Activity of sitafloxacin against extracellular and intracellular Staphylococcus aureus in vitro and in vivo: comparison with levofloxacin and moxifloxacin

Fascaplysin derivatives binding to DNA via unique cationic five-ring coplanar backbone showed potent antimicrobial/antibiofilm activity against MRSA in vitro and in vivo

Methicillin-resistant Staphylococcus aureus (MRSA) is considered as one of the most dangerous clinical pathogens. Biofilms forming ability of MRSA is also a major cause of drug resistance. Hence, it is in urgent need to develop novel antibacterial/antibiofilm drugs. Fascaplysin with a unique cationic five-ring coplanar backbone is emerging as a potential antibacterial compound. In this study, aiming at developing novel and more effective agents, a series of fascaplysin derivatives and their corresponding β-carboline precursors have been synthesized. Then their antibacterial/antibiofilm activity and mechanisms against MRSA were investigated for the first time. The results showed that most fascaplysins rather than β-carboline precursors exhibit superior antimicrobial activity against MRSA ATCC43300, demonstrating the important role of cationic five-ring coplanar backbone playing in antibacterial activity. Among them, 14 and 18 are the most potent compounds with MIC value of 0.098 μg/ml (10-fold lower than vancomycin), and 18 featuring the lowest toxicity. Subsequent mechanisms exploration indicates that 18 has relatively stronger ability to destroy bacterial cell wall and membrane, higher binding affinity to bacterial genomic DNA. Molecular docking study revealed that besides the key role of cationic five-ring coplanar backbone, introduction of N-aryl amide at 9-position of fascaplysin promoted the combination of compound 18 and DNA via additional π-π stacking and hydrogen bonding of the naphthyl group. Moreover, fascaplysins could inhibit MRSA biofilm formation in vitro and bacterial infection in vivo. All these results illustrate that fascaplysin derivative 18 is a strong and safe multi-target antibacterial agent, which makes it an attractive candidate for the treatment of MRSA and its biofilm infections.

Ginsenoside 20(S)-Rh2 promotes cellular pharmacokinetics and intracellular antibacterial activity of levofloxacin against Staphylococcus aureus through drug efflux inhibition and subcellular stabilization

Intracellular Staphylococcus aureus (S. aureus) often causes clinical failure and relapse after antibiotic treatment. We previously found that 20(S)-ginsenoside Rh2 [20(S)-Rh2] enhanced the therapeutic effect of quinolones in a mouse model of peritonitis, which we attributed to the increased concentrations of quinolones within bacteria. In this study, we investigated the enhancing effect of 20(S)-Rh2 on levofloxacin (LVF) from a perspective of intracellular bacteria. In S. aureus 25923-infected mice, coadministration of LVF (1.5 mg/kg, i.v.) and 20(S)-Rh2 (25, 50 mg/kg, i.g.) markedly increased the survival rate, and decreased intracellular bacteria counts accompanied by increased accumulation of LVF in peritoneal macrophages. In addition, 20(S)-Rh2 (1, 5, 10 μM) dose-dependently increased the uptake and accumulation of LVF in peritoneal macrophages from infected mice without drug treatment. In a model of S. aureus 25923-infected THP-1 macrophages, we showed that 20(S)-Rh2 (1, 5, 10 μM) dose-dependently enhanced the intracellular antibacterial activity of LVF. At the cellular level, 20(S)-Rh2 increased the intracellular accumulation of LVF by inhibiting P-gp and BCRP. PK-PD modeling revealed that 20(S)-Rh2 altered the properties of the cell but not LVF. At the subcellular level, 20(S)-Rh2 did not increase the distribution of LVF in lysosomes but exhibited a stronger sensitizing effect in acidic environments. Molecular dynamics (MD) simulations showed that 20(S)-Rh2 improved the stability of the DNA gyrase-LVF complex in lysosome-like acidic conditions. In conclusion, 20(S)-Rh2 promotes the cellular pharmacokinetics and intracellular antibacterial activities of LVF against S. aureus through efflux transporter inhibition and subcellular stabilization, which is beneficial for infection treatment.

Synthesis, structure, photophysical, electrochemical properties and antibacterial activity of brominated BODIPYs as an inhibitor of DNA gyrase B of S. aureus

BODIPYs with 3-thienyl and 4-acetamido phenyl groups substituted at the meso-position are subjected to regioselective bromination using three equivalents of [Formula: see text]-bromosuccinimide (NBS) to yield their 2-mono and 2,6-di bromoderivatives. Their photophysical, electrochemical and antimicrobial properties are investigated. This paper presents a mechanistic investigation of the antibacterial effect of brominated BODIPYs, particularly against Staphylococcus aureus. Fluorescence microscopic images reveal that the compounds are internalized effectively within the bacterial cells, making it an ideal antibacterial drug. Morphological analysis of the bacterial cells after the treatment with the test compounds showed that the compounds did not affect the cell membrane or cell wall and the antibacterial effect of these compounds is achieved via a different mechanism. The most effective compound was selected to explore the target of action. Molecular docking studies were performed on 22 selected proteins in S. aureus and the in silico results were validated by in vitro experiments. It was observed that the supercoiling activity of DNA gyrase was completely inhibited by the 2,6-dibromo-1,3,5,7-tetramethyl-8-(4-acetamido)-4-bora-3a,4a-diaza-[Formula: see text]-indacene, 3c by forming H-bonds with the ASP 81 residue of the enzyme.

Exosome-encapsulated antibiotic against intracellular infections of methicillin-resistant Staphylococcus aureus

Background

Staphylococcus aureus survival inside phagocytes is considered to provide a reservoir of bacteria that are relatively protected from antibiotics, thus enabling long-term colonization of the host and explaining clinical failures and relapses after antibiotic therapy.

Purpose

The objective of this study was to develop a nanovesicle using exosomes loaded with linezolid to overcome intracellular infections by pathogenic bacteria.

Methods

Exosomes were collected from the culture supernatants of RAW 264.7 cells. Their size distribution and zeta potential were characterized by dynamic light scattering, their morphology was characterized by transmission electron microscopy, and their protein content (CD63 and Flotillin 1) was assessed by Western blotting. Linezolid was incorporated into exosomes by co-incubation at 37°C and it’s accumulation in RAW264.7 cells and release in vitro were determined by high performance liquid chromatography. The intracellular bactericidal effect was evaluated in methicillin-resistant S. aureus (MRSA)-infected macrophages in vitro and MRSA peritonitis model in vivo.

Results

We prepared a nanoformulation of the antibiotic linezolid using exosomes harvested from mouse RAW264.7 macrophages. The exosomal formulation of linezolid was more effective against intracellular MRSA infections in vitro and in vivo than the free linezolid. Our data also showed no signs of cytotoxicity in macrophages.

Conclusion

Exosomes provide an effective alternative for intracellular antibiotic delivery of antibiotic that is efficacious, cost-effective, and safe. This regimen can be viewed as a potential antimicrobial agent for use against intracellular infections.

Macrophage-Instructed Intracellular Staphylococcus aureus Killing by Targeting Photodynamic Dimers

The survival of Staphylococcus aureus inside phagocytes is considered to be the sticking point of long-term chronic inflammation. Here, we fabricate peptide-chlorophyll-based photodynamic therapy (PDT) agents with "sandwich" dimeric structure to enhance the PDT effect and active targeting property to eliminate intracellular infections, which could be seen as prospective antibacterial agents for inflammation.

Enhancing the antimicrobial activity of natural extraction using the synthetic ultrasmall metal nanoparticles

The use of Catechin as an antibacterial agent is becoming ever-more common, whereas unstable and easy oxidation, have limited its application. A simple and low-energy-consuming approach to synthesize highly stable and dispersive Catechin-Cu nanoparticles(NPs) has been developed, in which the stability and dispersivity of the NPs are varied greatly with the pH value and temperature of the reaction. The results demonstrate that the optimal reaction conditions are pH 11 at room temperature. As-synthesized NPs display excellent antimicrobial activity, the survival rates of bacterial cells exposed to the NPs were evaluated using live/dead Bacterial Viability Kit. The results showed that NPs at the concentration of 10 ppm and 20 ppm provided rapid and effective killing of up to 90% and 85% of S. aureus and E. coli within 3 h, respectively. After treatment with 20 ppm and 40 ppm NPs, the bacteria are killed completely. Furthermore, on the basis of assessing the antibacterial effects by SEM, TEM, and AFM, it was found the cell membrane damage of the bacteria caused by direct contact of the bacteria with the NPs was the effective mechanism in the bacterial inactivation.

Severe autogenously fecal peritonitis in Wistar rats with permanent bilateral carotid occlusion. Response to intra peritoneal moxifloxacin combined with dexamethasone

PURPOSE

To evaluate the treatment outcome of severe peritonitis in rats submitted to permanent bilateral carotid occlusion (PBCO).

METHODS

Sixteen Wistar rats (mean age of 8.5 months) with PBCO underwent autogenously fecal peritonitis, and were treated with moxifloxacin combined with dexamethasone, and followed-up for 45 days. Ten rats (mean age five months) without PBCO were used as a control group. The variables were expressed by their mean and standard error of the mean (SEM). p<0.05 was used for rejecting the null hypothesis. The study was approved by the Ethics Committee.

RESULTS

There was a significant increase (p=0.0002) in the mortality and morbidity in older rats that underwent PBCO (study group). However, even among the survival rats presenting with severe residual abscesses both in the abdomen and thorax cavities, they present an almost normal life.

CONCLUSIONS

The treatment of severe autogenously fecal peritonitis with intraperitoneal moxifloxacin combined with dexamethasone was very effective in young rats without permanent bilateral carotid occlusion. The treatment reached reasonable results in older rats with PBCO, even considering residual abscesses on abdomen and thorax. Older age was the greater risk factor for the outcome of the treatment of severe peritonitis. Sepsis remains a challenging situation, especially in elderly.