Lowest MIC Research Articles

Synthesis and Antibacterial Evaluation of Novel Psoralen Derivatives against Methicillin-Resistant Staphylococcus aureus (MRSA).

Today, the bacterial infections caused by multidrug-resistant pathogens seriously threaten human health. Thereby, there is an urgent need to discover antibacterial drugs with novel mechanism. Here, novel psoralen derivatives had been designed and synthesized by a scaffold hopping strategy. Among these targeted twenty-five compounds, compound ZM631 showed the best antibacterial activity against methicillin-resistant S. aureus (MRSA) with the low MIC of 1 μg/mL which is 2-fold more active than that of the positive drug gepotidacin. Molecular docking study revealed that compound ZM631 fitted well in the active pockets of bacterial S. aureus DNA gyrase and formed a key hydrogen bond binding with the residue ASP-1083. These findings demonstrated that the psoralen scaffold could serve as an antibacterial lead compound for further drug development against multidrug-resistant bacterial infections.

Study of the Antimicrobial Activity of the Human Peptide SQQ30 against Pathogenic Bacteria.

Given the continuous increase in antibiotic resistance, research has been driven towards the isolation of new antimicrobial molecules. Short, charged, and very hydrophobic antimicrobial peptides have a direct action against biological membranes, which are less prone to developing resistance. Using a bioinformatic tool, we chose the SQQ30 peptide, isolated from the human SOGA1 protein. The antimicrobial activity of this peptide against various Gram-negative and Gram-positive bacterial strains and against a fungal strain was studied. A mechanism of action directed against biological membranes was outlined. When administered in combination with the antibiotic ciprofloxacin and with the TRS21 (buforin II), another antimicrobial peptide, SQQ30 can be used with a lower MIC, showing additivity and synergism, respectively. Particularly interesting is the ability of SQQ30 to bind LPS in Gram-negative strains, preventing the eukaryotic cell from releasing inflammatory mediators. Our study indicates SQQ30 as a novel and promising antimicrobial agent.

Phytochemical Constituents and Potential of Different Extracts from Eleutherine bulbosa on Skin Infectious Treatment : Anti-fungal, Anti-bacterial, Anti-inflammatory and Cytotoxic Activities

Eleutherine bulbosa is a plant commonly employed in traditional medicine across various tropical regions, including Thailand. The aim of this study was to identify the phytochemical constituents of E. bulbosa, evaluate the inhibitory effects on skin fungal and bacterial pathogens, and examine the anti-inflammatory and cytotoxic properties of extracts obtained from E. bulbosa bulbs through n-Hexane, EtOAc, and EtOH extraction methods. Agar diffusion, MIC, and MBC assays were employed to determine the fungistatic, bacteriostatic, and bactericidal activities. The EtOAc extract of E. bulbosa bulbs demonstrated the highest inhibition against fungal and bacterial strains when compared to other solvents. The results revealed that the EtOAc extract exhibited a potent anti-fungal effect on T. rubrum (the zones of inhibition = 35.00 ± 0.00 mm) comparable to Ketoconazole (the zones of inhibition = 34.33 ± 1.16 mm). The highest antibacterial activity against S. pyogenes was observed, with a zone diameter of 23.00 ± 1.00 mm, while the lowest MIC and MBC values were recorded at 19.53 and 78.12 μg/ml, respectively. Additionally, we demonstrated significant inhibitory properties of E. bulbosa bulbs extracted with n-Hexane on NO production in LPS-stimulated RAW 264.7 cells compared to other solvent extracts. This occurred without affecting cell viability across a concentration range of 6.25 to 25 μg/ml. Moreover, the less affected viability of fibroblasts suggests that the extract may be useful in preventing inflammatory diseases mediated by excessive production of NO with low toxicity to normal cells. Phytochemical screening indicated the presence of various compounds with biological activities including alkaloids, flavonoids, phenols, and tannins in all different solvent extracts. These findings suggest that E. bulbosa bulb extracts possess beneficial effects and hold potential for further development as a new natural source of multifunctional therapeutic agents, which are safe and effective for a broad spectrum of skin infectious microorganisms and also potentially reduce inflammation that is associated with an infection caused by microorganisms.

Genetic analysis of vancomycin-variable Enterococcus faecium clinical isolates in Italy

PurposeTo investigate the occurrence of vancomycin-variable enterococci (VVE) in a hospital in central Italy.MethodsvanA positive but vancomycin-susceptible Enterococcus faecium isolates (VVE-S) were characterized by antibiotic susceptibility tests, molecular typing (PFGE and MLST), and WGS approach. The reversion of VVE-S to a resistant phenotype was assessed by exposure to increasing vancomycin concentrations, and the revertant isolates were used in filter mating experiments. qPCR was used to analyze the plasmid copy number.ResultsEleven putative VVE-S were selected. WGS revealed two categories of vanA cluster plasmid located: the first type showed the lack of vanR, the deletion of vanS, and an intact vanH/vanA/vanX cluster; the second type was devoid of both vanR and vanS and showed a deletion of 544-bp at the 5′-end of the vanH. Strains (n = 7) carrying the first type of vanA cluster were considered VVE-S and were able to regain a resistance phenotype (VVE-R) in the presence of vancomycin, due to a 44-bp deletion in the promoter region of vanH/vanA/vanX, causing its constitutive expression. VVE-R strains were not able to transfer resistance by conjugation, and the resistance phenotype was unstable: after 11 days of growth without selective pressure, the revertants were still resistant but showed a lower vancomycin MIC. A higher plasmid copy number in the revertant strains was probably related to the resistance phenotype.ConclusionWe highlight the importance of VVE transition to VRE under vancomycin therapy resulting in a potential failure treatment. We also report the first-time identification of VVE-S isolates pstS-null belonging to ST1478.

Assessment of antibacterial efficacy and toxicological implications of emperor scorpion (Pandinus imperator) venom using animal model

This research work was carried out by collecting 50 Pandinus imperator Scorpions and ascetically extracting venom locally from them and testing the venom on some selected bacteria. The extracted venom used was both in the lyophilized and crude (non-lyophilized) state to determine their different efficacy and was passed through a membrane filter to ensure sterility. Bacterial (Pseudomonas aeruginosa, Escherichia coli, and Acetinibacter baumannii) were isolated from drinking water sources of the University of Abuja after which it was preserved in slant for further use. Serotyped bacteria were also obtained and used in this study. Appropriate differential and selective agar were used to culture and sub-culture the isolates and serotyped while Analytical Profile Index (API) kits were used to confirm the isolated bacteria. A sensitivity test was carried out on each bacterium with the venom at concentrations of 25%, 50%, 75%, and 100% for crude venom while 10, 20, 30, and 40 mg/ml for the lyophilized venom, minimum inhibitory concentration, and minimum bactericidal concentration were also determined. The result shows lowest zone for crude venom against isolated bacteria was 3mm at 25% against Acinetobacter baumanni while the highest was 11.5 mm at 100% against Pseudomonas aeruginosa, the lowest for crude venom against serotyped was 4 mm at 25% against Acinetobacter baumanni and highest was 12.2 mm at 100% against Pseudomonas aeruginosa, lowest zone for lyophilized venom against isolated bacteria was 2.8 mm at 10 mg/ml against Acinetobacter baumanni while highest was 10.8 mm at 40 mg/ml against Pseudomonas aeruginosa, also the lowest for lyophilized venom serotyped was 3.8 mm at 10 mg/ml against Acinetobacter baumanni and highest was 11.5 mm at 40 mg/ml against Pseudomonas aeruginosa. The lowest MIC was 25% and 20 mg/ml while the highest was 50% and 30 mg/ml, the lowest MBC was 50% and 30 mg/ml while the lowest was 75% and 40 mg/ml. The toxicity of the venom was carried out by testing the venom on mice which shows no harmful effect on them. ANOVA statistical analysis carried out showed no significant difference in the activities of both venom states.

Pistacia terebinthus MEYVESİ: GIDA BOZULMASINI ÖNLEMEK İÇİN BİR ALTERNATİF

The aim of this work was to investigate the usage possibilities of P. terebinthus fruit, which has a limited usage area, in the food industry. Antimicrobial activity of hexane extract obtained from P. terebinthus fruits from Adıyaman (Turkey) was determined by disc diffusion and micro-dilution assays against test microorganisms. In addition, the antibacterial activity of the extract on Escherichia coli O157:H7, one of the most important food-borne pathogens, was determined by viable cell count using a macro-dilution assay. The potential for use of the extract with probiotic candidate lactic acid bacteria (LAB) strains was also investigated. The hexane extract presented antimicrobial activity against all the tested microorganisms, with good inhibition zone diameters between 10.51 mm and 18.02 mm. MIC and MFC or MBC values of P. terebinthus fruit extract were determined as 5-80 µg/µL against all tested microorganisms. The lowest MIC and MBC values (5 µg/µL) of the extract were obtained against E. coli O157:H7. Macro-dilution assay results indicated that the P. terebinthus extract at various concentrations (5-10-20 mg/mL) inhibited the growth of E. coli O157:H7 more than the control group after all of the incubation hours. No viable E. coli O157:H7 cells were detected after 48 hours at all concentrations. The extract showed low antimicrobial activity, and relatively high bactericidal concentration on probiotic candidate LAB strains. This shows that P. terebinthus hexane extract at appropriate concentrations can be used together with probiotic strains as a natural preservative and biopreservative to prevent food spoilage and extend shelf life.

LL-37_Renalexin hybrid peptide exhibits antimicrobial activity at lower MICs than its counterpart single peptides

An alarming global public health and economic peril has been the emergence of antibiotic resistance resulting from clinically relevant bacteria pathogens, including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species constantly exhibiting intrinsic and extrinsic resistance mechanisms against last-resort antibiotics like gentamycin, ciprofloxacin, tetracycline, colistin, and standard ampicillin prescription in clinical practices. The discovery and applications of antimicrobial peptides (AMPs) with antibacterial properties have been considered and proven as alternative antimicrobial agents to antibiotics. In this study, we have designed, produced, and purified a recombinant novel multifunctional hybrid antimicrobial peptide LL-37_Renalexin for the first time via the application of newly designed flexible GS peptide linker coupled with the use of our previously characterized small metal-binding proteins SmbP and CusF3H+ as carrier proteins that allow for an enhanced bacterial expression, using BL21(DE3) and SHuffle T7(DE3) Escherichia coli strains, and purification of the hybrid peptide via immobilized metal affinity chromatography. The purified tag-free LL-37_Renalexin hybrid peptide exhibited above 85% reduction in bacteria colony-forming units and broad-spectrum antimicrobial effects against Staphylococcus aureus, Escherichia coli, Methicillin-resistant Staphylococcus aureus (MRSA), and Klebsiella pneumoniae bacteria clinical isolates at a lower minimum inhibition concentration level (10–33 μM) as compared to its counterpart single-AMPs LL-37 and Renalexin (50–100 μM).Key points• The hybrid antimicrobial peptide LL-37_Renalexin has been designed using a GS linker.• The peptide was expressed with the carrier proteins SmbP and CusF3H+.• The hybrid peptide shows antibacterial potency against clinical bacterial isolates.

Bioactivity assay of Arundina graminifolia (D.Don) Hochr. extracts from diverse plant parts in Thailand: An assay-based investigation

This research involved surveying and collecting 16 samples of Arundina graminifolia from 8 different subpopulation areas. The main objectives were to analyze the preliminary phytochemical fingerprints and biological activity of the crude extracts obtained from various parts of the plant (roots, rhizomes, stems, and leaves). The findings indicated that rhizome extracts generally yielded a higher percentage of crude extract compared to the dry plant weight in comparison to other plant parts. Moreover, the Thin layer chromatography (TLC) fingerprint data revealed distinct compositions for each part of the plant, with rhizomes exhibiting more prevalent bands of compounds than other parts. Regarding antioxidant activity, the root and rhizome crude extracts from various populations displayed stronger inhibitory activity against DPPH, ABTS, and FRAP methods compared to stems and leaves. High total phenolic content was also found to effectively inhibit free radicals. The lipoxygenase inhibition test, which serves as an in vitro anti-inflammatory activity evaluation, demonstrated that most root extracts exhibited higher lipoxygenase inhibitory activity than the rhizome extracts at a concentration of 0.1 mg/mL. The antibacterial activity demonstrated that rhizome extracts from different regions exerted lower MIC and MBC values against all tested bacteria compared to the root extracts. The findings offer valuable information for selecting specific populations of A. graminifolia as potential sources of bioactive compounds for future nutraceutical applications.

Green synthesis of nanocellulose supported cu-bionanocomposites and their profound applicability in the synthesis of amide derivatives and controlling of food-borne pathogens

Copper bionanocomposites (CBNCS) were synthesized using Ipomoea carnea- sourced nanocellulose as support via an eco-friendly and cost-effective method. X-ray Diffractometer (XRD) pattern of CBNCS confirmed the octahedral structure of Cu2O, the face-centered cubic (FCC) crystal structure of Cu(0). XRD also revealed the crystal lattice of cellulose II. Surface Electron Microscope (SEM) and Transmission Electron Microscope (TEM) revealed the uniform distribution of copper nanoparticles (Cu NPs) with an average size of 10 nm due to the presence of nanocellulose. X-ray photoelectron spectroscopy (XPS) provided information about the electronic, chemical state and elemental composition of CBNCS. Thermogravimetric Analysis (TGA) showed the thermal stability of CBNCS. CBNCS catalyzed the rearrangement of oximes to primary amides in a very mild condition with a high yield of up to 92 %. CBNCS effectively inhibited the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with lower minimum inhibitory concentration MIC values. Antioxidant activity and electrical conductivity of CBNCS were also determined.

Mechanism of action of pseudopteroxazole and pseudopterosin G: Diterpenes from marine origin.

Pseudopteroxazole (Ptx) and the pseudopterosins are marine natural products with promising antibacterial potential. While Ptx has attracted interest for its antimycobacterial activity, pseudopterosins are active against several clinically relevant pathogens. Both compound classes exhibit low cytotoxicity and accessibility to targeted synthesis, yet their antibacterial mechanisms remain elusive. In this study, we investigated the modes of action of Ptx and pseudopterosinG (PsG) in Bacillus subtilis employing an unbiased approach that combines gel-based proteomics with a mathematical similarity analysis of response profiles. Proteomic responses to sublethal concentrations of Ptx and PsG were compared to a library of antibiotic stress response profiles revealing that both induce a stress response characteristic for agents targeting the bacterial cell envelope by interfering with membrane-bound steps of cell wall biosynthesis. Microscopy-based assays confirmed that both compounds compromise the integrity of the bacterial cell wall without disrupting the membrane potential. Furthermore, LC-MSE analysis showed that the greater potency of PsG against B.subtilis, reflected in a lower MIC and a more pronounced proteomic response, may be rooted in a more effective association with and penetration of B. subtilis cells. We conclude that Ptx and PsG target the integrity of the gram-positive cell wall.

O03 Phenotypic antimicrobial resistance to last-resort antibiotics in carbapenemase-producing bacteria from Ukrainian patients

Abstract Background Since March 2022, there has been an emergence of MDR microorganisms (MDRO) in Europe because of an increasing number of Ukrainian patients with MDRO. The goal was to collect large-scale phenotypic susceptibility data to assess implications for clinical practice. Methods For 122 MDRO (carbapenemase-producing Enterobacterales (CPE, n=96), Pseudomonas aeruginosa CPPA (n=20), carbapenem-resistant Acinetobacter baumannii-calcoaceticus (CRAB, n=6), collected from March to December 2022, broth microdilution (BMD), fosfomycin agar dilution, gradient strip ampicillin/sulbactam, sulbactam/durlobactam, ceftazidime-avibactam-aztreonam and disc diffusion (DD) cefiderocol was performed. Epidemiological data was obtained as part of mandatory reporting by Municipal Health Services (CPE), and surveillance questionnaires (CPPA/CRAB). Results Admission at a Ukrainian hospital in the last year was a risk factor for acquiring MDRO. Of all isolates, 65% (79/122) were blaNDM-positive. For meropenem, aminoglycosides, ceftazidime-avibactam, ceftolozane-tazobactam and imipenem-relebactam susceptibility rates were low (0-30%). For cefiderocol, results depended on reading with or without microcolonies, applying EUCAST or CLSI breakpoints, and whether DD or BMD was used: e.g. for Klebsiella pneumoniae, 30%–97% were susceptible, depending on these variables. For colistin, 103/111 (93%) non-intrinsically resistant CPE/CPPA/CRAB isolates were susceptible. For the majority of CPE, a low MIC of <0.5 mg/L was measured for tigecycline and ceftazidime-avibactam-aztreonam. For CPPA, cefiderocol tested susceptible in 65%–100% of isolates. For CRAB, ampicillin/sulbactam MICs were ≥128 mg/L, for sulbactam/durlobactam 1–2 mg/L. Conclusions There is extensive phenotypic resistance to last-resort antibiotics in carbapenemase-producing bacteria from Ukrainian patients. For cefiderocol, interpretation of susceptibility results depends on a number of variables. In case of infection, treatment options are colistin, cefiderocol (CPE/CPPA/CRAB), tigecycline (CPE/CRAB), ceftazidime-avibactam-aztreonam (CPE), sulbactam/durlobactam (CRAB).

Investigating the Effectiveness of Spirocyclopropane-Oxindole Derivatives on Clinical Isolates of Candida albicans

Objectives: Given the spread of azole resistance in Candida albicans (C. albicans), searching for new potent compounds, such as spirocyclopropane-oxindole derivatives is important. This study evaluates the antifungal susceptibility of spirocyclopropane-oxindole derivatives on clinical isolates of C. albicans. Methods: Antifungal susceptibility of 50 clinical isolates of C. albicans to spirocyclopropane-oxindole derivatives (4a, 4b, and 4c), nystatin, and fluconazole were evaluated according to Clinical Laboratory Standards Institute (M27-S4) guidelines. The medicinal dilution range of the compounds, fluconazole, and nystatin was 0.256 to 128, 0.128 to 64, and 0.032 to 16 μg/mL, respectively. The minimum inhibitory concentration (MIC) was defined as the concentration that caused at least 50% growth inhibition compared to the positive control. Statistical analysis was performed using the SPSS software, version 20. The significance level was set at P≤0.05. Results: There was a significant difference between the MIC values of spirocyclopropane-oxindole derivatives (4a, 4b, and 4c), nystatin, and fluconazole against C. albicans. The comparison of the MICs of the spirocyclopropane-oxindole derivatives (4a, 4b, and 4c) against C. albicans showed that derivative 4a had a lower MIC50 (8 μg/mL), MIC90 (16 μg/mL), and Geometric (G) Mean (10.126) than derivatives 4b (MIC50=64, MIC90=128, G Mean=76.638), and 4c (MIC50=64, MIC90=128, G Mean=60.547). Discussion: Antifungal effects of spirocyclopropane-oxindole derivatives (4a, 4b, and 4c) on C. albicans isolates were significantly less than nystatin and fluconazole. Therefore, with structural changes, the antifungal effects of these compounds will increase.

Antioxidative and Antibacterial Hydro-Ethanolic Fraction from an Asian Edible Mushroom Lentinus sajor-caju (Agaricomycetes) Suppresses Inflammatory Responses by Downregulating COX-2 and iNOS Expression.

Mushrooms are prevalently important sources of pharmaceutically active metabolites. Various mushroom species belonging to the Lentinus genus are recognized for their nutritional and therapeutic properties. One such species is L. sajor-caju, which is renowned in Southeast Asian nations for its culinary value. The primary goal of this study is to investigate the potential medicinal properties of L. sajor-caju, specifically its antioxidant, antibacterial, and anti-inflammatory effects. A hydroethanolic extract was formulated using dried basidiocarps, which exhibited a high phenolic content of approximately 14% and a flavonoid content of approximately 2.7%. The extract demonstrated significant antioxidant potential in in vitro reactions. The extract is sufficiently capable of scavenging free radicals (DPPH and ABTS) and chelate Fe2+ with EC50 values spanning from 186 to 390 μg/mL. In addition, considerable antimicrobial activity against tested pathogenic microorganisms was observed, as indicated by low MIC50 values (256-358 μg/mL). Moreover, the fraction was found to prevent heat-induced protein denaturation which signifies its anti-inflammatory potential. When tested on the RAW 264.7 cell line, reduction in the nitrite production, and downregulation of COX-2 and iNOS mRNA expression was observed which are the key regulator of inflammatory signalling systems. The study, therefore, recommends the use of L. sajor-caju in the medical and pharmaceutical industries for the benefit of humanity.

LEGO-lipophosphonoxins: length of hydrophobic module affects permeabilizing activity in target membranes of different phospholipid composition.

In the past few decades, society has faced rapid development and spreading of antimicrobial resistance due to antibiotic misuse and overuse and the immense adaptability of bacteria. Difficulties in obtaining effective antimicrobial molecules from natural sources challenged scientists to develop synthetic molecules with antimicrobial effect. We developed modular molecules named LEGO-Lipophosphonoxins (LEGO-LPPO) capable of inducing cytoplasmic membrane perforation. In this structure-activity relationship study we focused on the role of the LEGO-LPPO hydrophobic module directing the molecule insertion into the cytoplasmic membrane. We selected three LEGO-LPPO molecules named C9, C8 and C7 differing in the length of their hydrophobic chain and consisting of an alkenyl group containing one double bond. The molecule with the long hydrophobic chain (C9) was shown to be the most effective with the lowest MIC and highest perforation rate both in vivo and in vitro. We observed high antimicrobial activity against both G+ and G- bacteria with significant differences in LEGO-LPPOs mechanism of action on these two cell types. We observed a highly cooperative mechanism of LEGO-LPPO action on G- bacteria as well as on liposomes resembling G- bacteria. LEGO-LPPO action on G- bacteria was significantly slower compared to G+ bacteria suggesting the role of the outer membrane in affecting the LEGO-LPPOs perforation rate. This notion was supported by the higher sensitivity of the E. coli strain with a compromised outer membrane. Finally, we noted that the composition of the cytoplasmic membrane affects the activity of LEGO-LPPOs since the presence of phosphatidylethanolamine increases their membrane disrupting activity.

A Preliminary Evaluation of the Antibacterial Activity of Lemon Fruit Juice, Mondia whitei Ethanolic Extract, and Their Combination Against Streptococcus mutans.

Dental caries has gained momentum as one of the main public healthcare concerns worldwide. Although the occurrence of dental caries in Uganda is on the rise, little attention has been paid to promoting oral healthcare in the country. Thus, this study aimed to evaluate the citrus lemon extracts, and Mondia whitei root bark ethanolic extract as candidate alternative therapeutic agents for streptococcus mutans, the causative agent of dental caries. In this study, the citrus lemon juice, pulp citrus lemon juice, and Mondia whitei ethanolic extract were screened for phytochemicals. Furthermore, the anti-Streptococcus mutans activity of the citrus lemon juice, citrus lemon pulp juice, and Mondia whitei ethanolic extract was determined by the agar well diffusion method while the minimum inhibitory concentration and minimum bactericidal concentration were determined by serial broth dilution. Phytochemical screening revealed the presence of alkaloids, flavonoids, terpenoids, and tannins in the Mondia whitei ethanolic extract and citrus lemon juices, while glycosides were only detected in lemon extracts. The zones of inhibition of Mondia whitei ethanolic extract, citrus lemon juice, citrus lemon pulp juice, and the cocktail were 13.67 ± 0.33 mm, 18.67 ± 0.33 mm, 18.33 ± 0.67 mm, and 18.00 ± 0.58 mm, respectively. The citrus lemon juice and citrus lemon pulp juice exhibited significantly lower MIC of 0.195 mg/mL, and 0.391mg/mL, respectively. The efficacy of the extract/juices increased with an increase in the concentration. The study findings revealed that Mondia whitei ethanolic extract and lemon extracts have potent antibacterial activity against streptococcus mutans, the main causative agent of dental caries; thus, can be further explored to formulate a herbal concoction for the prevention and treatment of oral cavity infections in resources-limited low-income communities.

Peptide lipidation and shortening optimises antibacterial, antibiofilm and membranolytic actions of an amphiphilic polylysine-polyphenyalanine octapeptide

The demand for broad-spectrum antibacterial agents continues with increasing rates of resistance of microbial pathogens to traditional antibiotics. Peptides and lipopeptides are gaining traction as promising novel, class-reference antibiotics for tackling difficult-to-treat infections caused by multi-drug resistant bacteria. To identify novel candidates and expand treatment options in clinical settings, we explored the in vitro antibacterial potential and mode of action of a short octapeptide combining a cationic block of four lysines and a highly hydrophobic segment of four phenylalanines (K4F4), and two K4F4-inspired lipopeptides (Palmitoyl-K4F4 and K4-NH-Palmitoyl). Preliminary AI-based screening had revealed the antimicrobial potential of the K4F4 peptide coupled with limited haemolytic activity. Broth dilution and haemolytic assays have confirmed these in silico predictions. Overall, our lipidated peptides were more active at lower MIC values compared to non-lipidated species, indicating the beneficial impact of tailing lipidation on design of peptide-based antimicrobials. An integrated view of the membrane-active mechanism of these novel therapeutic templates was obtained using a combination of flow cytometry, fluorescence microscopy and dye-based permeabilization assays. K4F4 and its lipidated derivatives act via a fast-disrupting mechanism without inducing bacterial resistance mechanisms in a long-term exposure assay. A K4F4-inspired lipopeptide together with its shorter version (K4-NH-Palmitoyl), were more stable in environments closer emulating physiological conditions, showing a higher antibacterial response in physiological salts and serum than their parent peptide. Our findings reveal the antibacterial and antibiofilm potential of a novel polylysine-polyphenyalanine peptide and highlight the significant contribution of lipidation and shortening as molecular engineering strategies to improve and guide the future design of next-generation membrane-targeting antibiotics.

Sustainable preparation of AuAg alloy@AgBr Janus nanoparticles via dissipative self-assembly for photocatalysis.

We report a facile synthesis of cetyltrimethylammonium bromide (CTAB) templated AuAg alloy@AgBr Janus-nanoparticles (JNPs) using a non-conventional top-down approach with precise control over symmetry breaking. The addition of AgNO3 to a micellar solution of CTAB results in micelle-stabilized AgBr colloids having excess Ag+ at the interstitial sites of AgBr. AgBr colloids undergo weak self-assembly supported by inter-micellar interactions. The interfacial disturbance of self-assembled colloids via electrostatic adsorption of AuCl4- or Au(OH)4- at the micelle-AgBr interface downsizes the colloids. This is followed by the growth of the AuAg phase onto AgBr resulting in AuAg alloy@AgBr JNPs via different reduction pathways (photoreduction or chemical reduction) in the presence of ascorbic acid. The prepared JNPs act as efficient visible light photocatalysts for the degradation of aqueous rhodamine B. Interestingly, the trapping of holes favors the photocatalytic efficiency. Furthermore, the JNPs have shown proficiency in inhibiting the growth of both Gram-positive and Gram-negative bacteria as compared to the commercial antibiotic kanamycin, with a very low MIC value of ∼35 μg ml-1. In this way, a new single-pot strategy for the controlled preparation of photo-catalytically active and antimicrobial AuAg alloy@AgBr JNPs governed by dissipative self-assembly is reported for the first time.

Antitubercular evaluation of dihydropyridine-triazole conjugates: design, synthesis, in vitro screening, SAR and in silico ADME predictions.

This study investigates the potential of click chemistry for the development of novel anti-tuberculosis agents. A targeted library of 1,4-dihydropyridine-1,2,3-triazole conjugates was synthesized and evaluated for their in vitro activity against Mycobacterium tuberculosis H37Ra using the resazurin microtiter assay (REMA). Among the synthesized derivatives, compounds J10, J11, J14, J22 and J23 demonstrated significant antimycobacterial activity. These compounds exhibited low MIC values ranging from 6.24 to 6.64 μg mL-1, highlighting their promising potential as lead compounds for further developing novel tuberculosis therapeutics. In addition to the promising in vitro activity, structure-activity relationship (SAR) analysis revealed that electron-withdrawing groups on the aryl-substituted ring of the dihydropyridines (J10-J24), a triazole with an unsubstituted aryl ring or with electron-donating groups (methyl or methoxy), and a geminal dimethyl group are essential structural features for the observed antitubercular activity. Furthermore, in silico ADME (absorption, distribution, metabolism, and excretion) parameters and pharmacokinetic studies supported the potential of these conjugates for oral bioavailability. These findings collectively highlight the 1,4-dihydropyridine-1,2,3-triazole scaffold as a promising platform for developing novel orally active anti-tuberculosis drugs.

Discovery of benzopyridone cyanoacetates as new type of potential broad-spectrum antibacterial candidates

Unique benzopyridone cyanoacetates (BCs) as new type of promising broad-spectrum antibacterial candidates were discovered with large potential to combat the lethal multidrug-resistant bacterial infections. Many prepared BCs showed broad antibacterial spectrum with low MIC values against the tested strains. Some highly active BCs exhibited rapid sterilization capacity, low resistant trend and good predictive pharmacokinetic properties. Furthermore, the highly active sodium BCs (NaBCs) displayed low hemolysis and cytotoxicity, and especially octyl NaBC 5g also showed in vivo potent anti-infective potential and appreciable pharmacokinetic profiles. A series of preliminary mechanistic explorations indicated that these active BCs could effectively eliminate bacterial biofilm and destroy membrane integrity, thus resulting in the leakage of bacterial cytoplasm. Moreover, their unique structures might further bind to intracellular DNA, DNA gyrase and topoisomerase IV through various direct noncovalent interactions to hinder bacterial reproduction. Meanwhile, the active BCs also induced bacterial oxidative stress and metabolic disturbance, thereby accelerating bacterial apoptosis. These results provided a bright hope for benzopyridone cyanoacetates as potential novel multitargeting broad-spectrum antibacterial candidates to conquer drug resistance.

Effect of CaCl2 Crosslinker Concentration On The Characteristics, Release and Stability of Ciprofloxacin HCl-Alginate-Carrageenan Microspheres

Background: Ciprofloxacin HCl is a broad-spectrum fluoroquinolone antibiotic that has the lowest MIC against Mycobacterium tuberculosis but has limitations in oral use, so inhalation microspheres are made. Objective: This study aimed to investigate the effect of CaCl2 crosslinker concentration on the characteristics, release and stability of ciprofloxacin-alginate-carrageenan microspheres. Methods: Microspheres were prepared by ionotropic gelation using aerosolization with calcium chloride 0.5M (F1), 1.0M (F2), 1.5M (F3), 2.0M (F4) as crosslinker and then dried using freeze dryer. Results: Ciprofloxacin-alginate-carrageenan microspheres formed of yellowish-white powder, smooth morphology and excellent flow properties with the particle size of less than 5µm, drug loading and entrapment efficiency were between 2.05% - 2.42% and 75.34% - 98.09%, yield was between 84.69% - 97.57%, moisture content of less than 10%. Ciprofloxacin-alginate-carrageenan microspheres with 1.5M crosslinker (F3) was the optimal formula. For 12 hours, ciprofloxacin released was 49.89% - 63.78% at pH 7.4, and the kinetics of drug release showed that of Korsmeyer-peppas with a mechanism based on fickian diffusion. The microspheres were discovered to be stable for up to 28 days of storage. Conclusion: The increased concentration of the CaCl2 crosslinker from 0.5M to 2.0M decreased the particle size and drug release but increased the yield, drug loading and entrapment efficiency.