Braided silk sutures coated with photoreduced silver nanoparticles for eradicating Staphylococcus aureus and Streptococcus mutans infections.

BACKGROUND: Infections resulting from surgical procedures and wound closures continue to pose significant challenges in healthcare settings. To address this issue, the investigators have developed antibacterial non-resorbable braided silk sutures using in situ deposited silver nanoparticles (AgNPs) and investigated their efficacy in eradicating Staphylococcus aureus and Streptococcus mutans infections. METHODS: The braided silk sutures were modified through a simple and efficient in situ photoreduction method, resulting in the uniform distribution of AgNPs along the suture surface. The synthesized AgNPs were characterized using scanning electron microscopy (SEM), dynamic light scattering analysis (DLS) and Fourier Transform Infrared Spectroscopy analysis (FTIR) confirming their successful integration onto the silk sutures. The antibacterial activity of the nanoparticle coated sutures were compared and evaluated with non-coated braided silk sutures through in vitro assays against both S. aureus and S. mutans. RESULTS: The surface and cross-sectional analysis of the treated sutures revealed a uniform and homogeneous distribution of silver particles achieved through the photoreduction of silver solution. This observation confirms the successful coating of silver nanoparticles (AgNPs) on the sutures. The antimicrobial studies conducted, demonstrated significant reductions in bacterial colonies when exposed to the silver nanoparticle-coated sutures. Notably, the width of the inhibition zone surrounding the coated sutures remained consistently wide and stable for duration up to 7 days. This sustained and robust inhibitory effect against gram-positive bacteria, specifically S. aureus and S. mutans, serves as strong evidence of the antibacterial efficacy of the coated sutures. CONCLUSION: The coating of silk sutures with AgNPs provided a significant and effective antibacterial capacity to the surgical sutures, with this activity being sustained for a period of 7 days. This suggests that AgNPs-in situ photoreduction deposited sutures have the potential to effectively manage S. aureus and S. mutans infections.

Targeting the Pseudomonas aeruginosa quorum sensing system to inhibit virulence factors and eradicate biofilm formation using AHL-analogue phytochemicals.

Quorum sensing plays a major role in the expression of virulence and development of biofilm in the human pathogen Pseudomonas aeruginosa. Natural compounds are well-known for their antibacterial characteristics by blocking various metabolic pathways. The goal of this study is to find natural compounds that mimic AHL (Acyl homoserine lactone) and suppress virulence in P. aeruginosa, which is triggered by quorum sensing-dependent pathways as an alternative drug development strategy. To support this rationale, functional network analysis and in silico investigations were carried out to find natural AHL analogues, followed by molecular docking studies. Out of the 16 top-hit AHL analogues derived from phytochemicals, seven ligands were found to bind to the quorum sensing activator proteins. Cassialactone, an AHL analogue, exhibited the highest binding affinity for RhlI, RhlR, and PqsE of P. aeruginosa, with a docking score of -9.4, -8.9, and -8.7 kcal/mol, respectively. 2(5H)-Furanone, a well-known inhibitor, was also docked to compare the docking score and intermolecular interactions between the ligand and the target protein. Furthermore, molecular dynamics simulations and binding free energy calculations were performed to determine the stability of the docked complexes. Additionally, the ADME properties of the analogues were also analyzed to evaluate the pharmacological parameters. Functional network analysis further showed that the interconnectedness of proteins such as RhlI, RhlR, LasI, and PqsE with the virulence and biofilm phenotype of the pathogen could offer potential as a therapeutic target.Communicated by Ramaswamy H. Sarma.

Synergistic effects of COVID-19 and Pseudomonas aeruginosa in chronic obstructive pulmonary disease: a polymicrobial perspective.

This article discusses the connection between the novel coronavirus disease 2019 (COVID-19) caused by the coronavirus-2 (SARS-CoV-2) and chronic obstructive pulmonary disease (COPD). COPD is a multifaceted respiratory illness that is typically observed in individuals with chronic exposure to chemical irritants or severe lung damage caused by various pathogens, including SARS-CoV-2 and Pseudomonas aeruginosa. The pathogenesis of COPD is complex, involving a variety of genotypes and phenotypic characteristics that result in severe co-infections and a poor prognosis if not properly managed. We focus on the role of SARS-CoV-2 infection in severe COPD exacerbations in connection to P.  aeruginosa infection, covering pathogenesis, diagnosis, and therapy. This review also includes a thorough structural overview of COPD and recent developments in understanding its complicated and chronic nature. While COVID-19 is clearly linked to emphysema and chronic bronchitis at different stages of the disease, our understanding of the precise interaction between microbial infections during COPD, particularly with SARS-CoV-2 in the lungs, remains inadequate. Therefore, it is crucial to understand the host-pathogen relationship from the clinician's perspective in order to effectively manage COPD. This article aims to provide a comprehensive overview of the subject matter to assist clinicians in their efforts to improve the treatment and management of COPD, especially in light of the COVID-19 pandemic.

3-(Bromoacetyl) coumarin is a potential therapeutic agent against neonatal sepsis-associated Pseudomonas extremorientalis.

Neonatal sepsis is a severe bacterial infection that can lead to life-threatening complications in newborns. Pseudomonas extremorientalis is a Gram-negative bacterium and these Gram-negative organisms have been identified as a major cause of neonatal sepsis. The virulence factors produced by this bacterium play a crucial role in its pathogenicity. Therefore, targeting these virulence factors could be a potential strategy to treat neonatal sepsis caused by P. extremorientalis. In this study, we investigated the efficacy of 3-(bromoacetyl) coumarin (3-BC) in reducing the virulence factors of P. extremorientalis strains isolated from neonatal sepsis. Our results showed that 3-BC effectively reduced the production of various virulence factors, including protease, elastase, siderophore, and exopolysaccharide in these strains. Furthermore, at a concentration of 125 µg/ml, 3-BC also inhibited the biofilm formation ability of these strains in combination with ciprofloxacin. It was discovered that 3-BC was functionally effective in protecting C. elegans against bacterial infection. Moreover, the in vitro and in vivo outcomes were strongly correlated with docking studies of various activator proteins. Overall, our findings suggest that 3-BC could be a potential therapeutic agent for the treatment of neonatal sepsis caused by P. extremorientalis. Further studies are needed to explore the mechanism of action of 3-BC and its potential use in clinical settings.

Exploring the complex role of gut microbiome in the development of precision medicine strategies for targeting microbial imbalance-induced colon cancer.

The gut microbiome has been increasingly recognized as a key player in the development and progression of colon cancer. Alterations in the gut microbiota, known as dysbiosis, can lead to a variety of medical issues. Microbial adaptation through signals and small molecules can enhance pathogen colonization and modulate host immunity, significantly impacting disease progression. Quorum sensing peptides and molecules have been linked to the progression of colon cancer. Various interventions, such as fecal microbiota transplantation, probiotics, prebiotics, synbiotics, and antibiotics, have been used to reverse dysbiosis with mixed results and potential side effects. Thus, a personalized approach to treatment selection based on patient characteristics, such as individual gut microbiota manipulation, is necessary to prevent and treat diseases like colon cancer. With advances in metagenomic sequencing and other omics technologies, there has been a growing interest in developing precision medicine strategies for microbial imbalance-induced colon cancer. This review serves as a comprehensive synthesis of current knowledge on the gut microbiome involvement in colon cancer. By exploring the potential of utilizing the gut microbiome as a target for precision medicine, this review underscores the exciting opportunities that lie ahead. Although challenges exist, the integration of microbiome data into precision medicine approaches has the potential to revolutionize the management of colon cancer, providing patients with more personalized and effective treatment options.

Functional network analysis identifies multiple virulence and antibiotic resistance targets in Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia, an emerging multidrug-resistant opportunistic bacterium in humans is of major concern for immunocompromised individuals for causing pneumonia and bloodborne infections. This bacterial pathogen is associated with a considerable fatality/case ratio, with up to 100%, when presented as hemorrhagic fever. It is resistant to commonly used drugs as well as to antibiotic combinations. In-silico based functional network analysis is a key approach to get novel insights into virulence and resistance in pathogenic organisms. This study included the protein-protein interaction (PPI) network analysis of 150 specific genes identified for antibiotic resistance mechanism and virulence pathways. Eight proteins, namely, PilL, FliA, Smlt2260, Smlt2267, CheW, Smlt2318, CheZ, and FliM were identified as hub proteins. Further docking studies of 58 selected phytochemicals were performed against the identified hub proteins. Deoxytubulosine and corosolic acid were found to be potent inhibitors of hub proteins of pathogenic S. maltophilia based on protein-ligand interactive study. Further pharmacophore studies are warranted with these molecules to develop them as novel antibiotics against S. maltophilia.

7-Ethoxycoumarin rescued Caenorhabditis elegans from infection of COPD derived clinical isolate Pseudomonas aeruginosa through virulence and biofilm inhibition via targeting Rhl and Pqs quorum sensing systems.

Pseudomonas aeruginosa is an ambidextrous Gram-negative contagium with density convoluted network defined quorum sensing, which enables the persistent survival within the host environment, contributing to various lung related diseases including Chronic Obstructive Pulmonary Disease (COPD). It is clear that P. aeruginosa is a powerful, exquisite pathogen that has adopted a variety of virulence properties through quorum sensing (QS) regulated phenomenon and that it dominates both in the development and exacerbations of COPD. Interestingly, 7-Ethoxycoumarin (7-EC), a compound that adequately mimics QS signaling molecule of P. aeruginosa, was introduced as part of the process of developing novel ways to treat the severe exacerbations. The results showed that, introduction of 7-EC significantly decreased exopolysaccharide-mediated biofilm development of strains isolated from COPD sputum, as evidenced by SEM analysis. Furthermore, 7-EC was able to modulate a variety of virulence factors and motility without subjecting planktonic cells to any selection pressure. Bacterial invasion assay revealed the potential activity of the 7-EC in preventing the active entry to A549 cells without causing any damage to the cells and found functionally active in protecting the C. elegans from P. aeruginosa infection and being non-toxic to the worms. Docking analysis was further proved that 7-EC to be the potential anti-QS compound competing specifically with Rhl and Pqs Systems. Therefore, 7-EC in the utilisation against the P. aeruginosa based infections, may open an avenue for the futuristic mechanistic study in chronic respiratory diseases and a initiator for the development of non-antibiotic based antibacterial therapy.

Unveiling the role of hub proteins in controlling quorum sensing regulated virulence through analogues in Pseudomonas aeruginosa PAO1: A functional protein-protein network biology approach.

The protein-protein interaction (PPI) network analysis of specific genes identified for biofilm production and virulence/secretion system mediated by quorum sensing. The PPI depicted 13 hub proteins (namely rhlR, lasR, pscU, vfr, exsA, lasI, gacA, toxA, pilJ, pscC, fleQ, algR, and chpA) out of 160 nodes involving 627 edges. The PPI network analysis based on topographical features depicted pcrD with the highest degree value and vfr gene with the greatest betweenness centrality and closeness centrality (BC and CC) values. Based on in silico results, curcumin used as an Acyl homo-serine lactone (AHL) mimicker in P. aeruginosa, was also found effective in suppressing the quorum sensing regulated virulence factors such as elastase and pyocyanin. Based on in vitro experiment, curcumin suppressed biofilm formation at 62 µg/ml concentration. Host-pathogen interaction experiment showed that curcumin was also proved to be efficient in saving C. elegans from paralysis and killing effects of P. aeruginosa PAO1.

Prevalence and heterogeneity of antibiotic resistance genes in Orientia tsutsugamushi and other rickettsial genomes.

Despite a million infections every year and an estimated one billion people at risk, scrub typhus is regarded as a neglected tropical disease. The causative bacterium Orientia tsutsugamushi, a member of rickettsiae, seems to be intrinsically resistant to several classes of antibiotics. The emergence of antibiotic-resistant scrub typhus is likely to become a global public health concern. Yet, it is unknown as to how common antibiotic resistance genes are in O. tsutsugamushi, and how variable these loci are among the genomes of rickettsiae. By using the comprehensive antibiotic resistance database, we explored 79 complete genomes from 24 species of rickettsiae for antibiotic resistance loci. There were 244 unique antibiotic resistance genes in rickettsiae. Both the total and unique antibiotic resistance genes in O. tsutsugamushi were significantly less compared to other members of rickettsiae. However, antibiotic resistance genes in O. tsutsugamushi genomes were more unique and highly variable. Many genes such as resistant variants of evgS, and vanS A/G were present in numerous copies. These results will have important implications in the context of antibiotic-resistant scrub typhus.

Genomic potential for exopolysaccharide production and differential polysaccharide degradation in closely related Alteromonas sp. PRIM-21 and Alteromonas fortis 1T.

Members of the genus Alteromonas are widely distributed in diverse marine environments and are often associated with marine organisms. Their ability to produce exopolysaccharides (EPS) and depolymerize sulfated algal polysaccharides has provided industrial importance to some species. Here, we describe the draft genome of an algae-associated strain namely, Alteromonas sp. PRIM-21 isolated from the southwest coast of India to understand the EPS biosynthetic pathways as well as polysaccharide depolymerization system in comparison to the closely related strain Alteromonas fortis 1T that shares 99.8% 16S rRNA gene sequence similarity. Whole-genome shotgun sequencing of Alteromonas sp. PRIM-21 yielded 50 contigs with a total length of 4,638,422 bp having 43.86% GC content. The resultant genome shared 95.9% OrthoANI value with A. fortis 1 T, and contained 4125 predicted protein-coding genes, 71 tRNA and 10 rRNA genes. Genes involved in Wzx/Wzy-, ABC transporter- and synthase-dependent pathways for EPS production and secretion were common in both Alteromonas sp. PRIM-21 and A. fortis 1T. However, the distribution of carbohydrate-active enzymes (CAZymes) was heterogeneous. The strain PRIM-21 harbored polysaccharide lyases for the degradation of alginate, ulvan, arabinogalactan and chondroitin. This was further validated from the culture-based assays using seven different polysaccharides. The depolymerizing ability of the bacteria may be useful in deriving nutrients from the biopolymers produced in the algal host while the EPS biosynthesis may provide additional advantages for life in the stressful marine environment. The results also highlight the genetic heterogeneity in terms of polysaccharide utilization among the closely related Alteromonas strains.

6-Methylcoumarin rescues bacterial quorum sensing induced ribosome-inactivating stress in Caenorhabditis elegans.

INTRODUCTION: Bacterial pathogenicity has for long posed severe effects on patient care. Pseudomonas aeruginosa is a common cause of hospital-acquired infections and nosocomial illnesses. It is known to infect the host by colonizing through quorum sensing and the production of exotoxins. METHODS: The current effort is an analysis of proteomic alterations caused by P. aeruginosa PAO1 to study the effects of quorum sensing inhibitor 6-Methylcoumarin on PAO1 infectivity in the Caenorhabditis elegans model. RESULTS: Through tandem mass tag-based quantitative proteomics approaches, 229 proteins were found to be differentially regulated in infection and upon inhibition. Among these, 34 proteins were found to be dysregulated in both infection and quorum-sensing inhibition conditions. Along with the dysregulation of proteins involved in host-pathogen interaction, PAO1 was found to induce ribosome-inactivating stress accompanied by the downregulating mitochondrial proteins. This in turn caused dysregulation of apoptosis. The expression of multiple proteins involved in ribosome biogenesis and structure, oxidative phosphorylation, and mitochondrial enzymes were altered due to infection. This mechanism, adapted by PAO1 to survive in the host, was inhibited by 6-Methylcoumarin by rescuing the downregulation of ribosomal and mitochondrial proteins. CONCLUSIONS: Taken together, the data reflect the molecular alterations due to quorum sensing and the usefulness of inhibitors in controlling pathogenesis.

Vanillin derivative inhibits quorum sensing and biofilm formation in Pseudomonas aeruginosa: a study in a Caenorhabditis elegans infection model.

Vanillin and its derivative, (4-((E)-(4-hydroxy-2-methylphenylimino) methyl)-2-methoxyphenol (MMP) were showed clear inhibition of violacein and pyocyanin at sub-MICs indicating a possible quorum quenching effect of both the compounds. MMP was able to inhibit the biofilm formation in Pseudomonas aeruginosa PAO1 at 125 µg/mL (p < 0.05), while vanillin at 250 µg/mL (p < 0.05) indicating that they act against quorum sensing regulated biofilm formation. The inhibition of biofilm was confirmed by visualization through fluorescence microscopy followed by docking analysis of molecules against quorum sensing activator proteins. Caenorhabditis elegans survival assay revealed that vanillin and MMP were able to increase survival of C. elegans from P. aeruginosa PAO1 infection. The study showed that the potent features of the MMP and vanillin in inhibiting the quorum sensing regulated virulence and biofilm, which was proved in C. elegans infection model as well as molecular docking studies.

Isoeugenol suppresses multiple quorum sensing regulated phenotypes and biofilm formation of Pseudomonas aeruginosa PAO1.

The potential strategy to prevent bacterial pathogenicity is disabling quorum sensing circuits with structural mimicking molecules. Here, we analyzed a synthetic molecule isoeugenol, for inhibition of quorum sensing regulated phenotype and biofilm formation. Isoeugenol was an effective inhibitor, i.e., more than 70% of virulence factors were inhibited including pyocyanin, rhamnolipid, exopolysaccharide, swarming motility and biofilm formation. Interestingly, these quorum sensing regulated phenotypes in Pseudomonas aeruginosa PAO1 were inhibited without affecting the planktonic cells. Moreover, the presence of isoeugenol exhibited more than 70% inhibition of biofilm formation through inhibition of the quorum sensing systems. Furthermore, docking studies suggest that isoeugenol bound to the quorum sensor regulators such as LasI, LasR PqsE and SidA with considerable binding interactions. Our results demonstrate the utility of isoeugenol as a blocker of quorum sensing, which will be functioning as an antivirulence compound.

6-Methylcoumarin attenuates quorum sensing and biofilm formation in Pseudomonas aeruginosa PAO1 and its applications on solid surface coatings with polyurethane.

Quorum sensing mediated biofilm formation has a major role in modern therapeutics due to adherence of cells on the solid surface. Here, we have developed a stable polyurethane blend with a 6-methylcoumarin (6-MC) composite that showed significant antibiofilm activity. The 6-MC was found to prominently inhibit P. aeruginosa PAO1 biofilm formation at 125 µg/ml and was able to inhibit various virulence factors such as pyocyanin, siderophore, exopolysaccharide, elastase and proteases, including motility of the bacteria. In addition, 6-MC was found functionally active in saving the C. elegans from P. aeruginosa PAO1 infection. Moreover, docking studies of different activator proteins correlate well with in vitro and in vivo results. To enhance this biological activity, 6-MC was blended with polyurethane, which also revealed superior antibiofilm activity on plastic and glass surfaces compared to a polyurethane coating. Therefore, the 6-MC could be used to combat P. aeruginosa infection for effective treatment and antibiofilm applications on solid surfaces through polyurethane blending and subsequent film fabrication strategies. KEY POINTS: • 6-Methylcoumarin significantly inhibits P. aeruginosa PAO1 biofilm • 6-MC was found functionally active in saving the C. elegans from PAO1 infection • 6-MC and polyurethane blend showed superior antibiofilm activity.

Bacterial cross talk with gut microbiome and its implications: a short review.

Human gut microbiota exists in a complicated symbiotic relationship which postulates to impact health and disease conditions on the host. Interestingly, the gut microbiome shows different mechanisms to regulate host physiology and metabolism including cell-to-cell communications. But microbiota imbalance is characterized to change in the host normal functioning and lead to the development and progression of major human diseases. Therefore, the direct cross talk through the microbial metabolites or peptides suggests the evidence of host health and disease. Recent reports highlight the adaptation signals/small molecules promoting microbial colonization which allows modulating immunity of host and leads to pathogen colonization. Moreover, quorum sensing peptides are also evident in the involvement of host disease conditions. Here, we review the current understanding of the gut microbiota cross talk with mammalian cells through metabolites and peptides. These studies are providing insight into the prediction of signature molecules which significantly provide information for the understanding of the interaction for precision medicine applications.

Microspheres containing biosynthesized silver nanoparticles with alginate-nano hydroxyapatite for biomedical applications.

Scaffolding system plays an important role in the development of artificial bone for treatment of defective or diseased bone tissue. In the present work, we have developed microspheres (COS-Ag-Alg-HA) containing chitooligosaccharide (COS) coated silver nanoparticles (Ag NPs) with alginate (Alg) and hydroxyapatite (HA) as bone graft substitutes. The developed microspheres were characterized through various analytical techniques such as UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scanning electron microscopy with EDX and evaluated the mechanical strength by using universal testing machine. In addition to this, antimicrobial activity and biocompatibility of the developed microspheres were evaluated with pathogenic microbes and osteoblast-like cells, respectively. Results suggest that microspheres are rigid, and strong chemical interactions were observed between the materials. The size of the microspheres was ranging from 1.5 ± 0.5 to 4.0 ± 0.5 mm. Significant microbial inhibition was observed against Staphylococcus aureus, and the developed microspheres are biocompatible with osteoblast-like cells. Based on the aforementioned finding results, the developed microsphere is proposed to be a potential candidate for bone tissue repair and regeneration.

Antioxidant Activity and Role of Culture Condition in the Optimization of Red Pigment Production by Talaromyces purpureogenus KKP Through Response Surface Methodology.

The red pigment production by Talaromyces purpureogenus KKP, a soil isolate, was optimized by response surface methodology (RSM) in the present study. The cultural parameters, such as pH, temperature, dextrose, and peptone concentrations, were optimized for red pigment production using the central composite design (CCD) experimental design. A second-order quadratic model was used to calculate the relationships between the values at different levels of response. The optimum values of the selected variables under coded factors are 6.0, 27 °C, 2.25%, and 1.10% for pH, temperature, dextrose, and peptone, respectively. The selected variables were most effective in the enhancement of red pigment production at optimized culture conditions. In addition to optimization, the antioxidant activity of the pigment isolated in the present study was found to be promising with IC50 value (40 µg/ml). The HRMS data revealed the identification of delphinidin, limonene, 6-hydroxymethyl-7,8-dihydropterin, D-mannose 6-phosphate, and CDP-DG (18:0/18:0). The results of the present investigation will be added to the existing literature of red pigment production and its optimization by T. purpureogenus.

The whole-genome sequence analysis of Enterobacter cloacae strain Ghats1: insights into endophytic lifestyle-associated genomic adaptations.

Enterobacter cloacae is normally considered to be an opportunistic human pathogen. Here, we report on the whole-genome sequence of an endophytic E. cloacae, strain "Ghats1", isolated from leaves of the medicinal plant Coscinium fenestratum Gaertn. Functional analysis of the Ghats1 genome revealed an enrichment for genes involved in the uptake and exchange of nutrients, for chemotaxis and for plant colonization. Unexpectedly though, there were no ORFs belonging to the "virulence factors and antibiotic resistance". Moreover, the presence of hydrolytic enzymes and motility functions reveals the characteristics of an endophyte lifestyle of a bacterium that can colonize and adapt to plant environment. These results provide a better understanding of an endophytic lifestyle through plant-microbe interaction, which can be further exploited as a biocontrol agent.