Aberrant Expression of SLC7A11 Impairs the Antimicrobial Activities of Macrophages in Staphylococcus Aureus Osteomyelitis in Mice.

Staphylococcus aureus (S. aureus) persistence in macrophages, potentially a reservoir for recurrence of chronic osteomyelitis, contributes to resistance and failure in treatment. As the mechanisms underlying survival of S. aureus in macrophages remain largely unknown, there has been no treatment approved. Here, in a mouse model of S. aureus osteomyelitis, we identified significantly up-regulated expression of SLC7A11 in both transcriptomes and translatomes of CD11b+F4/80+ macrophages, and validated a predominant distribution of SLC7A11 in F4/80+ cells around the S. aureus abscess. Importantly, pharmacological inhibition or genetic knockout of SLC7A11 promoted the bactericidal function of macrophages, reduced bacterial burden in the bone and improved bone structure in mice with S. aureus osteomyelitis. Mechanistically, aberrantly expressed SLC7A11 down-regulated the level of intracellular ROS and reduced lipid peroxidation, contributing to the impaired bactericidal function of macrophages. Interestingly, blocking SLC7A11 further activated expression of PD-L1 via the ROS-NF-κB axis, and a combination therapy of targeting both SLC7A11 and PD-L1 significantly enhanced the efficacy of clearing S. aureus in vitro and in vivo. Our findings suggest that targeting both SLC7A11 and PD-L1 is a promising therapeutic approach to reprogram the bactericidal function of macrophages and promote bacterial clearance in S. aureus osteomyelitis.

Antimicrobial Properties of Aloe vera Ethanol Extract as a Denture Disinfectant: An In Vitro Study.

Introduction The aim of this study was to evaluate the activity of an ethanolic extract of Aloe vera on Candida albicans and Staphylococcus aureus. Materials and methods A total of 42 heat-cured acrylic resin specimens were made and divided into three groups according to the disinfection method: (1) Corega disinfectant tablets; (2) ethanol extract of Aloe vera; and (3) distilled water (as a control group). Fresh Aloe vera whole leaves were washed with distilled water, chopped into small pieces, air-dried, and ground into powder. The powder was extracted with 95% ethanol. The acrylic specimens were contaminated with C. albicans and S. aureus, and then the specimens were immersed in study solutions for three minutes. The viable colonies were counted using the colony-forming units (CFU) method. Results The results showed a decrease in the number of C. albicans CFU for denture tablets and Aloe vera ethanoic extract groups compared to the negative control group. There were no significant statistical differences between the denture tablet group and the Aloe vera ethanolic extract group (P < 0.05). Aloe vera ethanolic extract groups significantly decreased the number of S. aureus CFU compared to the negative control group and less compared to the denture tablet, where significant statistical differences were found between the tablet group and the Aloe vera ethanolic extract group. Conclusions Within the limitations of this study, it was concluded that Aloe vera extract was effective against C. albicans and S. aureus when acrylic resin specimens were immersed for three minutes.

Antimicrobial Ionic Liquids: Ante-Mortem Mechanisms of Pathogenic EPEC and MRSA Examined by FTIR Spectroscopy.

Ionic liquids (ILs) have gained considerable attention due to their versatile and designable properties. ILs show great potential as antibacterial agents, but understanding the mechanism of attack on bacterial cells is essential to ensure the optimal design of IL-based biocides. The final aim is to achieve maximum efficacy while minimising toxicity and preventing resistance development in target organisms. In this study, we examined a dose-response analysis of ILs' antimicrobial activity against two pathogenic bacteria with different Gram types in terms of molecular responses on a cellular level using Fourier-transform infrared (FTIR) spectroscopy. In total, 18 ILs with different antimicrobial active motifs were evaluated on the Gram-negative enteropathogenic Escherichia coli (EPEC) and Gram-positive methicillin-resistant Staphylococcus aureus (MRSA). The results showed that most ILs impact bacterial proteins with increasing concentration but have a minimal effect on cellular membranes. Dose-response spectral analysis revealed a distinct ante-mortem response against certain ILs for MRSA but not for EPEC. We found that at sub-lethal concentrations, MRSA actively changed their membrane composition to counteract the damaging effect induced by the ILs. This suggests a new adaptive mechanism of Gram-positive bacteria against ILs and demonstrates the need for a better understanding before using such substances as novel antimicrobials.

Harnessing Nature's Defence: The Antimicrobial Efficacy of Pasteurised Cattle Milk-Derived Extracellular Vesicles on Staphylococcus aureus ATCC 25923.

Increasing antimicrobial resistance (AMR) challenges conventional antibiotics, prompting the search for alternatives. Extracellular vesicles (EVs) from pasteurised cattle milk offer promise, due to their unique properties. This study investigates their efficacy against five pathogenic bacteria, including Staphylococcus aureus ATCC 25923, aiming to combat AMR and to develop new therapies. EVs were characterised and tested using various methods. Co-culture experiments with S. aureus showed significant growth inhibition, with colony-forming units decreasing from 2.4 × 105 CFU/mL (single dose) to 7.4 × 104 CFU/mL (triple doses) after 12 h. Milk EVs extended lag time (6 to 9 h) and increased generation time (2.8 to 4.8 h) dose-dependently, compared to controls. In conclusion, milk EVs exhibit dose-dependent inhibition against S. aureus, prolonging lag and generation times. Despite limitations, this suggests their potential in addressing AMR.

Genome-based surveillance reveals cross-transmission of MRSA ST59 between humans and retail livestock products in Hanzhong, China.

Methicillin-resistant Staphylococcus aureus (MRSA) has been recognized in hospitals, community and livestock animals and the epidemiology of MRSA is undergoing a major evolution among humans and animals in the last decade. This study investigated the prevalence of MRSA isolates from ground pork, retail whole chicken, and patient samples in Hanzhong, China. The further characterization was performed by antimicrobial susceptibility testing and in-depth genome-based analysis to identify the resistant determinants and their phylogenetic relationship. A total of 93 MRSA isolates were recovered from patients (n = 67) and retail livestock products (n = 26) in Hanzhong, China. 83.9% (78/93) MRSA isolates showed multiple drug resistant phenotype. Three dominant livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) sequence types were identified: ST59-t437 (n = 47), ST9-t899 (n = 10) and ST398 (n = 7). There was a wide variation among sequence types in the distribution of tetracycline-resistance, scn-negative livestock markers and virulence genes. A previous major human MRSA ST59 became the predominant interspecies MRSA sequence type among humans and retail livestock products. A few LA-MRSA isolates from patients and livestock products showed close genetic similarity. The spreading of MRSA ST59 among livestock products deserving special attention and active surveillance should be enacted for the further epidemic spread of MRSA ST59 in China. Data generated from this study will contribute to formulation of new strategies for combating spread of MRSA.

A Case of Lemierre-Like Syndrome in a Pediatric Patient.

Lemierre-like syndrome is a rare, systemic sequelae following a persistent oropharyngeal infection, leading to septic thrombophlebitis of the internal jugular vein (IJV). Lemierre syndrome is caused by the obligate anaerobic organism Fusobacterium necrophorum, innate to the oropharyngeal tract. Lemierre-like syndrome is due to infections caused by other organisms, including methicillin-resistant Staphylococcus aureus (MRSA). We are reporting a case of a five-month-old male who presented with one week of fever that was not alleviated by acetaminophen, bilateral otitis media, and left-sided cervical lymphadenopathy not alleviated with medical therapy. The patient's clinical course continued to deteriorate as he developed respiratory distress that progressed to acute respiratory failure requiring mechanical ventilation support. Extensive laboratory investigation ruled out the causes of primary and secondary immunodeficiencies. Blood cultures were positive for MRSA, and he was treated initially with vancomycin, then switched to linezolid per ENT recommendations, and ultimately needed daptomycin and ceftaroline therapy. A computed tomography (CT) scan of the neck and chest showed deep neck space infection, bilateral loculated pleural empyema, and mediastinitis. The patient required a decortication video-assisted thoracoscopic surgery (VATS), multiple drains, and a mediastinal washout to control the MRSA infection. This report emphasizes that the rapid progression and spread of septic thrombus can become detrimental to a patient's recovery and survival; therefore, it should be recognized early and treated promptly.

Psoriasis vulgaris of the skin caused a L3-L4 lumbar epidural spinal abscess.

Background: In a 31-year-old male, psoriasis vulgaris (PV) of the skin caused paraparesis attributed to a L3-L4 epidural spinal abscess that required emergent surgical decompression. Case Description: A 31-year-old male presented with lower back pain and cauda equina compression attributed to a magnetic resonance-documented L34 enhancing lesion consistent with a spinal epidural abscess (SEA). The skin over the L3-L4 level revealed severe PV that proved to be the likely etiology of the right-sided paraspinal muscle abscess, infected right L3-L4 facet joint, and SEA. At surgery, the foci of infection were excised/decompressed, and cultures grew methicillin-susceptible Staphylococcus aureus. Following surgery, the patient was improved and was treated with appropriate antibiotic therapy. Conclusion: PV caused a L3-L4 epidural spinal abscess and cauda equina compression in a 31-year-old male who was successfully treated with operative decompression and appropriate antibiotic management.

An unusual case of Brodie's abscess in the humerus of an adult female.

Brodie's abscess is a manifestation of subacute to chronic osteomyelitis, characterized as intraosseous abscess formation, usually on the metaphysis of the long tubular bones in the lower extremities of male pediatric patients. Clinically, Brodie's abscess presents with atraumatic bone pain of an insidious onset, with absence of systemic findings. Delay in diagnosis is common, as diagnostic imaging, followed by biopsy for culture and histologic examination are generally required to secure a diagnosis of Brodie's abscess. Treatment of Brodie's abscess is non-standardized, and usually consists of surgical debridement and antibacterial therapy. Despite the variability in therapeutic approaches, outcomes of Brodie's abscess treated with surgery and antibiotics are favourable. Herein we report a case of a delayed diagnosis of Brodie's abscess in the upper extremity of an adult female. While she improved with treatment of Brodie's abscess, the case serves to remind clinicians to consider this entity in adult individuals who present with atraumatic bone pain.

Zinc oxide nanoparticles mediate bacterial toxicity in Mueller-Hinton Broth via Zn2.

As antibiotic resistance increases and antibiotic development dwindles, new antimicrobial agents are needed. Recent advances in nanoscale engineering have increased interest in metal oxide nanoparticles, particularly zinc oxide nanoparticles, as antimicrobial agents. Zinc oxide nanoparticles are promising due to their broad-spectrum antibacterial activity and low production cost. Despite many studies demonstrating the effectiveness of zinc oxide nanoparticles, the antibacterial mechanism is still unknown. Previous work has implicated the role of reactive oxygen species such as hydrogen peroxide, physical damage of the cell envelope, and/or release of toxic Zn2+ ions as possible mechanisms of action. To evaluate the role of these proposed methods, we assessed the susceptibility of S. aureus mutant strains, ΔkatA and ΔmprF, to zinc oxide nanoparticles of approximately 50 nm in size. These assays demonstrated that hydrogen peroxide and electrostatic interactions are not crucial for mediating zinc oxide nanoparticle toxicity. Instead, we found that Zn2+ accumulates in Mueller-Hinton Broth over time and that removal of Zn2+ through chelation reverses this toxicity. Furthermore, we found that the physical separation of zinc oxide nanoparticles and bacterial cells using a semi-permeable membrane still allows for growth inhibition. We concluded that soluble Zn2+ is the primary mechanism by which zinc oxide nanoparticles mediate toxicity in Mueller-Hinton Broth. Future work investigating how factors such as particle morphology (e.g., size, polarity, surface defects) and media contribute to Zn2+ dissolution could allow for the synthesis of zinc oxide nanoparticles that possess chemical and morphological properties best suited for antibacterial efficacy.

Staphylococcus aureus-specific skin resident memory T cells protect against bacteria colonization but exacerbate atopic dermatitis-like flares in mice.

BACKGROUND: The contribution of Staphylococcus aureus (S. aureus) to the exacerbation of atopic dermatitis (AD) is widely documented, but its role as a primary trigger of AD skin symptoms remains poorly explored. OBJECTIVE: To reappraise the main bacterial factors and underlying immune mechanisms by which S. aureus triggers AD-like inflammation. METHODS: We capitalized on a pre-clinical model, in which different clinical isolates were applied in the absence of any prior experimental skin injury. RESULTS: We report that the development of S. aureus-induced dermatitis depended on the nature of the S. aureus strain, its viability, the concentration of the applied bacterial suspension, the production of secreted and non-secreted factors, as well as the activation of accessory gene regulatory quorum sensing system. In addition, the rising dermatitis, which exhibited the well-documented AD cytokine signature, was significantly inhibited in inflammasome adaptor protein ASC- and monocyte/macrophage-deficient animals, but not in T- and B-cell-deficient mice, suggesting a major role for the innate response in the induction of skin inflammation. However, bacterial exposure generated a robust adaptive immune response against S. aureus, and an accumulation of S. aureus-specific γδ and CD4+ tissue resident memory T (Trm) cells at the site of previous dermatitis. The latter both contributed to worsen the flares of AD-like dermatitis upon new bacteria exposures, but also, protected the mice from persistent bacterial colonization. CONCLUSION: These data highlight the induction of unique AD-like inflammation, with the generation of pro-inflammatory but protective Trm cells in a context of natural exposure to pathogenic S. aureus strains.

Design, synthesis, and evaluation of N1,N3-dialkyldioxonaphthoimidazoliums as antibacterial agents against methicillin-resistant Staphylococcus aureus.

Increasing antibiotic resistance of bacterial pathogens poses a serious threat to human health worldwide. Methicillin-resistant Staphylococcus aureus (MRSA) is among the most deleterious bacterial pathogens owing to its multidrug resistance, necessitating the development of new antibacterial agents against it. We previously identified a novel dioxonaphthoimidazolium agent, c5, with moderate antibacterial activity against MRSA from an anticancer clinical candidate, YM155. In this study, we aimed to design and synthesize several novel cationic amphiphilic N1,N3-dialkyldioxonaphthoimidazolium bromides with enhanced lipophilicity of the two side chains in the imidazolium scaffold and improved antibacterial activities compared to those of c5 against gram-positive bacteria in vitro and in vivo. Our new antibacterial lead, N1,N3-n-octylbenzyldioxonaphthoimidazolium bromide (11), exhibited highly potent antibacterial activities against various gram-positive bacterial strains (MICs: 0.19-0.39 µg/mL), including MRSA, methicillin-sensitive S. aureus, and Bacillus subtilis. Moreover, antibacterial mechanism of 11 against MRSA based on the generation of reactive oxygen species (ROS) was evaluated. Although compound 11 exhibited cytotoxic effects in vitro and lacked a therapeutic index against the HEK293 and HDFa mammalian cell lines, it exhibited low toxicity in the Drosophila animal model. Remarkably, 11 exhibited better in vivo antibacterial efficacy than c5 and the clinically used antibiotic, vancomycin, in SA3-infected Drosophila model. Moreover, the development of bacterial resistance to 11 was not observed after 16 consecutive passages. Therefore, rational design of antibacterial cationic amphiphiles based on ROS-generating pharmacophores with optimized lipophilicity can facilitate the identification of potent antibacterial agents against drug-resistant infections.

Triggered Release of Ampicillin from Metallic Implant Coatings for Combating Periprosthetic Infections.

Periprosthetic infections caused by Staphylococcus aureus (S. aureus) pose unique challenges in orthopedic surgeries, in part due to the bacterium's capacity to invade surrounding bone tissues besides forming recalcitrant biofilms on implant surfaces. We previously developed prophylactic implant coatings for the on-demand release of vancomycin, triggered by the cleavage of an oligonucleotide (Oligo) linker by micrococcal nuclease (MN) secreted by the Gram-positive bacterium, to eradicate S. aureus surrounding the implant in vitro and in vivo. Building upon this coating platform, here we explore the feasibility of extending the on-demand release to ampicillin, a broad-spectrum aminopenicillin ß-lactam antibiotic that is more effective than vancomycin in killing Gram-negative bacteria that may accompany S. aureus infections. The amino group of ampicillin was successfully conjugated to the carboxyl end of an MN-sensitive Oligo covalently integrated in a polymethacrylate hydrogel coating applied to titanium alloy pins. The resultant Oligo-Ampicillin hydrogel coating released the ß-lactam in the presence of S. aureus and successfully cleared nearby S. aureus in vitro. When the Oligo-Ampicillin-coated pin was delivered to a rat femoral canal inoculated with 1000 cfu S. aureus, it prevented periprosthetic infection with timely on-demand drug release. The clearance of the bacteria from the pin surface as well as surrounding tissue persisted over 3 months, with no local or systemic toxicity observed with the coating. The negatively charged Oligo fragment attached to ampicillin upon cleavage from the coating did diminish the antibiotic's potency against S. aureus and Escherichia coli (E. coli) to varying degrees, likely due to electrostatic repulsion by the anionic surfaces of the bacteria. Although the on-demand release of the ß-lactam led to adequate killing of S. aureus but not E. coli in the presence of a mixture of the bacteria, strong inhibition of the colonization of the remaining E. coli on hydrogel coating was observed. These findings will inspire considerations of alternative broad-spectrum antibiotics, optimized drug conjugation, and Oligo linker engineering for more effective protection against polymicrobial periprosthetic infections.

Potential Anti-Infectious Activity of Essential Oil Chemotypes of Lippia origanoides Kunth on Antibiotic-Resistant Staphylococcus aureus Strains.

Staphylococcus aureus infections are prevalent in healthcare and community environments. Methicillin-resistant S. aureus is catalogued as a superbug of high priority among the pathogens. This Gram-positive coccus can form biofilms and produce toxins, leading to persistent infection and antibiotic resistance. Limited effective antibiotics have encouraged the development of innovative strategies, with a particular emphasis on resistance mechanisms and/or virulence factors. Medicinal aromatic plants have emerged as promising alternative sources. This study investigated the antimicrobial, antibiofilm, and antihemolysis properties of three different chemotypes of Lippia origanoides essential oil (EO) against susceptible and drug-resistant S. aureus strains. The chemical composition of the EO was analyzed using GC-MS, revealing high monoterpene concentrations, with carvacrol and thymol as the major components in two of the chemotypes. The third chemotype consisted mainly of the sesquiterpene ß-caryophyllene. The MIC values for the two monoterpene chemotypes ranged from 62.5 to 500 µg/mL for all strains, whereas the sesquiterpene chemotype showed activity against seven strains at concentrations of 125-500 µg/mL, which is the first report of its anti-S. aureus activity. The phenolic chemotypes inhibited biofilm formation in seven S. aureus strains, whereas the sesquiterpene chemotype only inhibited biofilm formation in four strains. In addition, phenolic chemotypes displayed antihemolysis activity, with IC50 values ranging from 58.9 ± 3.8 to 128.3 ± 9.2 µg/mL. Our study highlights the importance of L. origanoides EO from the Yucatan Peninsula, which has the potential for the development of anti-S. aureus agents.

Reducing Peptidoglycan Crosslinking by Chemical Modulator Reverts ß-lactam Resistance in Methicillin-Resistant Staphylococcus aureus.

Small molecule can be utilized to restore the effectiveness of existing major classes of antibiotics against antibiotic-resistant bacteria. In this study, it is demonstrated that celastrol, a natural compound, can modify the bacterial cell wall and subsequently render bacteria more suceptible to ß-lactam antibiotics. It is shown that celastrol leads to incomplete cell wall crosslinking by modulating levels of c-di-AMP, a secondary messenger, in methicillin-resistant Staphylococcus aureus (MRSA). This mechanism enables celastrol to act as a potentiator, effectively rendering MRSA susceptible to a range of penicillins and cephalosporins. Restoration of in vivo susceptibility of MRSA to methicillin is also demonstrated using a sepsis animal model by co-administering methicillin along with celastrol at a much lower amount than that of methicillin. The results suggest a novel approach for developing potentiators for major classes of antibiotics by exploring molecules that re-program metabolic pathways to reverse ß-lactam-resistant strains to susceptible strains.

Novel natural osthole-inspired amphiphiles as membrane targeting antibacterials against methicillin-resistant Staphylococcus aureus (MRSA).

Methicillin-resistant Staphylococcus aureus (MRSA) is a widespread pathogen causing clinical infections and is multi-resistant to many antibiotics, making it urgent need to develop novel antibacterials to combat MRSA. Herein, we designed and prepared a series of novel osthole amphiphiles 6a-6ad by mimicking the structures and function of antimicrobial peptides (AMPs). Antibacterial assays showed that osthole amphiphile 6aa strongly inhibited S. aureus and 10 clinical MRSA isolates with MIC values of 1-2 µg/mL, comparable to that of the commercial antibiotic vancomycin. Additionally, 6aa had the advantages of rapid bacteria killing without readily developing drug resistance, low toxicity, good membrane selectivity, and good plasma stability. Mechanistic studies indicated that 6aa possesses good membrane-targeting ability to bind to phosphatidylglycerol (PG) on the bacterial cell membranes, thereby disrupting the cell membranes and causing an increase in intracellular ROS as well as leakage of proteins and DNA, and accelerating bacterial death. Notably, in vivo activity results revealed that 6aa exhibits strong anti-MRSA efficacy than vancomycin as well as a substantial reduction in MRSA-induced proinflammatory cytokines, including TNF-α and IL-6. Given the impressive in vitro and in vivo anti-MRSA efficacy of 6aa, which makes it a potential candidate against MRSA infections.

Genomic epidemiology of Staphylococcus aureus from the Iberian Peninsula highlights the expansion of livestock associated-CC398 towards wildlife.

Staphylococcus aureus is a versatile pathobiont, exhibiting a broad host range, including humans, other mammals, and avian species. Host specificity determinants, virulence, and antimicrobial resistance genes are often shared by strains circulating at the animal-human interface. While transmission dynamics studies have shown strain exchange between humans and livestock, knowledge of the source, genetic diversification, and transmission drivers of S. aureus in wildlife lag behind. In this work, we explore a wide array of S. aureus genomes from different sources in the Iberian Peninsula to understand population structure, gene content and niche adaptation at the human-livestock-wildlife nexus. Through Bayesian inference, we address the hypothesis that S. aureus strains in wildlife originate from humanized landscapes, either from contact with humans or through interactions with livestock. Phylogenetic reconstruction applied to whole genome sequence data was completed with a dataset of 450 isolates featuring multiple clones from the 1990-2022 period and a subset of CC398 strains representing the 2008-2022 period. Phylodynamic signatures of S. aureus from the Iberian Peninsula suggest widespread circulation of most clones among humans before jumping to other hosts. The number of transitions of CC398 strains within each host category (human, livestock, wildlife) was high (88.26 %), while the posterior probability of transitions from livestock to wildlife was remarkably high (0.99). Microbial genome-wide association analysis did not evidence genome rearrangements nor biomarkers suggesting S. aureus niche adaptation to wildlife, thus supporting recent spill overs. Altogether, our findings indicate that S. aureus isolates collected in the past years from wildlife most likely represent multiple introduction events from livestock. The clonal origin of CC398 and its potential to disseminate and evolve through different animal host species are highlighted, calling for management practices at the livestock-wildlife axis to improve biosecurity and thus restrict S. aureus transmission and niche expansion along gradients of human influence.

Overcoming antibiotic resistance: non-thermal plasma and antibiotics combination inhibits important pathogens.

Antibiotic resistance (ATBR) is increasing every year as the overuse of antibiotics (ATBs) and the lack of newly emerging antimicrobial agents lead to an efficient pathogen escape from ATBs action. This trend is alarming and the World Health Organization warned in 2021 that ATBR could become the leading cause of death worldwide by 2050. The development of novel ATBs is not fast enough considering the situation, and alternative strategies are therefore urgently required. One such alternative may be the use of non-thermal plasma (NTP), a well-established antimicrobial agent actively used in a growing number of medical fields. Despite its efficiency, NTP alone is not always sufficient to completely eliminate pathogens. However, NTP combined with ATBs is more potent and evidence has been emerging over the last few years proving this is a robust and highly effective strategy to fight resistant pathogens. This minireview summarizes experimental research addressing the potential of the NTP-ATBs combination, particularly for inhibiting planktonic and biofilm growth and treating infections in mouse models caused by methicillin-resistant Staphylococcus aureus or Pseudomonas aeruginosa. The published studies highlight this combination as a promising solution to emerging ATBR, and further research is therefore highly desirable.

Staphylococcus Aureus Membrane Vesicles Kill Tumor Cells Through a Caspase-1-Dependent Pyroptosis Pathway.

Introduction: Nanosized outer membrane vesicles (OMVs) from Gram-negative bacteria have attracted increasing interest because of their antitumor activity. However, the antitumor effects of MVs isolated from Gram-positive bacteria have rarely been investigated. Methods: MVs of Staphylococcus aureus USA300 were prepared and their antitumor efficacy was evaluated using tumor-bearing mouse models. A gene knock-in assay was performed to generate luciferase Antares2-MVs for bioluminescent detection. Cell counting kit-8 and lactic dehydrogenase release assays were used to detect the toxicity of the MVs against tumor cells in vitro. Active caspase-1 and gasdermin D (GSDMD) levels were determined using Western blot, and the tumor inhibition ability of MVs was determined in B16F10 cells treated with a caspase-1 inhibitor. Results: The vesicular particles of S. aureus USA300 MVs were 55.23 ± 8.17 nm in diameter, and 5 µg of MVs remarkably inhibited the growth of B16F10 melanoma in C57BL/6 mice and CT26 colon adenocarcinoma in BALB/c mice. The bioluminescent signals correlated well with the concentrations of the engineered Antares2-MVs (R2 = 0.999), and the sensitivity for bioluminescence imaging was 4 × 10-3 µg. Antares2-MVs can directly target tumor tissues in vivo, and 20 µg/mL Antares2-MVs considerably reduced the growth of B16F10 and CT26 tumor cells, but not non-carcinomatous bEnd.3 cells. MV treatment substantially increased the level of active caspase-1, which processes GSDMD to trigger pyroptosis in tumor cells. Blocking caspase-1 activation with VX-765 significantly protected tumor cells from MV killing in vitro and in vivo. Conclusion: S. aureus MVs can kill tumor cells by activating the pyroptosis pathway, and the induction of pyroptosis in tumor cells is a promising strategy for cancer treatment.

Newly designed nanoparticle-drug delivery systems against Staphylococcus aureus infection: a systematic review.

A nanoparticle-drug delivery system against Staphylococcus aureus, especially Methicillin-resistant staphylococcus aureus, has been recently proposed as an alternative pathway therapy. Methicillin-resistant staphylococcus aureus is resistance to many antibiotics, making it a a threat to human life, especially for older and immunocompromised people. Treatment of Multidrug-resistant staphylococcus aureus is considered an urgent need. A variety of kinds of nanoparticle-drug delivery systems with different compositions, and biological properties have been extensively investigated against Staphylococcus aureus. This review summarizes the novel nanoparticle-drug delivery systems against Staphylococcus aureus. These nanoparticle-drug delivery systems could reduce antibiotic resistance and minimize side effects of the antibiotics. Also, they can deliver a high concentration of the drugs and eliminate the bacteria in a specific and targeted site of infection. Despite these benefits of nanoparticle-drug delivery systems, the cytotoxicity, stress oxidative, genotoxicity, and inflammation that may occur in vivo and in vitro should not be ignored. Therefore, we need a better knowledge of the pharmacological properties and safety concerns of nanoparticle-drug delivery systems. The limitations of each nanoparticle-drug delivery system with high therapeutic potential have to be considered for further design.

Isolation and characterization of two Staphylococcus aureus lytic bacteriophages "Huma" and "Simurgh".

Nowadays finding the new antimicrobials is necessary due to the emerging of multidrug resistant strains. The present study aimed to isolate and characterize bacteriophages against S. aureus. Strains Huma and Simurgh were the two podovirus morphology phages which isolated and then characterized. Huma and Simurgh had a genome size of 16,853 and 17,245 bp, respectively and both were Rosenblumvirus with G + C content of 29%. No lysogeny-related genes, nor virulence genes were identified in their genomes. They were lytic only against two out of four S. aureus strains. They also were able to inhibit S. aureus for 8 h in-vitro. Both showed a rapid adsorption. Huma and Simurgh had the latent period of 80 and 60 m and the burst sizes of 45 and 40 PFU/ml and also, they showed very low cell toxicity of 1.23%-1.79% on HT-29 cells, respectively. Thus, they can be considered potential candidates for biocontrol applications.