Investigation of bioactive components responsible for the antibacterial and anti-biofilm activities of Caroxylon volkensii by LC-QTOF-MS/MS analysis and molecular docking

Caroxylon volkensii is a wild desert plant of the family Amaranthaceae. This study represents the first report of the metabolomic profiling of C. volkensii by liquid chromatography quadrupole-time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS). The dereplication study of its secondary metabolites led to the characterization of 66 known compounds. These compounds include catecholamines, tyramine derivatives, phenolic acids, triterpenoids, flavonoids, and others. A new tyramine derivative, alongside other known compounds, was reported for the first time in the Amaranthaceae family. The new derivative and the first-reported compounds were putatively identified through MS/MS fragmentation data. Given the notorious taxonomical challenges within the genus Salsola, to which C. volkensii previously belonged, our study could offer a valuable insight into its chemical fingerprint and phylogenetic relationship to different Salsola species. The antibacterial potential of C. volkensii methanolic extract (CVM) against Pseudomonas aeruginosa was screened. The minimum inhibitory concentration (MIC) of CVM ranged from 32 to 256 μg mL-1. The anti-quorum sensing potential of CVM resulted in a decrease in the percentage of strong and moderate biofilm-forming isolates from 47.83% to 17.39%. It revealed a concentration-dependent inhibitory activity on violacein formation by Chromobacterium violaceum. Moreover, CVM exhibited an in vivo protective potential against the killing capacity of P. aeruginosa isolates. A molecular docking study revealed that the quorum-sensing inhibitory effect of CVM can be attributed to the binding of tyramine conjugates, ethyl-p-digallate, and isorhamnetin to the transcriptional global activator LasR.

Biofilm Formation, Pyocyanin Production, and Antibiotic Resistance Profile of Pseudomonas aeruginosa Isolates from Wounds

Pseudomonas aeruginosa is one of the most frequently resistant and dangerous bacteria isolated from infected wounds of patients. This study aimed to determine the prevalence of P. aeruginosa from infected wounds of patients in the Dschang District Hospital to evaluate their antibiotic susceptibility profiles and their ability to swarm and swim and correlate pyocyanin production with biofilm formation. Wound swab samples were collected and the identification of P. aeruginosa was performed using microbiological and biochemical tests. Their antimicrobial susceptibility was determined by the broth microdilution method. Swarming and swimming were determined by measuring the diameters of motility in semisolid/low-viscosity media. Furthermore, pyocyanin production and biofilm formation were evaluated spectrophotometrically using a microtiter plate. The prevalence of P. aeruginosa from infected wounds in our study population was 26%. All P. aeruginosa isolates were resistant to streptomycin and paromomycin, and the frequency of multidrug resistance (MDR) was 65.8%. All P. aeruginosa isolates showed the ability to produce biofilm and pyocyanin. Out of the 37 isolates screened, 19 including the reference strains (51.4%) were strong biofilm producers. A significant positive correlation was observed among biofilm formation, pyocyanin production, and the antibiotic resistance profile of the isolates. Findings from this study suggest that infected wounds could act as a reservoir for MDR and virulent P. aeruginosa. The presence of strong biofilm producers of P. aeruginosa in infected wounds is a serious public health concern. Therefore, surveillance programs to monitor and control MDR P. aeruginosa in these patients are required to prevent their dissemination in hospital settings.

Antimicrobial Activity of Trigonelline Hydrochloride Against Pseudomonas aeruginosa and Its Quorum-Sensing Regulated Molecular Mechanisms on Biofilm Formation and Virulence

Pseudomonas aeruginosa, a vivid biofilm-producing bacterium, is considered a dreadful opportunistic pathogen, and thus, management of biofilm-associated infections due to multidrug resistant strains by traditional drugs currently is of great concern. This study was aimed to assess the impact of trigonelline hydrochloride, a pyridine alkaloid, on P. aeruginosa PAO1, in search of an alternative therapeutant. The effect of trigonelline on colony morphology and motility was studied along with its role on biofilm and expression virulence factors. Trigonelline influenced the colony structure, motility, biofilm architecture, and the production of virulence factors in a dose-dependent manner. Alterations in quorum sending (QS)-regulated gene expression after treatment and molecular docking analysis for certain regulator proteins confirmed its effect on the QS-system network by affecting Las, Rhl, and Pqs signaling pathways and as possible molecular targets. Thus, trigonelline might be considered as a potential chemical lead to manage biofilm-associated pathogenesis or to develop other analogues with enhanced pharmacokinetic actions.

The action of phytochemicals in biofilm control

Covering: 2009 to 2021Antimicrobial resistance is now rising to dangerously high levels in all parts of the world, threatening the treatment of an ever-increasing range of infectious diseases. This has becoming a serious public health problem, especially due to the emergence of multidrug-resistance among clinically important bacterial species and their ability to form biofilms. In addition, current anti-infective therapies have low efficacy in the treatment of biofilm-related infections, leading to recurrence, chronicity, and increased morbidity and mortality. Therefore, it is necessary to search for innovative strategies/antibacterial agents capable of overcoming the limitations of conventional antibiotics. Natural compounds, in particular those obtained from plants, have been exhibiting promising properties in this field. Plant secondary metabolites (phytochemicals) can act as antibiofilm agents through different mechanisms of action from the available antibiotics (inhibition of quorum-sensing, motility, adhesion, and reactive oxygen species production, among others). The combination of different phytochemicals and antibiotics have revealed synergistic or additive effects in biofilm control. This review aims to bring together the most relevant reports on the antibiofilm properties of phytochemicals, as well as insights into their structure and mechanistic action against bacterial pathogens, spanning December 2008 to December 2021.

Phytochemical Analysis and Demonstration of Antioxidant, Antibacterial, and Antibiofilm Activities of Ethnomedicinal Plants of North East India

Ethnomedicinal plants are a rich reservoir of active compounds with potent pharmacological properties. Therefore, plants could serve as a source for the discovery of active antimicrobial and antioxidant agents and are focused because of their low toxicity, economic viability, easy availability, etc. In this regard, phytochemical analyses, viz. β-carotene, total sugar, reducing sugar, vitamin C, total carotenoids, protein, total phenolic content (TPC), and total flavonoid content (TFC) of 20 ethnomedicinal plants of North East India (NEI) were evaluated in this study. The antibacterial activity against human pathogens and antioxidant potential of plant extracts was also demonstrated. The minimum inhibitory concentration (MIC₈₀), minimum bactericidal concentration (MBC), and total antibacterial activity (TAA) of the active extracts were evaluated against Pseudomonas aeruginosa and Chromobacterium violaceum. The active extracts were also examined for antibiofilm as well as anti-pyocyanin activities against P. aeruginosa and anti-QS activity against C. violaceum at sub-MICs. The study demonstrated variable concentration of phytochemicals of the extracts, viz. β-carotene (0.29-8.91 mg g^-1), total sugar (2.92-30.6 mM), reducing sugar (0.44-14.5 mM), vitamin C (8.41-31.3 mg g^-1), total carotenoids (14.9-267.0 mg g^-1), protein (5.65-283 mg g^-1), TPC (5.32-31.0 mg GAE/g DW), and TFC (1.74-68.2 mg QE/g DW). The plant extracts also exhibited potent antioxidant and antibacterial activities against both Gram-positive and Gram-negative bacteria. Some of the extracts also demonstrated significant biofilm inhibition and eradication, anti-pyocyanin, and anti-QS activities at sub-MICs. The selected ethnomedicinal plants are rich in phytochemicals and demonstrated potent antioxidant, antibacterial, and antibiofilm activities, thus could serve as the important source of novel antioxidant and antimicrobial agents.

Anti-Quorum Sensing and Anti-Biofilm Activity of Pelargonium × hortorum Root Extract against Pseudomonas aeruginosa: Combinatorial Effect of Catechin and Gallic Acid

HPLC-UV was used to compare the major constituents of two Pelargonium × hortorum cultivars and Pelargonium sidoides root extract. It revealed the presence of catechin and gallic acid in high concentrations and the absence of umckalin in P. × hortorum root extracts. The antibacterial activity of these extracts was screened against 19 Pseudomonas aeruginosa clinical isolates. P. × hortorum root extracts showed the lowest MIC values (512-1024 µg/mL). This activity was concluded to be attributable to the high concentrations of catechin and gallic acid. The anti-biofilm activity of catechin, gallic acid, and their combination was examined by a crystal violet assay. The combination reduced the percentage of strong and moderate biofilm-forming isolates from 52.63% to 5.26%. The impact on lasI and lasR genes expression using qRT-PCR and simultaneous docking against LasR protein was explored. The combination downregulated lasI and lasR gene expression in eight and six P. aeruginosa isolates, respectively, and showed the greatest docking score. Additionally, the in vivo protection capability of this combination in infected mice showed enhancement in the survival rate. Our study revealed the potential biofilm and quorum-sensing-inhibitory activity of the catechin and gallic acid combination as a novel alternative to inhibit bacterial pathogenicity.

Quorum Quenching: A Drug Discovery Approach Against Pseudomonas aeruginosa

Pseudomonas aeruginosa, a ubiquitous opportunistic and nosocomial biofilm-forming pathogen with complex, interconnected and hierarchical nature of QS systems (Las, Rhl, PQS, and IQS), is posing the biggest challenge to the healthcare sector and have made current chemotherapies incapable. Conventional antibiotics designed to intercept the biochemical or physiological processes precisely of planktonic microorganisms exert extreme selective pressure and develop resistance against them thereby emphasizing the development of alternative therapeutic approaches. Additionally, quorum sensing induced pathogenic microbial biofilms and production of virulence factors have intensified the pathogenicity, drug resistance, recurrence of infections, hospital visits, morbidity, and mortality many-folds. In this regard, QS could be a potential druggable target and the discovery of QS inhibiting agents as an anti-virulent measure could serve as an alternative therapeutic approach to conventional antibiotics. Quorum quenching (QQ) is a preferred strategy to combat microbial infections since it attenuates the pathogenicity of microbes and enhances the microbial biofilm susceptibility to antibiotics, thus qualifying as a suitable target for drug discovery. This review discusses the QS-induced pathogenicity of P. aeruginosa, the hierarchical QS systems, and QS inhibition as a drug discovery approach to complement classical antibiotic strategy.

The Molecular Architecture of Pseudomonas aeruginosa Quorum-Sensing Inhibitors

The survival selection pressure caused by antibiotic-mediated bactericidal and bacteriostatic activity is one of the important inducements for bacteria to develop drug resistance. Bacteria gain drug resistance through spontaneous mutation so as to achieve the goals of survival and reproduction. Quorum sensing (QS) is an intercellular communication system based on cell density that can regulate bacterial virulence and biofilm formation. The secretion of more than 30 virulence factors of P. aeruginosa is controlled by QS, and the formation and diffusion of biofilm is an important mechanism causing the multidrug resistance of P. aeruginosa, which is also closely related to the QS system. There are three main QS systems in P. aeruginosa: las system, rhl system, and pqs system. Quorum-sensing inhibitors (QSIs) can reduce the toxicity of bacteria without affecting the growth and enhance the sensitivity of bacterial biofilms to antibiotic treatment. These characteristics make QSIs a popular topic for research and development in the field of anti-infection. This paper reviews the research progress of the P. aeruginosa quorum-sensing system and QSIs, targeting three QS systems, which will provide help for the future research and development of novel quorum-sensing inhibitors.

Interactions with Microbial Proteins Driving the Antibacterial Activity of Flavonoids

Flavonoids are among the most abundant natural bioactive compounds produced by plants. Many different activities have been reported for these secondary metabolites against numerous cells and systems. One of the most interesting is certainly the antimicrobial, which is stimulated through various molecular mechanisms. In fact, flavonoids are effective both in directly damaging the envelope of Gram-negative and Gram-positive bacteria but also by acting toward specific molecular targets essential for the survival of these microorganisms. The purpose of this paper is to present an overview of the most interesting results obtained in the research focused on the study of the interactions between flavonoids and bacterial proteins. Despite the great structural heterogeneity of these plant metabolites, it is interesting to observe that many flavonoids affect the same cellular pathways. Furthermore, it is evident that some of these compounds interact with more than one target, producing multiple effects. Taken together, the reported data demonstrate the great potential of flavonoids in developing innovative systems, which can help address the increasingly serious problem of antibiotic resistance.

Exploring the quorum sensing inhibition of isolated chrysin from Penicillium chrysogenum DXY-1

We recently and for the first time reported that ethyl acetate extracts isolated from Penicillium chrysogenum DXY-1 exhibited anti-quorum sensing (anti-QS) activity. Herein, another active molecule in the extracts was identified as chrysin by NMR and MS. A 20 μg/mL dose of chrysin inhibited violacein production regulated by QS in C. violaceum CV026 by 31.6%. A 40 μg/mL dose of chrysin suppressed pyocyanin production, elastase activity, proteolytic activity, and biofilm formation regulated by QS in P. aeruginosa PA01 by 41.4%, 13.8%, 8.3%, and 42.4%, respectively. And chrysin could inhibit the swarming activity of P. aeruginosa PA01. Further, molecular docking and CD analysis were used to address the mechanism of chrysin's activity in C. violaceum. Molecular docking results revealed that chrysin suppresses QS system by competing with the natural signal molecule C₆HSL for binding to the same pocket of CviR receptor. At the same time, CD results also showed that chrysin could change the secondary structure composition of CviR, which greatly prevented the binding of C₆HSL/CviR, and further playing its role on inhibiting bacterial QS system. All these data demonstate that chrysin may be used as a potential QS inhibitor to tackle increasing drug resistance.

Inhibition of biofilm and quorum sensing-regulated virulence factors in Pseudomonas aeruginosa by Cuphea carthagenensis (Jacq.) J. F. Macbr. Leaf extract: An in vitro study

ETHNOPHARMCOLOGICAL RELEVANCE

Microbial biofilm formation, a quorum sensing (QS) regulated process, is one of the major causes of nosocomial and chronic infections, foodborne diseases, and associated deaths. Various approaches have been used to eradicate the menace of biofilm. Ethnomedicinal plants as potent antibiofilm agents are gaining a lot of interest in an era where the drug resistance is increasing and the availability of potent antibiotics is no longer promised. In this context, the methanol extract of Cuphea carthagenensis (CCMD), an ethno-medicinal and culinary herb, was evaluated as an antibiofilm and anti-QS agent against Pseudomonas aeruginosa.

AIM OF THE STUDY

The aim of the study is to evaluate the antibiofilm and anti-QS activity of an ethnomedicinal plant against a strong biofilm forming microorganism, P. aeruginosa.

METHODS

Antibiofilm activity of CCMD was demonstrated at different concentrations by Tissue Culture Plate, Test Tube method and other microscopic techniques. The effect of CCMD on QS and QS-related virulence factors viz. Pyocyanin, exopolymeric substance matrix (EPS), total protease, elastase, pyoverdin and swimming motility in P. aeruginosa were also evaluated. Antioxidant activity (DPPH & FRAP), total phenolic and flavonoid content were also checked. In order to determine the composition of the extract HPLC analysis was also performed.

RESULTS

In vitro study demonstrated a significant inhibition of biofilm formation (81.88 ± 2.57%) as well as production of QS-dependent virulence factors in P. aeruginosa. The extract also inhibited violacein production (83.31 ± 2.77%) in Chromobacterium violaceum which correlates with the reduction in QS-mediated virulence factors. The extract showed 64.79% ± 0.83% DPPH scavenging activity and reduction of ferricyanide complex (Fe³⁺) to the ferrous form (Fe²⁺) in DPPH and FRAP assay, respectively. Furthermore, the extract showed thermal stability and does not have any growth inhibitory effect on P. aeruginosa. The HPLC analysis demonstrated the presence of ellagic acid, ascorbic acid and hippuric acid in the extract.

CONCLUSION

This work is the first to demonstrate that C. carthagenensis can attenuate biofilm formation and QS-mediated virulence factors of P. aeruginosa. Further investigation is required to use this ethnomedicinal plant (CCMD) as an important source of antibiofilm agents.

Genus Parkia: Phytochemical, Medicinal Uses, and Pharmacological Properties

The genus Parkia (Fabaceae, Subfamily, Mimosoideae) comprises about 34 species of mostly evergreen trees widely distributed across neotropics, Asia, and Africa. This review aims to provide an overview of the current status of the species from the genus Parkia in terms of its relationship between its phytochemistry and medical uses. Comprehensive information on Parkia species was retrieved from electronic databases, which were Web of Science, ScienceDirect, PubMed, and Google Scholar. This review identified nine species from genus Parkia with properties of medicinal use. They are used traditionally to treat several ailments, such as diabetes, diarrhea, wounds, hypertension, cough, chronic piles, conjunctivitis, and measles. The most common species studied are P. biglobosa, P. speciosa, P. javanica, P. bicolor, P. biglandulosa, P. filicoidea, and P. clappertoniana. A considerable number of secondary metabolites, such as terpenoids, phenolic acids, flavonoids (aglycone and glycosides), and numerous volatile compounds have been identified in this genus, which are responsible for their diverse pharmacological activities. Their extracts, pure compounds and seed lectins have been reported for their anticancer, antimicrobial, antihypertensive, antiulcer, antidiabetic, anti-inflammatory, antioxidant, antimalarial, hepatoprotective, and antidiarrheal activities. The information gathered in this review might be of help for future studies in terms of the current knowledge on the link between the phytochemical components and medicinal uses. This could facilitate more discoveries on its potentials particularly in the pharmacological characteristics and potential to be developed into modern medicines.

Attenuation of Pseudomonas aeruginosa biofilm by thymoquinone: an individual and combinatorial study with tetrazine-capped silver nanoparticles and tryptophan

Microbial biofilm indicates a cluster of microorganisms having the capability to display drug resistance property, thereby increasing its proficiency in spreading diseases. In the present study, the antibiofilm potential of thymoquinone, a black seed-producing natural molecule, was contemplated against the biofilm formation by Pseudomonas aeruginosa. Substantial antimicrobial activity was exhibited by thymoquinone against the test organism wherein the minimum inhibitory concentration of the compound was found to be 20 μg/mL. Thereafter, an array of experiments (crystal violet staining, protein count, and microscopic observation, etc.) were carried out by considering the sub-MIC doses of thymoquinone (5 and 10 μg/mL), each of which confirmed the biofilm attenuating capacity of thymoquinone. However, these concentrations did not show any antimicrobial activity. Further explorations on understanding the underlying mechanism of the same revealed that thymoquinone accumulated reactive oxygen species (ROS) and also inhibited the expression of the quorum sensing gene (lasI) in Pseudomonas aeruginosa. Furthermore, by taking up a combinatorial approach with two other reported antibiofilm agents (tetrazine-capped silver nanoparticles and tryptophan), the antibiofilm efficiency of thymoquinone was expanded. In this regard, the highest antibiofilm activity was observed when thymoquinone, tryptophan, and tetrazine-capped silver nanoparticles were applied together against Pseudomonas aeruginosa. These combinatorial applications of antibiofilm molecules were found to accumulate ROS in cells that resulted in the inhibition of biofilm formation. Thus, the combinatorial study of these antibiofilm molecules could be applied to control biofilm threats as the tested antibiofilm molecules alone or in combinations showed negligible or very little cytotoxicity.

Inhibition of quorum sensing-associated virulence factors and biofilm formation in Pseudomonas aeruginosa PAO1 by Mycoleptodiscus indicus PUTY1

Pseudomonas aeruginosa is the second most emerging multidrug-resistant, opportunistic pathogen after Acinetobacter baumannii that poses a threat in nursing homes, hospitals, and patients who need devices such as ventilators and blood catheters. Its ability to form quorum sensing-regulated virulence factors and biofilm makes it more resistant to top most therapeutic agents such as carbapenems and next-generation antibiotics. In the current study, we studied the quorum quenching potential of secondary metabolites of Mycoleptodiscus indicus PUTY1 strain. In vitro observation showed a mitigation in virulence factors such as rhamnolipids, protease, elastase pyocyanin, exopolysaccharides, and hydrogen cyanide gas. Furthermore, a significant reduction in the motility such as swimming, swarming, twitching, and inhibition in biofilm formation by Pseudomonas aeruginosa PAO1 was observed. Results of in vitro studies were further confirmed by in silico studies through docking and molecular dynamic simulation of GC-MS-detected compounds of Mycoleptodiscus indicus employing LasR and RhlR proteins. Both in vitro and in silico observations indicate a new alternative approach for combating virulence of Pseudomonas aeruginosa by targeting its protein receptors LasR and RhlR. Graphical abstract.

Musa acuminata and its bioactive metabolite 5-Hydroxymethylfurfural mitigates quorum sensing (las and rhl) mediated biofilm and virulence production of nosocomial pathogen Pseudomonas aeruginosa in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Musa acuminata, a tropical plant belongs to the family Musaceae. The fruit peels of this plant have been well documented for their therapeutic value in Asia and Africa. It has also been previously reported for numerous biological applications such as antimicrobial, antioxidant, itching, psoriasis and anti-diarrheal activities. Moreover, M. acuminata peels have been well known for its anti-healing and antiseptic properties and most commonly used for healing wounds and heat burns in South Asian and African traditional medicines.

AIM OF THE STUDY

To evaluate the QS-mediated antibiofilm and antivirulence potential of M. acuminata, and its bioactive metabolites 5-Hydroxymethylfurfural (5HMF) against Pseudomonas aeruginosa.

MATERIALS AND METHODS

The M. acuminata peel methanol extract (MAM) was evaluated for its antibiofilm potential against P. aeruginosa with increasing concentration. Besides, biofilm related phenomenon's such as total biofilm proteins, microcolony formation exopolysaccharides (EPS) and cell surface hydrophobicity (CSH) productions were also examined to support the antibiofilm potential of MAM. Further, MAM was evaluated for its antivirulence efficacy against P. aeruginosa by assessing the protease, LasA protease, LasB elastase, pyocyanin, alginate and rhamnolipid productions at 400 μg ml^-1 concentration. Transcriptional analysis of QS regulated virulence genes expression level was also done by real-time PCR analysis. Then, the MAM was subjected to column chromatography for further fractions and the bioactive compounds present in MAM were identified by gas chromatograph-mass spectrometry analysis. Further, the major compounds such as 5-hydroxymethylfurfural, vaccenic acid and pentanoic acid identified from active fraction of MAM were evaluated for their antibiofilm and antivirulence potential against P. aeruginosa.

RESULTS

MAM significantly inhibited the biofilm formation in P. aeruginosa at 400 μg ml^-1 concentration which also inhibited the production of biofilm proteins, biofilm adherence, EPS and CSH productions to the level of 79%, 82% and 77% respectively. Further, the antivirulence potential was confirmed through numerous virulence inhibition assays. The MAM at 400 μg ml^-1 concentration inhibited the QS-mediated virulence production such as protease, LasA protease, LasB elastase, pyocyanin, alginate and rhamnolipid productions to the level of 77%, 75%, 68%, 80%, 78% and 69% respectively. Moreover, the results of qPCR analysis confirmed the downregulation of QS regulated virulence genes expression upon treatment with MAM. The chromatographic analysis revealed the presence of 5-Hydroxymethylfurfural (5HMF), vaccenic acid and pentanoic acid in MAM and the potential bioactive compounds with antibiofilm and antivirulence was identified as 5-hydroxymethylfurfural, without exerting any growth inhibition in P. aeruginosa.

CONCLUSION

This study investigated the ideal antibiofilm and antivirulence potential of MAM and its bioactive compound 5HMF, and confirms the ethnopharmacological value of these peels against P. aeruginosa infections.

The anti-biofilm potential of triterpenoids isolated from Sarcochlamys pulcherrima (Roxb.) Gaud

Formation of biofilm is the major cause of Pseudomonas aeruginosa associated pathological manifestations in the urinary tract, respiratory system, gastrointestinal tract, skin, soft tissues etc. Triterpenoid group of compounds have shown their potential in reducing planktonic and biofilm form of bacteria. Sarcochlamys pulcherrima (Roxb.) Gaud. is an ethnomedicinal plant traditionally used for its anti-microbial and anti-inflammatory property. In the present study two triterpenoids, have been isolated from this plant, characterised and evaluated for their antibacterial and antibiofilm potential against P. aeruginosa. Compounds were characterised as 2α, 3β, 19α-trihydroxy-urs-12-ene-28-oic acid (Tormentic acid) and 2α, 3β, 23-trihydroxyurs-12-ene-28-oic acid (23-hydroxycorosolic acid) through spectroscopic studies viz. infrared (IR), nuclear magnetic resonance (NMR) and mass spectroscopy (MS). Depolarization of bacterial membrane and zone of inhibition studies revealed that both the compounds inhibited the growth of planktonic bacteria. Compounds were also found to inhibit the formation of P. aeruginosa biofilm. Inhibition of biofilm found to be mediated through suppressed secretion of pyoverdin, protease and swarming motility of P. aeruginosa. Gene expression study, in silico binding analysis, in vivo bacterial load and tissue histology observations also supported the antibiofilm activity of both the compounds. In vitro and in vivo study showed that both compounds were non-toxic. The study has explored the antibacterial and antibiofilm effect of two triterpenes isolated for the first time from S. pulcherrima.

Inhibition of biofilm formation of Pseudomonas aeruginosa by caffeine: a potential approach for sustainable management of biofilm

Pseudomonas aeruginosa is a potent biofilm forming organism causing several diseases on host involving biofilm. Several natural and synthetic molecules have been explored towards inhibiting the biofilm formation of Pseudomonas aeruginosa. In the current report, the role of a natural molecule namely caffeine was examined against the biofilm forming ability of P. aeruginosa. We have observed that caffeine shows substantial antimicrobial activity against P. aeruginosa wherein the minimum inhibitory concentration (MIC) of caffeine was found to be 200 μg/mL. The antibiofilm activity of caffeine was determined by performing a series of experiments using its sub-MIC concentrations (40 and 80 μg/mL). The results revealed that caffeine can significantly inhibit the biofilm development of P. aeruginosa. Caffeine has been found to interfere with the quorum sensing of P. aeruginosa by targeting the swarming motility. Molecular docking analysis further indicated that caffeine can interact with the quorum sensing proteins namely LasR and LasI. Thus, the result indicated that caffeine could inhibit the formation of biofilm by interfering with the quorum sensing of the organism. Apart from biofilm inhibition, caffeine has also been found to reduce the secretion of virulence factors from Pseudomonas aeruginosa. Taken together, the results revealed that in addition to biofilm inhibition, caffeine can also decrease the spreading of virulence factors from Pseudomonas aeruginosa.

Inhibition Activity of Compounds and Bacteriophages against Flavobacterium psychrophilum Biofilms In Vitro

Flavobacterium psychrophilum produces biofilms under laboratory conditions, and it has been inconclusively suggested that F. psychrophilum biofilms can be a potential reservoir for transmission of the pathogen to a fish population under fish farming conditions. Therefore, there is a need for anti-biofilm compounds. The main aim of this study was to determine the anti-biofilm properties of certain compounds and bacteriophages on F. psychrophilum biofilms under static conditions using a standard 96-well microtiter plate biofilm assay in vitro. Eight compounds (A-type proanthocyanidins, D-leucine, EDTA, emodin, fucoidan, L-alliin, parthenolide, and 2-aminoimidazole) at three sub-minimum inhibitory concentrations (sub-MICs), four bacteriophages (Fpv-3, Fpv-9, Fpv-10, and Fpv-21), and a phage combination (Fpv-9 + Fpv-10) were tested for inhibition of biofilm formation and reduction of the biomass of mature biofilms formed by two smooth isolates (P7-9/10 and P1-10B/10) and two rough isolates (P7-9/2R/10 and P1-10B/2R/10) of F. psychrophilum. The crystal violet staining method was used to stain the biofilms. Most of the compounds at sub-MICs inhibited the biofilm formation of mainly smooth isolates, attaining up to 80% inhibition. Additionally, the same reduction trend was also observed for 2-aminoimidazole, emodin, parthenolide, and D-leucine on the biomass of mature biofilms in a concentration-dependent manner. The anti-biofilm properties of the compounds are believed to lie in their ability to disturb the cellular interactions during biofilm formation and probably to cause cell dispersal in already formed biofilms. Lytic bacteriophages efficiently inhibited biofilm formation of F. psychrophilum, while they partially reduced the biomass of mature biofilms. However, the phage combination (Fpv-9 + Fpv-10) showed a successful reduction in the biomass of F. psychrophilum mature biofilms. We conclude that inhibiting compounds together with bacteriophages may supplement the use of disinfectants against bacterial biofilms (e.g., F. psychrophilum biofilms), leading to a reduced occurrence of bacterial coldwater disease outbreaks at fish farms.

Anti-bacterial activity of baicalin against APEC through inhibition of quorum sensing and inflammatory responses

Avian pathogenic Escherichia coli (APEC), collectively known as causative agent of extraintestinal infections, is an important cause of morbidity and mortality in poultry. Currently, quorum sensing (QS), biofilm formation and virulence factors are considered as novel prospective targets for antimicrobial therapy to control APEC invasion. In addition, inflammatory responses are also served as the major pathological features of APEC invasion. This study was aimed to explore the effect of baicalin on APEC and APEC-induced inflammatory responses. After treatment with baicalin, we mainly examined the AI-2 secretion, biofilm formation, expression of virulence genes of APEC, and the levels of inflammatory cytokines, as well as the expression of NF-κB pathway. Our results showed that baicalin significantly inhibited the QS via decreasing the AI-2 secretion, biofilm formation, and the expression of virulence genes of APEC such as LsrB, LsrK, LuxS, pfs, H-NS, fimA, fimB, fyuA, csgA, csgB, and rpoS. Moreover, baicalin significantly attenuated the release of lactate dehydrogenase (LDH), and the adhesion of APEC to chicken type II pneumocytes to reduce cell damage. Furthermore, baicalin also inhibited the expression of pro-inflammatory cytokines and NF-κB activation. Thus, our data revealed that baicalin could interfere with the quorum sensing, biofilm formation and virulence genes expression to relieve the APEC pathogenicity. Additionally, baicalin decreased the inflammatory responses of chicken type II pneumocytes induced by APEC. Taken together, these data provide a novel potential pharmaco-therapeutic approach to chicken colibacillosis.

Modulation of S. aureus and P. aeruginosa biofilm: an in vitro study with new coumarin derivatives

Coumarin is an important heterocyclic molecular framework of bioactive molecules against broad spectrum pathological manifestations. In the present study 18 new coumarin derivatives (CDs) were synthesized and characterized for antibiofilm activity against two model bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa. It was observed that all the CDs executed significant effect in moderating activities against both planktonic and biofilm forms of these selected bacteria. Hence, to interpret the underlying probable reason of such antibiofilm effect, in-silico binding study of CDs with biofilm and motility associated proteins of these organisms were performed. All CDs have shown their propensity for occupying the native substrate binding pocket of each protein with moderate to strong binding affinities. One of the CDs such as CAMN1 showed highest binding affinity with these proteins. Interestingly, the findings of in-silico studies coincides the experimental results of antibiofilm and motility affect of CDs against both S. aureus and P. aeruginosa. Moreover, in-silico studies suggested that the antibiofilm activity of test CDs may be due to the interference of biofilm and motility associated proteins of the selected model organisms (PilT from P. aeruginosa and TarK, TarO from S. aureus). The detailed synthesis, characterization, methodology and results of biological screening along with computational studies have been reported. This study could be of greater interest in the context of the development of new anti-bacterial agent in the future.

3,6-Di(pyridin-2-yl)-1,2,4,5-tetrazine (pytz)-capped silver nanoparticles (TzAgNPs) inhibit biofilm formation of Pseudomonas aeruginosa: a potential approach toward breaking the wall of biofilm through reactive oxygen species (ROS) generation

Microbial biofilms are factions of surface-colonized cells encompassed in a matrix of extracellular polymeric substances. Profound application of antibiotics in order to treat infections due to microbial biofilm has led to the emergence of several drug-resistant microbial strains. In this context, a novel type of 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine (pytz)-capped silver nanoparticles (TzAgNPs) was synthesized, and efforts were given to test its antimicrobial and antibiofilm activities against Pseudomonas aeruginosa, a widely used biofilm-forming pathogenic organism. The synthesized TzAgNPs showed considerable antimicrobial activity wherein the MIC value of TzAgNPs was found at 40 μg/mL against Pseudomonas aeruginosa. Antibiofilm activity of TzAgNPs was also tested against Pseudomonas aeruginosa by carrying out an array of experiments like microscopic observation, crystal violet assay, and protein count using the sub-MIC doses of TzAgNPs. Since TzAgNPs showed efficient antibiofilm activity, thus, in the present study, efforts were put together to investigate the underlying cause of biofilm attenuation of Pseudomonas aeruginosa by using TzAgNPs. To this end, we discerned that the sub-MIC doses of TzAgNPs increased ROS level considerably in the bacterial cell. The result showed that the ROS level and microbial biofilm formation are inversely proportional. Thus, the attenuation in microbial biofilm could be attributed to the accumulation of ROS level. Furthermore, it was also duly noted that microorganisms upon treatment with TzAgNPs exhibited considerable diminution in virulence factors (protease and pyocyanin) in contrast to the control where the organisms were not treated with TzAgNPs. Thus, the results indicated that TzAgNPs exhibit considerable reduction in the development of biofilms and spreading of virulence factors. Taken together, all the results indicated that TzAgNPs could be deemed to be a promising agent for the prevention of microbial biofilm development that might assist to fight against infections linked to biofilm.

Screening of Natural Product Derivatives Identifies Two Structurally Related Flavonoids as Potent Quorum Sensing Inhibitors against Gram-Negative Bacteria

Owing to the failure of conventional antibiotics in biofilm control, alternative approaches are urgently needed. Inhibition of quorum sensing (QS) represents an attractive target since it is involved in several processes essential for biofilm formation. In this study, a compound library of natural product derivatives (n = 3040) was screened for anti-quorum sensing activity using Chromobacterium violaceum as reporter bacteria. Screening assays, based on QS-mediated violacein production and viability, were performed in parallel to identify non-bactericidal QS inhibitors (QSIs). Nine highly active QSIs were identified, while 328 compounds were classified as moderately actives and 2062 compounds as inactives. Re-testing of the highly actives at a lower concentration against C. violaceum, complemented by a literature search, led to the identification of two flavonoid derivatives as the most potent QSIs, and their impact on biofilm maturation in Escherichia coli and Pseudomonas aeruginosa was further investigated. Finally, effects of these leads on swimming and swarming motility of P. aeruginosa were quantified. The identified flavonoids affected all the studied QS-related functions at micromolar concentrations. These compounds can serve as starting points for further optimization and development of more potent QSIs as adjunctive agents used with antibiotics in the treatment of biofilms.

In vitro anti- biofilm and anti-bacterial activity of Sesbania grandiflora extract against Staphylococcus aureus

The main objective of this research is to investigate the anti-biofilm and anti-bacterial activity of Sesbania grandiflora (S. grandiflora) against Staphylococcus aureus. S. grandiflora extract were prepared and analyzed with UV -Vis spectroscopy, Fourier transform infrared spectroscopy, Dynamic light scattering. Biofilm forming pathogens were identified by congo-red assay. Quantification of Extracellular polymeric substance (EPS) particularly protein and carbohydrate were calculated. The efficacy of the herbal extract S. grandiflora and its inhibition against the pathogenic strain of S. aureus was also evaluated. The gradual decrease or disappearance of peaks reveals the reduction of protein and carbohydrate content in the EPS of S. aureus when treated with S. grandiflora. The antibacterial activity of S. grandiflora extract against the bacterial strain S. aureus showed that the extract were more active against the strain. To conclude, anti-biofilm and antibacterial efficacy of S. grandiflora plays a vital role over biofilm producing pathogens and act as a good source for controlling the microbial population.