Synthesis, Antimicrobial, Anti-virulence and Anticancer Evaluation of New 5(4H)-Oxazolone-Based Sulfonamides

Quercetin: a promising virulence inhibitor of Pseudomonas aeruginosa LasB in vitro

With the inappropriate use of antibiotics, antibiotic resistance has emerged as a major dilemma for patients infected with Pseudomonas aeruginosa. Elastase B (LasB), a crucial extracellular virulence factor secreted by P. aeruginosa, has been identified as a key target for antivirulence therapy. Quercetin, a natural flavonoid, exhibits promising potential as an antivirulence agent. We aim to evaluate the impact of quercetin on P. aeruginosa LasB and elucidate the underlying mechanism. Molecular docking and molecular dynamics simulation revealed a rather favorable intermolecular interaction between quercetin and LasB. At the sub-MICs of ≤256 μg/ml, quercetin was found to effectively inhibit the production and activity of LasB elastase, as well as downregulate the transcription level of the lasB gene in both PAO1 and clinical strains of P. aeruginosa. Through correlation analysis, significant positive correlations were shown between the virulence gene lasB and the QS system regulatory genes lasI, lasR, rhlI, and rhlR in clinical strains of P. aeruginosa. Then, we found the lasB gene expression and LasB activity were significantly deficient in PAO1 ΔlasI and ΔlasIΔrhlI mutants. In addition, quercetin significantly downregulated the expression levels of regulated genes lasI, lasR, rhlI, rhlR, pqsA, and pqsR as well as effectively attenuated the synthesis of signaling molecules 3-oxo-C12-HSL and C4-HSL in the QS system of PAO1. Quercetin was also able to compete with the natural ligands OdDHL, BHL, and PQS for binding to the receptor proteins LasR, RhlR, and PqsR, respectively, resulting in the formation of more stabilized complexes. Taken together, quercetin exhibits enormous potential in combating LasB production and activity by disrupting the QS system of P. aeruginosa in vitro, thereby offering an alternative approach for the antivirulence therapy of P. aeruginosa infections. KEY POINTS: • Quercetin diminished the content and activity of LasB elastase of P. aeruginosa. • Quercetin inhibited the QS system activity of P. aeruginosa. • Quercetin acted on LasB based on the QS system.

Arctigenin from Burdock Root Exhibits Potent Antibacterial and Anti-Virulence Properties against Pseudomonas aeruginosa

Arctium lappa (Burdock) root is used in various culinary applications especially in Asian Cuisine. Arctigenin (ARC) is a polyphenolic compound abundant in the roots of the burdock plant from which it derives its name. The emergence of bacterial resistance is a growing global worry, specifically due to the declining availability of new antibiotics. Screening for the antibacterial candidates among the safe natural products is a promising approach. The present study was aimed to assess the antibacterial activity of ARC against Pseudomonas aeruginosa exploring its effect on the bacterial cell membrane. Furthermore, the anti-virulence activities and anti-quorum sensing (QS) activities of ARC were in vitro, in vivo and in silico assessed against P. aeruginosa. The current results showed the ARC antibacterial activity was owed to its disruption effect of the cell membrane. ARC at sub-MIC significantly decreased the formation of biofilm, motility, production of extracellular enzymes and in vivo protected mice against P. aeruginosa. These anti-virulence activities of ARC are owed to its interference with bacterial QS and its expression. Furthermore, ARC showed mild effect on mammalian erythrocytes, low probability to induce resistance and synergistically combined with antibiotics. In summary, the promising anti-virulence properties of ARC indicate its potential as an effective supplement to conventional antibiotics for treating severe P. aeruginosa infections.

Cilostazol is a promising anti-pseudomonal virulence drug by disruption of quorum sensing

Resistance to antibiotics is a critical growing public health problem that desires urgent action to combat. To avoid the stress on bacterial growth that evokes the resistance development, anti-virulence agents can be an attractive strategy as they do not target bacterial growth. Quorum sensing (QS) systems play main roles in controlling the production of diverse virulence factors and biofilm formation in bacteria. Thus, interfering with QS systems could result in mitigation of the bacterial virulence. Cilostazol is an antiplatelet and a vasodilator FDA approved drug. This study aimed to evaluate the anti-virulence activities of cilostazol in the light of its possible interference with QS systems in Pseudomonas aeruginosa. Additionally, the study examines cilostazol's impact on the bacterium's ability to induce infection in vivo, using sub-inhibitory concentrations to minimize the risk of resistance development. In this context, the biofilm formation, the production of virulence factors and influence on the in vivo ability to induce infection were assessed in the presence of cilostazol at sub-inhibitory concentration. Furthermore, the outcome of combination with antibiotics was evaluated. Cilostazol interfered with biofilm formation in P. aeruginosa. Moreover, swarming motility, biofilm formation and production of virulence factors were significantly diminished. Histopathological investigation revealed that liver, spleen and kidney tissues damage was abolished in mice injected with cilostazol-treated bacteria. Cilostazol exhibited a synergistic outcome when used in combination with antibiotics. At the molecular level, cilostazol downregulated the QS genes and showed considerable affinity to QS receptors. In conclusion, Cilostazol could be used as adjunct therapy with antibiotics for treating Pseudomonal infections. This research highlights cilostazol's potential to combat bacterial infections by targeting virulence mechanisms, reducing the risk of antibiotic resistance, and enhancing treatment efficacy against P. aeruginosa. These findings open avenues for repurposing existing drugs, offering new, safer, and more effective infection control strategies.

Recent development of azole-sulfonamide hybrids with the anticancer potential

Cancer exhibits heterogeneity that enables adaptability and remains grand challenges for effective treatment. Chemotherapy is a validated and critically important strategy for the treatment of cancer, but the emergence of multidrug resistance which may lead to recurrence of disease or even death is a major hurdle for successful chemotherapy. Azoles and sulfonamides are important anticancer pharmacophores, and azole-sulfonamide hybrids have the potential to simultaneously act on dual/multiple targets in cancer cells, holding great promise to overcome drug resistance. This review outlines the current scenario of azole-sulfonamide hybrids with the anticancer potential, and the structure-activity relationships as well as mechanisms of action are also discussed, covering articles published from 2020 onward.

Investigating Sulforaphane's anti-virulence and anti-quorum sensing properties against Pseudomonas aeruginosa

Background

P. aeruginosa, a significant bacterium, can cause severe illness and resistance to antibiotics. Quorum sensing (QS) systems regulate virulence factors production. Targeting QS could reduce bacteria pathogenicity and prevent antibiotic resistance. Cruciferous vegetables contain sulforaphane, known for its anti-inflammatory, antioxidant, anticancer, and antimicrobial properties.

Aim

We aimed to examine the inhibitory influences of sulforaphane, at a sub-inhibitory concentration (¼ minimum inhibitory concentration, MIC), on virulence and QS in P. aeruginosa.

Materials and methods

The sulforaphane's anti-virulence actions at sub-inhibitory concentrations were explored in vitro and in vivo. A sub-MIC concentration of sulforaphane was combined with anti-pseudomonal drugs, and the results of this combination were assessed. The virtual affinity of sulforaphane for the receptors of QS was studied, and its effect on the expression of QS genes was quantified.

Results

Sulforaphane significantly decreased the biofilm formation, motility, ability to withstand oxidative stress, and the synthesis of virulence extracellular enzymes such as proteases, hemolysins, and elastase, as well as other virulence factors like pyocyanin. In addition, sulforaphane lessened the severity of P. aeruginosa infection in mice. Sulforaphane reduced the antipseudomonal antibiotics' MICs when used together, resulting in synergistic effects. The observed anti-virulence impacts were attributed to the ability of sulforaphane to inhibit QS via suppressing the QS genes' expression.

Conclusion

Sulforaphane shows promise as a potent anti-virulence and anti-QS agent that can be used alongside conventional antimicrobials to manage severe infections effectively. Furthermore, this study paves the way for further investigation of sulforaphane and similar structures as pharmacophores for anti-QS candidates.

Piceatannol: a renaissance in antibacterial innovation unveiling synergistic potency and virulence disruption against serious pathogens

In the relentless battle against multi-drug resistant Gram-negative bacteria, piceatannol emerges as a beacon of hope, showcasing unparalleled antibacterial efficacy and a unique ability to disrupt virulence factors. Our study illuminates the multifaceted prowess of piceatannol against prominent pathogens-Proteus mirabilis, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. Notably, piceatannol demonstrated a remarkable ability to inhibit biofilm formation, reduce bacterial mobility, and diminish extracellular enzyme synthesis.Mechanistic insights into piceatannol's activity unraveled its impact on membrane potential, proton motive force, and ATP production. Furthermore, our study delved into piceatannol's anti-quorum sensing (QS) activity, showcasing its potential to downregulate QS-encoding genes and affirming its affinity to critical QS receptors through molecular docking. Crucially, piceatannol exhibited a low propensity for resistance development, positioning it as a promising candidate for combating antibiotic-resistant strains. Its mild effect on red blood cells (RBCs) suggests safety even at higher concentrations, reinforcing its potential translational value. In an in vivo setting, piceatannol demonstrated protective capabilities, significantly reducing pathogenesis in mice infected with P. aeruginosa and P. mirabilis. This comprehensive analysis positions piceatannol as a renaissance in antibacterial innovation, offering a versatile and effective strategy to confront the evolving challenges posed by resilient Gram-negative pathogens.

Assessing the antibacterial potential of 6-gingerol: Combined experimental and computational approaches

The rise of antibiotic resistance in bacteria is becoming a global concern, particularly due to the dwindling supply of new antibiotics. This situation mandates the discovery of new antimicrobial candidates. Plant-derived natural compounds have historically played a crucial role in the development of antibiotics, serving as a rich source of substances possessing antimicrobial properties. Numerous studies have supported the reputation of 6-gingerol, a prominent compound found in the ginger family, for its antibacterial properties. In this study, the antibacterial activities of 6-gingerol were evaluated against Gram-negative bacteria, Acinetobacter baumannii and Klebsiella pneumoniae, with a particular focus on the clinically significant Gram-negative Pseudomonas aeruginosa and Gram-positive bacteria Staphylococcus aureus. Furthermore, the anti-virulence activities were assessed in vitro, in vivo, and in silico. The current findings showed that 6-gingerol's antibacterial activity is due to its significant effect on the disruption of the bacterial cell membrane and efflux pumps, as it significantly decreased the efflux and disrupted the cell membrane of S. aureus and P. aeruginosa. Furthermore, 6-gingerol significantly decreased the biofilm formation and production of virulence factors in S. aureus and P. aeruginosa in concentrations below MICs. The anti-virulence properties of 6-gingerol could be attributed to its capacity to disrupt bacterial virulence-regulating systems; quorum sensing (QS). 6-Gingerol was found to interact with QS receptors and downregulate the genes responsible for QS. In addition, molecular docking, and molecular dynamics (MD) simulation results indicated that 6-gingerol showed a comparable binding affinity to the co-crystalized ligands of different P. aeruginosa QS targets as well as stable interactions during 100 ns MD simulations. These findings suggest that 6-gingerol holds promise as an anti-virulence agent that can be combined with antibiotics for the treatment of severe infections.

Antimicrobial and anti-virulence activities of 4-shogaol from grains of paradise against gram-negative bacteria: Integration of experimental and computational methods

ETHNOPHARMACOLOGICAL RELEVANCE

Bacterial resistance to antibiotics is a growing global concern, highlighting the urgent need for new antimicrobial candidates. Aframomum melegueta was traditionally used for combating urinary tract and soft tissue infections, which implies its potential as an antimicrobial agent.

AIM OF STUDY

This study was designed to explore the antibacterial and anti-virulence capabilities of 4-shogaol isolated from A. melegueta seeds versus gram-negative bacteria: Serratia marcescens, Klebsiella pneumoniae, Acinetobacter baumannii, and the clinically important pathogen Pseudomonas aeruginosa.

MATERIALS AND METHODS

4-Shogeol was isolated from A. melegueta seeds and its MICs were determined for Acinetobacter baumannii (ATCC-17978), Pseudomonas aeruginosa (ATCC-27853), Klebsiella pneumoniae (ATCC-700603), and Serratia marcescens clinical isolate. The anti-efflux activity and effect on the bacterial cell membrane for the compound were evaluated. Furthermore, the anti-virulence activities of the compound were evaluated. The effects of 4-shogeol at sub-MIC on bacterial motility, biofilm formation, and production of virulent enzymes and pigments were assessed. The anti-quorum sensing activities of 4-shogeol were evaluated virtually and by quantification its effect on the expression of quorum sensing encoding genes. The in vivo protection assay was conducted to evaluate the effect of 4-shogaol on the P. aeruginosa capacity to induce pathogenesis in mice. Finally, the effect of shogaol-antibiotics combination was assessed.

RESULTS

The research revealed that 4-shogaol's antibacterial action primarily involves disrupting the bacterial cell membrane and efflux pumps. It also exhibited significant anti-virulence effects by reducing biofilm development and repressing virulence factors production, effectively protecting mice against P. aeruginosa infection. Furthermore, when combined with antibiotics, 4-shogaol demonstrated synergistic effects, leading to reduced minimum inhibitory concentrations (MICs) against P. aeruginosa. Its anti-virulence properties were linked to its ability to disrupt bacterial quorum sensing (QS) mechanisms, as evidenced by its interaction with QS receptors and downregulation of QS-related genes. Notably, in silico analysis indicated that 4-shogaol exhibited strong binding affinity to different P. aeruginosa QS targets.

CONCLUSION

These findings suggest that 4-shogaol holds promise as an effective anti-virulence agent that can be utilized in combination with antibiotics for treating severe infections caused by gram-positive bacteria.

Thymoquinone is a natural antibiofilm and pathogenicity attenuating agent in Pseudomonas aeruginosa

Pseudomonas aeruginosa belongs to the critical pathogens that represent a global public health problem due to their high rate of resistance as listed by WHO. P. aeruginosa can result in many nosocomial infections especially in individuals with compromised immune systems. Attenuating virulence factors by interference with quorum sensing (QS) systems is a promising approach to treat P. aeruginosa-resistant infections. Thymoquinone is a natural compound isolated from Nigella sativa (black seed) essential oil. In this study, the minimum inhibitory concentration of thymoquinone was detected followed by investigating the antibiofilm and antivirulence activities of the subinhibitory concentration of thymoquinone against P. aeruginosa PAO1. The effect of thymoquinone on the expression of QS genes was assessed by quantitative real-time PCR, and the protective effect of thymoquinone against the pathogenesis of PAO1 in mice was detected by the mouse survival test. Thymoquinone significantly inhibited biofilm, pyocyanin, protease activity, and swarming motility. At the molecular level, thymoquinone markedly downregulated QS genes lasI, lasR, rhlI, and rhlR. Moreover, thymoquinone could protect mice from the pathologic effects of P. aeruginosa increasing mouse survival from 20% to 100%. In conclusion, thymoquinone is a promising natural agent that can be used as an adjunct therapeutic agent with antibiotics to attenuate the pathogenicity of P. aeruginosa.

Design, synthesis, in-vitro biological profiling and molecular docking of some novel oxazolones and imidazolones exhibiting good inhibitory potential against acetylcholine esterase

Heterocyclic compounds with oxazole and imidazole rings in their structure have disclosed momentous biological aptitudes. Taking into account their superlative attributes, the present study was designed to introduce a new synthetic scheme to make new derivatives with tremendous futuristic pharmacological potentialities. Series of Oxazolones were synthesized by using substituted benzaldehyde with benzyl halides to produce respective benzaldehyde derivatives 1 (a-d) which further reacted with hippuric acid to yield oxazolones 2 (a-e). Newly synthesized oxazolones then reacted with 4-chloroaniline to yield corresponding imidazolones 3 (a-e). All the compounds were characterized by using FTIR and NMR spectroscopic techniques. Docking studies of Compounds were conducted using AutoDock Vina and analyzed with PYMOL. All synthesized oxazolone and imidazolone derivatives exhibited antioxidant potential, demonstrated by their IC50 values compared to ascorbic acid standard. Oxazolone derivatives (2a-2e) exhibited good acetyl cholinesterase inhibitory potential whereas Imidazolone series did not show significant inhibition as shown by their IC50 values compared to donepezil as a standard. Docking studies of all compounds against acetylcholinesterase demonstrated favorable binding affinity, indicating their potential for further in-vivo studies. It is notable that novel compounds of both oxazolones and Imidazolone series exhibited antioxidant potential with maximum percentage inhibition of 75.9 (IC50 12.9 ± 0.0573 µM/mL) by compound 2d while compound 2a showed AChE inhibitory potential with maximum %age inhibition of 75.49 (IC50 7.8 ± 0.0218 µM/mL).Communicated by Ramaswamy H. Sarma.

The anti-staphylococcal fusidic acid as an efflux pump inhibitor combined with fluconazole against vaginal candidiasis in mouse model

BACKGROUND

Candida albicans is the most common fungus that causes vaginal candidiasis in immunocompetent women and catastrophic infections in immunocompromised patients. The treatment of such infections is hindered due to the increasing emergence of resistance to azoles in C. albicans. New treatment approaches are needed to combat candidiasis especially in the dwindled supply of new effective and safe antifungals. The resistance to azoles is mainly attributed to export of azoles outside the cells by means of the efflux pump that confers cross resistance to all azoles including fluconazole (FLC).

OBJECTIVES

This study aimed to investigate the possible efflux pump inhibiting activity of fusidic acid (FA) in C. albicans resistant isolates and the potential use of Fusidic acid in combination with fluconazole to potentiate the antifungal activity of fluconazole to restore its activity in the resistant C. albicans isolates.

METHODS

The resistance of C. albicans isolates was assessed by determination of minimum inhibitory concentration. The effect of Fusidic acid at sub-inhibitory concentration on efflux activity was assayed by rhodamine 6G efflux assay and intracellular accumulation. Mice model studies were conducted to evaluate the anti-efflux activity of Fusidic acid and its synergistic effects in combination with fluconazole. Impact of Fusidic acid on ergosterol biosynthesis was quantified. The synergy of fluconazole when combined with Fusidic acid was investigated by determination of minimum inhibitory concentration. The cytotoxicity of Fusidic acid was tested against erythrocytes. The effect of Fusidic acid on efflux pumps was tested at the molecular level by real-time PCR and in silico study. In vivo vulvovaginitis mice model was used to confirm the activity of the combination in treating vulvovaginal candidiasis.

RESULTS

Fusidic acid showed efflux inhibiting activity as it increased the accumulation of rhodamine 6G, a substrate for ABC-efflux transporter, and decreased its efflux in C. albicans cells. The antifungal activity of fluconazole was synergized when combined with Fusidic acid. Fusidic acid exerted only minimal cytotoxicity on human erythrocytes indicating its safety. The FA efflux inhibitory activity could be owed to its ability to interfere with efflux protein transporters as revealed by docking studies and downregulation of the efflux-encoding genes of both ABC transporters and MFS superfamily. Moreover, in vivo mice model showed that using fluconazole-fusidic acid combination by vaginal route enhanced fluconazole antifungal activity as shown by lowered fungal burden and a negligible histopathological change in vaginal tissue.

CONCLUSION

The current findings highlight FA's potential as a potential adjuvant to FLC in the treatment of vulvovaginal candidiasis.

The Anti-Virulence Activities of the Antihypertensive Drug Propranolol in Light of Its Anti-Quorum Sensing Effects against Pseudomonas aeruginosa and Serratia marcescens

The development of bacterial resistance is an increasing global concern that requires discovering new antibacterial agents and strategies. Bacterial quorum sensing (QS) systems play important roles in controlling bacterial virulence, and their targeting could lead to diminishing bacterial pathogenesis. In this context, targeting QS systems without significant influence on bacterial growth is assumed as a promising strategy to overcome resistance development. This study aimed at evaluating the anti-QS and anti-virulence activities of the β-adrenoreceptor antagonist propranolol at sub-minimal inhibitory concentrations (sub-MIC) against two Gram-negative bacterial models Pseudomonas aeruginosa and Serratia marcescens. The effect of propranolol on the expression of QS-encoding genes was evaluated. Additionally, the affinity of propranolol to QS receptors was virtually attested. The influence of propranolol at sub-MIC on biofilm formation, motility, and production of virulent factors was conducted. The outcomes of the propranolol combination with different antibiotics were assessed. Finally, the in vivo protection assay in mice was performed to assess propranolol's effect on lessening the bacterial pathogenesis. The current findings emphasized the significant ability of propranolol at sub-MIC to reduce the formation of biofilms, motility, and production of virulence factors. In addition, propranolol at sub-MIC decreased the capacity of tested bacteria to induce pathogenesis in mice. Furthermore, propranolol significantly downregulated the QS-encoding genes and showed significant affinity to QS receptors. Finally, propranolol at sub-MIC synergistically decreased the MICs of different antibiotics against tested bacteria. In conclusion, propranolol might serve as a plausible adjuvant therapy with antibiotics for the treatment of serious bacterial infections after further pharmacological and pharmaceutical studies.

A new type of convergent paired electrochemical synthesis of sulfonamides under green and catalyst-free conditions

Our main goal in this work is to synthesize valuable sulfonamide compounds according to the principles of green chemistry and also to present a unique convergent paired mechanism for their synthesis. In this study, we introduced a new type of convergent paired electro-organic synthesis of sulfonamide derivatives via a catalyst, oxidant, halogen and amine-free method. In this research, instead of using toxic amine compounds, an innovative mechanism based on the reduction of nitro compounds and in-situ production of amine compounds was used. The mechanism of electrophile generation is the cathodic reduction of the nitro compound to the hydroxylamine compound and then the anodic oxidation of the hydroxylamine to the nitroso compound. On the other hand, the nucleophile generation mechanism involves the two-electron oxidation of sulfonyl hydrazide to related sulfinic acid at the anode surface. The reaction leading to the synthesis of sulfonamides involves a one-pot reaction of the generated nitroso compound with the produced sulfinic compound.

Relocating Glyceryl Trinitrate as an Anti-Virulence Agent against Pseudomonas aeruginosa and Serratia marcescens: Insights from Molecular and In Vivo Investigations

The problem of antibiotic resistance is a global critical public health concern. In light of the threat of returning to the pre-antibiotic era, new alternative approaches are required such as quorum-sensing (QS) disruption and virulence inhibition, both of which apply no discernible selective pressure on bacteria, therefore mitigating the potential for the development of resistant strains. Bearing in mind the significant role of QS in orchestrating bacterial virulence, disrupting QS becomes essential for effectively diminishing bacterial virulence. This study aimed to assess the potential use of sub-inhibitory concentration (0.25 mg/mL) of glyceryl trinitrate (GTN) to inhibit virulence in Serratia marcescens and Pseudomonas aeruginosa. GTN could decrease the expression of virulence genes in both tested bacteria in a significant manner. Histopathological study revealed the ability of GTN to alleviate the congestion in hepatic and renal tissues of infected mice and to reduce bacterial and leukocyte infiltration. This study recommends the use of topical GTN to treat topical infection caused by P. aeruginosa and S. marcescens in combination with antibiotics.

Analytical Methodologies for the Estimation of Oxazolidinone Antibiotics as Key Members of anti-MRSA Arsenal: A Decade in Review

Gram-positive bacterial infections are among the most serious diseases related with high mortality rates and huge healthcare costs especially with the rise of antibiotic-resistant strains that limits treatment options. Thus, development of new antibiotics combating these multi-drug resistant bacteria is crucial. Oxazolidinone antibiotics are the only totally synthetic group of antibiotics that showed activity against multi-drug resistant Gram positive bacteria including MRSA because of their unique mechanism of action in targeting protein synthesis. This group include approved marketed members (tedizolid, linezolid and contezolid) or those under development (delpazlolid, radezolid and sutezolid). Due to the significant impact of this class, larger number of analytical methods were required to meet the needs of both clinical and industrial studies. Analyzing these drugs either alone or with other antimicrobial agents commonly used in ICU, in the presence of pharmaceutical or endogenous biological interferences, or in the presence of matrix impurities as metabolites and degradation products poses a big analytical challenge. This review highlights current analytical approaches published in the last decade (2012-2022) that dealt with the determination of these drugs in different matrices and discusses their advantages and disadvantages. Various techniques have been described for their determination including chromatographic, spectroscopic, capillary electrophoretic and electroanalytical methods. The review comprises six sections (one for each drug) with their related tables that depict critical figures of merit and some experimental conditions for the reviewed methods. Furthermore, future perspectives about the analytical methodologies that can be developed in the near future for determination of these drugs are suggested.

New Heterocyclic Compounds from Oxazol-5(4H)-one and 1,2,4-Triazin-6(5H)-one Classes: Synthesis, Characterization and Toxicity Evaluation

This paper describes the synthesis of new heterocycles from oxazol-5(4H)-one and 1,2,4-triazin-6(5H)-one classes containing a phenyl-/4-bromophenylsulfonylphenyl moiety. The oxazol-5(4H)-ones were obtained via condensation of 2-(4-(4-X-phenylsulfonyl)benzamido)acetic acids with benzaldehyde/4-fluorobenzaldehyde in acetic anhydride and in the presence of sodium acetate. The reaction of oxazolones with phenylhydrazine, in acetic acid and sodium acetate, yielded the corresponding 1,2,4-triazin-6(5H)-ones. The structures of the compounds were confirmed using spectral (FT-IR, ¹H-NMR, ¹³C-NMR, MS) and elemental analysis. The toxicity of the compounds was evaluated on Daphnia magna Straus crustaceans and on the budding yeast Saccharomyces cerevisiae. The results indicate that both the heterocyclic nucleus and halogen atoms significantly influenced the toxicity against D. magna, with the oxazolones being less toxic than triazinones. The halogen-free oxazolone had the lowest toxicity, and the fluorine-containing triazinone exhibited the highest toxicity. The compounds showed low toxicity against yeast cells, apparently due to the activity of plasma membrane multidrug transporters Pdr5 and Snq2. The predictive analyses indicated an antiproliferative effect as the most probable biological action. The PASS prediction and CHEMBL similarity studies show evidence that the compounds could inhibit certain relevant oncological protein kinases. These results correlated with toxicity assays suggest that halogen-free oxazolone could be a good candidate for future anticancer investigations.

What’s old is new again: Insights into diabetic foot microbiome

Diabetes is a chronic disease that is considered one of the most stubborn global health problems that continues to defy the efforts of scientists and physicians. The prevalence of diabetes in the global population continues to grow to alarming levels year after year, causing an increase in the incidence of diabetes complications and health care costs all over the world. One major complication of diabetes is the high susceptibility to infections especially in the lower limbs due to the immunocompromised state of diabetic patients, which is considered a definitive factor in all cases. Diabetic foot infections continue to be one of the most common infections in diabetic patients that are associated with a high risk of serious complications such as bone infection, limb amputations, and life-threatening systemic infections. In this review, we discussed the circumstances associated with the high risk of infection in diabetic patients as well as some of the most commonly isolated pathogens from diabetic foot infections and the related virulence behavior. In addition, we shed light on the different treatment strategies that aim at eradicating the infection.

Synergistic Benefits: Exploring the Anti-Virulence Effects of Metformin/Vildagliptin Antidiabetic Combination against Pseudomonas aeruginosa via Controlling Quorum Sensing Systems

The repurposing of drugs is one of the most competent strategies for discovering new antimicrobial agents. Vildagliptin is a dipeptidyl peptidase-4 inhibitor (DPI-4) that is used effectively in combination with metformin to control blood glucose levels in diabetic patients. This study was designed to evaluate the anti-virulence activities of this combination against one of the most clinically important pathogens, Pseudomonas aeruginosa. The current findings show a significant ability of the vildagliptin-metformin combination to diminish biofilm formation, bacterial motility, and the production of virulent extracellular enzymes and pyocyanin pigment. Furthermore, this drug combination significantly increased the susceptibility of P. aeruginosa to oxidative stress, indicating immunity enhancement in the eradication of bacterial cells. In compliance with the in vitro findings, the histopathological photomicrographs of mice showed a considerable protective effect of the metformin-vildagliptin combination against P. aeruginosa, revealing relief of inflammation due to P. aeruginosa-induced pathogenesis. P. aeruginosa mainly employs quorum sensing (QS) systems to control the production of its huge arsenal of virulence factors. The anti-virulence activities of the metformin-vildagliptin combination can be interrupted by the anti-QS activities of both metformin and vildagliptin, as both exhibited a considerable affinity to QS receptors. Additionally, the metformin-vildagliptin combination significantly downregulated the expression of the main three QS-encoding genes in P. aeruginosa. These findings show the significant anti-virulence activities of metformin-vildagliptin at very low concentrations (10, 1.25 mg/mL, respectively) compared to the concentrations (850, 50 mg/mL, respectively) used to control diabetes.

Drug repositioning: doxazosin attenuates the virulence factors and biofilm formation in Gram-negative bacteria

The resistance development is an increasing global health risk that needs innovative solutions. Repurposing drugs to serve as anti-virulence agents is suggested as an advantageous strategy to diminish bacterial resistance development. Bacterial virulence is controlled by quorum sensing (QS) system that orchestrates the expression of biofilm formation, motility, and virulence factors production as enzymes and virulent pigments. Interfering with QS could lead to bacterial virulence mitigation without affecting bacterial growth that does not result in bacterial resistance development. This study investigated the probable anti-virulence and anti-QS activities of α-adrenoreceptor blocker doxazosin against Proteus mirabilis and Pseudomonas aeruginosa. Besides in silico study, in vitro and in vivo investigations were conducted to assess the doxazosin anti-virulence actions. Doxazosin significantly diminished the biofilm formation and release of QS-controlled Chromobacterium violaceum pigment and virulence factors in P. aeruginosa and P. mirabilis, and downregulated the QS encoding genes in P. aeruginosa. Virtually, doxazosin interfered with QS proteins, and in vivo protected mice against P. mirabilis and P. aeruginosa. The role of the membranal sensors as QseC and PmrA was recognized in enhancing the Gram-negative virulence. Doxazosin downregulated the membranal sensors PmR and QseC encoding genes and could in silico interfere with them. In conclusion, this study preliminary documents the probable anti-QS and anti-virulence activities of doxazosin, which indicate its possible application as an alternative or in addition to antibiotics. However, extended toxicological and pharmacological investigations are essential to approve the feasible clinical application of doxazosin as novel efficient anti-virulence agent. KEY POINTS: • Anti-hypertensive doxazosin acquires anti-quorum sensing activities • Doxazosin diminishes the virulence of Proteus mirabilis and Pseudomonas aeruginosa • Doxazosin could dimmish the bacterial espionage.

Diminishing the Pathogenesis of the Food-Borne Pathogen Serratia marcescens by Low Doses of Sodium Citrate

Protecting food from bacterial contamination is crucial for ensuring its safety and avoiding foodborne illness. Serratia marcescens is one of the food bacterial contaminants that can form biofilms and pigments that spoil the food product and could cause infections and illness to the consumer. Food preservation is essential to diminish such bacterial contaminants or at least reduce their pathogenesis; however, it should not affect food odor, taste, and consistency and must be safe. Sodium citrate is a well-known safe food additive and the current study aims to evaluate its anti-virulence and anti-biofilm activity at low concentrations against S. marcescens. The anti-virulence and antibiofilm activities of sodium citrate were evaluated phenotypically and genotypically. The results showed the significant effect of sodium citrate on decreasing the biofilm formation and other virulence factors, such as motility and the production of prodigiosin, protease, and hemolysins. This could be owed to its downregulating effect on the virulence-encoding genes. An in vivo investigation was conducted on mice and the histopathological examination of isolated tissues from the liver and kidney of mice confirmed the anti-virulence activity of sodium citrate. In addition, an in silico docking study was conducted to evaluate the sodium citrate binding ability to S. marcescens quorum sensing (QS) receptors that regulates its virulence. Sodium citrate showed a marked virtual ability to compete on QS proteins, which could explain sodium citrate’s anti-virulence effect. In conclusion, sodium citrate is a safe food additive and can be used at low concentrations to prevent contamination and biofilm formation by S. marcescens and other bacteria.

Clinical Resistant Strains of Enterococci and Their Correlation to Reduced Susceptibility to Biocides: Phenotypic and Genotypic Analysis of Macrolides, Lincosamides, and Streptogramins

Enterococci are troublesome nosocomial, opportunistic Gram-positive cocci bacteria showing enhanced resistance to many commonly used antibiotics. This study aims to investigate the prevalence and genetic basis of antibiotic resistance to macrolides, lincosamides, and streptogramins (MLS) in Enterococci, as well as the correlation between MLS resistance and biocide resistance. From 913 clinical isolates collected from King Khalid Hospital, Hail, Saudi Arabia, 131 isolates were identified as Enterococci spp. The susceptibility of the clinical enterococcal isolates to several MLS antibiotics was determined, and the resistance phenotype was detected by the triple disk method. The MLS-involved resistance genes were screened in the resistant isolates. The current results showed high resistance rates to MLS antibiotics, and the constitutive resistance to all MLS (cMLS) was the most prevalent phenotype, observed in 76.8% of resistant isolates. By screening the MLS resistance-encoding genes in the resistant isolates, the erythromycin ribosome methylase (erm) genes that are responsible for methylation of bacterial 23S rRNA were the most detected genes, in particular, ermB. The ereA esterase-encoding gene was the most detected MLS modifying-encoding genes, more than lnuA (adenylation) and mphC (phosphorylation). The minimum inhibitory concentrations (MICs) of commonly used biocides were detected in resistant isolates and correlated with the MICs of MLS antibiotics. The present findings showed a significant correlation between MLS resistance and reduced susceptibility to biocides. In compliance with the high incidence of the efflux-encoding genes, especially mefA and mefE genes in the tolerant isolates with higher MICs to both MLS antibiotics and biocides, the efflux of resistant isolates was quantified, and there was a significant increase in the efflux of resistant isolates with higher MICs as compared to those with lower MICs. This could explain the crucial role of efflux in developing cross-resistance to both MLS antibiotics and biocides.

Biofilm Lifestyle in Recurrent Urinary Tract Infections

Urinary tract infections (UTIs) represent one of the most common infections that are frequently encountered in health care facilities. One of the main mechanisms used by bacteria that allows them to survive hostile environments is biofilm formation. Biofilms are closed bacterial communities that offer protection and safe hiding, allowing bacteria to evade host defenses and hide from the reach of antibiotics. Inside biofilm communities, bacteria show an increased rate of horizontal gene transfer and exchange of resistance and virulence genes. Additionally, bacterial communication within the biofilm allows them to orchestrate the expression of virulence genes, which further cements the infestation and increases the invasiveness of the infection. These facts stress the necessity of continuously updating our information and understanding of the etiology, pathogenesis, and eradication methods of this growing public health concern. This review seeks to understand the role of biofilm formation in recurrent urinary tact infections by outlining the mechanisms underlying biofilm formation in different uropathogens, in addition to shedding light on some biofilm eradication strategies.

Hiring of the Anti-Quorum Sensing Activities of Hypoglycemic Agent Linagliptin to Alleviate the Pseudomonas aeruginosa Pathogenesis

Bacteria communicate with each other using quorum sensing (QS) which works in an inducer/receptor manner. QS plays the main role in orchestrating diverse bacterial virulence factors. Pseudomonas aeruginosa is one of the most clinically important bacterial pathogens that can cause infection in almost all body tissues. Besides its efficient capability to develop resistance to different antibiotics, P. aeruginosa acquires a huge arsenal of virulence factors that are controlled mainly by QS. Challenging QS with FDA-approved drugs and natural products was proposed as a promising approach to mitigate bacterial virulence enabling the host immunity to complete the eradication of bacterial infection. The present study aims to evaluate the dipeptidase inhibitor-4 inhibitor hypoglycemic linagliptin anti-QS and anti-virulence activities against P. aeruginosa in vitro, in vivo, and in silico. The current results revealed the significant ability to diminish the production of protease and pyocyanin, motility, and biofilm formation in P. aeruginosa. Furthermore, the histopathological examination of liver and kidney tissues of mice injected with linagliptin-treated bacteria showed an obvious reduction of pathogenesis. Linagliptin downregulation to QS-encoding genes, besides the virtual ability to interact with QS receptors, indicates its anti-QS activities. In conclusion, linagliptin is a promising anti-virulence and anti-QS candidate that can be used solely or in combination with traditional antimicrobial agents in the treatment of P. aeruginosa aggressive infections.

Controlling of Bacterial Virulence: Evaluation of Anti-Virulence Activities of Prazosin against Salmonella enterica

Salmonella enterica is a Gram-negative orofecal transmitted pathogen that causes a wide diversity of local and systemic illnesses. Salmonella enterica utilizes several interplayed systems to regulate its invasion and pathogenesis: namely, quorum sensing (QS) and type three secretion system (T3SS). In addition, S. enterica could sense the adrenergic hormones in the surroundings that enhance its virulence. The current study aimed to evaluate the ability of α-adrenoreceptor antagonist prazosin to mitigate the virulence of S. enterica serovar Typhimurium. The prazosin effect on biofilm formation and the expression of sdiA, qseC, qseE, and T3SS-type II encoding genes was evaluated. Furthermore, the prazosin intracellular replication inside macrophage and anti-virulence activity was evaluated in vivo against S. typhimurium. The current finding showed a marked prazosin ability to compete on SdiA and QseC and downregulate their encoding genes. Prazosin significantly downregulated the virulence factors encoding genes and diminished the biofilm formation, intracellular replication inside macrophages, and in vivo protected mice. To sum up, prazosin showed significant inhibitory activities against QS, T3SS, and bacterial espionage, which documents its considered anti-virulence activities.

Ibrahim T, Khafagy ES, Lopes BS, Ali MAM, Hegazy WAH, Elfaky MA. Characterization of the Anti-Biofilm and Anti-Quorum Sensing Activities of the β-Adrenoreceptor Antagonist Atenolol against Gram-Negative Bacterial Pathogens

The development of bacterial resistance to antibiotics is an increasing public health issue that worsens with the formation of biofilms. Quorum sensing (QS) orchestrates the bacterial virulence and controls the formation of biofilm. Targeting bacterial virulence is promising approach to overcome the resistance increment to antibiotics. In a previous detailed in silico study, the anti-QS activities of twenty-two β-adrenoreceptor blockers were screened supposing atenolol as a promising candidate. The current study aims to evaluate the anti-QS, anti-biofilm and anti-virulence activities of the β-adrenoreceptor blocker atenolol against Gram-negative bacteria Serratia marcescens, Pseudomonas aeruginosa, and Proteus mirabilis. An in silico study was conducted to evaluate the binding affinity of atenolol to S. marcescens SmaR QS receptor, P. aeruginosa QscR QS receptor, and P. mirabilis MrpH adhesin. The atenolol anti-virulence activity was evaluated against the tested strains in vitro and in vivo. The present finding shows considerable ability of atenolol to compete with QS proteins and significantly downregulated the expression of QS- and virulence-encoding genes. Atenolol showed significant reduction in the tested bacterial biofilm formation, virulence enzyme production, and motility. Furthermore, atenolol significantly diminished the bacterial capacity for killing and protected mice. In conclusion, atenolol has potential anti-QS and anti-virulence activities against S. marcescens, P. aeruginosa, and P. mirabilis and can be used as an adjuvant in treatment of aggressive bacterial infections.

Analyzing the metabolic fate of oral administration drugs: A review and state-of-the-art roadmap

The key orally delivered drug metabolism processes are reviewed to aid the assessment of the current in vivo/vitro experimental systems applicability for evaluating drug metabolism and the interaction potential. Orally administration is the most commonly used state-of-the-art road for drug delivery due to its ease of administration, high patient compliance and cost-effectiveness. Roles of gut metabolic enzymes and microbiota in drug metabolism and absorption suggest that the gut is an important site for drug metabolism, while the liver has long been recognized as the principal organ responsible for drugs or other substances metabolism. In this contribution, we explore various experimental models from their development to the application for studying oral drugs metabolism of and summarized advantages and disadvantages. Undoubtedly, understanding the possible metabolic mechanism of drugs in vivo and evaluating the procedure with relevant models is of great significance for screening potential clinical drugs. With the increasing popularity and prevalence of orally delivered drugs, sophisticated experimental models with higher predictive capacity for the metabolism of oral drugs used in current preclinical studies will be needed. Collectively, the review seeks to provide a comprehensive roadmap for researchers in related fields.

Silencing of Salmonella typhimurium Pathogenesis: Atenolol Acquires Efficient Anti-Virulence Activities

The targeting of bacterial virulence is proposed as a promising approach to overcoming the bacterial resistance development to antibiotics. Salmonella enterica is one of the most important gut pathogens that cause a wide diversity of local and systemic illnesses. The Salmonella virulence is controlled by interplayed systems namely Quorum sensing (QS) and type three secretion system (T3SS). Furthermore, the Salmonella spy on the host cell via sensing the adrenergic hormones enhancing its virulence. The current study explores the possible anti-virulence activities of β-adrenoreceptor blocker atenolol against S. enterica serovar Typhimurium in vitro, in silico, and in vivo. The present findings revealed a significant atenolol ability to diminish the S. typhimurium biofilm formation, invasion into HeLa cells, and intracellular replication inside macrophages. Atenolol significantly downregulated the encoding genes of the T3SS-type II, QS receptor Lux analogs sdiA, and norepinephrine membranal sensors qseC and qseE. Moreover, atenolol significantly protected mice against S. typhimurium. For testing the possible mechanisms for atenolol anti-virulence activities, an in silico molecular docking study was conducted to assess the atenolol binding ability to QS receptor SdiA and norepinephrine membranal sensors QseC. Atenolol showed the ability to compete on the S. typhimurium targets. In conclusion, atenolol is a promising anti-virulence candidate to alleviate the S. typhimurium pathogenesis by targeting its QS and T3SS systems besides diminishing the eavesdropping on the host cells.

Discovery of novel drugs for Chagas disease: is carbonic anhydrase a target for antiprotozoal drugs?

INTRODUCTION

Carbonic anhydrase (CA) arose significant interest as a potential new target for Chagas disease since its discovery in Trypanosoma cruzi in 2013. Benznidazole and Nifurtimox have been used for Chagas disease treatment for 60 years despite all efforts done for obtaining more efficient treatments, acting in the acute and chronic phases of illness, with fewer side effects and resistance induction.

AREAS COVERED

We discuss the positive and negative aspects of T. cruzi CA (TcCA) studies as a target for developing new drugs. The current research discoveries and the classes of TcCA inhibitors are reviewed. The sulfonamides and their derivatives are the main inhibitor classes, but hydroxamates and the thiols, were investigated too. These compounds inhibited the growth of the evolutive forms of the parasite. A comparative analysis was done with CAs from other Trypanosomatids and protozoans.

EXPERT OPINION

The search for new targets and drugs is a significant challenge worldwide, and TcCA is a potential candidate for developing new drugs. Several studied inhibitors were active against Trypanosoma cruzi, but their penetration and toxicity problems emerged. New approaches are in progress to obtain inhibitors with desired properties, allowing further steps such as tests using an adequate animal model and subsequent developments for the preclinical testing.

Muting Bacterial Communication: Evaluation of Prazosin Anti-Quorum Sensing Activities against Gram-Negative Bacteria Pseudomonas aeruginosa, Proteus mirabilis, and Serratia marcescens

Simple Summary

Bacterial infections are considered one of the main challenges to global health. Bacterial virulence is controlled by interplayed systems to regulate bacterial invasion and infection in host tissues. Quorum sensing (QS) plays a crucial role in regulating virulence factor production, thus could be considered as the bacterial communication system in the bacterial population. The current study aimed to assess the anti-QS and anti-virulence activities of α-adrenoreceptor prazosin against three virulent Gram-negative bacteria. It was demonstrated that prazosin significantly downregulates the expression of QS-encoding genes and shows considered ability to compete on QS proteins in tested strains. Prazosin can significantly diminish biofilm formation and production of virulent enzymes and mitigate the virulence factors of tested strains. However, more testing is required alongside pharmacological and toxicological studies to assure the potential clinical use of prazosin as an adjuvant anti-QS and anti-virulence agent.

Abstract

Quorum sensing (QS) controls the production of several bacterial virulence factors. There is accumulative evidence to support that targeting QS can ensure a significant diminishing of bacterial virulence. Lessening bacterial virulence has been approved as an efficient strategy to overcome the development of antimicrobial resistance. The current study aimed to assess the anti-QS and anti-virulence activities of α-adrenoreceptor prazosin against three virulent Gram-negative bacteria Pseudomonades aeruginosa, Proteus mirabilis, and Serratia marcescens. The evaluation of anti-QS was carried out on a series of in vitro experiments, while the anti-virulence activities of prazosin were tested in an in vivo animal model. The prazosin anti-QS activity was assessed on the production of QS-controlled Chromobacterium violaceum pigment violacein and the expression of QS-encoding genes in P. aeruginosa. In vitro tests were performed to evaluate the prazosin effects on biofilm formation and production of extracellular enzymes by P. aeruginosa, P. mirabilis, and S. marcescens. A protective assay was conducted to evaluate the in vivo anti-virulence activity of prazosin against P. aeruginosa, P. mirabilis, and S. marcescens. Moreover, precise in silico molecular docking was performed to test the prazosin affinity to different QS receptors. The results revealed that prazosin significantly decreased the production of violacein and the virulent enzymes, protease and hemolysins, in the tested strains. Prazosin significantly diminished biofilm formation in vitro and bacterial virulence in vivo. The prazosin anti-QS activity was proven by its downregulation of QS-encoding genes and its obvious binding affinity to QS receptors. In conclusion, prazosin could be considered an efficient anti-virulence agent to be used as an adjuvant to antibiotics, however, it requires further pharmacological evaluations prior to clinical application.

Sodium Citrate Alleviates Virulence in Pseudomonas aeruginosa

The development of bacterial resistance is an insistent global health care issue, especially in light of the dwindled supply of new antimicrobial agents. This mandates the development of new innovative approaches to overcome the resistance development obstacle. Mitigation of bacterial virulence is an interesting approach that offers multiple advantages. Employing safe chemicals or drugs to mitigate bacterial virulence is an additive advantage. In the current study, the in vitro antivirulence activities of citrate were evaluated. Significantly, sodium citrate inhibited bacterial biofilm formation at sub-MIC concentrations. Furthermore, sodium citrate decreased the production of virulence factors protease and pyocyanin and diminished bacterial motility. Quorum sensing (QS) is the communicative system that bacterial cells utilize to communicate with each other and regulate the virulence of the host cells. In the present study, citrate in silico blocked the Pseudomonas QS receptors and downregulated the expression of QS-encoding genes. In conclusion, sodium citrate showed a significant ability to diminish bacterial virulence in vitro and interfered with QS; it could serve as a safe adjuvant to traditional antibiotic treatment for aggressive resistant bacterial infections such as Pseudomonas aeruginosa infections.

Anti-Quorum Sensing Activities of Gliptins against Pseudomonas aeruginosa and Staphylococcus aureus

The development of bacterial resistance to traditional antibiotics constitutes an emerging public health issue. Promising approaches have been innovated to conquer bacterial resistance, and targeting bacterial virulence is one of these approaches. Bacterial virulence mitigation offers several merits, as antivirulence agents do not affect the growth of bacteria and hence do not induce bacteria to develop resistance. In this direction, numerous drugs have been repurposed as antivirulence agents prior to their clinical use alone or in combination with traditional antibiotics. Quorum sensing (QS) plays a key role in controlling bacterial virulence. In the current study, dipeptidase inhibitor-4 (DPI-4) antidiabetic gliptins were screened for their antivirulence and anti-quorum sensing (anti-QS) activities against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. Upon assessing their antibiofilm activities, the ten tested gliptins significantly diminished biofilm formation. In particular, sitagliptin exhibited the most efficient antibiofilm activity, so it was chosen as a representative of all gliptins to further investigate its antivirulence activity. Sitagliptin significantly protected mice from P. aeruginosa and S. aureus pathogenesis. Furthermore, sitagliptin downregulated QS-encoding genes in P. aeruginosa and S. aureus. To test the anti-QS activities of gliptins, a detailed molecular docking study was conducted to evaluate the gliptins’ binding affinities to P. aeruginosa and S. aureus QS receptors, which helped explain the anti-QS activities of gliptins, particularly sitagliptin and omarigliptin. In conclusion, this study evaluates the possible antivirulence and anti-QS activities of gliptins that could be promising novel candidates for the treatment of aggressive Gram-negative or -positive bacterial infections either alone or as adjuvants to other antibiotics.

Anti-Quorum Sensing Activities of Gliptins against Pseudomonas aeruginosa and Staphylococcus aureus

The development of bacterial resistance to traditional antibiotics constitutes an emerging public health issue. Promising approaches have been innovated to conquer bacterial resistance, and targeting bacterial virulence is one of these approaches. Bacterial virulence mitigation offers several merits, as antivirulence agents do not affect the growth of bacteria and hence do not induce bacteria to develop resistance. In this direction, numerous drugs have been repurposed as antivirulence agents prior to their clinical use alone or in combination with traditional antibiotics. Quorum sensing (QS) plays a key role in controlling bacterial virulence. In the current study, dipeptidase inhibitor-4 (DPI-4) antidiabetic gliptins were screened for their antivirulence and anti-quorum sensing (anti-QS) activities against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. Upon assessing their antibiofilm activities, the ten tested gliptins significantly diminished biofilm formation. In particular, sitagliptin exhibited the most efficient antibiofilm activity, so it was chosen as a representative of all gliptins to further investigate its antivirulence activity. Sitagliptin significantly protected mice from P. aeruginosa and S. aureus pathogenesis. Furthermore, sitagliptin downregulated QS-encoding genes in P. aeruginosa and S. aureus. To test the anti-QS activities of gliptins, a detailed molecular docking study was conducted to evaluate the gliptins' binding affinities to P. aeruginosa and S. aureus QS receptors, which helped explain the anti-QS activities of gliptins, particularly sitagliptin and omarigliptin. In conclusion, this study evaluates the possible antivirulence and anti-QS activities of gliptins that could be promising novel candidates for the treatment of aggressive Gram-negative or -positive bacterial infections either alone or as adjuvants to other antibiotics.

Terazosin Interferes with Quorum Sensing and Type Three Secretion System and Diminishes the Bacterial Espionage to Mitigate the Salmonella Typhimurium Pathogenesis

Salmonella enterica is an invasive intracellular pathogen and hires diverse systems to manipulate its survival in the host cells. Salmonella could eavesdrop on the host cells, sensing and responding to the produced adrenergic hormones and other neurotransmitters, which results in the augmentation of its virulence and establishes its accommodation in host cells. The current study aims to assess the anti-virulence effect of α-adrenergic antagonist terazosin on S. Typhimurium. Our findings show that terazosin significantly reduced S. Typhimurium adhesion and biofilm formation. Furthermore, terazosin significantly decreased invasion and intracellular replication of S. Typhimurium. Interestingly, in vivo, terazosin protected the mice from S. Typhimurium pathogenesis. To understand the terazosin anti-virulence activity, its effect on quorum sensing (QS), bacterial espionage, and type three secretion system (T3SS) was studied. Strikingly, terazosin competed on the membranal sensors that sense adrenergic hormones and down-regulated their encoding genes, which indicates the ability of terazosin to diminish the bacterial eavesdropping on the host cells. Moreover, terazosin significantly reduced the Chromobacterium violaceum QS-controlled pigment production and interfered with the QS receptor Lux-homolog Salmonella SdiA, which indicates the possible terazosin-mediated anti-QS activity. Furthermore, terazosin down-regulated the expression of T3SS encoding genes. In conclusion, terazosin may mitigate S. Typhimurium virulence owing to its hindering QS and down-regulating T3SS encoding genes besides its inhibition of bacterial espionage.