Dual action of benzaldehydes: Inhibiting quorum sensing and enhancing antibiotic efficacy for controlling Pseudomonas aeruginosa biofilms.

Quorum sensing (QS) has a central role in biofilm lifestyle and antimicrobial resistance, and disrupting these signaling pathways is a promising strategy to control bacterial pathogenicity and virulence. In this study, the efficacy of three structurally related benzaldehydes (4-hydroxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 4-hydroxy-3,5-dimethoxybenzaldehyde (syringaldehyde)) in disrupting the las and pqs systems of Pseudomonas aeruginosa was investigated using bioreporter strains and computational simulations. Additionally, these benzaldehydes were combined with tobramycin and ciprofloxacin antibiotics to evaluate their ability to increase antibiotic efficacy in preventing and eradicating P. aeruginosa biofilms. To this end, the total biomass, metabolic activity and culturability of the biofilm cells were determined. In vitro assays results indicated that the aromatic aldehydes have potential to inhibit the las and pqs systems by > 80 %. Molecular docking studies supported these findings, revealing the aldehydes binding in the same pocket as the natural ligands or receptor proteins (LasR, PQSA, PQSE, PQSR). Benzaldehydes were shown to act as virulence factor attenuators, with vanillin achieving a 48 % reduction in pyocyanin production. The benzaldehyde-tobramycin combination led not only to a 60 % reduction in biomass production but also to a 90 % reduction in the metabolic activity of established biofilms. A similar result was observed when benzaldehydes were combined with ciprofloxacin. 4-Hydroxybenzaldehyde demonstrated relevant action in increasing biofilm susceptibility to ciprofloxacin, resulting in a 65 % reduction in biomass. This study discloses, for the first time, that the benzaldehydes studied are potent QS inhibitors and also enhancers of antibiotics antibiofilm activity against P. aeruginosa.

Size-Controlled Synthesis of Gold Nanoparticles Tethering Antimicrobial Peptides with Potent Broad-Spectrum Antimicrobial and Antibiofilm Activities.

New antimicrobials are urgently needed to combat the rising global health concern of antibiotic resistance. Antimicrobial peptides (AMPs) are one of the leading candidates as new antimicrobials since they target bacterial membranes and are therefore less prone to bacterial resistance. However, poor enzymatic stability, high production costs, and toxicity are drawbacks that limit their clinical use. Conjugation of AMPs to gold nanoparticles (NPs) may help to improve enzymatic stability and, thus, their overall antimicrobial efficiency. We did a one-pot synthesis of size-controlled (10 nm) gold NPs selectively conjugated to lipopeptides and determined their antibacterial activity. The conjugates exhibited potent (0.13-1.25 µM) antimicrobial activity against clinical isolates, including Gram-positive methicillin-resistant Staphylococcus aureus (S. aureus) ATCC33593, Gram-negative Escherichia coli (E. coli) CTX-M-14, multidrug-resistant Pseudomonas aeruginosa LESB58 and Acinetobacter baumannii ATCC19606, and showed promising activity (90% inhibition of initial biofilms and 80% reduction of preformed biofilms) against S. aureus and E. coli DH5α biofilms at low micromolar concentrations. The conjugates were stable in rat serum and not toxic to representative mammalian cell lines in vitro (≤64 µM) and in vivo (≤100 µM).

Antibiofilm potential of nanonized eugenol against Pseudomonas aeruginosa.

AIMS: The purpose of this study was to synthesize a nanoform of eugenol (an important phytochemical with various pharmacological potentials) and to investigate its antibiofilm efficacy on Pseudomonas aeruginosa biofilm. METHODS AND RESULTS: Colloidal suspension of eugenol-nanoparticles (ENPs) was synthesized by the simple ultrasonic cavitation method through the emulsification of hydrophobic eugenol into hydrophilic gelatin. Thus, the nanonization process made water-insoluble eugenol into water-soluble nano-eugenol, making the nanoform bioavailable. The size of the ENPs was 20-30 nm, entrapment efficiency of eugenol within gelatin was 80%, and release of eugenol from the gelatin cap was slow and sustained over 5 days. Concerning the clinically relevant pathogen P. aeruginosa, ENPs had higher antibiofilm (for both formation and eradication) activities than free eugenol. Minimal biofilm inhibitory concentration and minimal biofilm eradication concentration of ENP on P. aeruginosa biofilm were 2.0 and 4.0 mM, respectively. In addition, the measurement of P. aeruginosa biofilm biomass, biofilm thickness, amount of biofilm extra-polymeric substance, cell surface hydrophobicity, cell swarming and twitching efficiencies, cellular morphology, and biofilm formation in catheter demonstrated that the antibiofilm efficacy of nano-eugenol was 30%-40% higher than that of bulk eugenol. CONCLUSION: These results signify that future pharmacological and clinical studies are very much required to investigate whether ENPs can act as an effective drug against P. aeruginosa biofilm-mediated diseases. Thus, the problem of intrinsic antibiotic tolerance of biofilm-forming cells may be minimized by ENPs. Moreover, ENP may be used as a potential catheter-coating agent to inhibit pseudomonal colonization on catheter surfaces and, therefore, to reduce catheter-associated infections and complications.

Evaluating the antimicrobial and anti-biofilm activity of three synthetic antimicrobial Citropin analogs and their ability to fight against Staphylococcus aureus and Staphylococcus pseudintermedius.

AIMS: We developed three new analogs of the antimicrobial peptide (AMP) Citropin 1.1: DAN-1-13, AJP-1-1, and HHX-2-28, and tested their potential antimicrobial and antibiofilm activities against Staphylococcus aureus and S. pseudintermedius. Potential cytotoxic or hemolytic effects were determined using cultured human keratinocytes and erythrocytes to determine their safety. METHODS AND RESULTS: To assess the antimicrobial activity of each compound, minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined against methicillin-resistant and methicillin-susceptible strains of S. aureus and S. pseudintermedius. Activity against newly formed and mature biofilms was determined in two clinical isolates using spectrophotometry and scanning electron microscopy (SEM). All three compounds exhibited antimicrobial and bactericidal activity against all studied S. aureus and S. pseudintermedius strains, with MICs ranging from 4-32 µg ml-1 and MBCs ranging from 8-128 µg ml-1. Subinhibitory concentrations of all compounds also showed ant-biofilm activity in the two tested isolates. All compounds exhibited limited cytotoxic and hemolytic activity. CONCLUSIONS: Novel analogs of Citropin 1.1 exhibit antimicrobial and bactericidal activities against S. aureus and S. pseudintermedius isolates and inhibit the biofilm formation of these bacteria.

Montelukast and cefoperazone act as antiquorum sensing and antibiofilm agents against Pseudomonas aeruginosa.

AIMS: Drug repurposing is an attractive strategy to control biofilm-related infectious diseases. In this study, two drugs (montelukast and cefoperazone) with well-established therapeutic applications were tested on Pseudomonas aeruginosa quorum sensing (QS) inhibition and biofilm control. METHODS AND RESULTS: The activity of montelukast and cefoperazone was evaluated for Pqs signal inhibition, pyocyanin synthesis, and prevention and eradication of Ps. aeruginosa biofilms. Cefoperazone inhibited the Pqs system by hindering the production of the autoinducer molecules 2-heptyl-4-hydroxyquinoline (HHQ) and 2-heptyl-3-hydroxy-4(1H)-quinolone (the Pseudomonas quinolone signal or PQS), corroborating in silico results. Pseudomonas aeruginosa pyocyanin production was reduced by 50%. The combination of the antibiotics cefoperazone and ciprofloxacin was synergistic for Ps. aeruginosa biofilm control. On the other hand, montelukast had no relevant effects on the inhibition of the Pqs system and against Ps. aeruginosa biofilm. CONCLUSION: This study provides for the first time strong evidence that cefoperazone interacts with the Pqs system, hindering the formation of the autoinducer molecules HHQ and PQS, reducing Ps. aeruginosa pathogenicity and virulence. Cefoperazone demonstrated a potential to be used in combination with less effective antibiotics (e.g. ciprofloxacin) to potentiate the biofilm control action.

Inhibition of biofilm, quorum-sensing, and swarming motility in pathogenic bacteria by magnetite, manganese ferrite, and nickel ferrite nanoparticles.

Resistance to antibiotics by pathogenic bacteria constitutes a health burden and nanoparticles (NPs) are being developed as alternative and multipurpose antimicrobial substances. Magnetite (Fe3O4 np), manganese ferrite (MnFe2O4 np) and nickel ferrite (NiFe3O4 np) NPs were synthesized and characterized using thermogravimetric analysis, transmission electron microscopy, Fourier transformed infra-red, and X-ray diffraction. The minimal inhibitory concentrations (MIC) ranged from 0.625 to 10 mg/mL against gram-positive (Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212), gram-negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) and candida (Candida albicans ATCC 10239 and Candida tropicalis ATCC 13803) species. The NPs exhibited violacein inhibition against Chromobacterium violaceum CV12472 of 100% at MIC and reduced to 27.2% ± 0.8% for magnetite NPs, 12.7% ± 0.3% for manganese ferrite NPs and 43.1% ± 0.2% for nickel ferrite NPs at MIC/4. Quorum-sensing (QS) inhibition zones against C. violaceum CV026 were 12.5 ±0.6 mm for Fe3O4 np, 09.1 ± 0.5 mm for MnFe3O4 NP and 17.0 ± 1.2 mm for NiFe3O4 np. The NPs inhibited swarming motility against P. aeruginosa PA01 and biofilm against six pathogens and the gram-positive biofilms were more susceptible than the gram-negative ones. The NiFe2O4 np had highest antibiofilm activity against gram-positive and gram-negative bacteria as well as highest QS inhibition while Fe3O4 NP had highest biofilm inhibition against candida species. The synthesized magnetic NPs can be used in developing anti-virulence drugs which reduce pathogenicity of bacteria as well as resistance.

Synergistic activity of gold nanoparticles with amphotericin B on persister cells of Candida tropicalis biofilms.

AIM: The antifungal activity was studied on sessile and persister cells (PCs) of Candida tropicalis biofilms of gold nanoparticles (AuNPs) stabilized with cetyltrimethylammonium bromide (CTAB-AuNPs) and those conjugated with cysteine, in combination with Amphotericin B (AmB). MATERIALS/METHODS: The PC model was used and synergistic activity was tested by the checkerboard assay. Biofilms were studied by crystal violet and scanning electron microscopy. RESULTS/CONCLUSIONS: After the combination of both AuNPs and AmB the biofilm biomass was reduced, with significant differences in architecture being observed with a reduced biofilm matrix. In addition, the CTAB-AuNPs-AmB combination significantly reduced PCs. Understanding how these AuNPs aid in the fight against biofilms and the development of new approaches to eradicate PCs has relevance for chronic infection treatment.

Pseudomonas otitidis-mediated synthesis of silver nanoparticles: characterization, antimicrobial and antibiofilm potential.

This study explores the eco-friendly synthesis of silver nanoparticles (AgNPs) using soil bacteria, Pseudomonas otitidis. The bio-synthesized AgNPs were characterized using various techniques, including UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). UV-visible spectroscopy revealed a distinct broad absorption band in the range of 443 nm, indicating the reduction of silver nitrate to AgNPs. XRD analysis provided evidence of the crystalline nature of the particles, with sharp peaks confirming their crystallinity and an average size of 82.76 nm. FTIR spectroscopy identified extracellular protein compounds as capping agents. SEM examination revealed spherical agglomeration of the crystalline AgNPs. The antimicrobial assay by a disc diffusion method, minimum inhibitory concentration, and minimum bactericidal concentration testing revealed that the biosynthesized AgNPs showed moderate antibacterial activity against both pathogenic Gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii) and Gram-positive (Bacillus cereus, Staphylococcus aureus, and Streptococcus mutans) bacterial strains. Furthermore, the AgNPs significantly disrupted the biofilm of P. aeruginosa, as confirmed by crystal violet assay and fluorescent microscopy. Overall, this study underscores the potential of microbial-synthesized nanoparticles in biomedical applications, particularly in combating pathogenic bacteria, offering a promising avenue for future research and development.

Exploring the frontiers of therapeutic breadth of antifungal peptides: A new avenue in antifungal drugs.

The growing prevalence of fungal infections alongside rising resistance to antifungal drugs poses a significant challenge to public health safety. At the close of the 2000s, major pharmaceutical firms began to scale back on antimicrobial research due to repeated setbacks and diminished economic gains, leaving only smaller companies and research labs to pursue new antifungal solutions. Among various natural sources explored for novel antifungal compounds, antifungal peptides (AFPs) emerge as particularly promising. Despite their potential, AFPs receive less focus than their antibacterial counterparts. These peptides have been sourced extensively from nature, including plants, animals, insects, and especially bacteria and fungi. Furthermore, with advancements in recombinant biotechnology and computational biology, AFPs can also be synthesized in lab settings, facilitating peptide production. AFPs are noted for their wide-ranging efficacy, in vitro and in vivo safety, and ability to combat biofilms. They are distinguished by their high specificity, minimal toxicity to cells, and reduced likelihood of resistance development. This review aims to comprehensively cover AFPs, including their sources-both natural and synthetic-their antifungal and biofilm-fighting capabilities in laboratory and real-world settings, their action mechanisms, and the current status of AFP research. ONE-SENTENCE SUMMARY: This comprehensive review of AFPs will be helpful for further research in antifungal research.

Synergistic interaction of nanoparticles and probiotic delivery: A review.

Nanotechnology is an expanding and new technology that prompts production with nanoparticle-based (1-100 nm) organic and inorganic materials. Such a tool has an imperative function in different sectors like bioengineering, pharmaceuticals, electronics, energy, nuclear energy, and fuel, and its applications are helpful for human, animal, plant, and environmental health. In exacting, the nanoparticles are synthesized by top-down and bottom-up approaches through different techniques such as chemical, physical, and biological progress. The characterization is vital and the confirmation of nanoparticle traits is done by various instrumentation analyses like UV-Vis spectrophotometry (UV-Vis), Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscopy, X-ray diffraction, atomic force microscopy, annular dark-field imaging, and intracranial pressure. In addition, probiotics are friendly microbes which while administered in sufficient quantity confer health advantages to the host. Characterization investigation is much more significant to the identification of good probiotics. Similarly, haemolytic activity, acid and bile salt tolerance, autoaggregation, antimicrobial compound production, inhibition of pathogens, enhance the immune system, and more health-beneficial effects on the host. The synergistic effects of nanoparticles and probiotics combined delivery applications are still limited to food, feed, and biomedical applications. However, the mechanisms by which they interact with the immune system and gut microbiota in humans and animals are largely unclear. This review discusses current research advancements to fulfil research gaps and promote the successful improvement of human and animal health.

Chemical Composition and Phytotoxic and Antibiofilm Activity of the Essential Oils of Two Moroccan Retama Species.

This study reports chemical composition, phytotoxic and antibiofilm activities of essential oils (EOs) of R. dasycarpa and R. sphaerocarpa from Morocco. EOs were analyzed by GC/MS and their phytotoxicities were evaluated against germination and seedling growth of Lolium multiflorum, Sinapis alba and Raphanus sativus. The antimicrobial and anti-biofilm activities were studied against Gram-negative (Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii) and Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes). Both EOs were abundant in oxygenated monoterpenes (40.01% and 23.57 %, respectively). Carvacrol is the predominant component in R. dasycarpa EO (17.80 %), and it also represents an appreciable amount in R. sphaerocarpa (8.96 %). R. sphaerocarpa showed total inhibition at high doses against all seeds. S. alba seeds were the most sensitive to all EOs. Minimum inhibitory concentration (MIC) values indicated significant inhibition for R. sphaerocarpa, between 24 and 30 µg/mL, with a remarkable antibacterial potential and biofilm formation inhibition. R. sphaerocarpa EO showed significant biofilm inhibition with variable efficacy depending on the strain and concentration, except for S. aureus. R. dasycarpa exhibited activity against all bacterial strains and effect on metabolism with activity also on mature biofilms. Results suggest that Retama EOs could have potential applications in the fields of food and health.

Halogenated Analogs to Natural A-Type Proanthocyanidins: Evaluation of Their Antioxidant and Antimicrobial Properties and Possible Application in Food Industries.

A description of new antimicrobial agents suitable for food industries has become necessary, and natural compounds are being considered as promising sources of new active derivatives to be used with the aim of improving food safety. We have previously described desirable antimicrobial and antibiofilm activities against foodborne bacteria by analogs to A-type proanthocyanidins (PACs) with a nitro (NO2) group at carbon 6 of the A-ring. We report herein the synthesis of eight additional analogs with chloro and bromo atoms at the A-ring and the systematic study of their antimicrobial and antioxidant activities in order to evaluate their possible application as biocides or food preservatives, as well as to elucidate new structure-activity relationships. The results from this study show that halogenated analogs to natural A-type proanthocyanidins rise above the nitro derivatives previously reported in their antimicrobial activities. Gram-positive bacteria are the most sensitive to all the analogs and combinations assayed, showing MICs from 10 to 50 µg/mL in most cases, as well as reductions in biofilm formation and the disruption of preformed biofilms of at least 75%. Some structure-activity relationships previously described have also been corroborated. Analogs with just one OH group at the B-ring show better antimicrobial activities than those with two OH groups, and those analogs with two or three OH groups in the whole structure are more active than those with four OH groups. In addition, the analogs with two OH groups at the B-ring and chloro at the A-ring are the most effective when antibiofilm activities are studied, especially at low concentrations.

The antibiofilm potential of a heteropolysaccharide produced and characterized from the isolated marine bacterium Glutamicibacter nicotianae BPM30.

Biofilms are the significant causes of 80% of chronic infections in the oral cavity, urinary tract, biliary tube, lungs, gastrointestinal tract, and so on to the general public. Treatment of pathogenic biofilm using bacterial exopolysaccharides (EPS) is an effective and promising strategy. In the present work, a marine bacterium was isolated, studied for exopolysaccharide production, and tested for its antibiofilm activity. Approximately 1.31 ± 0.07 g/L of a purified extracellular polysaccharide was produced and characterized from the isolated marine bacterium Glutamicibacter nicotianae BPM30. The hydrolyzed EPS contains multiple monosaccharides such as rhamnose, fructose, glucose, and galactose. The EPS demonstrated potential antibiofilm activity on four tested pathogens in a concentration-dependent mode. The antibiofilm activity of the purified EPS was studied by crystal violet assay and fluorescence staining method. Comparative inhibition results obtained for the tested strains are 93.25% ± 5.25 and 88.56% ± 2.25 for K. pneumoniae; 92.65% ± 7.6 and 98.33% ± 0.85 for P. aeruginosa; 90.36% ± 6.3 and 52.08% ± 7.74 for S. typhi; 84.62% ± 5.6 and 77.90% ± 5.90 for S. dysenteriae. The results of the present work demonstrated the antibiofilm potential of EPS, which could be helpful in the invention of novel curative approaches in battling bacterial biofilm-related medical complications.

Biofilm-disrupting effects of phage endolysins LysAm24, LysAp22, LysECD7, and LysSi3: breakdown the matrix.

The ability of most opportunistic bacteria to form biofilms, coupled with antimicrobial resistance, hinder the efforts to control widespread infections, resulting in high risks of negative outcomes and economic costs. Endolysins are promising compounds that efficiently combat bacteria, including multidrug-resistant strains and biofilms, without a low probability of subsequent emergence of stable endolysin-resistant phenotypes. However, the details of antibiofilm effects of these enzymes are poorly understood. To elucidate the interactions of bacteriophage endolysins LysAm24, LysAp22, LysECD7, and LysSi3 with bacterial films formed by Gram-negative species, we estimated their composition and assessed the endolysins' effects on the most abundant exopolymers in vitro. The obtained data suggests a pronounced efficiency of these lysins against biofilms with high (Klebsiella pneumoniae) and low (Acinetobacter baumannii) matrix contents, or dual-species biofilms, resulting in at least a twofold loss of the biomass. These peptidoglycan hydrolases interacted diversely with protective compounds of biofilms such as extracellular DNA and polyanionic carbohydrates, indicating a spectrum of biofilm-disrupting effects for bacteriolytic phage enzymes. Specifically, we detected disruption of acid exopolysaccharides by LysAp22, strong DNA-binding capacity of LysAm24, both of these interactions for LysECD7, and neither of them for LysSi3.

Effect of post-harvest drying period on the chemical composition of Zingiber zerumbet Sm. Rhizomes essential oil and its biological activities.

Zingiber zerumbet Sm. (Family: Zingiberaceae) is an important perennial medicinal oil-bearing herb that is native to the Southeast Asia. This study examines the impact of different durations of post-harvest shade drying (ranging from 1 to 12 months) on essential oil yield and chemical composition of Z. zerumbet, in comparison to the freshly collected oil sample. This study explores how post-harvest shade drying impact the composition and longevity of Z. zerumbet rhizomes as well as its antimicrobial, antibiofilm activity. The oils were analyzed for their chemical composition analysis using a gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The post-harvest periods of drying (1-12 months) were discovered to enhance the concentration of marker constituents in the oil. The primary constituent, Zerumbone, was detected in concentrations ranging from 69.38 ± 5.63% to a maximum of 80.19 ± 1.53% as the drying duration of the rhizome was extended. The output of the essential oil was not significantly affected by drying times; however, it did have a noticeable impact on the proportions of monoterpenes. Both disc diffusion and broth microdilution assay were used in freshly collected Z. zerumbet oil for its antimicrobial potential against S. aureus, L. monocytogens, S. hominis, Salmonella enterica serovar Typhimurium, P. aeruginosa, S. intermedius, E. coli, and C. albicans. For the first time, the oil reported to exhibit antibiofilm activity against S. aureus which was validated using fluorescence microscopy, and effectively disrupts the biofilm by 47.38% revealing that essential oil was able to disintegrate the clusters of the pathogen. Z. zerumbet rhizome oil is effective to reduce food-borne microorganisms. Therefore, its essential oil, a natural source of bioactive zerumbone, may improve flavor, aroma, and preservation.

Biochemical and Antioxidant Properties as well as Antimicrobial and Antibiofilm Activities of Allium scorodoprasum subsp. jajlae (Vved.) Stearn.

In this study, the chemical composition and biological activity of Allium scorodoprasum subsp. jajlae (Vved.) Stearn were investigated for the first time, focusing on its antimicrobial, antioxidant, and antibiofilm properties. A GC-MS analysis was employed to evaluate the composition of its secondary metabolites, identifying linoleic acid, palmitic acid, and octadecanoic acid 2,3-dihydroxypropyl ester as the major compounds in ethanol extract. The antimicrobial activity of A. scorodoprasum subsp. jajlae was assessed against 26 strains, including standard, food isolate, clinical isolate, and multidrug-resistant ones, as well as three Candida species using the disc diffusion method and the determination of the minimum inhibitory concentration (MIC). The extract showed strong antimicrobial activity against Staphylococcus aureus strains, including methicillin-resistant and multidrug-resistant strains, as well as Candida tropicalis and Candida glabrata. Its antioxidant capacity was evaluated using the DPPH method, revealing a high level of antioxidant activity in the plant. Additionally, the antibiofilm activity of A. scorodoprasum subsp. jajlae was determined, demonstrating a reduction in biofilm formation for the Escherichia coli ATCC 25922 strain and an increase in biofilm formation for the other tested strains. The findings suggest potential applications of A. scorodoprasum subsp. jajlae in the development of novel antimicrobial, antioxidant, and antibiofilm agents.

Characterization of an antimicrobial pentapeptide produced by a drug-sensitive Pseudomonas aeruginosa strain PAST18.

The members of the genus Pseudomonas can secrete a wide range of ribosomally encoded antagonistic peptides and proteins, ranging from small microcins to large tailocins. In this study, a drug-sensitive Pseudomonas aeruginosa strain isolated from a high-altitude virgin soil sample showed a broad range of antibacterial activity against Gram-positive and Gram-negative bacteria. The antimicrobial compound, purified by affinity chromatography, ultrafiltration, and high-performance liquid chromatography, showed a molecular weight (M + H)+ of 494.7667 daltons, as revealed by ESI-MS analysis. The MS-MS analysis divulged the compound as an antimicrobial pentapeptide with the sequence NH2-Thr-Leu-Ser-Ala-Cys-COOH (TLSAC) and was further verified by evaluating the antimicrobial activity of the chemically synthesized pentapeptide. The extracellularly released pentapeptide, which is relatively hydrophobic in nature, is encoded in a symporter protein, as appraised from the whole genome sequence analysis of strain PAST18. The influence of different environmental factors was examined to determine the stability of the antimicrobial peptide (AMP), which was also assessed for several other biological functions, including antibiofilm activity. Further, the antibacterial mechanism of the AMP was evaluated by a permeability assay. Overall, the characterised pentapeptide, as revealed in this study, may find use as a potential biocontrol agent in various commercial applications.

Cell selectivity and antibiofilm and anti-inflammatory activities and antibacterial mechanism of symmetric-end antimicrobial peptide centered on D-Pro-Pro.

This study aimed to develop a new symmetric-end antimicrobial peptide (AMP) with cell selectivity, antibiofilm, and anti-inflammatory activities. Two symmetric-end AMPs, Lf6-pP and Lf6-GG, were designed based on the sequence RRWQWRzzRWQWRR, which contains two symmetric repeat sequences connected by a ß-turn-promoting sequence (zz) that can be a rigid turn by D-Pro-Pro (pP) or a flexible turn by Gly-Gly (GG). Both Lf6-pP and Lf6-GG exhibited potent antibacterial activity without causing hemolysis, but Lf6-pP exhibited better cell selectivity, likely due to the more significant impact of the rigid pP turn. Compared to Lf6-GG, Lf6-pP demonstrated approximately three times higher antimicrobial activity against drug-resistant bacteria, had a low incidence of drug resistance, and maintained its activity in the presence of physiological salts and human serum. Additionally, Lf6-pP was more effective than Lf6-GG in inhibiting biofilm formation and eradicating mature biofilms. The BODIPY-cadaverine assay indicated that the potent anti-inflammatory activity of Lf6-pP may be attributed to its direct interaction with LPS, resulting in decreased TNF-α and IL-6 levels in LPS-stimulated macrophages. Mechanistic studies, including membrane depolarization, outer/inner membrane permeation, and membrane integrity change, demonstrated that Lf6-pP exerts its antibacterial action through an intracellular-target mechanism. Overall, we propose that Lf6-pP has potential as a novel antibacterial, antibiofilm, and anti-inflammatory agent against drug-resistant bacterial infections.

Hesperidin methyl chalcone, a citrus flavonoid, inhibits Aeromonas hydrophila infection mediated by quorum sensing.

Plant-derived phytocompounds are effective in treating a variety of ailments and disorders, the most common of which are bacterial infections in humans, which are a major public health concern. Flavonoids, one of the groups of phytocompounds, are known to have significant antimicrobial and anti-infective properties. Hence, the current study investigates the efficacy of the citrus flavonoid hesperidin methylchalcone (HMC) in addressing this major issue. The results of this study indicate that the anti-quorum sensing (anti-QS) action against Aeromonas hydrophila infections is exhibited with a decrease in biofilm development and virulence factors production through in vitro and in silico analyses. In addition, the qPCR findings indicate that HMC has antivirulence action on A. hydrophila by reducing the expression of QS-related virulence genes, including ahyR, ahyB, ahh1, aerA, and lip. Interestingly, HMC significantly rescued the A. hydrophila-infected zebrafish by reducing the internal colonization, demonstrating the in vivo anti-infective potential of HMC against A. hydrophila infection. Based on these results, this study recommends that HMC could be employed as a possible therapeutic agent to treat A. hydrophila-related infections in humans.

Antimicrobial and anti-biofilm activity of silver nanoparticles biosynthesized with Cystoseira algae extracts.

Antimicrobial resistance is an ever-growing global concern to public health with no clear or immediate solution. Silver nanoparticles (AgNPs) have long been proposed as efficient agents to fight the growing number of antibiotic-resistant strains. However, the synthesis of these particles is often linked to high costs and the use of toxic, hazardous chemicals, with environmental and health impact. In this study, we successfully produced AgNPs by green synthesis with the aid of the extract of two brown algae-Cystoseira baccata (CB) and Cystoseira tamariscifolia (CT)-and characterized their physico-chemical properties. The NPs produced in both cases (Ag@CB and Ag@CT) present similar sizes, with mean diameters of around 22 nm. The antioxidant activity of the extracts and the NPs was evaluated, with the extracts showing important antioxidant activity. The bacteriostatic and bactericidal properties of both Ag@CB and Ag@CT were tested and compared with gold NPs produced in the same algae extracts as previously reported. AgNPs demonstrated the strongest bacteriostatic and bactericidal properties, at concentrations as low as 2.16 µg/mL against Pseudomonas aeruginosa and Escherichia coli. Finally, the capacity of these samples to prevent the formation of biofilms characteristic of infections with a poorer outcome was assessed, obtaining similar results. This work points towards an alternative for the treatment of bacterial infections, even biofilm-inducing, with the possibility of minimizing the risk of drug resistance, albeit the necessary caution implied using metallic NPs.