Rhamnus prinoides (gesho): A source of diverse anti-biofilm activity

Inhibition of the Biofilm Formation of Plant Streptococcus mutans

This review is devoted to a systematic analysis of studies aimed at investigating plant extracts, essential oils and phytochemical compounds capable of inhibiting Streptococcus mutans biofilm formation. This paper investigates the effect of extracts, essential oils and individual plant compounds on inhibiting the biofilm formation of Streptococcus mutans, one of the major pathogens responsible for the development of dental caries. Using cultural microbiology and molecular biology techniques, the authors describe the mechanisms by which plant samples reduce Streptococcus mutans adhesion and growth. The results show that several plant components have antibacterial properties, contributing to the reduction of Streptococcus mutans colony numbers and inhibiting the synthesis of extract-exopolysaccharide matrices required for biofilm formation. This work highlights the potential of botanicals in inhibiting Streptococcus mutans biofilm formation, which can be applied as natural antimicrobial agents in the prevention and treatment of dental diseases. Views on the use of these plant extracts and their components in dental preparations such as toothpastes, rinses and gels aimed at preventing dental caries are evaluated. The review shows the relevance of the research to optimizing the use of plant extracts, essential oils, individual compounds and their active actions in the control of Streptococcus mutans biofilms.

Rhamnus prinoides leaf extract loaded polycaprolactone-cellulose acetate nanofibrous scaffold as potential wound dressing: An in vitro study

Rhamnus prinoides leaf contains carbohydrates, saccharides, phenolic acids, and diterpenes with antibacterial, wound-healing, and anti-inflammatory properties. In this study, Rhamnus prinoides leaf extract was successfully incorporated into polycaprolactone-cellulose acetate (PCL-CA) nanofibers through electrospinning technique for the first time. The mats' morphology, diameter, chemical, and crystalline structure were characterized. The study investigated the mats' antibacterial activity, wound healing, cytotoxicity, drug release behaviour, hydrophilicity, and water absorbency properties. The results revealed that the mats exhibited continuous, smooth, without-beads, and interconnected structures, with average fiber diameters ranging from 385 ± 21 nm to 332 ± 74 nm. The antibacterial effeciency was remarkable against S. aureus and E. coli, achieving bacterial reduction percentages exceeding 99 % at concentrations of 3 % and above against S. aureus and 5 % and above against E. coli. Cytotoxic tests showed low-cytotoxicity up to an extract concentration of 7 %. The extract release increases with an increase in concentration. In vitro wound healing assay, the mats enhanced cell migration to the wound area. Additionally, the incorporation of Rhamnus prinoides significantly improved the hydrophilicity and water absorbency of the nanofibers. Overall, the study highlights the mats' broad antimicrobial and wound healing properties with less cytotoxicity, hydrophilicity, and water absorbency, making them promising for use as wound dressings.

Determination of the rate and frequency of Natura 250 EW fungicide for the management of cedar rust from Gesho (Rhamnus prinoides) in the north west Amhara Region, Ethiopia

Rhamnus prinoides (Gesho) is grown in the homesteads of farmers in western Amhara. The leaves, twigs, and stems of Gesho are indispensable ingredients in traditional beverages. Its production has recently suffered from cedar rust caused by the fungus Gymnosporangium. To manage this disease, different fungicides have been recommended. Therefore, this research was designed to determine the rate and frequency of the use of the Natura 250 EW system for managing this disease in Gesho during 2020. Five application rates of Natura 250 EW and three spray frequencies were used as treatments to manage the disease in infected Gesho plants via the Randomized Complete Block Design (RCBD). Statistically significant differences (P ≤ 0.05) were found between treatments for most parameters. Among these 0.75 litter ha-1 treatments, two spray applications resulted in the lowest severity and greatest relative efficacy, followed by three spray applications of 0.50 litter ha-1 at Bahir Dar Zuria district. However, at Yilmana Densa district, the lowest severity and greatest relative efficacy were found for the 0.75 litter ha-1 spray, followed by the 0.50 litter ha-1 spray, compared with the other treatments. Even though 0.75 litter ha-1 had greater relative efficacy and lower disease severity than the other treatments, there was no statistically significant difference between the three sprays of 0.50 litter ha-1 at both locations. Therefore, three sprays of Natura 250 EW at 0.50 litter ha-1 in 15-day intervals should be recommended and demonstrated for the management of cedar rust disease on Gesho.

Analysis and comparison of bioactive phytochemical composition and antibacterial property of two Ethiopian indigenous medicinal plants

Indigenous medicinal plants with naturally inherited antimicrobial properties are promising sources of antimicrobial agents. Two indigenous Ethiopian traditional medicinal plants (Rhamnus prinoide and Croton macrostachyus) extracted using different solvents and the yield percentage, phytochemical analysis and antimicrobial activity of the plant extracts were examined and compared. The results of this study revealed that Rhamnus prinoide leaf extract using aqueous methanol/ethanol (1 : 1) had the highest yield (15.12 %), a minimum inhibitory concentration of 0.625 mg/mL, and a minimum bactericidal concentration of 10 mg/mL against S. aureus. Croton macrostachyus leaves showed a yield of 14.7 ±0.37 %, a minimum inhibitory concentration of 40 mg/mL, and a minimum bactericidal concentration of 40 mg/mL against S. aureus and E. coli. GC-MS analysis revealed that aqueous methanol/ethanol (1 : 1) of Rhamnus prinoide and Croton macrostachyus leaf extracts were composed of bioactive carbohydrates, flavonoid acid phenols, and terpenoids, while Croton macrostachyus extract contained primarily phytol (30.08 %). The presence of bioactive compounds confirms the traditional use of these plant leaves to treat various diseases, including wounds, leading to the conclusion that they could be applied to textiles for wound dressing in future studies.

Evolving biofilm inhibition and eradication in clinical settings through plant-based antibiofilm agents

BACKGROUND

After almost 100 years since evidence of biofilm mode of growth and decades of intensive investigation about their formation, regulatory pathways and mechanisms of antimicrobial tolerance, nowadays there are still no therapeutic solutions to eradicate bacterial biofilms and their biomedical related issues.

PURPOSE

This review intends to provide a comprehensive summary of the recent and most relevant published studies on plant-based products, or their isolated compounds with antibiofilm activity mechanisms of action or identified molecular targets against bacterial biofilms. The objective is to offer a new perspective of most recent data for clinical researchers aiming to prevent or eliminate biofilm-associated infections caused by bacterial pathogens.

METHODS

The search was performed considering original research articles published on PubMed, Web of Science and Scopus from 2015 to April 2023, using keywords such as "antibiofilm", "antivirulence", "phytochemicals" and "plant extracts".

RESULTS

Over 180 articles were considered for this review with a focus on the priority human pathogens listed by World Health Organization, including Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. Inhibition and detachment or dismantling of biofilms formed by these pathogens were found using plant-based extract/products or derivative compounds. Although combination of plant-based products and antibiotics were recorded and discussed, this topic is currently poorly explored and only for a reduced number of bacterial species.

CONCLUSIONS

This review clearly demonstrates that plant-based products or derivative compounds may be a promising therapeutic strategy to eliminate bacterial biofilms and their associated infections. After thoroughly reviewing the vast amount of research carried out over years, it was concluded that plant-based products are mostly able to prevent biofilm formation through inhibition of quorum sensing signals, but also to disrupt mature biofilms developed by multidrug resistant bacteria targeting the biofilm extracellular polymeric substance. Flavonoids and phenolic compounds seemed the most effective against bacterial biofilms.

Production of antibacterial compounds using Bacillus spp. isolated from thermal springs in Saudi Arabia

Seventeen water samples were collected from four different thermal springs in Saudi Arabia. Microbiological assays were used to assess the antibacterial activities of bacterial colonies against antibiotic-resistant and susceptible-bacterial strains, and 16S rRNA gene sequencing was used to identify the genus and species of these antibiotic-producing bacteria. Chromatography and spectroscopy were used to separate the active compounds and help figuring out what their structures were. Four compounds were isolated using bacteria: N-acetyltryptamine (1), isovaleric acid (2), ethyl-4-ethoxybenzoate (3) and phenylacetic acid (4). Compounds 1, 2 and 4 were produced from Bacillus pumilus and 3 was from Bacillus licheniformis (AH-E1). The outcomes of the minimum inhibitory concentrations (MICs) showed that all pure compounds produced in this work had antibacterial activities against Gram-positive pathogens (between 128 mg/L and 512 mg/L compared to the control) and compound 2 had activity against E. coli.

Trichoderma-Mediated ZnO Nanoparticles and Their Antibiofilm and Antibacterial Activities

Antimicrobial resistance is a major global health concern and one of the gravest challenges to humanity today. Antibiotic resistance has been acquired by certain bacterial strains. As a result, new antibacterial drugs are urgently required to combat resistant microorganisms. Species of Trichoderma are known to produce a wide range of enzymes and secondary metabolites that can be exploited for the synthesis of nanoparticles. In the present study, Trichoderma asperellum was isolated from rhizosphere soil and used for the biosynthesis of ZnO NPs. To examine the antibacterial activity of ZnO NPs against human pathogens, Escherichia coli and Staphylococcus aureus were used. The obtained antibacterial results show that the biosynthesized ZnO NPs were efficient antibacterial agents against the pathogens E. coli and S. aureus, with an inhibition zone of 3-9 mm. The ZnO NPs were also effective in the prevention of S. aureus biofilm formation and adherence. The current work shows that the MIC dosages of ZnO NPs (25, 50, and 75 μg/mL) have effective antibacterial activity and antibiofilm action against S. aureus. As a result, ZnO NPs can be used as a part of combination therapy for drug-resistant S. aureus infections, where biofilm development is critical for disease progression.

Paeoniflorin reduce luxS/AI-2 system-controlled biofilm formation and virulence in Streptococcus suis

Streptococcus suis (S. suis), more specifically serotype 2, is a bacterial pathogen that threatens the lives of pigs and humans. Like many other pathogens, S. suis exhibits quorum sensing (QS) system-controlled virulence factors, such as biofilm formation that complicates treatment. Therefore, impairing the QS involving LuxS/AI-2 cycle in S. suis, may be a promising alternative strategy for overcoming S. suis infections. In this study, we investigated paeoniflorin (PF), a monoterpenoid glycoside compound extracted from peony, as an inhibitor of S. suis LuxS/AI-2 system. At a sub-minimal inhibitory concentration (MIC) (1/16 MIC; 25 μg/ml), PF significantly reduced biofilm formation by S. suis through inhibition of extracellular polysaccharide (EPS) production, without affecting bacterial growth. Moreover, evidence was brought that PF reduces AI-2 activity in S. suis biofilm. Molecular docking indicated that LuxS may be the target of PF. Monitoring LuxS enzymatic activity confirmed that PF had a partial inhibitory effect. Finally, we showed that the use of PF in a mouse model can relieve S. suis infections. This study highlighted the anti-biofilm potential of PF against S. suis, and brought evidence that it may as an inhibitor of the LuxS/AI-2 system to prevent S. suis biofilm-related infections. PF can thus be used as a new type of natural biofilm inhibitor for clinical application.

Inhibition of Bacterial Biofilm Formation by Phytotherapeutics with Focus on Overcoming Antimicrobial Resistance

Bacteria within biofilms are more resistant to antibiotics and chemical agents than planktonic bacteria in suspension. Treatment of biofilm-associated infections inevitably involves high dosages and prolonged courses of antimicrobial agents; therefore, there is a potential risk of the development of antimicrobial resistance (AMR). Due to the high prevalence of AMR and its association with biofilm formation, investigation of more effective anti-biofilm agents is required. From ancient times, herbs and spices have been used to preserve foods, and their antimicrobial, anti-biofilm and anti-quorum sensing properties are well known. Moreover, phytochemicals exert their anti-biofilm properties at sub-inhibitory concentrations without providing the opportunity for the emergence of resistant bacteria or harming the host microbiota. With increasing scientific attention to natural phytotherapeutic agents, numerous experimental investigations have been conducted in recent years. The present paper aims to review the articles published in the last decade in order to summarize a) our current understanding of AMR in correlation with biofilm formation and b) the evidence of phytotherapeutic agents against bacterial biofilms and their mechanisms of action. The main focus has been put on herbal anti-biofilm compounds tested to date in association with Staphylococcus aureus, Pseudomonas aeruginosa and food-borne pathogens (Salmonella spp., Campylobacter spp., Listeria monocytogenes and Escherichia coli).

4-Ethoxybenzoic acid inhibits Staphylococcus aureus biofilm formation and potentiates biofilm sensitivity to vancomycin

The adverse health effects of Staphylococcus aureus biofilm infections coupled with an increased global prevalence of antibiotic resistance highlight the need for novel anti-pathogenic, anti-biofilm compounds. The authors recently determined that ethyl-4-ethoxybenzoic acid (EEB) had anti-pathogenic, anti-biofilm activity. Based on this finding, a structure-activity analysis was undertaken to identify more effective compounds. Microtitre crystal violet assays followed by plate counts were conducted to measure the dose-dependent anti-biofilm and antimicrobial activities of 13 phenolic compounds related to EEB. By displaying these characteristics on a two-component plot, 4-ethoxybenzoic acid (4EB) and methyl gallate were identified as two anti-pathogenic, anti-biofilm compounds of interest. To characterize their mechanisms of activity, their effects on cell hydrophobicity, hemolysis activity, membrane integrity, extracellular polymeric substance production and vancomycin sensitivity were examined. Both 4EB and methyl gallate inhibited up to 87% of biofilm formation with minimal impact on the viability of stationary-phase cells or bacterial growth. Combination treatments of 4EB and vancomycin decreased the viability of biofilm-dwelling cells by up to 85% compared with vancomycin alone, indicating a synergistic effect. Methyl gallate did not potentiate vancomycin. 4EB decreased the percentage of hydrophobic cells in culture from 78% to 49%, indicating that 4EB may prevent biofilm formation by altering cell membrane hydrophobicity. These findings suggest that 4EB has potential as an anti-pathogenic, anti-biofilm agent for the prevention of S. aureus biofilms, or as a treatment for established biofilms when combined with antibiotics.