Combination of kaempferol and azithromycin attenuates Staphylococcus aureus-induced osteomyelitis via anti-biofilm effects and by inhibiting the phosphorylation of ERK1/2 and SAPK

Gallic acid synergistically enhances the antibacterial activity of azithromycin in MRSA

The rise of antibiotic resistance in existing pathogens has been identified as a major threat to global healthcare in the twenty-first century. This resistance has consequences such as increased cost and prolonged hospital stays, treatment failure, and ultimately increased risk of patient mortality. It is therefore imperative to develop strategies to combat drug resistance. Combined treatment of common antibiotics and natural compounds is one of the most effective methods against resistant bacterial infections. Gallic acid (GA) is a natural secondary metabolite abundantly found in plants and has significant medicinal effects in various aspects of health. In this research, the antibacterial effects of azithromycin (AZM) and GA alone and in combination with each other were investigated on planktonic and biofilm forms of methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa (P. aeruginosa). The results showed that the combination of AZM/GA had an additive effect against MSSA and P. aeruginosa and a synergistic effect against MRSA. In addition, combining these two agents significantly reduced the minimum biofilm inhibitory concentration (MBIC) of AZM and GA in the MRSA strain. Finally, the level of ROS generation in the effect of AZM plus GA was evaluated in the bacteria. Among the studied strains, ROS production was significantly increased in combination treatment compared to AZM alone in MRSA. The results show that the combination of AZM and GA has a significant effect against MRSA and can be considered as an effective treatment option.

Study of the effect of azithromycin on airway remodeling in asthma via the SAPK/JNK pathway

OBJECTIVE

Asthma is a prevalent status attributing to lower respiratory tract chronic inflammation. Azithromycin (AZM) is known to be effective against asthma. Thus, this study delved into the mechanism of AZM repressing airway remodeling (AR) via the SAPK/JNK pathway in asthma.

METHODS

Simulated asthmatic AR mouse model was developed by induction with ovalbumin (OVA) and intervened with AZM or dexamethasone (DEX) and anisomycin (JNK activator). Pathological changes in mouse lung tissues and AR were assessed by HE and Masson staining. The numbers of inflammatory cells, macrophages, eosinophils, neutrophils and lymphocytes in bronchoalveolar lavage fluid (BALF) were detected by Diff-Quik staining. Inflammatory factor levels (IL-6, TNF-α, IL-4) in BALF, and Collagen I, Collagen III, SAPK/JNK and p-SAPK/JNK protein levels in lung tissues were measured by ELISA and Western blot.

RESULTS

The OVA-led asthmatic mouse model was successfully established. Relative to the OVA group, AZM and DEX treatment improved pulmonary smooth muscle thickening and bronchial epithelial fibrosis, reduced inflammatory cells, macrophages, eosinophils, neutrophils and lymphocytes in BALF, inhibited inflammatory factor TNF-α, IL-6, and IL-4 levels in BALF, and down-regulated Collagen I, Collagen III, and p-SAPK/JNK protein levels in lung tissues, with no prominent difference between the two regimens. JNK activator partially reversed the protective effect of AZM against OVA-induced asthma in mice.

CONCLUSION

AZM alleviated airway inflammation by inhibiting the SAPK/JNK pathway, thereby repressing AR in asthmatic mice. This study provided partial theoretical basis for clarifying asthma pathogenesis and new ideas for treating asthma.

Silk fibroin/chitosan thiourea hydrogel scaffold with vancomycin and quercetin-loaded PLGA nanoparticles for treating chronic MRSA osteomyelitis in rats

Chronic osteomyelitis presents significant treatment challenges, necessitating an efficient system for infection elimination and bone repair. This study developed a natural hydrogel scaffold using silk fibroin (SF) and chitosan thiourea (CST), incorporating vancomycin (VC) and quercetin (QC) loaded PLGA nanoparticles (NPs) for dual-purpose treatment. SF/CST hydrogel scaffolds exhibited homogeneous porosity and smaller interconnected pore size than pure SF and pure CST hydrogel scaffolds. Optimal PLGA/QC NPs measured 206 nm in size, displayed spherical morphology, had uniform distribution, and achieved 87 % QC loading. The release study showed sustained long-term release of VC and QC from the hydrogel scaffolds for over 20 days. Biocompatibility tests indicated that hydrogel scaffolds promoted osteoblast adhesion without cytotoxicity, with QC-containing scaffolds enhancing osteoblast growth. Antibacterial tests confirmed retained VC activity against methicillin-resistant Staphylococcus aureus (MRSA) in SF/CST. An experimental study assessed the efficacy of the hydrogel scaffolds in a MRSA-infected rat osteomyelitis model. Radiographic scores demonstrated a significant reduction for SF/CST-VC-PLGA/QC NPs compared to control, indicating reduced osteomyelitis effects. Macroscopic evaluations showed notable reductions in gross pathological effects for VC-containing groups. Histopathological assessments revealed significantly lower osteomyelitis scores and higher healing scores in the SF/CST-VC-PLGA/QC NPs, with reduced inflammatory cell infiltration and more organized connective tissue formation. In conclusion, SF/CST-VC-PLGA/QC NPs is an effective dual drug delivery system for osteomyelitis treatment, demonstrating significant antibacterial activity, enhanced bone regeneration, and reduced infection rate.

Pharmacological Potential of Kaempferol, a Flavonoid in the Management of Pathogenesis via Modulation of Inflammation and Other Biological Activities

Natural products and their bioactive compounds have been used for centuries to prevent and treat numerous diseases. Kaempferol, a flavonoid found in vegetables, fruits, and spices, is recognized for its various beneficial properties, including its antioxidant and anti-inflammatory potential. This molecule has been identified as a potential means of managing different pathogenesis due to its capability to manage various biological activities. Moreover, this compound has a wide range of health-promoting benefits, such as cardioprotective, neuroprotective, hepatoprotective, and anti-diabetic, and has a role in maintaining eye, skin, and respiratory system health. Furthermore, it can also inhibit tumor growth and modulate various cell-signaling pathways. In vivo and in vitro studies have demonstrated that this compound has been shown to increase efficacy when combined with other natural products or drugs. In addition, kaempferol-based nano-formulations are more effective than kaempferol treatment alone. This review aims to provide detailed information about the sources of this compound, its bioavailability, and its role in various pathogenesis. Although there is promising evidence for its ability to manage diseases, it is crucial to conduct further investigations to know its toxicity, safety aspects, and mechanism of action in health management.

Synthesis and study of antibiofilm and antivirulence properties of flavonol analogues generated by palladium catalyzed ligand free Suzuki-Miyaura coupling against Pseudomonas aeruginosa PAO1

The Suzuki-Miyaura coupling is one of the ubiquitous method for the carbon-carbon bond-forming reactions in organic chemistry. Its popularity is due to its ability to undergo extensive coupling reactions to generate a broad range of biaryl motifs in a straightforward manner displaying a high level of functional group tolerance. A convenient and efficient synthetic route to arylate different substituted flavonols through the Suzuki-Miyaura cross-coupling reaction has been explained in this study. The arylated products were acquired by the coupling of a variety of aryl boronic acids with flavonols under Pd(OAc)2 catalyzed reaction conditions in a ligand-free reaction strategy. Subsequently, the antibiofilm and antivirulence properties of the arylated flavonols against Pseudomonas aeruginosa PAO1 were studied thoroughly. The best ligands for quorum sensing proteins LasR, RhlR, and PqsR were identified using molecular docking study. These best fitting ligands were then studied for their impact on gene expression level of P. aeruginosa by RT-PCR towards quorum sensing genes lasB, rhlA, and pqsE. The downregulation in the gene expression with the effect of synthesized flavonols endorse the antibiofilm efficiency of the compounds.

Efflux Pump Inhibition-Based Screening and Anti-Infective Evaluation of Punica granatum Against Bacterial Pathogens

Drug efflux pumps contribute to bacterial multidrug resistance (MDR), reducing antibiotic effectiveness and causing treatment failures. Besides their role in MDR, efflux pumps also assist in the transportation of quorum sensing (QS) signal molecules and increased the tolerance of biofilms. Recently, the search for efflux pump inhibitors from natural sources, including anti-infective plants, has gained attention as a potential therapy against drug-resistant bacteria. In this study, 19 traditional Indian medicinal plants were screened for their efflux pump inhibitory activity against Escherichia coli TGI. The promising extract, i.e., Punica granatum was subsequently fractioned in the solvents of increasing polarity. Among them, at sub-MIC active EPI fraction was PGEF (P. granatum ethyl acetate fraction), further investigated for anti-infective potential against Chromobacterium violaceum 12,472, Pseudomonas aeruginosa PAO1, and Serratia marcescens MTCC 97. PGEF was also evaluated for in vivo efficacy in Caenorhabditis elegans model. Major phytocompounds were analyzed by mass spectroscopic techniques. At respective Sub-MIC, PGEF reduced violacein production by 71.14% in C. violaceum 12,472. Moreover, PGEF inhibited pyocyanin (64.72%), pyoverdine (48.17%), protease (51.35%), and swarming motility (44.82%) of P. aeruginosa PAO1. Furthermore, PGEF reduced the production of prodigiosin and exoprotease by 64.73% and 61.80%, respectively. Similarly, at sub-MIC, PGEF inhibited (≥ 50%) biofilm development in all test pathogens. The key phytocompounds detected in active fraction include 5-hydroxymethylfurfural, trans-p-coumaric acid 4- glucoside, (-)-Epicatechin 3'-O-glucuronide, and ellagic acid. Interestingly, PGEF also demonstrated anti-infective efficacy against the PAO1-infected C. elegans test model and highlighting its therapeutic potential as an anti-infective agent to combat drug-resistant problems.

Antimicrobial Susceptibility of Staphylococcus aureus Strains and Effect of Phloretin on Biofilm Formation

Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) are known to be responsible of various infections, including biofilm-associated diseases. The aim of this study was to analyze 19 strains of S. aureus from orthopedic sites in terms of phenotypic antimicrobial susceptibility against 13 selected antibiotics, slime/biofilm formation, molecular analysis of specific antibiotic resistance genes (mecA, cfr, rpoB), and biofilm-associated genes (icaADBC operon). Furthermore, the effect of phloretin on the production of biofilm was evaluated on 8 chosen isolates. The susceptibility test confirmed almost all strains were resistant to cefoxitin and oxacillin. Most strains possess the mecA, whereas none of the strains had the cfr gene. Four strains (1, 7, 10, and 24) presented single-nucleotide polymorphisms (SNPs) in rpoB, which confer rifampicin resistance. IcaD was detected in all tested strains, whereas icaR was only found in two strains (24 and 30). Phloretin had a dose-dependent effect on biofilm production. Specifically, 0.5 × MIC determined biofilm inhibition in 5 out of 8 strains (8, 24, 25, 27, 30), whereas an increase in biofilm production was detected with phloretin at the 0.125 × MIC across all tested strains. These data are useful to potentially develop novel compounds against antibiotic-resistant S. aureus.

Metabolic profiling of Chimonanthus grammatus via UHPLC-HRMS-MS with computer-assisted structure elucidation and its antimicrobial activity

Chimonanthus grammatus is used as Hakka traditional herb to treat cold, flu, etc. So far, the phytochemistry and antimicrobial compounds have not been well investigated. In this study, the orbitrap-ion trap MS was used to characterize its metabolites, combined with a computer-assisted structure elucidation method, and the antimicrobial activities were assessed by a broth dilution method against 21 human pathogens, as well as the bioassay-guided purification work to clarify its main antimicrobial compounds. A total of 83 compounds were identified with their fragmentation patterns, including terpenoids, coumarins, flavonoids, organic acids, alkaloids, and others. The plant extracts can strongly inhibit the growth of three Gram-positive and four Gram-negative bacteria, and nine active compounds were bioassay-guided isolated, including homalomenol C, jasmonic acid, isofraxidin, quercitrin, stigmasta-7,22-diene-3β,5α,6α-triol, quercetin, 4-hydroxy-1,10-secocadin-5-ene-1,10-dione, kaempferol, and E-4-(4,8-dimethylnona-3,7-dienyl)furan-2(5H)-one. Among them, isofraxidin, kaempferol, and quercitrin showed significant activity against planktonic Staphylococcus aureus (IC50 = 13.51, 18.08 and 15.86 µg/ml). Moreover, their antibiofilm activities of S. aureus (BIC50 = 15.43, 17.31, 18.86 µg/ml; BEC50 = 45.86, ≥62.50, and 57.62 µg/ml) are higher than ciprofloxacin. The results demonstrated that the isolated antimicrobial compounds played the key role of this herb in combating microbes and provided benefits for its development and quality control, and the computer-assisted structure elucidation method was a powerful tool for chemical analysis, especially for distinguishing isomers with similar structures, which can be used for other complex samples.

A comprehensive and mechanistic review on protective effects of kaempferol against natural and chemical toxins: Role of NF-κB inhibition and Nrf2 activation

Different toxins, including chemicals and natural, can be entered from various routes and influence human health. Herbal medicines and their active components can attenuate the toxicity of agents via multiple mechanisms. For example, kaempferol, as a flavonoid, can be found in fruits and vegetables, and has an essential role in improving disorders such as cardiovascular disorders, neurological diseases, cancer, pain, and inflammation situations. The beneficial effects of kaempferol may be related to the inhibition of oxidative stress, attenuation of inflammatory factors such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2) and nuclear factor ĸB (NF-ĸB) as well as the modulation of apoptosis and mitogen-activated protein kinase (MAPK) signaling pathways. This flavonoid boasts a wide spectrum of toxin targeting effects in tissue fibrosis, inflammation, and oxidative stress thus shows promising protective effects against natural and chemical toxin induced hepatotoxicity, nephrotoxicity, cardiotoxicity, neurotoxicity, lung, and intestinal in the in vitro and in vivo setting. The most remarkable aspect of kaempferol is that it does not focus its efforts on just one organ or one molecular pathway. Although its significance as a treatment option remains questionable and requires more clinical studies, it seems to be a low-risk therapeutic option. It is crucial to emphasize that kaempferol's poor bioavailability is a significant barrier to its use as a therapeutic option. Nanotechnology can be a promising way to overcome this challenge, reviving optimism in using kaempferol as a viable treatment agent against toxin-induced disorders.

Comparative metabolite profiling of four polyphenol rich Morus leaves extracts in relation to their antibiofilm activity against Enterococcus faecalis

Enterococci are a common cause of urinary tract infections. The severity of enterococcal infections is associated with their ability to form biofilms. Morus leaves are known as a natural antibacterial, however, their antibiofilm activity against Enterococcus remains unveiled. This study aimed to evaluate the ability of four polyphenol-rich Morus leaves extracts (Morus nigra, M. rubra, M. macroura, and M. alba) to inhibit biofilm formed by enterococcal clinical isolates in relation to their metabolic profiling. Results revealed that 48% of the isolates formed strong biofilm, 28% formed moderate biofilm, 20% formed weak biofilm, and only 4% did not form a biofilm. The strong biofilm-forming isolates were E. faecalis, and hence were chosen for this study. The antibiofilm activity of the four polyphenol-rich Morus leaves extracts revealed that the M. nigra extract exhibited the highest percentage of biofilm inhibition followed by M. rubra then M. macroura and the least inhibition was detected in M. alba, and these results were in accordance with the phenolic and flavonoid contents of each extract. UPLC-ESI-MS/MS identified 61 polyphenolic compounds in the four extracts. Further, multivariate analysis confirmed clear segregation of M. nigra from the other species suggesting disparity in its metabolome, with accumulation of flavonoids, anthocyanidins, phenolic acids and coumarin derivatives. Quercetin and kaempferol glycosides were found to be positively and significantly correlated to the antibiofilm activity. In conclusion, M. nigra ethanolic extracts showed the highest phenolic content and antibiofilm activity and they could be developed as a complementary treatment for the development of antimicrobial agents.

Targeting the Holy Triangle of Quorum Sensing, Biofilm Formation, and Antibiotic Resistance in Pathogenic Bacteria

Chronic and recurrent bacterial infections are frequently associated with the formation of biofilms on biotic or abiotic materials that are composed of mono- or multi-species cultures of bacteria/fungi embedded in an extracellular matrix produced by the microorganisms. Biofilm formation is, among others, regulated by quorum sensing (QS) which is an interbacterial communication system usually composed of two-component systems (TCSs) of secreted autoinducer compounds that activate signal transduction pathways through interaction with their respective receptors. Embedded in the biofilms, the bacteria are protected from environmental stress stimuli, and they often show reduced responses to antibiotics, making it difficult to eradicate the bacterial infection. Besides reduced penetration of antibiotics through the intricate structure of the biofilms, the sessile biofilm-embedded bacteria show reduced metabolic activity making them intrinsically less sensitive to antibiotics. Moreover, they frequently express elevated levels of efflux pumps that extrude antibiotics, thereby reducing their intracellular levels. Some efflux pumps are involved in the secretion of QS compounds and biofilm-related materials, besides being important for removing toxic substances from the bacteria. Some efflux pump inhibitors (EPIs) have been shown to both prevent biofilm formation and sensitize the bacteria to antibiotics, suggesting a relationship between these processes. Additionally, QS inhibitors or quenchers may affect antibiotic susceptibility. Thus, targeting elements that regulate QS and biofilm formation might be a promising approach to combat antibiotic-resistant biofilm-related bacterial infections.

Exebacase: A Novel Approach to the Treatment of Staphylococcal Infections

Lysins are bacteriophage-derived enzymes that degrade essential components of bacteria. Exebacase (Lysin CF-301) is an attractive antimicrobial agent because it demonstrates rapid bacteriolytic activity against staphylococcal species, including Staphylococcus aureus, has a low resistance profile, eradicates biofilms, and acts synergistically with other antibiotics. Combinations including exebacase and standard of care antibiotics represent an alternative to antibiotic monotherapies currently used to treat invasive staphylococcal infections. This manuscript reviews what is known about exebacase and explores how this novel agent may be used in the future to treat human bacterial pathogens.