Benzotriazole-Mediated Synthesis and Antibacterial Activity of Novel N-Acylcephalexins

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.

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.

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.

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.

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.

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.

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.

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

Since the synthesis of prontosil the first prodrug shares their chemical moiety, sulfonamides exhibit diverse modes of actions to serve as antimicrobials, diuretics, antidiabetics, and other clinical applications. This inspiring chemical nucleus has promoted several research groups to investigate the synthesis of new members exploring new clinical applications. In this study, a novel series of 5(4H)-oxazolone-based-sulfonamides (OBS) 9a–k were synthesized, and their antibacterial and antifungal activities were evaluated against a wide range of Gram-positive and -negative bacteria and fungi. Most of the tested compounds exhibited promising antibacterial activity against both Gram-positive and -negative bacteria particularly OBS 9b and 9f. Meanwhile, compound 9h showed the most potent antifungal activity. Moreover, the OBS 9a, 9b, and 9f that inhibited the bacterial growth at the lowest concentrations were subjected to further evaluation for their anti-virulence activities against Pseudomonas aeruginosa and Staphylococcus aureus. Interestingly, the three tested compounds reduced the biofilm formation and diminished the production of virulence factors in both P. aeruginosa and S. aureus. Bacteria use a signaling system, quorum sensing (QS), to regulate their virulence. In this context, in silico study has been conducted to assess the ability of OBS to compete with the QS receptors. The tested OBS showed marked ability to bind and hinder QS receptors, indicating that anti-virulence activities of OBS could be due to blocking QS, the system that controls the bacterial virulence. Furthermore, anticancer activity has been further performed for such derivatives. The OBS compounds showed variable anti-tumor activities, specifically 9a, 9b, 9f and 9k, against different cancer lines. Conclusively, the OBS compounds can serve as antimicrobials, anti-virulence and anti-tumor agents.