Adjuvant effect of cranberry proanthocyanidin active fraction on antivirulent property of ciprofloxacin against Pseudomonas aeruginosa

Research Progress on the Combination of Quorum-Sensing Inhibitors and Antibiotics against Bacterial Resistance

Bacterial virulence factors and biofilm development can be controlled by the quorum-sensing (QS) system, which is also intimately linked to antibiotic resistance in bacteria. In previous studies, many researchers found that quorum-sensing inhibitors (QSIs) can affect the development of bacterial biofilms and prevent the synthesis of many virulence factors. However, QSIs alone have a limited ability to suppress bacteria. Fortunately, when QSIs are combined with antibiotics, they have a better therapeutic effect, and it has even been demonstrated that the two together have a synergistic antibacterial effect, which not only ensures bactericidal efficiency but also avoids the resistance caused by excessive use of antibiotics. In addition, some progress has been made through in vivo studies on the combination of QSIs and antibiotics. This article mainly expounds on the specific effect of QSIs combined with antibiotics on bacteria and the combined antibacterial mechanism of some QSIs and antibiotics. These studies will provide new strategies and means for the clinical treatment of bacterial infections in the future.

Bioactive Compounds from Plant Origin as Natural Antimicrobial Agents for the Treatment of Wound Infections

The rising prevalence of drug-resistant bacteria underscores the need to search for innovative and nature-based solutions. One of the approaches may be the use of plants that constitute a rich source of miscellaneous compounds with a wide range of biological properties. This review explores the antimicrobial activity of seven bioactives and their possible molecular mechanisms of action. Special attention was focused on the antibacterial properties of berberine, catechin, chelerythrine, cinnamaldehyde, ellagic acid, proanthocyanidin, and sanguinarine against Staphylococcus aureus, Enterococcus spp., Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa. The growing interest in novel therapeutic strategies based on new plant-derived formulations was confirmed by the growing number of articles. Natural products are one of the most promising and intensively examined agents to combat the consequences of the overuse and misuse of classical antibiotics.

Plant-derived virulence arresting drugs as novel antimicrobial agents: Discovery, perspective, and challenges in clinical use

Antimicrobial resistance (AMR) emerges as a severe crisis to public health and requires global action. The occurrence of bacterial pathogens with multi-drug resistance appeals to exploring alternative therapeutic strategies. Antivirulence treatment has been a positive substitute in seeking to circumvent AMR, which aims to target virulence factors directly to combat bacterial infections. Accumulated evidence suggests that plant-derived natural products, which have been utilized to treat infectious diseases for centuries, can be abundant sources for screening potential virulence-arresting drugs (VADs) to develop advanced therapeutics for infectious diseases. This review sums up some virulence factors and their actions in various species of bacteria, as well as recent advances pertaining to plant-derived natural products as VAD candidates. Furthermore, we also discuss natural VAD-related clinical trials and patents, the perspective of VAD-based advanced therapeutics for infectious diseases and critical challenges hampering clinical use of VADs, and genomics-guided identification for VAD therapeutic. These newly discovered natural VADs will be encouraging and optimistic candidates that may sustainably combat AMR.

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.

Bioaccessibility and Bioavailability of Diet Polyphenols and Their Modulation of Gut Microbiota

It is generally accepted that diet-derived polyphenols are bioactive compounds with several potentially beneficial effects on human health. In general, polyphenols have several chemical structures, and the most representative are flavonoids, phenolic acids, and stilbenes. It should be noted that the beneficial effects of polyphenols are closely related to their bioavailability and bioaccessibility, as many of them are rapidly metabolized after administration. Polyphenols-with a protective effect on the gastrointestinal tract-promote the maintenance of the eubiosis of the intestinal microbiota with protective effects against gastric and colon cancers. Thus, the benefits obtained from dietary supplementation of polyphenols would seem to be mediated by the gut microbiota. Taken at certain concentrations, polyphenols have been shown to positively modulate the bacterial component, increasing Lactiplantibacillus spp. and Bifidobacterium spp. involved in the protection of the intestinal barrier and decreasing Clostridium and Fusobacterium, which are negatively associated with human well-being. Based on the diet-microbiota-health axis, this review aims to describe the latest knowledge on the action of dietary polyphenols on human health through the activity of the gut microbiota and discusses micro-encapsulation of polyphenols as a strategy to improve the microbiota.

Guaiacol augments quorum quenching potential of Ciprofloxacin against Pseudomonas aeruginosa

AIM

The present study aims to investigate the antimicrobial as well as antivirulence potential and the principle mechanism of action of guaiacol against Pseudomonas aeruginosa.

METHODS AND RESULTS

Quorum sensing inhibition and membrane disruption studies were performed to check effect of guaiacol on the virulence of P. aeruginosa. Production of various virulence factors and biofilm formation were studied at sub-MIC concentration of guaiacol alone (1/8 MIC) and in combination with ciprofloxacin (1/2 FIC). Guaiacol exhibited synergistic interactions with ciprofloxacin and further reduced production of all virulence factors and biofilm formation. Using crystal violet (CV) assay and quantification of exopolysaccharide we observed weak biofilm formation, together with reduced motilities at sub MIC which was further visualized by confocal laser microscopy and Field Emission Scanning Electron Microscopy (FESEM).The antibacterial activity of guaiacol against P. aeruginosa upon 2×MIC exposure coincided with enhanced membrane permeability leading to disruption and release of cellular material as quantified by CV uptake assay and Sodium dodecyl suphate-polyacrylamide gel electrophoresis (SDS-PAGE). The results demonstrated that sub MICs of guaiacol in combination with ciprofloxacin can act as a potent alternate compound for attenuation of quorum sensing in P. aeruginosa.

CONCLUSION

Study reports that guaiacol in combination with ciprofloxacin at 1/2 FIC significantly compromised the bacterial growth and motilities alongside inducing quorum quenching potential. This was accompanied by inhibition of biofilm which subsequently decreased EPS production at sub MIC concentration. Furthermore, guaiacol in combination displayed a severe detrimental effect on bacterial membrane disruption, thereby enhancing cellular material release.

SIGNIFICANCE AND IMPACT OF STUDY

For the first time, the potential of guaiacol in combination with ciprofloxacin in attenuation of virulence factors and biofilm formation in P. aeruginosa were described. Results corroborate on how plant bioactive in synergism with antibiotics can act as alternate treatment regime to tackle the menace of drug resistance.

The dissimilarity of antibiotic and quorum sensing inhibitor on activated sludge nitrification system: Microbial communities and antibiotic resistance genes

Effects of antibiotics (azithromycin, AZM, 1-40 mg/L) and quorum sensing inhibitor (QSI, 2(5H)-furanone, 1-40 mg/L) combined pollution with environmental concentration of copper on bacterial/archaeal community and antibiotic resistance genes (ARGs) in activated sludge system were explored. QSI inhibited nitrification more obviously than AZM. AZM and QSI were synergistic inhibitions on bacterial diversity, and AZM inhibited bacterial compositions more than QSI. While, QSI had more impacts on archaeal diversity/compositions. Less interactions among bacteria and archaea communities with Aquimonas as keystone genus. Functional differences in bacteria/archaea communities were little, and AZM had more effects on metabolism. AZM mainly affected nitrifying bacteria (Candidatus Nitrospira nitrificans and Nitrosomonas). Specific denitrifying bacteria were enriched by AZM (Brevundimonas, 1.76-31.69%) and QSI (Comamonas, 0.61-9.61%), respectively. AZM enriched ARGs more easily than QSI and they were antagonistic to proliferation of ARGs. Bacteria were main hosts of ARGs (macrolide-lincosamide-streptogramin B, other/efflux, etc.) and archaea (Methanosphaerula, Methanolobus) carried multiple ARGs.

Polyphenol-Mediated Gut Microbiota Modulation: Toward Prebiotics and Further

The genome of gut microbes encodes a collection of enzymes whose metabolic functions contribute to the bioavailability and bioactivity of unabsorbed (poly)phenols. Datasets from high throughput sequencing, metabolome measurements, and other omics have expanded the understanding of the different modes of actions by which (poly)phenols modulate the microbiome conferring health benefits to the host. Progress have been made to identify direct prebiotic effects of (poly)phenols; albeit up to date, these compounds are not recognized as prebiotics sensu stricto. Interestingly, certain probiotics strains have an enzymatic repertoire, such as tannase, α-L-rhamnosidase, and phenolic acid reductase, involved in the transformation of different (poly)phenols into bioactive phenolic metabolites. In vivo studies have demonstrated that these (poly)phenol-transforming bacteria thrive when provided with phenolic substrates. However, other taxonomically distinct gut symbionts of which a phenolic-metabolizing activity has not been demonstrated are still significantly promoted by (poly)phenols. This is the case of Akkermansia muciniphila, a so-called antiobesity bacterium, which responds positively to (poly)phenols and may be partially responsible for the health benefits formerly attributed to these molecules. We surmise that (poly)phenols broad antimicrobial action free ecological niches occupied by competing bacteria, thereby allowing the bloom of beneficial gut bacteria. This review explores the capacity of (poly)phenols to promote beneficial gut bacteria through their direct and collaborative bacterial utilization and their inhibitory action on potential pathogenic species. We propose the term duplibiotic, to describe an unabsorbed substrate modulating the gut microbiota by both antimicrobial and prebiotic modes of action. (Poly)phenol duplibiotic effect could participate in blunting metabolic disturbance and gut dysbiosis, positioning these compounds as dietary strategies with therapeutic potential.

Effects of Gentamicin-Loaded Chitosan-ZnO Nanocomposite on Quorum-Sensing Regulation of Pseudomonas Aeruginosa

Cell density-based intercellular signaling mechanism is known as Quorum sensing (QS); it serves a significant role in regulating the pathogenic factors. The objective of the present study was to assess the influence of chitosan-zinc oxide nanocomposite (CH-ZnO nanocomposite), alone and in combination with gentamicin, on the sensitivity to hydrogen peroxide (H₂O₂), the production of pathogenic factors and QS-regulated genes of Pseudomonas aeruginosa. The efficacy of the minimum inhibitory concentration (MIC) and 1/4 MIC of the CH-ZnO nanocomposite, alone and in combination with gentamicin, on the sensitivity to H₂O₂, pyocyanin secretion, swarming and twitching motilities was evaluated. In addition, the expression of some QS-regulated genes including rhlI, rhlR, lasI and lasR genes was measured by Real-time quantitative PCR (RT-qPCR) following exposure to the nanocomposite. The results demonstrated that at MIC concentrations, the gentamicin-loaded CH-ZnO nanocomposite significantly inhibited QS-regulated phenotypes such as pyocyanin secretion (82.4%), swarming (76%) and twitching (73.6%) motilities; further it increased the inhibition growth zone (134.5%), as well as, at 1/4 MIC concentration decreased the expression of lasI (72%), lasR (78%), rhlI (76%) and rhlR (82%) genes; as compared to untreated P. aeruginosa PAO1 (P < 0.05). Our results also demonstrated that the CH-ZnO nanocomposite combined with gentamicin could be a potential innovative candidate, which could be broadly applied in the treatment of P. aeruginosa infections.

Could Azithromycin Be Part of Pseudomonas aeruginosa Acute Pneumonia Treatment?

Azithromycin (AZM) is a 15-membered-ring macrolide that presents a broad-spectrum antimicrobial activity against Gram-positive bacteria and atypical microorganisms but suffers from a poor diffusion across the outer-membrane of Gram-negative bacilli, including Pseudomonas aeruginosa (PA). However, AZM has demonstrated clinical benefits in patients suffering from chronic PA respiratory infections, especially cystic fibrosis patients. Since the rise of multidrug-resistant PA has led to a growing need for new therapeutic options, this macrolide has been proposed as an adjunctive therapy. Clinical trials assessing AZM in PA acute pneumonia are scarce. However, a careful examination of the available literature provides good rationales for its use in that context. In fact, 14- and 15-membered-ring macrolides have demonstrated immunomodulatory and immunosuppressive effects that could be of major interest in the management of acute illness. Furthermore, growing evidence supports a downregulation of PA virulence dependent on direct interaction with the ribosomes, and based on the modulation of several key regulators from the Quorum Sensing network. First highlighted in vitro, these interesting properties of AZM have subsequently been confirmed in the animal models. In this review, we systematically analyzed the literature regarding AZM immunomodulatory and anti-PA effects. In vitro and in vivo studies, as well as clinical trials were reviewed, looking for rationales for AZM use in PA acute pneumonia.

Resistance risk induced by quorum sensing inhibitors and their combined use with antibiotics: Mechanism and its relationship with toxicity

The abuse of antibiotics has brought out serious bacterial resistance, which threatens the ecological environment and human health. Quorum sensing inhibitors (QSIs), as a new kind of potential antibiotic substitutes that are theoretically difficult to trigger bacterial resistance, are recommended to individually use or jointly use with traditional antibiotics. However, there are few studies on the resistance risk in the use of QSIs. In this study, the influence of QSIs alone or in combination with sulfonamides (SAs) on conjugative transfer and mutation of Escherichia coli (E. coli) was investigated to explore whether QSIs have the potential to induce bacterial resistance. The results show that QSIs may facilitate plasmid RP4 conjugative transfer by binding with SdiA protein to regulate pilus expression, and interact with LsrR protein to increase SOS gene expression, inducing gene mutation. The QSIs-SAs mixtures could promote plasmid RP4 conjugative transfer and mutation in E. coli, and the main joint effects are synergism and antagonism. Furthermore, there is a good correlation among conjugative transfer, mutation, and growth inhibition of QSIs-SAs to E. coli. It could be speculated that bacteria may delay cell division to provide sufficient energy and time for regulating conjugative transfer and mutation under the stress of QSIs and their combined exposure with antibiotics, which is essentially a balance between bacterial resistance and toxicity. This study provides a reference for the resistance risk assessment of QSIs and benefits the clinical application of QSIs.

Medicinal plants consumption against urinary tract infections: a narrative review of the current evidence

INTRODUCTION

Urinary tract infections (UTIs) are usual diseases caused by different strains of microorganisms. Many antibiotics have been applied for the treatment of these infections. However, the development of multidrug-resistant strains is a major problem in these treatments. As alternative complementary agents, several medicinal plants are often used to prevent and/or treat these diseases.

AREAS COVERED

This review summarized the current evidence about the efficacy of medicinal plants' consumption to prevent and/or co-treat UTIs. The most precise scientific databases, e.g. Medline, Scopus, and Web of Science were comprehensively searched, using relative keywords to identify the relative in vivo and ex vivo animal and human studies.

EXPERT OPINION

Current studies supported evidence for potential benefit overall concerning medicinal plants' consumption against UTIs by preventing bacterial adherence and inhibiting inflammation cascades through responding immunologically to bacteria invasion. However, most of the current evidence have been focused on in vivo and ex vivo animal studies, while human studies are currently limited and did not focus on a specific medicinal plant. Thus, well-designed clinical trials for long study periods focused on individual medicinal plants are intensely recommended to delineate their effectiveness on the prevention and/or co-treatment of UTIs.

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.

Proanthocyanidin Interferes with Intrinsic Antibiotic Resistance Mechanisms of Gram-Negative Bacteria

Antibiotic resistance is spreading at an alarming rate among pathogenic bacteria in both medicine and agriculture. Interfering with the intrinsic resistance mechanisms displayed by pathogenic bacteria has the potential to make antibiotics more effective and decrease the spread of acquired antibiotic resistance. Here, it is demonstrated that cranberry proanthocyanidin (cPAC) prevents the evolution of resistance to tetracycline in Escherichia coli and Pseudomonas aeruginosa, rescues antibiotic efficacy against antibiotic-exposed cells, and represses biofilm formation. It is shown that cPAC has a potentiating effect, both in vitro and in vivo, on a broad range of antibiotic classes against pathogenic E. coli, Proteus mirabilis, and P. aeruginosa. Evidence that cPAC acts by repressing two antibiotic resistance mechanisms, selective membrane permeability and multidrug efflux pumps, is presented. Failure of cPAC to potentiate antibiotics against efflux pump-defective mutants demonstrates that efflux interference is essential for potentiation. The use of cPAC to potentiate antibiotics and mitigate the development of resistance could improve treatment outcomes and help combat the growing threat of antibiotic resistance.

Efficacy of intravesical targeting of novel quorum sensing inhibitor nanoparticles against Pseudomonas aeruginosa biofilm-associated murine pyelonephritis

Pseudomonas aeruginosa biofilm-associated pyelonephritis is a severe infection that can lead to mortality. There are no strategies that can effectively manage this infection since the pathogenesis is controlled by quorum sensing (QS) regulated virulence and recalcitrant biofilms. QS inhibitors (QSIs) are emerging therapeutics against such infections but are associated with cytotoxicity or low bioactivity. Hence, we developed novel quorum sensing inhibitor loaded nanoparticles (QSINPs) using the biopolymers, chitosan (CS) and dextran sulphate (DS) and were intravesically targeted against biofilm-associated murine pyelonephritis. The in-vivo targeting of QSINPs was confirmed by tracking the fluorescein isothiocyanate (FITC) tagged QSINPs in bladder and kidney of mice. On characterising, the QSINPs showed a size of 685.7 nm with a zeta potential of 37.9 and polydispersity index (PDI) of 0.5. Scanning electron microscopy (SEM) indicated spherical shape and bioactivity assays indicated QSI activity till 8 months. Fourier transform infra-red (FTIR) analysis indicated possibility of isothiocyanate bonding in CS with DS and with QSI. The QSINPs showed excellent in vitro antivirulence activity by reducing the virulence factors and biofilm of P. aeruginosa and in vivo therapeutic efficacy with ciprofloxacin (CIP). Hence, we propose a novel next-generation therapeutic and its appropriate targeting route against biofilm-associated pyelonephritis.

Proanthocyanidins-Will they effectively restrain conspicuous bacterial strains devolving on urinary tract infection?

Struvite or infection stones are one of the major clinical burdens among urinary tract infection, which occur due to the interaction between microbes and urine mineral components. Numerous urinary tract infection (UTI) causing microbes regulate through biofilm formation for survival from host defense, it is often found difficult in its eradication with simple anti-microbial agents and also the chance of recurrence and resistance development is significantly high. Cranberry consumption and maintenance of urinary tract health have been supported by clinical, epidemiological, and mechanistic studies. It predominantly contains proanthocyanidins that belong to the class of polyphenols with repeating catechin and epicatechin monomeric units. Numerous studies have correlated proanthocyanidin consumption and prevention of bacterial adhesion to uroepithelial cells. Quorum sensing (QS) is the prime mechanism that drives bacteria to coordinate biofilm development and virulence expression. Reports have shown that proanthocyanidins are effective in disrupting cell-cell communication by quenching signal molecules. Overall, this review assesses the merits of proanthocyanidins and its effective oppression on adherence, motility, QS, and biofilm formation of major UTI strains such as Escherichia coli, Pseudomonas aeruginosa, and Proteus mirabilis by comparing and evaluating results from many significant findings.

UroPathogenic Escherichia coli (UPEC) Infections: Virulence Factors, Bladder Responses, Antibiotic, and Non-antibiotic Antimicrobial Strategies

Urinary tract infections (UTIs) are one of the most common pathological conditions in both community and hospital settings. It has been estimated that about 150 million people worldwide develop UTI each year, with high social costs in terms of hospitalizations and medical expenses. Among the common uropathogens associated to UTIs development, UroPathogenic Escherichia coli (UPEC) is the primary cause. UPEC strains possess a plethora of both structural (as fimbriae, pili, curli, flagella) and secreted (toxins, iron-acquisition systems) virulence factors that contribute to their capacity to cause disease, although the ability to adhere to host epithelial cells in the urinary tract represents the most important determinant of pathogenicity. On the opposite side, the bladder epithelium shows a multifaceted array of host defenses including the urine flow and the secretion of antimicrobial substances, which represent useful tools to counteract bacterial infections. The fascinating and intricate dynamics between these players determine a complex interaction system that needs to be revealed. This review will focus on the most relevant components of UPEC arsenal of pathogenicity together with the major host responses to infection, the current approved treatment and the emergence of resistant UPEC strains, the vaccine strategies, the natural antimicrobial compounds along with innovative anti-adhesive and prophylactic approaches to prevent UTIs.

Antimicrobial and antifouling efficacy of urinary catheters impregnated with a combination of macrolide and fluoroquinolone antibiotics against Pseudomonas aeruginosa

The incidence of catheter associated urinary tract infections (CAUTIs) is increasing worldwide. This study was designed to modify a biomaterial by impregnating a silicone urinary catheter with combination of a macrolide, azithromycin (AZM) and a fluoroquinolone, ciprofloxacin (CIP). Drug release profiles showed slow yet continuous release of antibiotics from catheters for one month. In vitro efficacy testing showed that group B catheters [3% (w v(-1)) CIP + 6% (w v(-1)) AZM] outperformed group A catheters [2% (w v(-1)) CIP + 5% (w v(-1)) AZM] by (1) showing larger zones of inhibition (>31 mm) compared to group A (<28 mm) for up to 30 days against Pseudomonas aeruginosa PAO1; (2) killing adhered bacteria in 24 h compared to 24-48 h in group A; (3) showing longer antimicrobial durability for four weeks; and (4) exhibiting a stable real-time shelf life of one year, suggesting that these catheters can be explored in clinical settings, especially in long-term CAUTI.