wounds infected with Pseudomonas aeruginosa in the mice burn wound model. In drug-development programs, the identification of lead antimicrobial agents is always challenging and involves screening a large number of molecules which is time-consuming and expensive. This work demonstrates the utility of artificial intelligence based in silico analysis programs in discovering novel antimicrobial agents in an economical, robust way.

Propionic Acid Fermentation—Study of Substrates, Strains, and Antimicrobial Properties

Since milk whey is an abundant dairy by-product and a significant threat to the environment, its utilization is of great interest. The study compares valorization of lactose and lactates—the main carbon sources of whey—by fermentation—an environmentally friendly process. Antimicrobials released during fermentation by food-grade bacteria can help increase the microbiological safety of food. Propionic acid—a strong antimicrobial—is obtained mainly by the petrochemical route, yet there is increasing interest in its synthesis in biotechnological pathway. Five strains of propionic acid bacteria (Acidipropionibacterium acidipropionici, Propionibacterium cyclohexanicum, Propionibacterium freudenreichii, Acidipropionibacterium jensenii and Acidipropionibacterium thoenii) were investigated for their ability to produce organic acids and biomass using Na lactate or lactose as carbon sources. Selected fermentates were investigated for their antimicrobial efficacy during in vitro studies with foodborne pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Results confirm that the production of acids and biomass is considerably influenced by the added carbon source. The tested fermentates have strong and specific antimicrobial activity against Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. In addition, inhibition of Staphylococcus aureus and Klebsiella pneumonia depends on the activity of produced bacteriocins. The article also discusses the possibility of increasing the antimicrobial activity of fermentates by acidification.

Characterization and functional analysis of three novel liver-expressed antimicrobial peptide 2 (LEAP-2) in Glyptothorax zanaensis

Liver-expressed antimicrobial peptide 2 (LEAP-2) is an important component of innate immunity, a well-conserved, evolutionarily ancient host defensive mechanism. In this study, three novel full-length LEAP-2 cDNAs were identified and characterized from G. zanaensis. The deduced precursors of GzLEAP-2A, GzLEAP-2B and GzLEAP-2 C, are composed of 94, 74, and 83 amino acids, which possess four, three, and four conserved cysteine residues in the mature peptide, respectively. GzLEAP-2 s are highly conserved in evolution, with GzLEAP-2A and GzLEAP-2 C showing a close topologic relationship with LEAP-2 from Ictalurus furcatus and Danio rerio, respectively. Quantitative real-time polymerase chain reaction analysis indicated that GzLEAP-2 s ubiquitously existed in all examined tissues, with higher mRNA expression levels observed in muscle, intestine, and liver. Antimicrobial assay showed that synthetic GzLEAP-2A and GzLEAP-2B displayed specific antimicrobial activity against aquatic strains, whereas GzLEAP-2 C did not show any detectable antimicrobial activity. All GzLEAP-2 s were found to possess potent 2,2-diphenyl-1-picrythydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)+ radical scavenging activities, and high doses of GzLEAP-2B and GzLEAP-2 C pre-treatment significantly promoted macrophage phagocytic activity. Moreover, no toxicity of GzLEAP-2 s against tested cells was observed at the effective concentrations. The distinct tissue distribution and pleiotropic roles of GzLEAP-2 s suggest a sophisticated and multilevel antimicrobial defensive network of G. zanaensis.

Robotic Construction and Screening of Lanthipeptide Variant Libraries in Escherichia coli.

Lanthipeptides are a major class of ribosomally synthesized and post-translationally modified peptides (RiPPs) characterized by thioether cross-links called lanthionine (Lan) and methyllanthionine (MeLan). Previously, we developed a method to produce mature lanthipeptides in recombinant Escherichia coli, but manual steps hinder large-scale analogue screening. Here we devised an automated workflow for creating and screening variant libraries of haloduracin, a two-component class II lanthipeptide. An integrated work cell of a synthetic biology foundry was programmed to robotically execute DNA library construction, host transformation, peptide production, mass spectrometry analysis, and activity screening by agar diffusion assay. For recombinantly produced Halα peptides, the sequence-activity relationship of 380 single-residue variants and >1300 triple-residue combinatorial variants were rapidly analyzed in microplates within weeks. The peptide expression levels in E.coli were also visualized via robotic creation and analysis of GFP-lanthipeptide fusions for select peptide mutants. Following shake-flask fermentation and purification, one Halα mutant was confirmed with enhanced specific antimicrobial activity relative to the wild-type peptide. Overall, this approach may be generally applicable for the high-throughput characterization and engineering of RiPP natural products.

Handcrafted versus non-handcrafted (self-supervised) features for the classification of antimicrobial peptides: complementary or redundant?

Antimicrobial peptides (AMPs) have received a great deal of attention given their potential to become a plausible option to fight multi-drug resistant bacteria as well as other pathogens. Quantitative sequence-activity models (QSAMs) have been helpful to discover new AMPs because they allow to explore a large universe of peptide sequences and help reduce the number of wet lab experiments. A main aspect in the building of QSAMs based on shallow learning is to determine an optimal set of protein descriptors (features) required to discriminate between sequences with different antimicrobial activities. These features are generally handcrafted from peptide sequence datasets that are labeled with specific antimicrobial activities. However, recent developments have shown that unsupervised approaches can be used to determine features that outperform human-engineered (handcrafted) features. Thus, knowing which of these two approaches contribute to a better classification of AMPs, it is a fundamental question in order to design more accurate models. Here, we present a systematic and rigorous study to compare both types of features. Experimental outcomes show that non-handcrafted features lead to achieve better performances than handcrafted features. However, the experiments also prove that an improvement in performance is achieved when both types of features are merged. A relevance analysis reveals that non-handcrafted features have higher information content than handcrafted features, while an interaction-based importance analysis reveals that handcrafted features are more important. These findings suggest that there is complementarity between both types of features. Comparisons regarding state-of-the-art deep models show that shallow models yield better performances both when fed with non-handcrafted features alone and when fed with non-handcrafted and handcrafted features together.

Improving the Antimicrobial Performance of Amphiphilic Cationic Antimicrobial Peptides Using Glutamic Acid Full-Scan and Positive Charge Compensation Strategies.

Nonselective toxicity of antimicrobial peptides (AMPs) needs to be solved urgently for their application. Temporin-PE (T-PE, FLPIVAKLLSGLL-NH2), an AMP extracted from skin secretions of frogs, has high toxicity and specific antimicrobial activity against Gram-positive bacteria. To improve the antimicrobial performance of T-PE, a series of T-PE analogues were designed and synthesized by glutamic acid full-scan, and then their key positions were replaced with lysine. Finally, E11K4K10, the highest therapeutic indicial AMP, was screened out. E11K4K10 was not easy to induce and produce drug-resistant bacteria when used alone, as well as it could also inhibit the development of the drug resistance of traditional antibiotics when it was used in combination with the traditional antibiotics. In addition, E11K4K10 had an excellent therapeutic effect on a mouse model of pulmonary bacterial infection. Taken together, this study provides a new approach for the further improvement of new antimicrobial peptides against the antimicrobial-resistance crisis.

Lignin as a Natural Carrier for the Efficient Delivery of Bioactive Compounds: From Waste to Health.

Lignin is a fascinating aromatic biopolymer with high valorization potentiality. Besides its extensive value in the biorefinery context, as a renewable source of aromatics lignin is currently under evaluation for its huge potential in biomedical applications. Besides the specific antioxidant and antimicrobial activities of lignin, that depend on its source and isolation procedure, remarkable progress has been made, over the last five years, in the isolation, functionalization and modification of lignin and lignin-derived compounds to use as carriers for biologically active substances. The aim of this review is to summarize the current state of the art in the field of lignin-based carrier systems, highlighting the most important results. Furthermore, the possibilities and constraints related to the physico–chemical properties of the lignin source will be reviewed herein as well as the modifications and processing required to make lignin suitable for the loading and release of active compounds.

Targeted isolation of biocontrol agents from plants through phytopathogen co-culture and pathogen enrichment

In a long-term symbiotic relationship between plants and pathogens, plants have evolved to harbor beneficially endophytic microbiomes, thereby conferring them the ability to resist infection by pathogens. This prompted us to establish a phytopathogen-based co-culture platform for the targeted isolation of potential biocontrol agents from plants via specific pathogen enrichment. In this study, we investigated three different phytopathogenic systems, including kiwifruit, turfgrass, and rice, and their infectious bacterial and/or fungal pathogens. By using the developed mono- or co-enrichment platform, we efficiently isolated three antimicrobial agents, including Bacillus safensis ZK-1 against Pseudomonas syringae pv. actinidiae that causes kiwifruit canker, Pseudomonas alcaligenes ZK-2 against Clarireedia paspali that causes dollar spot disease in turfgrass, and Bacillus velezensis ZK-3 against rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae and rice blast fungus Magnaporthe oryzae. We believe that the phytopathogenic co-culture and pathogen enrichment platform developed here is versatile and effective for the isolation of potential biocontrol agents with specific or broad-spectrum antimicrobial activities from plants of interest in a targeted and large-scale manner.

Comparative genomics reveals the organic acid biosynthesis metabolic pathways among five lactic acid bacterial species isolated from fermented vegetables

Lactic acid bacteria (LAB) comprise a widespread bacterial group, inhabiting the niches of fermented vegetables and capable of producing beneficial organic acids. In the present study, several bioinformatics approaches were used to perform whole-genome sequencing and comparative genomics of five LAB species, Lactobacillus plantarum PC1–1, Pediococcus pentosaceus PC2–1(F2), Weissella hellenica PC1A, Lactobacillus buchneri PC-C1, and Enterococcus sp. YC2–6, to enhance understanding of their different genetic functionalities and organic acid biosynthesis. The results revealed major carbohydrate-active enzymes, putative operons and unique mobile genetic elements, including plasmids, resistance genes, insertion sequences and composite transposons involved in organic acid biosynthesis. The metabolic pathways of organic acid biosynthesis emphasize the key genes encoding specific enzymes required for organic acid metabolism. The five genomes were found to contain various regions of secondary metabolite biosynthetic gene clusters, including the type III polyketide synthases (T3PKS) enriched with unique genes encoding a hydroxymethylglutaryl-CoA synthase, capable of exhibiting specific antimicrobial activity with biopreservative potential, and a cyclic AMP receptor protein (CRP) transcription factor acting as a glucose sensor in organic acid biosynthesis. This could enable the organisms to prevail in the fermentation process, suggesting potential industrial applications.

Antisense Peptide Nucleic Acid-Diaminobutanoic Acid Dendron Conjugates with SbmA-Independent Antimicrobial Activity against Gram-Negative Bacteria.

Precision antisense antibacterial agents may be developed into novel antibiotics in the fight against multidrug-resistant Gram-negative bacteria. In this study, a series of diaminobutanoic acid (DAB) dendrons are presented as novel carriers for the delivery of antisense antibacterial peptide nucleic acids (PNAs). The dendron–PNA conjugates targeting the essential acpP gene exhibit specific antisense antimicrobial bactericidal activity against Escherichia coli and Klebsiella pneumoniae at one-digit micromolar concentrations, while showing low toxicity to human cells. One compound selected from a structure–activity relationship series showed high stability in mouse and human serum (t1/2 ≫ 24 h) as well as in vivo activity against a multidrug-resistant, extended spectrum beta-lactamase-producing E. coli in a murine peritonitis model. The compound was also well tolerated in mice upon i.v. administration up to a dose of 20 mg/kg, and in vivo fluorescence imaging indicated clearance via renal excretion with slight accumulation in the kidneys and liver. Thus, DAB-based dendrons constitute a promising new chemistry platform for development of effective delivery agents for antibacterial drugs with possible in vivo use.

Potentials of Endophytes of Andrographis Paniculata for the Production of Plant Growth Promoters, Enzymes and Antimicrobial Compounds

In the present study, 9 bacterial and 6 fungal endophytes were isolated from surface sterilized leaf, stem and root samples of the medicinal plant - Andrographis paniculata (Kalmegh). The endophytes were screened for plant growth promoting traits (IAA, phosphate solubilization and N2 fixation), enzymes (cellulase and amylase) and antimicrobial compounds against 3 potent human pathogens- E. coli, Staphylococcus sp. and Vibrio sp. The majority of the isolated endophytes produced the phytohormone - IAA (ranging 2-45μg/ml), and 1 endophyte solubilized phosphate and fixed N2. All the fungal endophytes possessed cellulase and amylase activity. In the preliminary screening, 4 bacterial and 4 fungal endophytic isolates extract showed antagonistic activity against the 3 potent human pathogens which are known causative agents of urinary tract, skin and gastrointestinal tract infections, respectively. The endophytes of A. paniculata exhibiting broad and specific antimicrobial activity make them ideal candidates in medical purposes. SAARC J. Agric., 19(2): 157-170 (2021)

Comparison of medium chain organic acids with zinc oxide and benzoic acid; effect on growth performance of pigs

Medium chain organic acids (MCOA) show strong and specific antimicrobial activity and may be useful as part of an antibiotic reduction strategy. Two trials were conducted to evaluate the effect of MCOA on growth performance of pigs in comparison with benzoic acid (BA) and ZnO (ZnO). Each used 240 pigs in a randomised complete block design with six treatments in eight replicate pens. Trial 1 tested a blend of C6:0, C8:0, C10:0 and C12:0 for 56 d post-weaning. Treatments were (1) control basal diet (BD), (2) BD+ZnO (3) BD+ZnO+BA, (4) BD+MCOA (5) BD+MCOA+ZnO, (6) BD+MCOA+BA. Pigs receiving MCOA+BA showed higher average daily liveweight gain in the grower period (849 g/d) than pigs receiving the control diet (773 g/d) or the ZnO treatment (779 g/d; P=0.040), grew 7% more efficiently (P=0.008) and were 3.02 kg heavier at 56 d than control pigs. Trial 2 tested the MCOA blend at two inclusion levels in comparison with C6:0/C12:0 (50/50) and C6:0/C12 monolaurin (C12M; 50/50), for 28 d post-weaning. Treatments were (1) control basal diet, (2) BD+ZnO (3) BD+1,500 mg/kg MCOA (4) BD+750 mg/kg MCOA (5) BD+ C6/C12 (total 3,000 mg/kg), (6) BD + C6/C12M (total 3,000 mg/kg). Pigs receiving 750 mg/kg MCOA grew more slowly than those receiving C6/C12M or ZnO (P<0.05) to d 21. Pigs fed ZnO were 1.61 kg heavier than these pigs (P<0.05), while those fed C6/C12M were 1.29 kg heavier (P<0.05) at d 21. During 0-14 d pigs fed ZnO showed the best feed conversion ratio (FCR), but at 15-28 d the improvement was no longer seen. Both the C6/C12 and the C6/C12M treatments appeared to improve FCR during this second phase (P<0.01). The results suggested that supplementation with a combination of MCOA and BA may be a promising strategy to improve growth performance while replacing ZnO and reducing antibiotic dependence.

Antimicrobial properties of Pediococcus acidilactici and Pediococcus pentosaceus isolated from silage.

The objective of this study was to isolate multifunctional bacteriocin-producing strains; to characterize the expressed bacteriocin for the control of Listeria monocytogenes and vancomycin-resistant Enterococcus; to evaluate the safety of studied strains; and to explore their antifungal activity. Two Pediococcus strains were isolated from silage samples obtained from an organic farm in Belogradchik, Bulgaria. The strains were identified by 16S rRNA sequencing analysis and characterized as bacteriocins producers. Strong antimicrobial activity was detected against more than 74 different strains of Listeria monocytogenes, 27 different vancomycin-resistant Enterococcus strains. In addition, studied strains were able to inhibit the growth of strains of Alternaria alternate, Aspergillus flavus, Aspergillus niger, Cladosporium sphaerospermum, Penicillium chrysogenum and Penicillium expansum. Some aspects of the antimicrobial mode of action were evaluated, including killing curves and aggregation properties. Both strains generated positive PCR results for the presence of pediocin PA-1, but not for other bacteriocins evaluated in this screening process. Metabolomic analysis of the cell-free supernatants from both strains was performed in order to explain the observed antifungal activity against different moulds. According to PCA and PLS-DA score plot, P. acidilactici ST3522BG and P. pentosaceus ST3633BG were clearly clustered from control (MRS). Increases in the production of benzoic acid, 2-hydroxyisocaproic acid, β-phenyl-lactic acid, α-hydroxybutyric acid and 1,3-butanediol were recorded, these metabolites were previously described as antifungal. Pediococcus acidilactici ST3522BG and P. pentosaceus ST3633BG were evaluated as producing bacteriocin strains with high specificity against Listeria and vancomycin-resistant Enterococcus species. In addition, both investigated Pediococcus strains were evaluated as producer of effective antifungal metabolites with potential for the inhibition of mycotoxin-producing moulds. To the best of our knowledge, this report is a pioneer in the evaluation of Pediococcus strains isolated from silage with highly specific bacteriocinogenic antimicrobial activity against Listeria spp. and vancomycin-resistant Enterococcus spp., and antifungal activity against mycotoxin-producing moulds.