Discovery of phosphorylated lantibiotics with proimmune activity that regulate the oral microbiome.

Lantibiotics are ribosomally synthesized and posttranslationally modified peptides (RiPPs) that are produced by bacteria. Interest in this group of natural products is increasing rapidly as alternatives to conventional antibiotics. Some human microbiome-derived commensals produce lantibiotics to impair pathogens' colonization and promote healthy microbiomes. Streptococcus salivarius is one of the first commensal microbes to colonize the human oral cavity and gastrointestinal tract, and its biosynthesis of RiPPs, called salivaricins, has been shown to inhibit the growth of oral pathogens. Herein, we report on a phosphorylated class of three related RiPPs, collectively referred to as salivaricin 10, that exhibit proimmune activity and targeted antimicrobial properties against known oral pathogens and multispecies biofilms. Strikingly, the immunomodulatory activities observed include upregulation of neutrophil-mediated phagocytosis, promotion of antiinflammatory M2 macrophage polarization, and stimulation of neutrophil chemotaxis-these activities have been attributed to the phosphorylation site identified on the N-terminal region of the peptides. Salivaricin 10 peptides were determined to be produced by S. salivarius strains found in healthy human subjects, and their dual bactericidal/antibiofilm and immunoregulatory activity may provide new means to effectively target infectious pathogens while maintaining important oral microbiota.

Intestinal biofilms: pathophysiological relevance, host defense, and therapeutic opportunities.

SUMMARYThe human intestinal tract harbors a profound variety of microorganisms that live in symbiosis with the host and each other. It is a complex and highly dynamic environment whose homeostasis directly relates to human health. Dysbiosis of the gut microbiota and polymicrobial biofilms have been associated with gastrointestinal diseases, including irritable bowel syndrome, inflammatory bowel diseases, and colorectal cancers. This review covers the molecular composition and organization of intestinal biofilms, mechanistic aspects of biofilm signaling networks for bacterial communication and behavior, and synergistic effects in polymicrobial biofilms. It further describes the clinical relevance and diseases associated with gut biofilms, the role of biofilms in antimicrobial resistance, and the intestinal host defense system and therapeutic strategies counteracting biofilms. Taken together, this review summarizes the latest knowledge and research on intestinal biofilms and their role in gut disorders and provides directions toward the development of biofilm-specific treatments.

pH-Responsive Charge Convertible Hyperbranched Poly(ionic liquid) Nanoassembly with High Biocompatibility for Resistance-Free Antimicrobial Applications.

As a potential alternative to antibiotics, hyperbranched poly(ionic liquid)s (HPILs) have demonstrated significant potential in combating bacterial biofilms. However, their high cation density poses a high risk of toxicity, greatly limiting their in vivo applications. In this study, we constructed a biocompatible HPIL (HPIL-Glu) from a hyperbranched polyurea core with modified terminals featuring charge-convertible ionic liquids. These ionic liquid moieties consist of an ammonium-based cation and a gluconate (Glu) organic counter. HPIL-Glu could form a homogeneous nanoassembly in water and exhibited a pH-responsive charge conversion property. Under neutral conditions, Glu shielded the positively charged surface, minimizing the toxicity. In a mildly acidic environment, Glu protonation exposes cationic moieties to biofilm eradication. Comprehensive antimicrobial assessments demonstrate that HPIL-Glu effectively kills bacteria and promotes the healing of bacteria-infected chronic wounds. Furthermore, prolonged exposure to HPIL-Glu does not induce antimicrobial resistance.

HOCl-producing electrochemical bandage for treating Pseudomonas aeruginosa-infected murine wounds.

The growing threat of antibiotic-resistant bacterial pathogens necessitates the development of alternative antimicrobial approaches. This is particularly true for chronic wound infections, which commonly harbor biofilm-dwelling bacteria. A novel electrochemical bandage (e-bandage) delivering low-levels of hypochlorous acid (HOCl) was evaluated against Pseudomonas aeruginosa murine wound biofilms. 5 mm skin wounds were created on the dorsum of mice and infected with 106 colony-forming units (CFU) of P. aeruginosa. Biofilms were formed over 2 days, after which e-bandages were placed on the wound beds and covered with Tegaderm. Mice were administered Tegaderm-only (control), non-polarized e-bandage (no HOCl production), or polarized e-bandage (using an HOCl-producing potentiostat), with or without systemic amikacin. Purulence and wound areas were measured before and after treatment. After 48 hours, wounds were harvested for bacterial quantification. Forty-eight hours of polarized e-bandage treatment resulted in mean biofilm reductions of 1.4 log10 CFUs/g (P = 0.0107) vs non-polarized controls and 2.2 log10 CFU/g (P = 0.004) vs Tegaderm-only controls. Amikacin improved CFU reduction in Tegaderm-only (P = 0.0045) and non-polarized control groups (P = 0.0312) but not in the polarized group (P = 0.3876). Compared to the Tegaderm-only group, there was less purulence in the polarized group (P = 0.009). Wound closure was neither impeded nor improved by either polarized or non-polarized e-bandage treatment. Concurrent amikacin did not impact wound closure or purulence. In conclusion, an HOCl-producing e-bandage reduced P. aeruginosa in wound biofilms with no impairment in wound healing, representing a promising antibiotic-free approach for addressing wound infection.

High efficacy treatment of murine Pseudomonas aeruginosa catheter-associated urinary tract infections using the c-di-GMP modulating anti-biofilm compound Disperazol in combination with ciprofloxacin.

Persistent urinary tract infections (UTIs) in hospitalized patients constitute an important medical problem. It is estimated that 75% of nosocomial UTIs are associated with urinary tract catheters with P. aeruginosa being a species that forms biofilms on these catheters. These infections are highly resistant to standard-of-care antibiotics, and the effects of the host immune defenses, which allows for development of persistent infections. With antibiotics losing their efficacy, new treatment options against resilient infections, such as catheter-associated urinary tract infections (CAUTIs), are critically needed. Central to our anti-biofilm approach is the manipulation of the c-di-GMP signaling pathway in P. aeruginosa to switch bacteria from the protective biofilm to the unprotected planktonic mode of life. We recently identified a compound (H6-335-P1), that stimulates the c-di-GMP degrading activity of the P. aeruginosa BifA protein which plummets the intracellular c-di-GMP content and induces dispersal of P. aeruginosa biofilm bacteria into the planktonic state. In the present study, we formulated H6-335-P1 as a hydrochloride salt (Disperazol), which is water-soluble and facilitates delivery via injection or oral administration. Disperazol can work as a monotherapy, but we observed a 100-fold improvement in efficacy when treating murine P. aeruginosa CAUTIs with a Disperazol/ciprofloxacin combination. Biologically active Disperazol reached the bladder 30 min after oral administration. Our study provides proof of concept that Disperazol can be used in combination with a relevant antibiotic for effective treatment of CAUTIs.

Induction of antimicrobial, antioxidant metabolites production by co-cultivation of two red-sea-sponge-associated Aspergillus sp. CO2 and Bacillus sp. COBZ21.

The growing spread of infectious diseases has become a potential global health threat to human beings. According to WHO reports, in this study, we investigated the impact of co-cultivating the isolated endophytic fungus Aspergillus sp. CO2 and Bacillus sp. COBZ21 as a method to stimulate the production of natural bioactive substances. (GC/MS)-based metabolomics profiling of two sponge-associated microbes, Aspergillus sp. CO2 and Bacillus sp. COBZ21, revealed that the co-culture of these two isolates induced the accumulation of metabolites that were not traced in their axenic cultures. By detection of different activities of extracts of Bacillus sp. COBZ21 and Aspergillus sp. CO2 and coculture between Bacillus sp. COBZ21 and Aspergillus sp. CO2. It was noted that the coculture strategy was the reason for a notable increase in some different activities, such as the antimicrobial activity, which showed potent activity against Escherichia coli ATCC 25,922, Staphylococcus aureus NRRLB-767, and Candida albicans ATCC 10,231. The antibiofilm activity showed significant biofilm inhibitory activity toward Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa ATCC 10,145, and Staph aureus NRRLB-767, with activity up to 53.66, 71.17, and 47.89%, while it showed low activity against E. coli ATCC 25,922, while the antioxidant activity based on the DPPH assay showed maximum activity (75.25%). GC-MS investigations revealed the presence of variable chemical constituents belonging to different chemical categories, which reflected their chemical diversity. The main components are (+-) cis-Deethylburnamine (2.66%), Bis(3,6,9,12-tetraoxapentaethylene) crowno-N,N,N',N'-tetra methylpphanediamine (2.48%), and 11-phenyl-2,4,6,8-tetra(2-thienyl)-11-aza-5,13-dithiaeteracyclo[7.3.0.1(2,8)0.0(3,7)] trideca-3,6-diene-10,12,13-trione (3.13%), respectively, for Bacillus sp. axenic culture, Aspergillus sp. CO2, Aspergillus sp. CO2, and Bacillus sp. COBZ21 coculture. By studying the ADME-related physicochemical properties of coculture extract, the compound showed log Po/w values above 5 (8.82). The solubility of the substance was moderate. In order to provide a comprehensive definition of medicinal chemistry and leadlikness, it is important to note that the latter did not meet the criteria outlined in the rule of three (RO3). The toxicity prediction of the coculture extract was performed using the ProTox II web server, which showed that the selected compound has no pronounced toxicity.

Hindering the biofilm of microbial pathogens and cancer cell lines development using silver nanoparticles synthesized by epidermal mucus proteins from Clarias gariepinus.

Scientists know very little about the mechanisms underlying fish skin mucus, despite the fact that it is a component of the immune system. Fish skin mucus is an important component of defence against invasive infections. Recently, Fish skin and its mucus are gaining interest among immunologists. Characterization was done on the obtained silver nanoparticles Ag combined with Clarias gariepinus catfish epidermal mucus proteins (EMP-Ag-NPs) through UV-vis, FTIR, XRD, TEM, and SEM. Ag-NPs ranged in size from 4 to 20 nm, spherical in form and the angles were 38.10°, 44.20°, 64.40°, and 77.20°, Where wavelength change after formation of EMP-Ag-NPs as indicate of dark brown, the broad band recorded at wavelength at 391 nm. Additionally, the antimicrobial, antibiofilm and anticancer activities of EMP-Ag-NPs was assessed. The present results demonstrate high activity against unicellular fungi C. albicans, followed by E. faecalis. Antibiofilm results showed strong activity against both S. aureus and P. aeruginosa pathogens in a dose-dependent manner, without affecting planktonic cell growth. Also, cytotoxicity effect was investigated against normal cells (Vero), breast cancer cells (Mcf7) and hepatic carcinoma (HepG2) cell lines at concentrations (200-6.25 µg/mL) and current results showed highly anticancer effect of Ag-NPs at concentrations 100, 5 and 25 µg/mL exhibited rounding, shrinkage, deformation and granulation of Mcf7 and HepG2 with IC50 19.34 and 31.16 µg/mL respectively while Vero cells appeared rounded at concentration 50 µg/mL and normal shape at concentration 25, 12.5 and 6.25 µg/ml with IC50 35.85 µg/mL. This study evidence the potential efficacy of biologically generated Ag-NPs as a substitute medicinal agent against harmful microorganisms. Furthermore, it highlights their inhibitory effect on cancer cell lines.

Antimicrobial and anti-biofilm properties of oleuropein against Escherichia coli and fluconazole-resistant isolates of Candida albicans and Candida glabrata.

BACKGROUND: Side effects associated with antimicrobial drugs, as well as their high cost, have prompted a search for low-cost herbal medicinal substances with fewer side effects. These substances can be used as supplements to medicine or to strengthen their effects. The current study investigated the effect of oleuropein on the inhibition of fungal and bacterial biofilm in-vitro and at the molecular level. MATERIALS AND METHODS: In this experimental study, antimicrobial properties were evaluated using microbroth dilution method. The effect of oleuropein on the formation and eradication of biofilm was assessed on 96-well flat bottom microtiter plates and their effects were observed through scanning electron microscopy (SEM). Its effect on key genes (Hwp1, Als3, Epa1, Epa6, LuxS, Pfs) involved in biofilm formation was investigated using the quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) method. RESULTS: The minimum inhibitory concentration (MIC) and minimum fungicidal/bactericidal concentration (MFC/MBC) for oleuropein were found to be 65 mg/ml and 130 mg/ml, respectively. Oleuropein significantly inhibited biofilm formation at MIC/2 (32.5 mg/ml), MIC/4 (16.25 mg/ml), MIC/8 (8.125 mg/ml) and MIC/16 (4.062 mg/ml) (p < 0.0001). The anti-biofilm effect of oleuropein was confirmed by SEM. RT-qPCR indicated significant down regulation of expression genes involved in biofilm formation in Candida albicans (Hwp1, Als3) and Candida glabrata (Epa1, Epa6) as well as Escherichia coli (LuxS, Pfs) genes after culture with a MIC/2 of oleuropein (p < 0.0001). CONCLUSIONS: The results indicate that oleuropein has antifungal and antibacterial properties that enable it to inhibit or destroy the formation of fungal and bacterial biofilm.

Thiolated chitosan nanoparticles encapsulated nisin and selenium: antimicrobial/antibiofilm/anti-attachment/immunomodulatory multi-functional agent.

BACKGROUND: The increase in the resistance of bacterial strains to antibiotics has led to research into the bactericidal potential of non-antibiotic compounds. This study aimed to evaluate in vitro antibacterial/ antibiofilm properties of nisin and selenium encapsulated in thiolated chitosan nanoparticles (N/Se@TCsNPs) against prevalent enteric pathogens including standard isolates of Vibrio (V.) cholerae O1 El Tor ATCC 14,035, Campylobacter (C.) jejuni ATCC 29,428, Salmonella (S.) enterica subsp. enterica ATCC 19,430, Shigella (S.) dysenteriae PTCC 1188, Escherichia (E.) coli O157:H7 ATCC 25,922, Listeria (L.) monocytogenes ATCC 19,115, and Staphylococcus (S.) aureus ATCC 29,733. METHODS: The synthesis and comprehensive analysis of N/Se@TCsNPs have been completed. Antibacterial and antibiofilm capabilities of N/Se@TCsNPs were evaluated through broth microdilution and crystal violet assays. Furthermore, the study included examining the cytotoxic effects on Caco-2 cells and exploring the immunomodulatory effects of N/Se@TCsNPs. This included assessing the levels of both pro-inflammatory (IL-6 and TNFα) and anti-inflammatory (IL-10 and TGFß) cytokines and determining the gene expression of TLR2 and TLR4. RESULTS: The N/Se@TCsNPs showed an average diameter of 136.26 ± 43.17 nm and a zeta potential of 0.27 ± 0.07 mV. FTIR spectroscopy validated the structural features of N/Se@TCsNPs. Scanning electron microscopy (SEM) images confirmed their spherical shape and uniform distribution. Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC) tests demonstrated the thermal stability of N/Se@TCsNPs, showing minimal weight loss of 0.03%±0.06 up to 80 °C. The prepared N/Se@TCsNPs showed a thiol content of 512.66 ± 7.33 µmol/g (p < 0.05), an encapsulation efficiency (EE) of 69.83%±0.04 (p ≤ 0.001), and a drug release rate of 74.32%±3.45 at pH = 7.2 (p ≤ 0.004). The synthesized nanostructure demonstrated potent antibacterial activity against various isolates, with effective concentrations ranging from 1.5 ± 0.08 to 25 ± 4.04 mg/mL. The ability of N/Se@TCsNPs to reduce bacterial adhesion and internalization in Caco-2 cells underscored their antibiofilm properties (p ≤ 0.0001). Immunological studies indicated that treatment with N/Se@TCsNPs led to decreased levels of inflammatory cytokines IL-6 (14.33 ± 2.33 pg/mL) and TNFα (25 ± 0.5 pg/mL) (p ≤ 0.0001), alongside increased levels of anti-inflammatory cytokines IL-10 (46.00 ± 0.57 pg/mL) and TGFß (42.58 ± 2.10 pg/mL) in infected Caco-2 cells (p ≤ 0.0001). Moreover, N/Se@TCsNPs significantly reduced the expression of TLR2 (0.22 ± 0.09) and TLR4 (0.16 ± 0.05) (p < 0.0001). CONCLUSION: In conclusion, N/Se@TCsNPs exhibited significant antibacterial/antibiofilm/anti-attachment/immunomodulatory effectiveness against selected Gram-positive and Gram-negative enteric pathogens. However, additional ex-vivo and in-vivo investigations are needed to fully assess the performance of nanostructured N/Se@TCsNPs.

Unveiling biological activities of biosynthesized starch/silver-selenium nanocomposite using Cladosporium cladosporioides CBS 174.62.

BACKGROUND AND OBJECTIVES: Microbial cells capability to tolerate the effect of various antimicrobial classes represent a major worldwide health concern. The flexible and multi-components nanocomposites have enhanced physicochemical characters with several improved properties. Thus, different biological activities of biosynthesized starch/silver-selenium nanocomposite (St/Ag-Se NC) were assessed. METHODOLOGY: The St/Ag-Se NC was biosynthesized using Cladosporium cladosporioides CBS 174.62 (C. cladosporioides) strain. The shape and average particle size were investigated using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HR-TEM), respectively. On the other hand, the St/Ag-Se NC effect on two cancer cell lines and red blood cells (RBCs) was evaluated and its hydrogen peroxide (H2O2) scavenging effect was assessed. Moreover, its effects on various microbial species in both planktonic and biofilm growth forms were examined. RESULTS: The St/Ag-Se NC was successfully biosynthesized with oval and spherical shape and a mean particle diameter of 67.87 nm as confirmed by the HR-TEM analysis. St/Ag-Se NC showed promising anticancer activity toward human colorectal carcinoma (HCT-116) and human breast cancer (MCF-7) cell lines where IC50 were 21.37 and 19.98 µg/ml, respectively. Similarly, little effect on RBCs was observed with low nanocomposite concentration. As well, the highest nanocomposite H2O2 scavenging activity (42.84%) was recorded at a concentration of 2 mg/ml. Additionally, Staphylococcus epidermidis (S. epidermidis) ATCC 12,228 and Candida albicans (C. albicans) ATCC 10,231 were the highly affected bacterial and fungal strains with minimum inhibitory concentrations (MICs) of 18.75 and 50 µg/ml, respectively. Moreover, the noticeable effect of St/Ag-Se NC on microbial biofilm was concentration dependent. A high biofilm suppression percentage, 87.5% and 68.05%, were recorded with S. epidermidis and Staphylococcus aureus (S. aureus) when exposed to 1 mg/ml and 0.5 mg/ml, respectively. CONCLUSION: The biosynthesized St/Ag-Se NC showed excellent antioxidant activity, haemocompatibility, and anti-proliferative effect at low concentrations. Also, it exhibited promising antimicrobial and antibiofilm activities.

Anti-biofilm mechanism of a synthetical low molecular weight poly-d-mannose on Salmonella Typhimurium.

In this study, a low molecular weight poly-d-mannose (LMWM) was separated from a mixed polysaccharide synthesized previously. Monosaccharide composition, Fourier-Transform infrared spectroscopy (FT-IR), periodate oxidation and smith degradation were determined. After safety evaluation, the inhibition of LMWM on the different biofilm formation stages of Salmonella enterica serovar Typhimurium (S. Typhimurium) was tested in vitro. Furthermore, the effect of LMWM on the adhesion of S. Typhimurium to Caco-2 cells and cell surface hydrophobicity (CSH) were observed. Results indicated that LMWM was a homopolysaccharide without cytotoxicity and hemolysis, containing both α-mannose and ß-mannose. It showed obvious anti-biofilm activity on S. Typhimurium and mainly activated on the initial adhesion and formation stage, even better than the commercial S. cerevisiae mannan (CM). LMWM inhibited the adhesion of S. Typhimurium on Caco-2 cells with the inhibition rate of 61.04 % at 2 mg/ml. Meanwhile, LMWM decreased the hydrophobicity of S. Typhimurium cell surface. In conclusion, the inhibitory effect on S. Typhimurium biofilm was not caused by bacteriostatic or bactericidal activity of LMWM. The specific anti-adhesion and the decrease of bacterial CSH by LMWM may closely relate to anti-biofilm mechanism. This study provides some supports for the application of LMWM as antibiotics alternative on S. Typhimurium in the future.

Antibiofilm and antivirulence activity of selenium nanoparticles synthesized from cell-free extract of moderately halophilic bacteria.

Biofilm-forming microbes can pose a major health risk that is difficult to combat. Nanotechnology, on the other hand, represents a novel technique for combating and eliminating biofilm-forming microbes. In this study, the selenium nanoparticles (SeNPs) were biosynthesized from moderate halophilic bacteria isolated from Pichavaram mangrove sediments. The bacterial strain S8 was found to be efficient for SeNPs synthesis and hence identified by 16s r RNA sequencing as Shewanella sp. In UV- spectral analysis the SeNPs displayed a peak at 320 nm due to surface plasmon resonance (SPR). The cell-free extract of Shewanella sp. and SeNPs indicates that the various functional groups in the cell-free extract were mainly involved in the synthesis and stabilization of SeNPs. The SeNPs had a spherical form with average diameter of 49 ± 0.01 nm, according to the FESEM analysis. The EDX shows the distinctive peaks of selenium at 1.37, 11.22.12.49 Kev. In the agar well diffusion method, the SeNPs show inhibitory activity against all the test pathogens with the highest activity noted against P.aeruginosa with a zone of inhibition of 22.7 ± 0.3 mm. The minimal inhibitory concentration (MIC) value of 80 µg/ml, minimal bactericidal concentration (MBC) of 160 µg/ml, and susceptibility constant of 0.043 µg/ml show that SeNPs highly effective against P.aeruginosa. The Sub-MIC value of SeNPs of 20 µg/ml was found to inhibit P.aeruginosa biofilm by 85% as compared to the control. Further, the anti-virulence properties viz., pyocyanin, pyoverdine, hemolytic, and protease inhibition revealed the synthesized SeNPs from halophilic bacteria control the pathogenicity of P.aeruginosa.

Biological activity of silver nanoparticles synthesized using viticultural waste.

This research paper presents a novel approach to the green synthesis of silver nanoparticles (AgNPs) using viticultural waste, allowing to obtain NP dispersions with distinct properties and morphologies (monodisperse and polydisperse AgNPs, referred to as mAgNPs and pAgNPs) and to compare their biological activities. Our synthesis method utilized the ethanolic extract of Vitis vinifera pruning residues, resulting in the production of mAgNPs and pAgNPs with average sizes of 12 ± 5 nm and 19 ± 14 nm, respectively. Both these AgNPs preparations demonstrated an exceptional stability in terms of size distribution, which was maintained for one year. Antimicrobial testing revealed that both types of AgNPs inhibited either the growth of planktonic cells or the metabolic activity of biofilm sessile cells in Gram-negative bacteria and yeasts. No comparable activity was found towards Gram-positives. Overall, pAgNPs exhibited a higher antimicrobial efficacy compared to their monodisperse counterparts, suggesting that their size and shape may provide a broader spectrum of interactions with target cells. Both AgNP preparations showed no cytotoxicity towards a human keratinocyte cell line. Furthermore, in vivo tests using a silkworm animal model indicated the biocompatibility of the phytosynthesized AgNPs, as they had no adverse effects on insect larvae viability. These findings emphasize the potential of targeted AgNPs synthesized from viticultural waste as environmentally friendly antimicrobial agents with minimal impact on higher organisms.

Attenuation of biofilm and virulence factors of Pseudomonas aeruginosa by tetramethylpyrazine-gold nanoparticles.

Pseudomonas aeruginosa is often identified as the causative agent in nosocomial infections. Their adapted resistance makes them strong towards antimicrobial treatments. They protect and empower their survival behind strong biofilm architecture that works as their armor toward antimicrobial therapy. Additionally, P. aeruginosa generates virulence factors, contributing to chronic infection and recalcitrant phenotypic characteristics. The current study utilizes the benevolence of nanotechnology to develop an alternate technique to control the spreading of P. aeruginosa by limiting its biofilm and virulence development. This study used a natural compound, tetramethylpyrazine, to generate gold nanoparticles. Tetramethylpyrazine-gold nanoparticles (Tet-AuNPs) were presented in spherical shapes, with an average size of 168 ± 52.49 nm and a zeta potential of -12.22 ± 2.06 mV. The minimum inhibition concentration (MIC) of Tet-AuNPs that proved more than 90 % effective in inhibiting P. aeruginosa was 256 µg/mL. Additionally, it also shows antibacterial activities against Staphylococcus aureus (MIC, 256 µg/mL), Streptococcus mutans (MIC, 128 µg/mL), Klebsiella pneumoniae (MIC, 128 µg/mL), Listeria monocytogenes (MIC, 256 µg/mL), and Escherichia coli (MIC, 256 µg/mL). The sub-MIC values of Tet-AuNPs significantly inhibited the early-stage biofilm formation of P. aeruginosa. Moreover, this concentration strongly affected hemolysis, protease activity, and different forms of motilities in P. aeruginosa. Additionally, Tet-AuNPs destroyed the well-established mature biofilm of P. aeruginosa. The expression of genes linked with the biofilm formation and virulence in P. aeruginosa treated with sub-MIC doses of Tet-AuNPs was shown to be significantly suppressed. Gene expression studies support biofilm- and virulence-suppressing effects of Tet-AuNPs at the phenotypic level.

Antimicrobial, antibiofilm, and antivirulence properties of Eisenia bicyclis-extracts and Eisenia bicyclis-gold nanoparticles towards microbial pathogens.

Nanomaterials derived from seaweed have developed as an alternative option for fighting infections caused by biofilm-forming microbial pathogens. This research aimed to discover potential seaweed-derived nanomaterials with antimicrobial and antibiofilm action against bacterial and fungal pathogens. Among seven algal species, the extract from Eisenia bicyclis inhibited biofilms of Klebsiella pneumoniae, Staphylococcus aureus, and Listeria monocytogenes most effectively at sub-MIC levels. As a result, in the present study, E. bicyclis was chosen as a prospective seaweed for producing E. bicyclis-gold nanoparticles (EB-AuNPs). Furthermore, the mass spectra of E. bicyclis reveal the presence of a number of potentially beneficial chemicals. The polyhedral shape of the synthesized EB-AuNP with a size value of 154.74 ± 33.46 nm was extensively described. The lowest inhibitory concentration of EB-AuNPs against bacterial pathogens (e.g., L.monocytogenes, S. aureus, Pseudomonas aeruginosa, and K. pneumoniae) and fungal pathogens (Candida albicans) ranges from 512 to >2048 µg/mL. Sub-MIC of EB-AuNPs reduces biofilm formation in P. aeruginosa, K. pneumoniae, L. monocytogenes, and S. aureus by 57.22 %, 58.60 %, 33.80 %, and 91.13 %, respectively. EB-AuNPs eliminate the mature biofilm of K. pneumoniae at > MIC, MIC, and sub-MIC concentrations. Furthermore, EB-AuNPs at the sub-MIC level suppress key virulence factors generated by P. aeruginosa, including motility, protease activity, pyoverdine, and pyocyanin, whereas it also suppresses the production of staphyloxanthin virulence factor from S. aureus. The current research reveals that seaweed extracts and a biocompatible seaweed-AuNP have substantial antibacterial, antibiofilm, and antivirulence actions against bacterial and fungal pathogens.

Anti-biofilm effect of enzymatic hydrolysates of ovomucin in Listeria monocytogenes and Staphylococcus aureus.

Despite modern advances in food hygiene, food poisoning due to microbial contamination remains a global problem, and poses a great threat to human health. Especially, Listeria monocytogenes and Staphylococcus aureus are gram-positive bacteria found on food-contact surfaces with biofilms. These foodborne pathogens cause a considerable number of food poisoning and infections annually. Ovomucin (OM) is a water-insoluble gel-type glycoprotein in egg whites. Enzymatic hydrolysis can be used to improve the bioactive properties of OM. This study aimed to investigate whether ovomucin hydrolysates (OMHs) produced using five commercial enzymes (Alcalase®, Bromelain, α-Chymotrypsin, Papain, and Pancreatin) can inhibit the biofilm formation of L. monocytogenes ATCC 15313, L. monocytogenes H7962, S. aureus KCCM 11593, and S. aureus 7. Particularly, OMH prepared with papain (OMPP; 500 µg/mL) significantly inhibited biofilm formation in L. monocytogenes ATCC 15313, L. monocytogenes H7962, S. aureus KCCM 11593, and S. aureus 7 by 85.56 %, 80.28 %, 91.70 %, and 79.00 %, respectively. In addition, OMPP reduced the metabolic activity, exopolysaccharide production (EPS), adhesion ability, and gene expression associated with the biofilm formation of these bacterial strains. These results suggest that OMH, especially OMPP, exerts anti-biofilm effects against L. monocytogenes and S. aureus. Therefore, OMPP can be used as a natural anti-biofilm agent to control food poisoning in the food industry.

Isolation and characterization of bacteriophages against E.coli urinary tract infection and evaluating their anti-biofilm activity and antibiotic synergy.

Urinary tract infections (UTIs) by Uropathogenic Escherichia coli (UPEC) are a significant health concern, especially due to the increasing prevalence of antibiotic resistance. This study focuses on isolating and characterizing bacteriophages specific to UPEC strains isolated from UTI samples. The isolated phages were assessed for their ability to target and lyse UPEC in vitro, focusing on their efficacy in disrupting biofilms, a key virulence factor contributing to UTI recurrence and antibiotic resistance. The morphological structure observed by TEM belongs to Myoviridae, the phage exhibited icosahedral symmetry with a long non-constricting tail, the approximate measurement of the phage head was 39 nm in diameter, and the phage tail was 105.317 nm in length. One-step growth experiments showed that the latent period was approximately 20 min, followed by a rise period of 40 min, and a growth plateau was reached within 20 min and the burst size observed was 26 phages/infected bacterial cells. These phages were capable of killing cells within the biofilms, leading to a reduction in living cell counts after a single treatment. This study highlights the potential of phages to play a significant role in disrupting, inactivating, and destroying Uropathogenic Escherichia coli (UPEC) biofilms. Such findings could be instrumental in developing treatment strategies that complement antibiotics and disinfectants. The phage-antibiotic synergistic activity was compared to have the possibility to facilitate the advancement of focused and enduring alternatives to traditional antibiotic therapies for UTIs.

Treatment of dental biofilm-forming bacterium Streptococcus mutans using tannic acid-mediated gold nanoparticles.

Biosynthesized gold nanoparticles (AuNPs) are highly attracted as a biocompatible nanodrug to treat various diseased conditions in humans. In this study, phytochemical tannic acid-mediated AuNPs (TA-AuNPs) are successfully synthesized and tested for antibacterial and antibiofilm activity against dental biofilm-forming Streptococcus mutans biofilm. The synthesized TA-AuNPs are appeared as spherical in shape with an average size of 19 nm. The antibacterial potential of TA-AuNPs was evaluated using ZOI and MIC measurements; while, antibiofilm efficacy was measured by checking the eradication of preformed biofilm on the tooth model. The ZOI and MIC values for TA-AuNPs are 25 mm in diameter and 4 µg/mL, respectively. The MTT assay, CLSM, and SEM results demonstrate that the preformed S. mutans biofilm is completely eradicated at 4xMIC (16 µg/mL) of TA-AuNPs. Finally, the present study reveals that the synthesized TA-AuNPs might be a great therapeutic drug to treat dental biofilm-forming bacterium S. mutans.

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.

Comparative evaluation of anti-biofilm and anti- adherence potential of plant extracts against Streptococcus mutans: A therapeutic approach for oral health.

Dental caries predominantly attributed to the cariogenic nature of Streptococcus mutans, continue to pose a substantial global challenge to oral health. In response to this challenge, this study aimed to evaluate the effectiveness of leaf extracts (LEs) and essential oils (EOs) derived from different medicinal plants in inhibiting the growth of Streptococcus mutans biofilm. In vitro and in silico approaches were employed to identify active compounds and assess their inhibitory effects on S. mutans. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were measured to determine the anti-biofilm and anti-adherence activity against S. mutans. Biofilm viability (CFU/mL) and extracellular polymeric substance (EPS) concentration were quantified. GC-MS analysis was utilized to identify active compounds in the most effective plant extracts exhibiting anti-S. mutans activity. A high-throughput screening focused on the interaction between these compounds and the target enzyme SortaseA (SrtA) using molecular docking was performed. Results indicated that Cymbopogon citratus displayed the highest efficacy in reducing S. mutans biofilm formation and adhesion activity, achieving 90 % inhibition at an MIC value of 12 µg/mL. Among the 12 bioactive compounds identified, trans-Carvyl acetate exhibited the lowest binding energy with SrtA (-6.0 Kcal/mole). Trans-Carvyl acetate also displayed favorable pharmacokinetic properties. This study provides novel insights into the anti-S. mutans properties of C. citratus and suggests its potential as a therapeutic approach for oral health. Further research is needed to explore the combined effect of plant extracts for enhanced protection against dental caries.