Antimicrobial, Antibiofilm, and Anti-persister Activities of Penfluridol Against Staphylococcus aureus

Bacillus subtilis-derived peptides disrupt quorum sensing and biofilm assembly in multidrug-resistant Staphylococcus aureus

Multidrug-resistant Staphylococcus aureus is one of the most clinically important pathogens in the world, with infections leading to high rates of morbidity and mortality in both humans and animals. The ability of S. aureus to form biofilms protects cells from antibiotics and promotes the transfer of antibiotic resistance genes; therefore, new strategies aimed at inhibiting biofilm growth are urgently needed. Probiotic species, including Bacillus subtilis, are gaining interest as potential therapies against S. aureus for their ability to reduce S. aureus colonization and virulence. Here, we search for strains and microbially derived compounds with strong antibiofilm activity against multidrug-resistant S. aureus by isolating and screening Bacillus strains from a variety of agricultural environments. From a total of 1,123 environmental isolates, we identify a single strain B. subtilis 6D1, with a potent ability to inhibit biofilm growth, disassemble mature biofilm, and improve antibiotic sensitivity of S. aureus biofilms through an Agr quorum sensing interference mechanism. Biochemical and molecular networking analysis of an active organic fraction revealed multiple surfactin isoforms, and an uncharacterized peptide was driving this antibiofilm activity. Compared with commercial high-performance liquid chromatography grade surfactin obtained from B. subtilis, we show these B. subtilis 6D1 peptides are significantly better at inhibiting biofilm formation in all four S. aureus Agr backgrounds and preventing S. aureus-induced cytotoxicity when applied to HT29 human intestinal cells. Our study illustrates the potential of exploring microbial strain diversity to discover novel antibiofilm agents that may help combat multidrug-resistant S. aureus infections and enhance antibiotic efficacy in clinical and veterinary settings.

IMPORTANCE

The formation of biofilms by multidrug-resistant bacterial pathogens, such as Staphylococcus aureus, increases these microorganisms' virulence and decreases the efficacy of common antibiotic regimens. Probiotics possess a variety of strain-specific strategies to reduce biofilm formation in competing organisms; however, the mechanisms and compounds responsible for these phenomena often go uncharacterized. In this study, we identified a mixture of small probiotic-derived peptides capable of Agr quorum sensing interference as one of the mechanisms driving antibiofilm activity against S. aureus. This collection of peptides also improved antibiotic killing and protected human gut epithelial cells from S. aureus-induced toxicity by stimulating an adaptive cytokine response. We conclude that purposeful strain screening and selection efforts can be used to identify unique probiotic strains that possess specially desired mechanisms of action. This information can be used to further improve our understanding of the ways in which probiotic and probiotic-derived compounds can be applied to prevent bacterial infections or improve bacterial sensitivity to antibiotics in clinical and agricultural settings.

Pheromone cCF10 inhibits the antibiotic persistence of Enterococcus faecalis by modulating energy metabolism

Introduction

Bacterial resistance presents a major challenge to both the ecological environment and human well-being, with persistence playing a key role. Multiple studies were recently undertaken to examine the factors influencing the formation of persisters and the underlying process, with a primary focus on Gram-negative bacteria and Staphylococcus aureus (Gram-positive bacteria). Enterococcus faecalis (E. faecalis) is capable of causing a variety of infectious diseases, but there have been few studies of E. faecalis persisters. Previous studies have shown that the sex pheromone cCF10 secreted by E. faecalis induces conjugative plasmid transfer. However, whether the pheromone cCF10 regulates the persistence of E. faecalis has not been investigated.

Methods

As a result, we investigated the effect and potential molecular mechanism of pheromone cCF10 in regulating the formation of persisters in E. faecalis OG1RF using a persistent bacteria model.

Results and discussion

The metabolically active E. faecalis OG1RF reached a persistence state and temporarily tolerated lethal antibiotic concentrations after 8  h of levofloxacin hydrochloride (20 mg/mL) exposure, exhibiting a persistence rate of 0.109 %. During the growth of E. faecalis OG1RF, biofilm formation was a critical factor contributing to antibiotic persistence, whereas 10 ng/mL cCF10 blocked persister cell formation. Notably, cCF10 mediated the antibiotic persistence of E. faecalis OG1RF via regulating metabolic activity rather than suppressing biofilm formation. The addition of cCF10 stimulated the Opp system and entered bacterial cells, inhibiting (p)ppGpp accumulation, thus maintaining the metabolically active state of bacteria and reducing persister cell generation. These findings offer valuable insights into the formation, as well as the control mechanism of E. faecalis persisters.

Biosurfactant complexed with arginine has antibiofilm activity against methicillin-resistant Staphylococcus aureus

Aim: The present study investigated the antimicrobial effectiveness of a rhamnolipid complexed with arginine (RLMIX_Arg) against planktonic cells and biofilms of methicillin-resistant Staphylococcus aureus (MRSA). Methodology: Susceptibility testing was performed using the Clinical & Laboratory Standards Institute protocol: M07-A10, checkerboard test, biofilm in plates and catheters and flow cytometry were used. Result: RLMIX_Arg has bactericidal and synergistic activity with oxacillin. RLMIX_Arg inhibits the formation of MRSA biofilms on plates at sub-inhibitory concentrations and has antibiofilm action against MRSA in peripheral venous catheters. Catheters impregnated with RLMIX_Arg reduce the formation of MRSA biofilms. Conclusion: RLMIX_Arg exhibits potential for application in preventing infections related to methicillin-resistant S. aureus biofilms.

Drug repurposing: insights into the antimicrobial effects of AKBA against MRSA

Staphylococcus aureus is a major threat in infectious diseases due to its varied infection types and increased resistance. S. aureus could form persister cells under certain condition and could also attach on medical apparatus to form biofilms, which exhibited extremely high resistance to antibiotics. 3-Acetyl-11-keto-beta-boswellic acid (AKBA) is a well-studied anti-tumor and antioxidant drug. This study is aimed to determine the antimicrobial effects of AKBA against S. aureus and its persister cells and biofilms. The in vitro antimicrobial susceptibility of AKBA was assessed by micro-dilution assay, disc diffusion assay and time-killing assay. Drug combination between AKBA and conventional antibiotics was detected by checkerboard assay. And the antibiofilm effects of AKBA against S. aureus were explored by crystal violet staining combined with SYTO/PI probes staining. Next, RBC lysis activity and CCK-8 kit were used to determine the cytotoxicity of AKBA. In addition, murine subcutaneous abscess model was used to assess the antimicrobial effects of AKBA in vivo. Our results revealed that AKBA was found to show effective antimicrobial activity against methicillin-resistant S. aureus (MRSA) with the minimal inhibitory concentration of 4-8 µg/mL with undetectable cytotoxicity. And no resistant mutation was induced by AKBA after 20 days of consecutive passage. Further, we found that AKBA could be synergy with gentamycin or amikacin against S. aureus and its clinical isolates. By crystal violet and SYTO9/PI staining, AKBA exhibited strong biofilm inhibitory and eradication effects at the concentration of 1 ~ 4 µg/mL. In addition, the effective antimicrobial effect was verified in vivo in a mouse model. And no detectable in vivo toxicity was found. These results indicated that AKBA has great potential to development as an alternative treatment for the refractory S. aureus infections.

Repurposing of the antimalarial agent tafenoquine to combat MRSA

IMPORTANCE

This study represents the first investigation into the antimicrobial effect of TAF against S. aureus and its potential mechanisms. Our data highlighted the effects of TAF against MRSA planktonic cells, biofilms, and persister cells, which is conducive to broadening the application of TAF. Through mechanistic studies, we revealed that TAF targets bacterial cell membranes. In addition, the in vivo experiments in mice demonstrated the safety and antimicrobial efficacy of TAF, suggesting that TAF could be a potential antibacterial drug candidate for the treatment of infections caused by multiple drug-resistant S. aureus.

Discovery of New Fusobacterium nucleatum Inhibitors to Attenuate Migratory Capability of Colon Cancer Cells by the Drug Repositioning Strategy

Recent studies revealed that intestinal microbiota played important roles in colorectal cancer (CRC) carcinogenesis. Particularly, Fusobacterium nucleatum was confirmed to promote the proliferation and metastasis of CRC. Therefore, targeting F. nucleatum may be a potential preventive and therapeutic approach for CRC. Herein, 2,272 off-patent drugs were screened inhibitory activity against F. nucleatum. Among the hits, nitisinone was identified as a promising anti-F. nucleatum lead compound. Further optimization of nitisinone led to the discovery of more potent derivatives. Particularly, compounds 19q and 22c showed potent anti-F. nucleatum activity (MIC50 = 1 and 2 μg/mL, respectively) with low cytotoxicity. Among them, compound 19q effectively attenuated the migratory ability of MC-38 cells induced by F. nucleatum. Preliminary mechanism studies suggested that nitisinone and its derivatives might act by downregulating nitroreductase and tryptophanase. Thus, the development of small molecule F. nucleatum inhibitors represents an effective strategy to treat CRC.

Simeprevir restores the anti-Staphylococcus activity of polymyxins

Methicillin-resistant Staphylococcus aureus (MRSA) infection poses a severe threat to global public health due to its high mortality. Currently, polymyxins are mainly used for the treatment of Gram-negative bacterial-related infection, while exhibiting limited antibacterial activities against Staphylococcus aureus (S. aureus). However, the combination of antibiotics with antibiotic adjuvants is a feasible strategy for the hard-treated infection and toxicity reducing. We will investigate the antibacterial activity of simeprevir (SIM), which treated for genotype 1 and 4 chronic hepatitis C, combined with polymyxins against MRSA through high-throughput screening technology. In our study, the synergistic antibacterial effect of SIM and polymyxins against S. aureus in vitro was found by checkerboard assay and time-growth curve. The cytotoxicity of SIM combined with polymyxin B sulfate [PB(S)] or polymyxin E (PE) in vitro was evaluated using CCK-8, human RBC hemolysis and scratch assays. In addition, we investigated the eradication of biofilm formation of S. aureus by biofilm inhibition assay and the killing of persister cells. Moreover, we evaluated the therapeutic effect and in vivo toxicity of the combination against MRSA in murine subcutaneous abscess model. Furthermore, it was preliminarily found that SIM significantly enhanced the destruction of MRSA membrane by SYTOX Green and DISC3(5) probes. In summary, these results reveal that the therapy of SIM combined with polymyxins (especially PE) is promising for the treatment of MRSA infection.

Penfluroidol Attenuates the Imbalance of the Inflammatory Response by Repressing the Activation of the NLRP3 Inflammasome and Reduces Oxidative Stress via the Nrf2/HO-1 Signaling Pathway in LPS-Induced Macrophages

Objectives

Excessive inflammatory responses and reactive oxygen species (ROS) formation play pivotal roles in the pathogenesis of sepsis. Penfluroidol (PF), an oral long-acting antipsychotic drug, has been suggested to possess diverse biological properties, including antischizophrenia, antitumour effect, and anti-inflammatory activity. The purpose of this research was to explore the anti-inflammatory and antioxidative effects of penfluroidol on lipopolysaccharide (LPS)-related macrophages.

Methods

The viability of RAW264.7 and THP-1 cells was measured by Enhanced Cell Counting Kit-8 (CCK-8). The production of nitric oxide was evaluated by the Nitric Oxide Assay Kit. The generation of pro-inflammatory monocytes was detected by qRT-PCR (quantitative real-time PCR) and ELISA (enzyme-linked immunosorbent assay). Oxidative stress was assessed by measuring ROS, malondialdehyde (MDA), and superoxide dismutase (SOD) activity. The protein expression of the Nrf2/HO-1/NLRP3 inflammasome was detected by western blotting.

Results

Our results indicated that no cytotoxic effect was observed when RAW264.7 and THP-1 cells were exposed to PF (0-1 μm) and/or LPS (1 μg/ml) for 24 hr. The data showed that LPS, which was repressed by PF, facilitated the generation of the pro-inflammatory molecules TNF-α and IL-6. In addition, LPS contributed to increased production of intracellular ROS compared with the control group, whereas the administration of PF effectively reduced LPS-related levels of ROS. Moreover, LPS induced the generation of MDA and suppressed the activities of SOD. However, PF treatment strongly decreased LPS-induced MDA levels and increased SOD activities in the RAW264.7 and THP-1 cells. Furthermore, our research confirmed that penfluroidol repressed the secretion of pro-inflammatory molecules by limiting the activation of the NLRP3 inflammasome and reducing oxidative effects via the Nrf2/HO-1 signaling pathway.

Conclusion

Penfluroidol attenuated the imbalance of the inflammatory response by suppressing the activation of the NLRP3 inflammasome and reduced oxidative stress via the Nrf2/HO-1 signaling pathway in LPS-induced macrophages.

Nontypeable Haemophilus influenzae released from biofilm residence by monoclonal antibody directed against a biofilm matrix component display a vulnerable phenotype

Bacterial biofilms contribute significantly to pathogenesis, recurrence and/or chronicity of the majority of bacterial diseases due to their notable recalcitrance to clearance. Herein, we examined kinetics of the enhanced sensitivity of nontypeable Haemophilus influenzae (NTHI) newly released (NRel) from biofilm residence by a monoclonal antibody against a bacterial DNABII protein (α-DNABII) to preferential killing by a β-lactam antibiotic. This phenotype was detected within 5 min and lasted for ~ 6 h. Relative expression of genes selected due to their known involvement in sensitivity to a β-lactam showed transient up-regulated expression of penicillin binding proteins by α-DNABII NTHI NRel, whereas there was limited expression of the β-lactamase precursor. Transient down-regulated expression of mediators of oxidative stress supported similarly timed vulnerability to NADPH-oxidase sensitive intracellular killing by activated human PMNs. Further, transient up-regulated expression of the major NTHI porin aligned well with observed increased membrane permeability of α-DNABII NTHI NRel, a characteristic also shown by NRel of three additional pathogens. These data provide mechanistic insights as to the transient, yet highly vulnerable, α-DNABII NRel phenotype. This heightened understanding supports continued validation of this novel therapeutic approach designed to leverage knowledge of the α-DNABII NRel phenotype for more effective eradication of recalcitrant biofilm-related diseases.

A Bacteriophage-Loaded Microparticle Laden Topical Gel for the Treatment of Multidrug-Resistant Biofilm-Mediated Burn Wound Infection

Klebsiella pneumoniae is regarded as one of the most profound bacteria isolated from the debilitating injuries caused by burn wounds. In addition, the multidrug resistance (MDR) and biofilm formation make treating burn patients with clinically available antibiotics difficult. Bacteriophage therapy has been proven an effective alternative against biofilm-mediated wound infections caused by MDR bacterial strains. In the current study, the bacteriophage (BPKPФ1) against MDR Klebsiella pneumoniae was isolated and loaded into the chitosan microparticles (CHMPs), which was later incorporated into the Sepineo P 600 to convert into a gel (BPKPФ1-CHMP-gel). BPKPФ1 was characterized for lytic profile, morphological class, and burst size, which revealed that the BPKPФ1 belongs to the family Siphoviridae. Moreover, BPKPФ1 exhibited a narrow host range with 128 PFU/host cell of burst size. The BPKPФ1-loaded CHMPs showed an average particle size of  1.96 ± 0.51 μm, zeta potential 32.16 ± 0.41 mV, and entrapment efficiency in the range of 82.44 ± 1.31%. Further, the in vitro antibacterial and antibiofilm effectiveness of BPKPФ1-CHMPs-gel were examined. The in vivo potential of the BPKPФ1-CHMPs-gel was assessed using a rat model with MDR Klebsiella pneumoniae infected burn wound, which exhibited improved wound contraction (89.22 ± 0.48%) in 28 days with reduced inflammation, in comparison with different controls. Data in hand suggest the potential of bacteriophage therapy to be developed as personalized therapy in case of difficult-to-treat bacterial infections.

A Bacteriophage Microgel Effectively Treats the Multidrug-Resistant Acinetobacter baumannii Bacterial Infections in Burn Wounds

Multidrug-resistant (MDR) Acinetobacter baumannii (A. baumannii) is one of the major pathogens present in burn wound infections. Biofilm formation makes it further challenging to treat with clinically available antibiotics. In the current work, we isolated the A. baumannii-specific bacteriophages (BPABΦ1), loaded into the chitosan microparticles followed by dispersion in gel, and evaluated therapeutic efficacy against MDR A. baumannii clinical strains. Isolated BPABΦ1 were found to belong to the Corticoviridae family, with burst size 102.12 ± 2.65 PFUs per infected host cell. The BPABΦ1 loaded chitosan microparticles were evaluated for quality attributes viz. size, PDI, surface morphology, in vitro release, etc. The developed formulation exhibited excellent antibiofilm eradication potential in vitro and effective wound healing after topical application.

Inhibitory effects of simeprevir on Staphylococcusepidermidis and itsbiofilm in vitro

OBJECTIVES

Staphylococcus epidermidis (S. epidermidis) is a Gram-positive opportunistic pathogen that often causes hospital infections. With the abuse of antibiotics, the resistance of S. epidermidis gradually increases, and drug repurposing has become a research hotspot in the treating of refractory drug-resistant bacterial infections. This study aims to study the antimicrobial and antibiofilm effects of simeprevir, an antiviral hepatitis drug, on S. epidermidis in vitro.

METHODS

The micro-dilution assay was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of simeprevir against S. epidermidis. Crystal violet staining assay was used to detect the biofilm inhibitory effect of simeprevir. The antimicrobial activity of simeprevir against S. epidermidis and its biofilm were explored by SYTO9/PI fluorescent staining. The combined effect between simeprevir and gentamycin was assessed by checkerboard assay and was confirmed by time-inhibition assay.

RESULTS

Simeprevir showed significant antimicrobial effects against S. epidermidis type strains and clinical isolates with the MIC and MBC at 2-16 μg/mL and 4-32 μg/mL, respectively. The antimicrobial effects of simeprevir were confirmed by SYTO9/PI staining. Simeprevir at MIC could significantly inhibit and break the biofilm on cover slides. Similarly, simeprevir also significantly inhibit the biofilm formation on the surface of urine catheters either in TSB [from (0.700±0.020) to (0.050±0.004)] (t=54.03, P<0.001), or horse serum [from (1.00±0.02) to (0.13±0.01)] (t=82.78, P<0.001). Synergistic antimicrobial effect was found between simeprevir and gentamycin against S. epidermidis with the fractional inhibitory concentration index of 0.5.

CONCLUSIONS

Simeprevir shows antimicrobial effect and anti-biofilm activities against S. epidermidis.

Repurposing CD5789 as an Antimicrobial Agent Against MRSA and Its High Resistant Phonotypes

Methicillin-resistant Staphylococcus aureus (MRSA) poses a great threat to human health, and the formation of biofilm and persister cells make the situation even worse. Drug repurposing is an effective way to solve this problem by shortening the drug development times and reducing the research costs. In this study, CD5789 (trifarotene), a fourth-generation retinoid to be approved by the FDA in 2019 for the topical acne vulgaris regimens, was exhibited antimicrobial activity against MRSA type strains and its clinical isolates with the minimal concentration (MIC) of 2-4 μg/mL and 4-16 μg/mL, respectively, in a dose-dependent manner. By crystal violet staining, we found that CD5789 could inhibit the biofilm formation by MRSA and could further eradicate the pre-formed biofilm at the concentration of 8 μg/mL. By checkerboard dilution assay, sub-MIC of CD5789 showed synergistic antimicrobial effects with sub-MIC of gentamycin against MRSA type strains as well as clinical isolates. In addition, CD5789 also exhibited effective bactericidal activity against MRSA persister cells at the concentration of 8 ~ 16 μg/mL. Extremely low cytotoxicity of CD5789 was observed by CCK-8 assay indicated the well tolerability to human body. In all, CD5789 has the potential to be an alternative for the treatment of refractory MRSA-related infections.

Mechanisms of Antibiotic and Biocide Resistance That Contribute to Pseudomonas aeruginosa Persistence in the Hospital Environment

Pseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for multiple hospital- and community-acquired infections, both in human and veterinary medicine. P. aeruginosa persistence in clinical settings is worrisome and is a result of its remarkable flexibility and adaptability. This species exhibits several characteristics that allow it to thrive under different environmental conditions, including the ability to colonize inert materials such as medical equipment and hospital surfaces. P. aeruginosa presents several intrinsic mechanisms of defense that allow it to survive external aggressions, but it is also able to develop strategies and evolve into multiple phenotypes to persevere, which include antimicrobial-tolerant strains, persister cells, and biofilms. Currently, these emergent pathogenic strains are a worldwide problem and a major concern. Biocides are frequently used as a complementary/combination strategy to control the dissemination of P. aeruginosa-resistant strains; however, tolerance to commonly used biocides has also already been reported, representing an impediment to the effective elimination of this important pathogen from clinical settings. This review focuses on the characteristics of P. aeruginosa responsible for its persistence in hospital environments, including those associated with its antibiotic and biocide resistance ability.

Bacteriostatic and Antibiofilm Efficacy of a Nisin Z Solution against Co-Cultures of Staphylococcus aureus and Pseudomonas aeruginosa from Diabetic Foot Infections

Diabetes mellitus (DM) patients frequently develop diabetic foot ulcers (DFU) which are generally infected by a community of microorganisms, mainly Staphylococcus aureus and Pseudomonas aeruginosa. These bacteria exhibit a multi-drug resistance profile and biofilm-forming ability which represent a hurdle in the treatment of diabetic foot infections (DFI). We aimed to evaluate the potential of Nisin Z, an antimicrobial peptide (AMP), as an alternative treatment for severe DFI. Nisin Z shows antibacterial activity against Gram-positive and Gram-negative bacteria and an increased antibacterial effect against Gram-negatives when added to EDTA. As such, Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Minimum Biofilm Inhibitory Concentration (MBIC), and Minimum Biofilm Eradication Concentration (MBEC) were determined for Nisin Z, Nisin Z + EDTA (0.4%), and Nisin Z + EDTA incorporated into guar gum, in order to test its efficacy against S. aureus and P. aeruginosa isolated from the same DFU. Results showed that Nisin Z added to the chelation agent EDTA displayed higher antibacterial and bacteriostatic efficacy against mono and dual co-cultures of S. aureus and P. aeruginosa, and higher antibiofilm efficiency against monocultures. Nisin Z was moderately cytotoxic at 200 µg/mL. Prospect in vivo studies are needed to confirm the potential of Nisin Z supplemented with EDTA to be used as a complement to conventional antibiotic therapy for severe DFI.

Novel copper-containing ferrite nanoparticles exert lethality to MRSA by disrupting MRSA cell membrane permeability, depleting intracellular iron ions, and upregulating ROS levels

Objective

The widespread use of antibiotics has inevitably led to the emergence of multidrug-resistant bacterial strains, such as methicillin-resistant Staphylococcus aureus (MRSA), making treatment of this infection a serious challenge. This study aimed to explore new treatment strategies for MRSA infection.

Methods

The structure of Fe₃O₄ NPs with limited antibacterial activity was optimized, and the Fe²⁺ ↔ Fe³⁺ electronic coupling was eliminated by replacing 1/2 Fe²⁺ with Cu²⁺. A new type of copper-containing ferrite nanoparticles (hereinafter referred to as Cu@Fe NPs) that fully retained oxidation-reduction activity was synthesized. First, the ultrastructure of Cu@Fe NPs was examined. Then, antibacterial activity was determined by testing the minimum inhibitory concentration (MIC) and safety for use as an antibiotic agent. Next, the mechanisms underlying the antibacterial effects of Cu@Fe NPs were investigated. Finally, mice models of systemic and localized MRSA infections was established for in vivo validation.

Results

It was found that Cu@Fe NPs exhibited excellent antibacterial activity against MRSA with MIC of 1 μg/mL. It effectively inhibited the development of MRSA resistance and disrupted the bacterial biofilms. More importantly, the cell membranes of MRSA exposed to Cu@Fe NPs underwent significant rupture and leakage of the cell contents. Cu@Fe NPs also significantly reduced the iron ions required for bacterial growth and contributed to excessive intracellular accumulation of exogenous reactive oxygen species (ROS). Therefore, these findings may important for its antibacterial effect. Furthermore, Cu@Fe NPs treatment led to a significant reduction in colony forming units within intra-abdominal organs, such as the liver, spleen, kidney, and lung, in mice with systemic MRSA infection, but not for damaged skin in those with localized MRSA infection.

Conclusion

The synthesized nanoparticles has an excellent drug safety profile, confers high resistant to MRSA, and can effectively inhibit the progression of drug resistance. It also has the potential to exert anti-MRSA infection effects systemically in vivo. In addition, our study revealed a unique multifaceted antibacterial mode of Cu@Fe NPs: (1) an increase in cell membrane permeability, (2) depletion of Fe ions in cells, (3) generation of ROS in cells. Overall, Cu@Fe NPs may be potential therapeutic agents for MRSA infections.

Cec4-Derived Peptide Inhibits Planktonic and Biofilm-Associated Methicillin Resistant Staphylococcus epidermidis

Staphylococcus epidermidis is part of the normal microbiota that colonizes the skin and mucosal surfaces of human beings. Previous studies suggested that S. epidermidis possessed low virulence, but recent studies confirmed that it can acquire high virulence from Staphylococcus aureus and with the increasing detection of methicillin-resistant S. epidermidis. It has become a major pathogen of graft-associated and hospital-acquired infections. In previous studies, we modified the antimicrobial peptide Cec4 (41 amino acids) and obtained the derived peptide C9 (16 amino acids) showing better antimicrobial activity against S. epidermidis with an MIC value of 8 μg/mL. The peptide has rapid bactericidal activity without detectable high-level resistance, showing certain inhibition and eradication ability on S. epidermidis biofilms. The damage of cell membrane structures by C9 was observed by scanning emission microscopy (SEM) and transmission electron microscopy (TEM). In addition, C9 altered the S. epidermidis cell membrane permeability, depolarization levels, fluidity, and reactive oxygen species (ROS) accumulation and possessed the ability to bind genomic DNA. Analysis of the transcriptional profiles of C9-treated cells revealed changes in genes involved in cell wall and ribosome biosynthesis, membrane protein transport, oxidative stress, and DNA transcription regulation. At the same time, the median lethal dose of C9 in mice was more than 128 mg/kg, and the intraperitoneal administration of 64 mg/kg was less toxic to the liver and kidneys of mice. Furthermore, C9 also showed a certain therapeutic effect on the mouse bacteremia model. In conclusion, C9 may be a candidate drug against S. epidermidis, which has the potential to be further developed as an antibacterial therapeutic agent. IMPORTANCE S. epidermidis is one of the most important pathogens of graft-related infection and hospital-acquired infection. The growing problem of antibiotic resistance, as well as the emergence of bacterial pathogenicity, highlights the need for antimicrobials with new modes of action. Antimicrobial peptides have been extensively studied over the past 30 years as ideal alternatives to antibiotics, and we report here that the derived peptide C9 is characterized by rapid bactericidal and antibiofilm activity, avoiding the development of resistance by acting on multiple nonspecific targets of the cell membrane or cell components. In addition, it has therapeutic potential against S. epidermidis infection in vivo. This study provides a rationale for the further development and application of C9 as an effective candidate antibiotic.

Pixantrone Sensitizes Gram-Negative Pathogens to Rifampin

The emergence of bacterial drug resistance poses a severe threat to global public health. In particular, antimicrobial-resistant pathogens lead to a high rate of treatment failure and significantly increase mortality. Repurposing FDA-approved compounds to sensitize superbugs to conventional antibiotics provides a promising strategy to alleviate such crises. Pixantrone (PIX) has been approved for treating aggressive B-cell non-Hodgkin's lymphoma. By high-throughput drug screening, we profiled the synergistic activity between PIX and rifampin (RFP) against Gram-negative extensively drug-resistant isolates by checkerboard assay. Mechanistic studies demonstrated that PIX impacted the flagellum assembly, induced irreversible intracellular reactive oxygen species accumulation and disrupted proton motive force. In addition, the combination of PIX with RFP possesses effective antimicrobial activity against multidrug-resistant strains in vivo without detected toxicity. Collectively, these results reveal the potential of PIX in combination with RFP as a therapy option for refractory infections caused by Gram-negative pathogens. IMPORTANCE Bacterial resistance has become increasingly serious because of the widespread use and abuse of antibiotics. In particular, the emergence of multidrug-resistant bacteria has posed a serious threat to human public health. Drug repurposing, the process of finding new uses for existing drugs, provide a promising pathway to solve antimicrobial resistance. Compared to the development of novel antibiotics, this strategy leverages well-characterized pharmacology and toxicology of known drugs and is more cost-effective.

Insights into the antimicrobial effects of ceritinib against Staphylococcus aureus in vitro and in vivo by cell membrane disruption

According to a 2019 report from the Centers of Disease Control and Prevention (CDC), methicillin-resistant Staphylococcus aureus (MRSA) was listed as one of the “serious threats” that had become a global public challenge in hospitals and community. Biofilm-associated infections and refractory persisters of S. aureus also impede the effectiveness of conventional antibiotics that have greatly increased difficulty in clinical therapy. There is an urgent need to develop new antimicrobials with antibiofilm and anti-persister capacities, and drug repurposing is the most effective and most economical solution to the problem. The present study profiles the antimicrobial activity of ceritinib, a tyrosine kinase inhibitor, against S. aureus in vitro and in vivo. We investigated the antimicrobial efficacy of ceritinib against planktonic and persistent S. aureus by a time-killing kinetics assay. Then, antibiofilm effect of ceritinib was assessed by crystal violet staining and laser confocal microscope observation. Ceritinib showed biofilm inhibition and mature biofilm eradication, and possesses robust bactericidal activity against S. aureus persisters. We also evaluated antimicrobial efficacy in vivo using a subcutaneous abscess infection model. Ceritinib ameliorated infection in a subcutaneous abscess mouse model and only showed negligible systemic toxicity in vivo. Mechanism exploration was conducted by transmission electron microscopy, fluorescently labeled giant unilamellar vesicle assays, and a series of fluorescent dyes. In conclusion, we find ceritinib represents potential bactericidal activity against MRSA by disrupting cell membrane integrity and inducing reactive oxygen species production, suggesting ceritinib has the potential to treat MRSA-related infections.

In vitro and in vivo Evaluation of the Bioactive Nanofibers-Encapsulated Benzalkonium Bromide for Accelerating Wound Repair with MRSA Skin Infection

Purpose

Developing the ideal drug or dressing is a serious challenge to controlling the occurrence of antibacterial infection during wound healing. Thus, it is important to prepare novel nanofibers for a wound dressing that can control bacterial infections. In our study, the novel self-assembled nanofibers of benzalkonium bromide with bioactive peptide materials of IKVAV and RGD were designed and fabricated.

Methods

Different drug concentration effects of encapsulation efficacy, swelling ratio and strength were determined. Its release profile in simulated wound fluid and its cytotoxicity were studied in vitro. Importantly, the antibacterial efficacy, inhibition of biofilm formation effect and wound healing against MRSA infections in vitro and in vivo were performed after observing the tissue toxicity in vivo.

Results

It was found that the optimized drug load (0.8%) was affected by the encapsulation efficacy, swelling ratio, and strength. In addition, the novel nanofibers with average diameter (222.0 nm) and stabile zeta potential (−11.2 mV) have good morphology and characteristics. It has a delayed released profile in the simulated wound fluid and good biocompatibility with L929 cells and most tissues. Importantly, the nanofibers were shown to improve antibacterial efficacy, inhibit biofilm formation, and lead to accelerated wound healing following infection with methicillin-resistant Staphylococcus aureus.

Conclusion

These data suggest that novel nanofibers could effectively shorten the wound-healing time by inhibiting biofilm formation, which make it promising candidates for treatment of MRSA-induced wound infections.

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Very rapid synthesis of highly efficient and biocompatible Ag2Se QD phytocatalysts using ultrasonic irradiation for aqueous/sustainable reduction of toxic nitroarenes to anilines with excellent yield/selectivity at room temperature

There are many problems associated with the synthesis of nanocatalysts and catalytic reduction of nitroarenes - e.g., high temperatures, costs, long reaction/synthesis process times, the toxicity of chemicals/solvents, undesirable byproducts, the toxic/harmful wastes, low efficiency/selectivity, etc. This study represents an attempt to overcome these challenges. To this purpose, biocompatible and highly efficient Ag₂Se quantum dots (QDs) catalysts with antibacterial activity were synthesized in a very rapid (30 sec, rt), simple, inexpensive, sustainable/green, and one-pot strategy in water using ultrasonic irradiation. Characterization of the QDs was performed using different techniques. UV-Vis absorption and fluorescence spectroscopic studies showed an absorption peak at 480-550 nm and a maximum emission peak around 675 nm, which confirmed the successful synthesis of Ag₂Se QDs via the applied biosynthetic method. Subsequently, catalytic reduction of nitroarenes by them was carried out under safe conditions (H₂O, rt, air atmosphere) in ∼ 60 min with excellent yield and selectivity (>99%). Their catalytic activity in the reduction of various toxic nitroarenes to aminoarenes under green conditions was investigated. Thus, a rapid and safe ultrasound-based method was employed to prepare stable and green Ag₂Se QDs phyto-catalysts with unique properties, including exquisite monodispersity in shape (orthorhombic) and size (∼7 nm), air-stability, and good purity and crystallinity. Importantly, instead of various toxic chemicals, the plant extract obtained by rapid ultrasonic method (10 min, rt) was used as natural reducing, capping, and stabilizing agents. Moreover, antibacterial assays results showed that Ag₂Se-QDs catalysts at low concentrations (ppm) have high activity against all tested bacteria, especially E. coli (MIC:31.25 ppm, MBC:125 ppm) which were significantly different from those of Fig extract (MIC = MBC:500 ppm). The data reflect the role of these bio-synthesized Ag₂Se-QDs catalysts in the development of versatile and very safe catalysts with biomedical properties.

Population-based high-throughput toxicity screen of human iPSC-derived cardiomyocytes and neurons

In this study, we establish a population-based human induced pluripotent stem cell (hiPSC) drug screening platform for toxicity assessment. After recruiting 1,000 healthy donors and screening for high-frequency human leukocyte antigen (HLA) haplotypes, we identify 13 HLA-homozygous "super donors" to represent the population. These "super donors" are also expected to represent at least 477,611,135 of the global population. By differentiating these representative hiPSCs into cardiomyocytes and neurons we show their utility in a high-throughput toxicity screen. To validate hit compounds, we demonstrate dose-dependent toxicity of the hit compounds and assess functional modulation. We also show reproducible in vivo drug toxicity results using mouse models with select hit compounds. This study shows the feasibility of using a population-based hiPSC drug screening platform to assess cytotoxicity, which can be used as an innovative tool to study inter-population differences in drug toxicity and adverse drug reactions in drug discovery applications.

Anti-hepatitis C virus drug simeprevir: a promising antimicrobial agent against MRSA

Staphylococcus aureus is a major human pathogen, and the appearance of methicillin-resistant S. aureus (MRSA) renders S. aureus infections more challenging to treat. Therefore, new antimicrobial drugs are urgently needed to combat MRSA infections. Drug repurposing is an effective and feasible strategy. Here, we reported that the clinically approved anti-hepatitis C virus drug simeprevir had strong antibacterial activity against MRSA, with a minimum inhibitory concentration of 2-8 µg/mL. Simeprevir did not easily induce in vitro resistance. In addition, simeprevir significantly prevented S. aureus biofilm formation. Furthermore, simeprevir displayed limited toxicity in in vitro and in vivo assays. Moreover, simeprevir showed synergistic antimicrobial effects against both type and clinical strains of S. aureus. Simeprevir combined with gentamicin effectively reduced the bacterial burden in an MRSA-infected subcutaneous abscess mouse model. Results from a series of experiments, including membrane permeability assay, membrane potential assay, intracellular ATP level assay, and electron microscope observation, demonstrated that the action of simeprevir may be by disrupting bacterial cell membranes. Collectively, these results demonstrated the potential of simeprevir as an antimicrobial agent for the treatment of MRSA infections. KEY POINTS: • Simeprevir showed strong antibacterial activity against MRSA. • The antibacterial mechanism of simeprevir was mediated by membrane disruption and intracellular ATP depletion. • In vitro and in vivo synergistic antimicrobial efficacy between simeprevir and gentamicin was found.