Down-regulation of biofilm-associated genes in mecA-positive methicillin-resistant S. aureus treated with M. communis extract and its antibacterial activity

A silver lining in MRSA treatment: The synergistic action of poloxamer-stabilized silver nanoparticles and methicillin against antimicrobial resistance

BACKGROUND

Increasing antibiotic resistance in bacterial infections, including drug-resistant strains like methicillin-resistant Staphylococcus aureus (MRSA), necessitates innovative therapeutic solutions. Silver nanoparticles are promising for combating infections, but toxicity concerns emphasize the importance of factors like dosage, size, shape, and surface chemistry. Hence, exploring poloxamer as a stabilizing agent to reduce its toxicity and enhance the antibacterial effect on MRSA is investigated.

METHODS

Silver nanoparticles stabilized with poloxamer (AgNPs@Pol) were synthesized through the chemical reduction method and characterized using UV-visible spectrophotometer, HR-TEM, DLS, and Zeta potential measurements. Subsequently, the antibacterial activity of AgNPs@Pol alone and in combination with methicillin against MRSA and methicillin-susceptible S. aureus (MSSA) was evaluated using the broth microdilution method.

RESULTS

AgNPs@Pol showed significant efficacy against MRSA and MSSA, achieving a 100 % reduction in colony-forming units (CFU) at 9.7 μg/ml. The minimum inhibitory concentration (MIC) against MRSA and MSSA was 8.6 μg/ml and 4.3 μg/ml, respectively. A synergistic effect was observed when AgNPs@Pol was combined with methicillin. Treatment with AgNPs@Pol increased reactive oxygen species (ROS) production in both strains, contributing to its antibacterial activity. Real-time qPCR analysis indicated the downregulation of genes involved in antimicrobial resistance and cell adhesion in both strains. Further, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated low cytotoxicity for AgNPs@Pol against MCF-7, MG-63, and NIH-3T3 cell lines.

CONCLUSION

The developed AgNPs@Pol demonstrated extensive colloidal stability, potent antibacterial activity and synergistic effect with methicillin against MRSA and MSSA. Further studies in primary cells and in vivo models may validate its potential for clinical applications.

Phytochemical profiling and antibacterial activities of Ziziphora tenuior root extracts: a molecular docking against VanA of vancomycin-resistant enterococci

Medicinal plants, renowned for their antibacterial phytocompounds and secondary metabolites, hold significant promise in addressing antibiotic-resistant bacterial strains. This study aimed to conduct phytochemical profiling of the methanolic and dichloromethane extracts of Ziziphora tenuior root using the GC-MS technique. These extracts' antioxidant potential was assessed via DPPH assay and their antibacterial activity was evaluated against S. aureus, E. coli, and VRE bacterial strains. Furthermore, the drug-ligand interactions between the extracts' biocompounds and d-alanyl-d-lactate ligase (VanA) protein of vancomycin-resistant enterococci strains (VRE) were analyzed using molecular docking. Based on the results, 74% of methanolic extract consisted of (3methyl, 24S)-stigmast-5-en-3-ol (which is a β-sitosterol), followed by Tetrasiloxane, decamethyl (15.5%), and 1-methyl-4-phenyl-5-thioxo-1,2,4-triazolidin-3-one (10.5%). Also, the only predominant compound identified in the dichloromethane extract was Benzo[h]quinoline, 2,4-dimethyl-. Both extracts showed antioxidant activity, while the antioxidant activity of the methanolic extract (IC50 = 95.33 μg/ml) was significantly higher than that of the dichloromethane extract (IC50 = 934.23 μg/ml). Also, both extracts displayed substantial antibacterial efficacy against the tested pathogens, particularly against VRE. Moreover, the in silico analysis revealed that (3methyl, 24S)-stigmast-5-en-3-ol and Benzo[h]quinoline,2,4-dimethyl- exhibited notable interactions with VanA through docking energy values of - 9.0 and - 9.1 kcal/mol, respectively. Furthermore, these compounds formed 2 and 1 hydrogen bonds with VanA, respectively, highlighting their potential as effective interactants. These findings provide valuable visions into the therapeutic potentials of these plant-derived biocompounds in combating antibiotic-resistant bacterial infections.

Phytochemical characterisation of dichloromethane and methanolic extracts of the Ziziphora tenuior leaves and evaluation of their antioxidant and antibacterial activities

Medicinal plants, known for their antibacterial phytocompounds and secondary metabolites, offer promising potential in combating antibiotic-resistant bacteria. This study aimed to perform a phytochemical analysis of the methanol and dichloromethane extracts obtained from Ziziphora tenuior leaves using GC-MS. Furthermore, the antioxidant activity of the extracts was evaluated through the DPPH assay. And, their antibacterial activity was assessed against S. aureus, E. coli, methicillin-resistant S. aureus, and vancomycin-resistant enterococcus (VRE) bacterial strains. Based on the results 90-92% of these extracts consisted of phytocompounds with pharmaceutical properties. Of these, 5-methyl- 2-(1-methylethylidele), Cyclohexanone (Pulegone; C10H16O) comprised the highest percentage of the extracts, constituting 62% of methanolic extract and 81% of dichloromethane extract. Also, both methanolic and dichloromethane extracts showed potent antioxidant activity with IC50 of 277.6 µg/ml and 49.6 µg/ml, respectively. Moreover, these extracts demonstrated considerable antibacterial activity against the tested pathogens, especially against S. aureus and VRE.

Methyl jasmonate ameliorates pain-induced learning and memory impairments through regulating the expression of genes involved in neuroinflammation

OBJECTIVE

Orofacial pain with high prevalence is one of the substantial human health issues. The importance of this matter became more apparent when it was revealed that orofacial pain, directly and indirectly, affects cognition performances. Currently, researchers have focused on investigating pharmaceutics to alleviate pain and ameliorate its subsequent cognitive impairments.

DESIGN

In this study, the rats were first treated with the central administration of methyl jasmonate (MeJA), which is an antioxidant and anti-inflammatory bio-compound. After 20 min, orofacial pain was induced in the rats by the injection of capsaicin in their dental pulp. Subsequently, the animals' pain behaviors were analyzed, and the effects of pain and MeJA treatments on rats learning and memory were evaluated/compared using the Morris water maze (MWM) test. In addition, the expression of tumor necrosis factor-α (TNF-α), IL-1β, BDNF, and COX-2 genes in the rats' hippocampus was evaluated using real-time polymerase chain reaction.

RESULTS

Experiencing orofacial pain resulted in a significant decline in the rats learning and memory. However, the central administration of 20 μg/rat of MeJA effectively mitigated these impairments. In the MWM, the performance of the MeJA-treated rats showed a two- to threefold improvement compared to the nontreated ones. Moreover, in the hippocampus of pain-induced rats, the expression of pro-inflammatory factors TNF-α, IL-1β, and COX-2 significantly increased, whereas the BDNF expression decreased. In contrast, MeJA downregulated the pro-inflammatory factors and upregulated the BDNF by more than 50%.

CONCLUSIONS

These findings highlight the notable antinociceptive potential of MeJA and its ability to inhibit pain-induced learning and memory dysfunction through its anti-inflammatory effect.

Sub-inhibitory concentrations of colistin and imipenem impact the expression of biofilm-associated genes in Acinetobacter baumannii

Acinetobacter baumannii is an opportunistic pathogen that is responsible for nosocomial infections. Imipenem and colistin are drugs that are commonly used to treat severe infections caused by A. baumannii, such as sepsis, ventilator-associated pneumonia, and bacteremia. However, some strains of A. baumannii have become resistant to these drugs, which is a concern for public health. Biofilms produced by A. baumannii increase their resistance to antibiotics and the cells within the inner layers of biofilm are exposed to sub-inhibitory concentrations (sub-MICs) of antibiotics. There is limited information available regarding how the genes of A. baumannii are linked to biofilm formation when the bacteria are exposed to sub-MICs of imipenem and colistin. Thus, this study's objective was to explore this relationship by examining the genes involved in biofilm formation in A. baumannii when exposed to low levels of imipenem and colistin. The study found that exposing an isolate of A. baumannii to low levels of these drugs caused changes in their drug susceptibility pattern. The relative gene expression profiles of the biofilm-associated genes exhibited a change in their expression profile during short-term and long-term exposure. This study highlights the potential consequences of overuse and misuse of antibiotics, which can help bacteria become resistant to these drugs.

Potential natural antimicrobial and antibiofilm properties of Piper betle L. against Staphylococcus pseudintermedius and methicillin-resistant strains

ETHNOPHARMACOLOGICAL RELEVANCE

Piper betle L. has potent of antimicrobial activity and is widely used as a traditional remedy to treat skin infections. However, no clear evidence exists concerning antimicrobial and antibiofilm activity against Staphylococcus pseudintermedius and methicillin-resistant S. pseudintermedius (MRSP) opportunistic pathogens that cause wound infections and pyoderma in canines and zoonotic disease.

AIM OF THE STUDY

The antimicrobial and antibiofilm activities of P. betle extract were assessed against S. pseudintermedius and MRSP strains.

MATERIALS AND METHODS

Ethanol leaf extract of P. betle was investigated for its antibacterial effect on S. pseudintermedius and MRSP by broth microdilution and time-kill assays. Biofilm inhibition and production assays were performed to evaluate antibiofilm and biofilm eradication effects, respectively. Biofilm-associated gene expression was further studied using real-time polymerase chain reaction (PCR). The possible interaction between IcaA and major compounds in P. betle was analyzed by molecular docking.

RESULTS

The extract showed minimum inhibitory concentration (MIC) at 250 μg/mL. Growth inhibition of P. betle at 1 MIC against the bacteria was initially observed after treatment for 4 h. All isolates were completely killed after 18 h exposure to the extract. Minimum biofilm inhibitory concentrations (MBICs) of the extract against the tested isolates ranged 1/2 MIC to 1 MIC, while minimum biofilm eradication concentration (MBEC) of P. betle was initialed at 8 MIC. Quantitative inhibition and eradication effects were observed in representative strains. The extract at 1/2 MIC and 1 MIC values inhibited biofilm formation up to 100%, with bacterial biofilm removed at up to 94.21% by 4 MIC of the extract. The extract downregulated the expression of the icaA gene among biofilm-producing isolates. The most abundant compounds, 4-allyl-1,2-diacetoxybenzene and eugenol showed a strong affinity with IcaA protein at -5.65 and -5.31 kcal/mol, respectively.

CONCLUSIONS

P. betle extract demonstrated the antibacterial, antibiofilm, and biofilm-removal activity against S. pseudintermedius and MRSP. Downregulation of the icaA gene expression and protein interaction were possible modes of action of the extract that impacted biofilm production. This extract showed promise as an alternative treatment for S. pseudintermedius infection, especially drug-resistant and biofilm-associated cases.

Oreoch-1: A Peptide from Oreochromis niloticus as a Potential Tool against Staphylococci

Staphylococci, including Staphylococcus aureus and Staphylococcus epidermidis, are important human pathogens associated with potentially life-threatening infections. Their great biofilm-producing ability and the development of resistance mechanisms often account for therapeutic failure. Hence, the scientific community has devoted intensive efforts to the development of antimicrobial compounds active against both planktonic and sessile bacterial populations. Contextually, antimicrobial peptides (AMPs) are natural peptides produced by the innate immunity of every organism, representing a potential new therapeutic solution against human microbial pathogens. Our work focused on the in vitro activity of Oreoch-1, an AMP from the gills of Nile tilapia (Oreochromis niloticus), against standard and clinical S. aureus and S. epidermidis strains. Firstly, the cytotoxicity profile of Oreoch-1 was determined in human colon carcinoma cells. Secondly, its antibacterial spectrum was explored against staphylococcal strains to set up the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Our results highlighted an antibacterial activity in the range 6.25-25 μM, with a general bacteriostatic effect. Therefore, the biofilm-inhibitory property was assessed against S. aureus ATCC 25923 and S. epidermidis ATCC 35984, indicating a significant reduction in S. aureus biomass at sub-MIC concentrations. Overall, our study indicates Oreoch-1 as a promising new therapeutic weapon against staphylococcal infections.

New Antimicrobials for Gram-Positive Sustained Infections: A Comprehensive Guide for Clinicians

Antibiotic resistance is a public health problem with increasingly alarming data being reported. Gram-positive bacteria are among the protagonists of severe nosocomial and community infections. The objective of this review is to conduct an extensive examination of emerging treatments for Gram-positive infections including ceftobiprole, ceftaroline, dalbavancin, oritavancin, omadacycline, tedizolid, and delafloxacin. From a methodological standpoint, a comprehensive analysis on clinical trials, molecular structure, mechanism of action, microbiological targeting, clinical use, pharmacokinetic/pharmacodynamic features, and potential for therapeutic drug monitoring will be addressed. Each antibiotic paragraph is divided into specialized microbiological, clinical, and pharmacological sections, including detailed and appropriate tables. A better understanding of the latest promising advances in the field of therapeutic options could lead to the development of a better approach in managing antimicrobial therapy for multidrug-resistant Gram-positive pathogens, which increasingly needs to be better stratified and targeted.

Neuroprotective activity of green synthesized silver nanoparticles against methamphetamine-induced cell death in human neuroblastoma SH-SY5Y cells

The present study aimed to investigate the neuroprotective activity of the black peel pomegranate extract, and silver nanoparticles (AgNPs) biosynthesized using the extract. We pretreated the human neuroblastoma SH-SY5 cells with the extract and AgNPs and evaluated the neuroprotective activity of these agents against methamphetamine (Meth) cytotoxicity. The NPs were spherical with 19 ± 8 nm size, - 28 mV surface charge, and 0.20 PDI. Meth killed the cells by increasing proapoptotic (Bax, PTEN, AKT, PI3K, NF-κB, P53, TNF-α, Cyt C, and Cas 3) and decreasing the antiapoptotic genes (Bcl-2) expression. Exposure to Meth caused DNA fragmentation and increased the intercellular ROS and malondialdehyde (MDA) levels while reducing the mitochondrial membrane potential (MMP). A 4-h pretreatment of the cells with the extract and AgNPs could retain the viability of the cells above 80% by increasing the Bcl-2 expression up to fourfold and inhibiting the cell death pathways. ROS, MDA, and MMP levels in the pretreated cells were close to the control group. The percentage of necrosis in cells pretreated with the extract and AgNPs declined to 32% and 8%, respectively. Our promising findings indicated that AgNPs could reduce Meth-induced oxidative stress and prevent necrotic and apoptotic cell death by regulating related genes' expression.

Quercetin-loaded Liposomes Effectively Induced Apoptosis and Decreased the Epidermal Growth Factor Receptor Expression in Colorectal Cancer Cells: An In Vitro Study

Background

Quercetin is a flavonoid having anti-cancer properties; however, it has low stability, insufficient bioavailability, and poor solubility. This study aimed to load quercetin on nanoliposomes to enhance its efficiency against SW48 colorectal cancer cells. The cytotoxicity of free-quercetin and quercetin-loaded nanoliposomes on the expression of the epidermal growth factor receptor (EGER) gene was investigated.

Methods

This present in vitro study was conducted at Yasuj University of Medical Sciences (Yasuj, Iran) in 2021. In this in vitro study, the lipid thin-film hydration method was used to synthesize quercetin-loaded liposomes. Additionally, high-performance liquid chromatography (HPLC) analyses, dynamic light scattering (DLS), and transmission electron microscopy (TEM) investigations were used to characterize nanomaterials. Following that, MTT, flow cytometry, and real-time PCR were used to investigate the cytotoxicity of quercetin-loaded liposomes on the colorectal cancer cells SW48 cell line, the incidence of apoptosis, and the expression of the EGFR gene in these cells. Statistical analysis was performed using the SPSS (version 26.0), and the graphs were created with the GraphPad Prism version 8.4.3. P<0.05 was considered statistically significant.

Results

The nanoparticles were spherical, homogenous, and 150±10 nm in size. According to HPLC, Quercetin had a 98% loading capacity. Although both free quercetin and quercetin-loaded liposomes indicated significant cytotoxicity against cancer cells (P˂0.001), the combined form was significantly more active (P=0.008). 50 µg/mL of this compound reduced the viability of SW48 cells by more than 80% (IC50 10.65 µg/mL), while the viability of cells treated with free quercetin was only 66% (IC50 18.74 µg/mL). The apoptosis was nearly doubled in the cells treated with quercetin-loaded nanoliposomes compared to free quercetin (54.8% versus 27.6%). EGFR gene expression, on the other hand, was significantly lower in cells treated with quercetin-loaded liposomes than the quercetin alone (P=0.006).

Conclusion

When combined with nanoliposomes, quercetin had greater anti-proliferative, apoptotic, and anti-EGFR expression than free quercetin.

Chemical composition, anticancer and antibacterial activity of Nepeta mahanensis essential oil

Background

Conventional cancer treatments, such as chemotherapy, radiation therapy, and surgery, often affect the patients’ quality of life due to their serious side effects, indicating the urgent need to develop less toxic and more effective alternative treatments. Medicinal plants and their derivatives are invaluable sources for such remedies. The present study aimed to determine the chemical composition, anticancer and antibacterial activities of Nepeta mahanesis essential oil (EO).

Methods

The chemical composition of EO was analyzed by gas chromatography-mass spectrometry (GC-MS). Cytotoxicity and apoptosis/necrosis induction of EO was analyzed by MTT assay and Flow cytometry. Real-time PCR was performed to evaluate the Bax/Bcl2 gene expression. Also, the effect of the EO on the cells’ mitochondrial membrane potential (MMP) and ROS level was assessed. DPPH assay was done to assess the free radical scavenging activity of the EO. The Antimicrobial activity, MIC, and MBC of the oil were determined via well-diffusion and broth microdilution methods.

Results

Based on the GC-MS analysis, 24 compounds were identified in the EO, of which 1,8-cineole (28.5%), Nepetalactone (18.8%), germacrene D (8.1%), and β-pinene (7.2%), were the major compounds. Also, the EO showed considerable cytotoxicity against MCF-7, Caco-2, SH-SY5Y, and HepG2 after 24 and 48 h treatment with IC₅₀ values between 0.0.47 to 0.81 mg/mL. It was revealed that this compound increased the Bax/Bcl2 ratio in the MCF-7 cells and induced apoptosis (27%) and necrosis (18%) in the cells. Moreover, the EO treatment led to a substantial decrease in MMP, which is indicative of apoptosis induction. A significant increase in ROS level was also detected in the cells following exposure to the EO. This compound showed strong DPPH radical scavenging activity (IC₅₀: 30). It was also effective against Gram-positive E. faecalis (ATCC 29,212) and Gram-negative E. coli (ATCC 11,333) bacteria.

Conclusions

The results of this study demonstrated that the EO of N. mahanesis could be considered a bioactive product with biomedical applications that can be used as an alternative cancer treatment and applied in the biomedical industries.