Diclofenac mitigates virulence of multidrug-resistant Staphylococcus aureus

Potential antivirulence and antibiofilm activities of sub-MIC of oxacillin against MDR S. aureus isolates: an in-vitro and in-vivo study

BACKGROUND

Multi-drug resistant Staphylococcus aureus is one of the most common causes of nosocomial and community-acquired infections, with high morbidity and mortality. Treatment of such infections is particularly problematic; hence, it is complicated by antibiotic resistance, and there is currently no reliable vaccine. Furthermore, it is well known that S. aureus produces an exceptionally large number of virulence factors that worsen infection. Consequently, the urgent need for anti-virulent agents that inhibit biofilm formation and virulence factors has gained momentum. Therefore, we focused our attention on an already-approved antibiotic and explored whether changing the dosage would still result in the intended anti-virulence effect.

METHODS

In the present study, we determined the antibiotic resistance patterns and the MICs of oxacillin against 70 MDR S. aureus isolates. We also investigated the effect of sub-MICs of oxacillin (at 1/4 and 1/8 MICs) on biofilm formation using the crystal violet assay, the phenol-sulphuric acid method, and confocal laser scanning microscopy (CLSM). We examined the effect of sub-MICs on virulence factors and bacterial morphology using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and electron microscopy, respectively. Moreover, we studied the effect of sub-MICs of oxacillin (OX) in-vivo using a wound infection model.

RESULTS

Oxacillin at 1/2 MIC showed a significant decrease in bacterial viability, while 1/4 and 1/8 MICs had negligible effects on treated bacterial isolates. Treatment of MDR isolates with 1/4 or 1/8 MICs of oxacillin significantly reduced biofilm formation (64% and 40%, respectively). The treated MDR S. aureus with sub-MICs of OX exhibited a dramatic reduction in several virulence factors, including protease, hemolysin, coagulase, and toxic shock syndrome toxin-1 (TSST-1) production. The sub-MICs of OX significantly decreased (P < 0.05) the gene expression of biofilm and virulence-associated genes such as agrA, icaA, coa, and tst. Furthermore, oxacillin at sub-MICs dramatically accelerated wound healing, according to the recorded scoring of histological parameters.

CONCLUSION

The treatment of MDR S. aureus with sub-MICs of oxacillin can help in combating the bacterial resistance and may be considered a promising approach to attenuating the severity of S. aureus infections due to the unique anti-biofilm and anti-virulence activities.

Miconazole and phenothiazine hinder the quorum sensing regulated virulence in Pseudomonas aeruginosa

Antibiotic resistance is a major health problem worldwide. Pseudomonas aeruginosa is a Gram-negative pathogen with an arsenal of virulence factors and elevated antimicrobial resistance. It is a leading cause of nosocomial infections with high morbidity and mortality. The significant time and effort required to develop new antibiotics can be circumvented using alternative therapeutic strategies, including anti-virulence targets. This study aimed to investigate the anti-virulence activity of the FDA-approved drugs miconazole and phenothiazine against P. aeruginosa. The phenotypic effect of sub-inhibitory concentrations of miconazole and phenothiazine on biofilm, pyocyanin, protease, rhamnolipid and hemolysin activities in PAO1 strain was examined. qRT-PCR was used to assess the effect of drugs on quorum-sensing genes that regulate virulence. Further, the anti-virulence potential of miconazole and phenothiazine was evaluated in silico and in vivo. Miconazole showed significant inhibition of Pseudomonas virulence by reducing biofilm-formation approximately 45-48%, hemolytic-activity by 59%, pyocyanin-production by 47-49%, rhamnolipid-activity by approximately 42-47% and protease activity by 36-40%. While, phenothiazine showed lower anti-virulence activity, it inhibited biofilm (31-35%), pyocyanin (37-39%), protease (32-40%), rhamnolipid (35-40%) and hemolytic activity (47-56%). Similarly, there was significantly reduced expression of RhlR, PqsR, LasI and LasR following treatment with miconazole, but less so with phenothiazine. In-silico analysis revealed that miconazole had higher binding affinity than phenothiazine to LasR, RhlR, and PqsR QS-proteins. Furthermore, there was 100% survival in mice injected with PAO1 treated with miconazole. In conclusion, miconazole and phenothiazine are promising anti-virulence agents for P. aeruginosa.

Potential Surviving Effect of Cleome droserifolia Extract against Systemic Staphylococcus aureus Infection: Investigation of the Chemical Content of the Plant

The increasing rates of morbidity and mortality owing to bacterial infections, particularly Staphylococcus aureus have necessitated finding solutions to face this issue. Thus, we elucidated the phytochemical constituents and antibacterial potential of Cleome droserifolia extract (CDE). Using LC-ESI-MS/MS, the main phytoconstituents of CDE were explored, which were kaempferol-3,7-O-bis-alpha-L-rhamnoside, isorhamnetin, cyanidin-3-glucoside, kaempferide, kaempferol-3-O-alpha-L-rhamnoside, caffeic acid, isoquercitrin, quinic acid, isocitrate, mannitol, apigenin, acacetin, and naringenin. The CDE exerted an antibacterial action on S. aureus isolates with minimum inhibitory concentrations ranging from 128 to 512 µg/mL. Also, CDE exhibited antibiofilm action using a crystal violet assay. A scanning electron microscope was employed to illuminate the effect of CDE on biofilm formation, and it considerably diminished S. aureus cell number in the biofilm. Moreover, qRT-PCR was performed to study the effect of CDE on biofilm gene expression (cna, fnbA, and icaA). The CDE revealed a downregulating effect on the studied biofilm genes in 43.48% of S. aureus isolates. Regarding the in vivo model, CDE significantly decreased the S. aureus burden in the liver and spleen of CDE-treated mice. Also, it significantly improved the mice's survival and substantially decreased the inflammatory markers (interleukin one beta and interleukin six) in the studied tissues. Furthermore, CDE has improved the histology and tumor necrosis factor alpha immunohistochemistry in the liver and spleen of the CDE-treated group. Thus, CDE could be considered a promising candidate for future antimicrobial drug discovery studies.

Alleviating the virulence of Pseudomonas aeruginosa and Staphylococcus aureus by ascorbic acid nanoemulsion

The high incidence of persistent multidrug resistant bacterial infections is a worldwide public health burden. Alternative strategies are required to deal with such issue including the use of drugs with anti-virulence activity. The application of nanotechnology to develop advanced Nano-materials that target quorum sensing regulated virulence factors is an attractive approach. Synthesis of ascorbic acid Nano-emulsion (ASC-NEs) and assessment of its activity in vitro against the virulence factors and its protective ability against pathogenesis as well as the effect against expression of quorum sensing genes of Pseudomonas aeruginosa and Staphylococcus aureus isolates. Ascorbic acid Nano-emulsion was characterized by DLS Zetasizer Technique, Zeta potential; Transmission Electron Microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). The antibacterial activity of ASC-NEs was tested by the broth microdilution method and the activity of their sub-MIC against the expression of quorum sensing controlled virulence was investigated using phenotypic experiments and RT-PCR. The protective activity of ASC-NEs against P. aeruginosa as well as S. aureus pathogenesis was tested in vivo. Phenotypically, ASC-NEs had strong virulence inhibitory activity against the tested bacteria. The RT-PCR experiment showed that it exhibited significant QS inhibitory activity. The in vivo results showed that ASC-NEs protected against staphylococcal infection, however, it failed to protect mice against Pseudomonal infection. These results suggest the promising use of nanoformulations against virulence factors in multidrug resistant P. aeruginosa and S. aureus. However, further studies are required concerning the potential toxicity, clearance and phamacokinetics of the nanoformulations.

Recent advances in the discovery of plant-derived antimicrobial natural products to combat antimicrobial resistant pathogens: insights from 2018-2022

Covering: 2018 to 2022Antimicrobial resistance (AMR) poses a significant global health threat. There is a rising demand for innovative drug scaffolds and new targets to combat multidrug-resistant bacteria. Before the advent of antibiotics, infections were treated with plants chosen from traditional medicine practices. Of Earth's 374 000 plant species, approximately 9% have been used medicinally, but most species remain to be investigated. This review illuminates discoveries of antimicrobial natural products from plants covering 2018 to 2022. It highlights plant-derived natural products with antibacterial, antivirulence, and antibiofilm activity documented in lab studies. Additionally, this review examines the development of novel derivatives from well-studied parent natural products, as natural product derivatives have often served as scaffolds for anti-infective agents.

Diclofenac and Meloxicam Exhibited Anti-Virulence Activities Targeting Staphyloxanthin Production in Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a worldwide leading versatile pathogen that causes a wide range of serious infections. The emergence of antimicrobial resistance against S. aureus resulted in an urgent need to develop new antimicrobials in the new era. The methicillin-resistant S. aureus (MRSA) prevalence in hospital and community settings necessitates the discovery of novel anti-pathogenic agents. Staphyloxanthin (STX) is a key virulence factor for the survival of MRSA against host innate immunity. The current work aimed to demonstrate the anti-virulence properties of meloxicam (MXM) as compared to diclofenac (DC), which was previously reported to mitigate the virulence of multidrug-resistant Staphylococcus aureus and test their activities in STX production. A total of 80 S. aureus clinical isolates were included, wherein a qualitative and quantitative assessment of STX inhibition by diclofenac and meloxicam was performed. The quantitative gene expression of STX biosynthetic genes (crtM, crtN and sigB) and hla (coded for α-hemolysin) as a virulence gene with and without DC and MXM was conducted, followed by molecular docking analysis for further confirmation. DC and MXM potently inhibited the synthesis of STX at 47 and 59 µg/mL to reach 79.3-98% and 80.6-96.7% inhibition, respectively. Treated cells also revealed a significant downregulation of virulence genes responsible for STX synthesis, such as crtM, crtN and global transcriptional regulator sigB along with the hla gene. Furthermore, computational studies unveiled strong interactions between the CrtM binding site and DC/MXM. In conclusion, this study highlights the potential role and repurposing of DC and MXM as adjuvants to conventional antimicrobials and as an anti-virulent to combat MRSA infections.

Antimicrobial potential of new diclofenac hydrogels for disinfection in regenerative endodontics: An in vitro and ex vivo study

AIM

There is a need to explore new alternatives for root canal disinfection in regenerative endodontics, since the current strategies are far from ideal. Currently, the potential use of diclofenac (DC) is being investigated for controlling root canal infections. The objective was to evaluate the antimicrobial efficacy of novel DC-based hydrogels (DCHs) against polymicrobial biofilms grown in radicular dentine and root canals and to compare results with triantibiotic (TAH) and diantibiotic (DAH) hydrogels, and calcium hydroxide (Ca[OH]₂ ).

METHODOLOGY

The in vitro antimicrobial activity of intracanal medicaments was evaluated against 3-week-old polymicrobial root canal biofilms grown on human radicular dentine. Dentine samples were obtained and randomly divided into the study groups (n = 4/group): (1) 1 mg/ml TAH; (2) 1 mg/ml DAH; (3) 5% diclofenac (DCH); (4) 2.5% DCH; (5) 1.25% DCH; (6) 1 mg/ml DAH + 5% DCH; (7) Ca(OH)₂ paste; (8) positive control. The microbial viability, in terms of percentage of intact cell membranes, was assessed after 7 days by confocal scanning laser microscopy (CSLM). The ex vivo efficacy of intracanal medications was evaluated in root canals infected with a polymicrobial suspension. Intracanal microbiological samples at baseline (S1) and 7 days post-treatment (S2) were taken; microbial quantification and cell viability were assessed by quantitative polymerase chain reaction (qPCR) and flow cytometry (FC). The mean Log₁₀ of bacterial DNA copies in root canal samples before (S1) and the Log₁₀ reduction of DNA copies S1-S2 in qPCR were recorded. The absolute value of total cells stained, and the percentage reduction of intact membrane cells after treatment (S1-S2), were analysed by FC. Global comparison was done using the Kruskal-Wallis test, whilst the Mann-Whitney U test was used for pair-by-pair comparison.

RESULTS

Confocal scanning laser microscopy analysis indicated that the greatest effectiveness was obtained with 5% DCH, showing significant differences with respect to the other groups (p < .001). In root canals, the highest Log₁₀ DNA reduction S1-S2 was obtained with 5% DCH and TAH, with no differences between them. The results of FC showed that only 5% DCH proved significantly superior to the other treatments.

CONCLUSIONS

Sodium DC hydrogels demonstrate antimicrobial efficacy against endodontic biofilms.

Antimicrobial and Antibiofilm Effects of Combinatorial Treatment Formulations of Anti-Inflammatory Drugs-Common Antibiotics against Pathogenic Bacteria

With the spread of multi-drug-resistant (MDR) bacteria and the lack of effective antibiotics to treat them, developing new therapeutic methods and strategies is essential. In this study, we evaluated the antibacterial and antibiofilm activity of different formulations composed of ibuprofen (IBP), acetylsalicylic acid (ASA), and dexamethasone sodium phosphate (DXP) in combination with ciprofloxacin (CIP), gentamicin (GEN), cefepime (FEP), imipenem (IPM), and meropenem (MEM) on clinical isolates of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) as well as the transcription levels of biofilm-associated genes in the presence of sub-MICs of IBP, ASA, and DXP. The minimal inhibitory concentrations (MICs), minimal biofilm inhibitory concentrations (MBICs), and minimum biofilm eradication concentrations (MBECs) of CIP, GEN, FEP, IPM, and MEM with/without sub-MICs of IBP (200 µg/mL), ASA (200 µg/mL), and DXP (500 µg/mL) for the clinical isolates were determined by the microbroth dilution method. Quantitative real-time-PCR (qPCR) was used to determine the expression levels of biofilm-related genes, including icaA in S. aureus and algD in P. aeruginosa at sub-MICs of IBP, ASA, and DXP. All S. aureus isolates were methicillin-resistant S. aureus (MRSA), and all P. aeruginosa were resistant to carbapenems. IBP decreased the levels of MIC, MBIC, and MBEC for all antibiotic agents in both clinical isolates, except for FEP among P. aeruginosa isolates. In MRSA isolates, ASA decreased the MICs of GEN, FEP, and IPM and the MBICs of IPM and MEM. In P. aeruginosa, ASA decreased the MICs of FEP, IPM, and MEM, the MBICs of FEP and MEM, and the MBEC of FEP. DXP increased the MICs of CIP, GEN, and FEP, and the MBICs of CIP, GEN, and FEP among both clinical isolates. The MBECs of CIP and FEP for MRSA isolates and the MBECs of CIP, GEN, and MEM among P. aeruginosa isolates increased in the presence of DXP. IBP and ASA at 200 µg/mL significantly decreased the transcription level of algD in P. aeruginosa, and IBP significantly decreased the transcription level of icaA in S. aureus. DXP at 500 µg/mL significantly increased the expression levels of algD and icaA genes in S. aureus and P. aeruginosa isolates, respectively. Our findings showed that the formulations containing ASA and IBP have significant effects on decreasing the MIC, MBIC, and MBEC levels of some antibiotics and can down-regulate the expression of biofilm-related genes such as icaA and algD. Therefore, NSAIDs represent appropriate candidates for the design of new antibacterial and antibiofilm therapeutic formulations.

Attenuating the virulence of the resistant superbug Staphylococcus aureus bacteria isolated from neonatal sepsis by ascorbic acid, dexamethasone, and sodium bicarbonate

Background

Infections affecting neonates caused by Staphylococcus aureus are widespread in healthcare facilities; hence, novel strategies are needed to fight this pathogen. In this study, we aimed to investigate the effectiveness of the FDA-approved medications ascorbic acid, dexamethasone, and sodium bicarbonate to reduce the virulence of the resistant Staphylococcus aureus bacteria that causes neonatal sepsis and seek out suitable alternatives to the problem of multi-drug resistance.

Methods

Tested drugs were assessed phenotypically and genotypically for their effects on virulence factors and virulence-encoding genes in Staphylococcus aureus. Furthermore, drugs were tested in vivo for their ability to reduce Staphylococcus aureus pathogenesis.

Results

Sub-inhibitory concentrations (1/8 MIC) of ascorbic acid, dexamethasone, and sodium bicarbonate reduced the production of Staphylococcus aureus virulence factors, including biofilm formation, staphyloxanthin, proteases, and hemolysin production, as well as resistance to oxidative stress. At the molecular level, qRT-PCR was used to assess the relative expression levels of crtM, sigB, sarA, agrA, hla, fnbA, and icaA genes regulating virulence factors production and showed a significant reduction in the relative expression levels of all the tested genes.

Conclusions

The current findings reveal that ascorbic acid, dexamethasone, and sodium bicarbonate have strong anti-virulence effects against Staphylococcus aureus. Thus, suggesting that they might be used as adjuvants to treat infections caused by Staphylococcus aureus in combination with conventional antimicrobials or as alternative therapies.

Drug repurposing strategy: An emerging approach to identify potential therapeutics for treatment of bovine mastitis

The current study was designed to characterize methicillin-resistant Staphylococcus aureus (MRSA) isolated from bovine milk, along with its response to antibiotics, and ultimately reverse its mechanism of resistance by modulation with non-antibiotics. The synergistic combination of antibiotics with NSAIDs were tested in-vivo by giving MRSA challenge to rabbits. The current study reported an overall 23.79% prevalence of MRSA. The BLAST alignment of current study sequences revealed 99% similarity with mecA gene of MRSA from NCBI database. The current study isolates were more similar to each other and also with reference sequences as compared to other mecA gene sequences from Turkey, India, and Russia. Antibiogram of MRSA isolates showed a highly resistant response to cefoxitin, amoxicillin, and gentamicin. Amoxicillin, gentamicin, tylosin, vancomycin, and ciprofloxacin elicited a significant response (p < 0.05) in combination with non-antibiotics against tested MRSA isolates. The highest zone of inhibition (ZOI) increase was noted for vancomycin in combination with flunixin meglumine (145.45%) and meloxicam (139.36%); gentamicin with flunixin meglumine (85.71%) and ciprofloxacin with ivermectin (71.13%). Synergistic behavior was observed in the combination of gentamicin with ketoprofen; sulfamethoxazole and oxytetracycline with meloxicam. Hematological analysis showed significant differences (p < 0.05) among lymphocyte count and bilirubin. On histopathological examination of skin tissue, hyperplasia of epithelium, sloughed off epidermis, hyperkeratosis, infiltration of inflammatory cells, and hemorrhages were observed. The highest cure rate was observed in case of gentamicin in combination with ketoprofen as compared to other treatment groups. The current study concluded antibiotics in combination with non-antibiotics as potential therapeutic agents for resistance modulation against MRSA. This study will help to devise treatment and control strategies against bovine mastitis. Although the prospect of using NSAIDs to manage infections caused by MRSA appears to be a promising direction, further studies should be conducted to test these medications using suitable in-vivo models in controlled clinical trials to justify their repurposing as a treatment for MRSA infections.

Promising FDA-approved drugs with efflux pump inhibitory activities against clinical isolates of Staphylococcus aureus

Background and objectives

Staphylococcus aureus is an opportunistic pathogen that causes wide range of nosocomial and community-acquired infections which have spread worldwide leading to an urgent need for developing effective anti-staphylococcal agents. Efflux is an important resistance mechanism that bacteria used to fight the antimicrobial action. This study aimed to investigate the efflux mechanism in S. aureus and assess diclofenac, domperidone, glyceryl trinitrate and metformin as potential efflux pump inhibitors that can be used in combination with antibiotics for treating topical infections caused by S. aureus.

Materials and methods

Efflux was detected qualitatively by the ethidium bromide Cart-Wheel method followed by investigating the presence of efflux genes by polymerase chain reaction. Twenty-six isolates were selected for further investigation of efflux by Cart-Wheel method in absence and presence of tested compounds followed by quantitative efflux assay. Furthermore, antibiotics minimum inhibitory concentrations in absence and presence of tested compounds were determined. The effects of tested drugs on expression levels of efflux genes norA, fexA and tetK were determined by quantitative real time-polymerase chain reaction.

Results

Efflux was found in 65.3% of isolates, the prevalence of norA, tetK, fexA and msrA genes were 91.7%, 77.8%, 27.8% and 6.9%. Efflux assay revealed that tested drugs had potential efflux inhibitory activities, reduced the antibiotic’s MICs and significantly decreased the relative expression of efflux genes.

Conclusion

Diclofenac sodium, domperidone and glyceryl trinitrate showed higher efflux inhibitory activities than verapamil and metformin. To our knowledge, this is the first report that shows that diclofenac sodium, glyceryl trinitrate and domperidone have efflux pump inhibitory activities against S. aureus.

Synergistic Antibacterial Activity with Conventional Antibiotics and Mechanism of Action of Shikonin against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a troublesome pathogen that poses a global threat to public health. Shikonin (SKN) isolated from Lithospermum erythrorhizon (L. erythrorhizon) possesses a variety of biological activities. This study aims to explore the effect of the combined application of SKN and traditional antibiotics on the vitality of MRSA and the inherent antibacterial mechanism of SKN. The synergies between SKN and antibiotics against MRSA and its clinical strain have been demonstrated by the checkerboard assay and the time-kill assay. The effect of SKN on disrupting the integrity and permeability of bacterial cell membranes was verified by a nucleotide and protein leakage assay and a bacteriolysis assay. As determined by crystal violet staining, SKN inhibited the biofilm formation of clinical MRSA strains. The results of Western blot and qRT-PCR showed that SKN could inhibit the expression of proteins and genes related to drug resistance and S. aureus exotoxins. SKN inhibited the ability of RAW264.7 cells to release the pro-inflammatory cytokines TNF-α and IL-6, as measured by ELISA. Our findings suggest that SKN has the potential to be developed as a promising alternative for the treatment of MRSA infections.

Quorum sensing inhibitory potential of vaccenic acid against Chromobacterium violaceum and methicillin-resistant Staphylococcus aureus

Quorum sensing (QS) is a potential target for inhibiting bacterial antibiotic resistance and associated pathogenicity. The present study aimed to investigate vaccenic acid anti-QS and antibiofilm potential against Chromobacterium violaceum and methicillin-resistant Staphylococcus aureus (MRSA). In the broth microdilution method, we determined the minimum inhibitory concentration (MIC) of vaccenic acid against C. violaceum and MRSA. Then, we determined the vaccenic acid anti-QS potential against C. violaceum via a violacein inhibition assay. Vaccenic acid at a sub-MIC concentration significantly inhibited violacein pigment production. Vaccenic acid also inhibits C. violaceum and MRSA biofilm formation at sub-MIC concentrations. The effect of vaccenic acid antivirulence potential was evaluated by phenotypic virulence assays. The results showed that vaccenic acid at a sub-MIC concentration significantly inhibited the virulence production of C. violaceum (chitinase and motility) and MRSA (hemolysin and staphyloxanthin production). Quantitative PCR analysis revealed the downregulation of QS associated genes upon vaccenic acid treatment. This resulted in the downregulation of genes involved in QS mechanisms such as cviI, cviR, and SarA and pigment production such as vioB and crtM. The results of the present study suggest that vaccenic acid is a promising agent to combat C. violaceum and MRSA.

Evaluation of the effect of ibuprofen in combination with ciprofloxacin on the virulence-associated traits, and efflux pump genes of Pseudomonas aeruginosa

Biofilm formation and antibiotic efflux are two determinant factors in the development of drug resistance phenotype by Pseudomonas aeruginosa. Non-steroid anti-inflammatory drugs have shown the antimicrobial potential to be used in combination with antibiotics against bacterial pathogens. In this work, the effect of ibuprofen alone and in combination with ciprofloxacin on some virulence traits and the expression of the alginate synthesis and efflux pump genes of clinical isolates of P. aeruginosa was investigated. The checkerboard titration assay was used to evaluate the synergism of the drugs. P. aeruginosa strains were grown in the presence of sub-inhibitory concentrations of the drug and their biofilm formation level, swarming, swimming, and hemolytic activity were assessed. Also, the relative expression of the alg44, algT/U, mexB, and oprM genes was determined by qPCR assay. The MIC of ibuprofen and ciprofloxacin were measured 2048 and 32 µg/mL and the drugs showed synergic antibacterial activity (FIC = 0.4). Moreover, ibuprofen alone and in combination with ciprofloxacin, significantly reduced the expression of alg44 (0.22 and 0.25 folds) and algT/U (0.26 and 0.37 folds) genes, while increased the expression of the mexB (1.64 and 1.83 folds) and oprM (1.36 and 1.92 folds) genes. Simultaneous treatment of bacterial cells with ibuprofen and ciprofloxacin significantly decreased bacterial biofilm formation (65%), swimming, swarming, and hemolytic activity (85%), compared with the control. This work suggests that ibuprofen has considerable anti-virulence potential against P. aeruginosa and could be employed for combination therapy with antibiotics after further characterizations.

Two Novel Phenylpropanoid Trimers From Ligusticum chuanxiong Hort With Inhibitory Activities on Alpha-Hemolysin Secreted by Staphylococcus aureus

The emergence of antibiotic resistance in Staphylococcus aureus has necessitated the development of innovative anti-infective agents acting on novel targets. Alpha-hemolysin (Hla), a key virulence factor of S. aureus, is known to cause various cell damage and death. In this study, with bioassay-guided fractionation, a pair of unusual epimeric lignan trimers, ligustchuanes A and B (1 and 2), were isolated from the rhizomes of Ligusticum chuanxiong Hort, together with two known phthalides being identified by UPLC-QTOF-MS. To the best of our knowledge, trimers with rare C8-C9″-type neolignan and ferulic acid fragments have not been identified in any natural product. Both of them were isolated as racemic mixtures, and their absolute configurations were determined by comparing experimental and calculated ECD spectra after enantioseparation. Ligustchuane B exhibited an outstanding inhibitory effect on α-hemolysin expression in both MRSA USA300 LAC and MSSA Newman strains at concentrations of 3 and 6 μM, respectively. Notably, a mouse model of infection further demonstrated that ligustchuane B could attenuate MRSA virulence in vivo.

Staphyloxanthin as a Potential Novel Target for Deciphering Promising Anti-Staphylococcus aureus Agents

Staphylococcus aureus is a fatal Gram-positive pathogen threatening numerous cases of hospital-admitted patients worldwide. The emerging resistance of the pathogen to several antimicrobial agents has pressurized research to propose new strategies for combating antimicrobial resistance. Novel strategies include targeting the virulence factors of S. aureus. One of the most prominent virulence factors of S. aureus is its eponymous antioxidant pigment staphyloxanthin (STX), which is an auspicious target for anti-virulence therapy. This review provides an updated outline on STX and multiple strategies to attenuate this virulence factor. The approaches discussed in this article focus on bioprospective and chemically synthesized inhibitors of STX, inter-species communication and genetic manipulation. Various inhibitor molecules were found to exhibit appreciable inhibitory effect against STX and hence would be able to serve as potential anti-virulence agents for clinical use.

The promising anti-virulence activity of candesartan, domperidone, and miconazole on Staphylococcus aureus

Staphylococcus aureus is a primary cause of hospital and community-acquired infections. With the emergence of multidrug-resistant S. aureus strains, there is a need for new drugs discovery. Due to the poor supply of new antimicrobials, targeting virulence of S. aureus may generate weaker selection for resistant strains, anti-virulence agents disarm the pathogen instead of killing it. In this study, the ability of the FDA-approved drugs domperidone, candesartan, and miconazole as inhibitors of S. aureus virulence was investigated. The effect of tested drugs was evaluated against biofilm formation, lipase, protease, hemolysin, and staphyloxanthin production by using phenotypic and genotypic methods. At sub-inhibitory concentrations, candesartan, domperidone, and miconazole showed a significant inhibition of hemolysin (75.8-96%), staphyloxanthin (81.2-85%), lipase (50-65%), protease (40-64%), and biofilm formation (71.4-90%). Domperidone and candesartan have similar activity and were more powerful than miconazole against S. aureus virulence. The hemolysins and lipase inhibition were the greatest under the domperidone effect. Candesartan showed a remarkable reduction in staphyloxanthin production. The highest inhibitory effect of proteolytic activity was obtained with domperidone and candesartan. Biofilm was significantly reduced by miconazole. Expression levels of crtM, sigB, sarA, agrA, hla, fnbA, and icaA genes were significantly reduced under candesartan (68.98-82.7%), domperidone (62.6-77.2%), and miconazole (32.96-52.6%) at sub-MIC concentrations. Candesartan showed the highest inhibition activity against crtM, sigB, sarA, agrA, hla, and icaA expression followed by domperidone then miconazole. Domperidone showed the highest downregulation activity against fnbA gene. In conclusion, candesartan, domperidone, and miconazole could serve as anti-virulence agents for attenuation of S. aureus pathogenicity.

Impeding Virulence of Candida albicans by Candesartan and Domperidone

Candida albicans is the most common human fungal pathogen that has developed extensive virulence factors which allows successful colonization and infection of the host. Anti-virulence agents can alleviate the pathogenesis of fungi and help the immune system to eradicate them easily. This study aimed to explore the anti-virulence effect of domperidone and candesartan against C. albicans standard strain. Sub-inhibitory concentrations (1/4 and 1/8 of minimum inhibitory concentration) of domperidone and candesartan significantly inhibited the virulence factors hemolysin, lipase, protease, phospholipase, and bioflim formation. It was found that candesartan inhibited biofilm formation by 60.48-67.91%, hemolysin activity (61.21-74.14%), phospholipase activity (40-49.67%), lipase activity (58.97-73%), and protease activity (52.63%), while domperidone was found to inhibit biofilm formation by 70.54-77.49%, hemolysin activity (64.84-69.84%), phospholipase activity (49.67-60%), lipase activity (50-54.87%), and protease activity (52.63-57.9%). Quantitative real time-PCR confirmed the anti-virulence activity of domperidone and candesartan as both drugs significantly reduce the expression of the virulence genes SAP2, SAP6, PLB1, PLB2, LIP4, LIP5. In conclusion, domperidone and candesartan could serve as anti-virulence agents for treatment of C. albicans infections.

Antimicrobial Activity of Non-steroidal Anti-inflammatory Drugs on Biofilm: Current Evidence and Potential for Drug Repurposing

It has been demonstrated that some non-steroidal anti-inflammatory drugs (NSAIDs), like acetylsalicylic acid, diclofenac, and ibuprofen, have anti-biofilm activity in concentrations found in human pharmacokinetic studies, which could fuel an interest in repurposing these well tolerated drugs as adjunctive therapies for biofilm-related infections. Here we sought to review the currently available data on the anti-biofilm activity of NSAIDs and its relevance in a clinical context. We performed a systematic literature review to identify the most commonly tested NSAIDs drugs in the last 5 years, the bacterial species that have demonstrated to be responsive to their actions, and the emergence of resistance to these molecules. We found that most studies investigating NSAIDs' activity against biofilms were in vitro, and frequently tested non-clinical bacterial isolates, which may not adequately represent the bacterial populations that cause clinically-relevant biofilm-related infections. Furthermore, studies concerning NSAIDs and antibiotic resistance are scarce, with divergent outcomes. Although the potential to use NSAIDs to control biofilm-related infections seems to be an exciting avenue, there is a paucity of studies that tested these drugs using appropriate in vivo models of biofilm infections or in controlled human clinical trials to support their repurposing as anti-biofilm agents.

Could the analgesic drugs, paracetamol and indomethacin, function as quorum sensing inhibitors?

The current failure of antimicrobials in treating life-threatening diseases, the high rate of multidrug resistant pathogens and the slow progress in the development of new antibiotics directed scientists to develop antivirulence drugs that targets quorum sensing (QS). In many microbes, QS acts as a communication system which control pathogenicity of microbes. Analgesics can be beneficial in controlling virulence traits of microbes and hence they may augment the efficacy of antimicrobials. In this study, two analgesics were screened for the inhibition of QS in Chromobacterium violaceum CV026 and their effects on virulence production in Pseudomonas aeruginosa PAO1 strain and clinical isolates of Acinetobacter baumannii were evaluated. The traits investigated were biofilm formation, pyocyanin and rhamnolipid production, twitching, swarming or surface associated motilities, production of protease, phospholipase and gelatinase enzymes and sensitivity to oxidative stress. Relative expression of abaI gene was calculated by performing qRT-PCR. Docking analysis of paracetamol as QSI (quorum sensing inhibitor) of AbaI and AbaR proteins was performed. Paracetamol inhibited QS in CV026, but indomethacin devoids anti-QS activity. Paracetamol inhibited virulence factors of PAO1. It strongly inhibited biofilm formation, and swarming by 66.4% and 57.1%, respectively. While, it moderately to slightly inhibited rhamnolipid, pyocyanin, gelatinase, resistance to oxidative stress, protease and twitching motility by 33.3%, 33.1% 17.5%, 9.1%, 8.7% and 7.7%, respectively. For A. baumannii, paracetamol strongly inhibited biofilm by 39.7-93% and phospholipase enzyme by 8.7-100%, reduced twitching and surface motility by 6.7-82.5% and 7.7-29.4%, respectively, And slightly reduced sensitivity to oxidative stress by 3.3-36.4%. Paracetamol at sub-MIC suppressed the expression of abaI gene by 32% in A. baumannii. Docking studies suggested that paracetamol can bind to AbaR and AbaI proteins and bind more to AbaR, hence it may act by inhibiting AHL signal reception. As a conclusion, paracetamol, beside its analgesic activity, has anti-QS activity and could be used in the eradication of P. aeruginosa and A. baumannii infections in combination with antibiotics.