Extracts of Cordia gilletii de wild (Boraginaceae) quench the quorum sensing of Pseudomonas aeruginosa PAO1

Unveiling the hidden language of bacteria: anti-quorum sensing strategies for gram-negative bacteria infection control

Quorum sensing (QS) is a communication mechanism employed by many bacteria to regulate gene expression in a population density-dependent manner. It plays a crucial role in coordinating various bacterial behaviors, including biofilm formation, virulence factor production, and antibiotic resistance. However, the dysregulation of QS can lead to detrimental effects, making it an attractive target for developing novel therapeutic strategies. Anti-QS approaches aim to interfere with QS signaling pathways, inhibiting the communication between bacteria, and disrupting their coordinated activities. Various strategies have been explored to achieve this goal. Advances in understanding QS mechanisms and the discovery of new targets have paved the way for the development of innovative anti-QS approaches. Combining multiple anti-QS strategies or utilizing them in combination with traditional antibiotics holds great promise for combating bacterial infections and addressing the challenges posed by antibiotic resistance. Anti-QS approaches offer a diverse range of strategies including natural compounds, antibody-mediated quorum quenching (QQ), computer-aided drug design for QQ, repurposing of Drugs approved by FDA as anti-QS agents and modulating quorum-sensing molecules which were discussed in detail in this review. This review, comprehensively and for the first time, sheds light on the significance of diverse anti-QS strategies in solving antimicrobial resistance problem in Gram-negative microbial infection.

Potential of Impatiens balsamina Leaf Extract against Quorum Sensing in Pseudomonas aeruginosa PA01

Bacteria control gene expression by quorum sensing (QS) mechanism owing to producing small signal molecules associated with population density. Both gram-positive and gram-negative bacteria use QS to manage various physiological characteristics, including bioluminescence, virulence gene expression, biofilm formation, and antibiotic resistance. Impatience balsamina is a flowering, perennial and annual herb indigenous to southern Asia in India. All parts of Impatience balsamina have a therapeutic effect on different diseases. This study evaluated the anti-quorum sensing activity of leaf extract of Impatience balsamina by examining its action on Violacein production by Chromobacterium violaceum, a biosensor strain, and Biofilm, Pyocyanin, Protease, and Chitinase production by the reference strain Pseudomonas aeruginosa PA 01. Minimum inhibitory concentration (MIC) for Pseudomonas aeruginosa PA 01was 3.125mg/ml. A concentration of 1.563mg/ml (sub-MIC) showed inhibition of 100% on Las A protease, 78.42% on chitinase, 30.75% on biofilm, and 93.33% on pyocyanin production by Pseudomonas aeruginosa PA 01. This article displayed the quorum quenching activity of Impatience balsamina by hindering the quorum-sensing controlled characteristics of bacteria without killing it, which reduces the proneness of drug resistance in bacteria, a globally accepted emerging problem in the medical field.

Effects of active compounds from Cassia fistula on quorum sensing mediated virulence and biofilm formation in Pseudomonas aeruginosa

Pseudomonas aeruginosa infections are attributed to its ability to form biofilms and are difficult to eliminate with antibiotic treatment.

African Plant-Based Natural Products with Antivirulence Activities to the Rescue of Antibiotics

The worldwide emergence of antibiotic-resistant bacteria and the thread of widespread superbug infections have led researchers to constantly look for novel effective antimicrobial agents. Within the past two decades, there has been an increase in studies attempting to discover molecules with innovative properties against pathogenic bacteria, notably by disrupting mechanisms of bacterial virulence and/or biofilm formation which are both regulated by the cell-to-cell communication mechanism called ‘quorum sensing’ (QS). Certainly, targeting the virulence of bacteria and their capacity to form biofilms, without affecting their viability, may contribute to reduce their pathogenicity, allowing sufficient time for an immune response to infection and a reduction in the use of antibiotics. African plants, through their huge biodiversity, present a considerable reservoir of secondary metabolites with a very broad spectrum of biological activities, a potential source of natural products targeting such non-microbicidal mechanisms. The present paper aims to provide an overview on two main aspects: (i) succinct presentation of bacterial virulence and biofilm formation as well as their entanglement through QS mechanisms and (ii) detailed reports on African plant extracts and isolated compounds with antivirulence properties against particular pathogenic bacteria.

Effect of Sub-Minimum Inhibitory Concentrations of Tyrosol and EDTA on Quorum Sensing and Virulence of Pseudomonas aeruginosa

Introduction

Pseudomonas aeruginosa is considered a dangerous pathogen, as it causes many human diseases, besides that it is resistant to almost all types of antibacterial agents. So, new strategies to overcome P. aeruginosa infection have evolved to attenuate its virulence factors and inhibit its quorum-sensing (QS) activity.

Purpose

This study investigated the effect of tyrosol and EDTA as anti-quorum-sensing and antivirulence agents against P. aeruginosa PAO1.

Methods

Anti-quorum activity of sub-minimum inhibitory concentrations (sub-MICs) of tyrosol and EDTA was tested using Chromobacterium violaceum (CV 12,472) biosensor bioassay. Miller assay was used to assess the inhibition of QS signal molecules by β-galactosidase activity determination. Also, their effects on the production of protease, lipase, lecithinase, and motility were tested. The inhibitory effects of these molecules on QS regulatory genes and exotoxins genes expression were evaluated by real-time PCR.

Results

Tyrosol and EDTA at sub-MICs inhibited the production of violacein pigment. Both compounds inhibited QS molecules production and their associated virulence factors (protease, lipase, lecithinase, and motility) (P≤ 0.05). Besides, the expression levels of QS regulatory genes (lasI, lasR, rhƖI, rhIR, pqsA, and pqsR) and exotoxins genes (exoS and exoY) were significantly reduced (P≤ 0.05).

Conclusion

Both tyrosol and EDTA can be used to fight P. aeruginosa infection as anti-quorum-sensing and antivirulence agents at their sub-MICs.

Quorum Quenching: A Potential Target for Antipseudomonal Therapy

There has been excessive rate of use of antibiotics to fight Pseudomonas aeruginosa (P. aeruginosa) infections worldwide, which has consequently caused the increased resistance to multiple antibiotics in this pathogen. Due to the widespread resistance and the current poor effect of antibiotics consumed to treat P. aeruginosa infections, finding some novel alternative therapeutic methods are necessary for the treatment of infections. The P. aeruginosa biofilms can cause severe infections leading to the increased antibiotic resistance and mortality rate among the patients. In this regard, there are no approaches that can efficiently manage these infections; therefore, novel and effective antimicrobial and antibiofilm agents are needed to control and treat these bacterial infections. Quorum sensing inhibitors (QSIs) or quorum quenchings (QQs) are now considered as potential therapeutic alternatives and/or adjuvants to the current failing antibiotics, which can control the virulence traits of the pathogens, so as a result, the host immune system can quickly eliminate bacteria. Thus, the aims of this review article were presenting a brief explanation of the research reports on the natural and synthetic QSIs of P. aeruginosa, and the assessment of the current understanding on the QS mechanisms and various QQ strategies in P. aeruginosa.

Anti-Quorum Sensing Natural Compounds

Increasing extent of pathogenic resistance to drugs has encouraged the seeking for new anti-virulence drugs. Many pharmacological and pharmacognostical researches are performed to identify new drugs or discover new structures for the development of novel therapeutic agents in the antibiotic treatments. Although many phytochemicals show prominent antimicrobial activity, their power lies in their anti-virulence properties. Quorum sensing (QS) is a bacterial intercellular communication mechanism, which depends on bacterial cell population density and controls the pathogenesis of many organisms by regulating gene expression, including virulence determinants. QS has become an attractive target for the development of novel anti-infective agents that do not rely on the use of antibiotics. Anti-QS compounds are known to have the ability to prohibit bacterial pathogenicity. Medicinal plants offer an attractive repertoire of phytochemicals with novel microbial disease-controlling potential, due to the spectrum of secondary metabolites present in extracts, which include phenolics, quinones, flavonoids, alkaloids, terpenoids, and polyacetylenes. They have recently received considerable attention as a new source of safe and effective QS inhibitory substances. The objective of this review is to give a brief account of the research reports on the plants and natural compounds with anti-QS potential.

Anti-Quorum Sensing Activity of Forsythia suspense on Chromobacterium violaceum and Pseudomonas aeruginosa

Background:

Quorum sensing (QS) plays an important role in the production of virulence factors and pathogenicity in Pseudomonas aeruginosa, and the interruption of QS will be a hopeful pathway to combat bacterial infection.

Objective:

In this study, we selected Forsythia suspense (Thunb.) Vahl from traditional Chinese herbal medicines for its anti-QS activity.

Materials and Methods:

Anti-QS of F. suspense extracts (FSE) was monitored using the Chromobacterium violaceum 12472 bioassay. Standard methods were used to investigate the effects of FSE on QS-controlled virulence factors production, swimming motility, and biofilm establishment in P. aeruginosa PAO1.

Results:

FSE could obviously inhibit the violacein production in C. violaceum 12472 and also could inhibit quorum sensing–regulated virulence factors production and biofilm formation in P. aeruginosa in a concentration-dependent manner. The elastase activity and pyocyanin production were inhibited at a maximum of 40.97 and 47.58% when P. aeruginosa was grown in the presence of 0.25 g/mL FSE, which can also inhibit swimming motility of P. aeruginosa. The biofilm formation ability was decreased about 72.45% when in PAO1 cultured with the 0.25 g/mL FSE. The results suggested that FSE may be used as an alternative drug to control and handle harmful infections caused by bacterial pathogens based on QS inhibition.

SUMMARY

Forsythia suspense water extract could obviously inhibit the purple pigment production in C. violaceum 12472

Forsythia suspense water extract could inhibit QS-regulated virulence factors production and biofilm formation in P. aeruginosa.

Abbreviations used: QS: Quorum sensing, Pseudomonas aeruginosa P. aeruginosa, Forsythia suspense F. suspense, FSE: F. suspense extracts, Chromobacterium violaceum 12472 C. violaceum 12472, AIs: autoinducers, AHLs: N-acyl-homoserinelactones, LB: Luria-Bertani, MICs: Minimum inhibitory concentrations, CFU: Colony-Forming Units, ATCC: American Type Culture Collection, PBS: phosphate buffered saline

Traditional uses, phytochemistry and pharmacology of the medicinal species of the genus Cordia (Boraginaceae)

OBJECTIVES

Cordia (family Boraginaceae) is a genus of deciduous flowering trees or shrubs comprising more than 300 species distributed widely in the tropical regions. The aim of this review was to provide exhaustive scientific information on traditional uses, phytochemistry and pharmacological activities of the 36 important species with medicinal value from the genus Cordia, to divulge prospects for further research on its therapeutic potential.

KEY FINDINGS

Leaves, fruit, bark and seed of a majority of the species were found to possess abundant ethnomedicinal value, but leaves were found to be used most frequently to treat many ailments such as respiratory disorders, stomach pain, wound, inflammation, myalgia, cough, dysentery and diarrhoea. The phytochemical investigation of 36 species resulted in isolation of 293 chemical constituents from various chemical classes. The crude extracts, fractions, essential oils and pure compounds isolated from various Cordia species were reported to have a varied range of pharmacological activities.

SUMMARY

Many of the traditional uses of the genus Cordia were supported by the results obtained from pharmacological studies performed using various extracts or pure compounds. More attention should be given to the biological evaluation using pure phytochemicals and to identify the mechanism of actions and exploring this genus for new drug discovery.