Discovery of Gambogic acid as an antibacterial adjuvant against vancomycin-resistant enterococci in vitro and in vivo.

BACKGROUND: The emergence and spread of vancomycin-resistant enterococci (VRE) have posed a significant challenge to clinical treatment, underscoring the need to develop novel strategies. As therapeutic options for VRE are limited, discovering vancomycin enhancer is a feasible way of combating VRE. Gambogic acid (GA) is a natural product derived from the resin of Garcinia hanburyi Hook.f. (Clusiaceae), which possesses antibacterial activity. PURPOSE: This study aimed to investigate the potential of GA as an adjuvant to restore the susceptibility of VRE to vancomycin. METHODS: In vitro antibacterial and synergistic activities were evaluated against vancomycin-susceptible and resistant strains by the broth microdilution method for the Minimal Inhibitory Concentrations (MICs) determination, and checkerboard assay and time-kill curve analysis for synergy evaluation. In vivo study was conducted on a mouse multi-organ infection model. The underlying antibacterial mechanism of GA was also explored. RESULTS: GA showed a potent in vitro activity against all tested strains, with MICs ranging from 2 to 4 µg/ml. The combination of GA and vancomycin exhibited a synergistic effect against 18 out of 23 tested VRE strains, with a median fractional inhibitory concentration index (FICI) of 0.254, and demonstrated a synergistic effect in the time-kill assay. The combination therapy exhibited a significant reduction in tissue bacterial load compared with either compound used alone. GA strongly binds to the ParE subunit of topoisomerase IV, a bacterial type II DNA topoisomerase, and suppresses its activity. CONCLUSIONS: The study suggests that GA has a significant antibacterial activity against enterococci, and sub-MIC concentrations of GA can restore the activity of vancomycin against VRE in vitro and in vivo. These findings indicate that GA has the potential to be a new antibacterial adjuvant to vancomycin in the treatment of infections caused by VRE.

Garlic-Derived Exosome-like Nanovesicles-Based Wound Dressing for Staphylococcus aureus Infection Visualization and Treatment.

Garlic-derived exosome-like nanovesicles (GELNs) could function in interspecies communication and may serve as natural therapeutics to regulate the inflammatory response or as nanocarriers to efficiently deliver specific drugs. Staphylococcus aureus (S. aureus) is able to hide within host cells to evade immune clearance and antibiotics, leading to life-threatening infections. On-site detection and efficient treatment of intracellular S. aureus infection in wounds remain challenging. Herein, we report a thermosensitive, injectable, visible GELNs-based wound dressing, Van@GELNs/F127 hydrogel (gel Van@GELNs), which is H2O2-responsive and can slowly release vancomycin into host cells forS. aureus infection visualization and treatment in wounds. GELNs show inherent antibacterial activity, which is significantly enhanced after loading vancomycin. Both GELNs and Van@GELNs have the ability to be internalized by cells, so Van@GELNs are more effective than free vancomycin in killing S. aureus in RAW 264.7 macrophages. When applied to an S. aureus-infected wound on a mouse, the colorless HRP&ABTS/Van@GELNs/F127 solution immediately changes to a green hydrogel and shows better therapeutic effect than vancomycin. Thus, direct visualization by the naked eye and effective treatment of S. aureus infection in wounds are achieved by gel Van@GELNs. We anticipate gel Van@GELNs be applied for the theranostics of S. aureus infection diseases in the clinic in the near future.

GSH/pH Cascade-Responsive Nanoparticles Eliminate Methicillin-Resistant Staphylococcus aureus Biofilm via Synergistic Photo-Chemo Therapy.

Bacterial biofilm infection threatens public health, and efficient treatment strategies are urgently required. Phototherapy is a potential candidate, but it is limited because of the off-targeting property, vulnerable activity, and normal tissue damage. Herein, cascade-responsive nanoparticles (NPs) with a synergistic effect of phototherapy and chemotherapy are proposed for targeted elimination of biofilms. The NPs are fabricated by encapsulating IR780 in a polycarbonate-based polymer that contains disulfide bonds in the main chain and a Schiff-base bond connecting vancomycin (Van) pendants in the side chain (denoted as SP-Van@IR780 NPs). SP-Van@IR780 NPs specifically target bacterial biofilms in vitro and in vivo by the mediation of Van pendants. Subsequently, SP-Van@IR780 NPs are decomposed into small size and achieve deep biofilm penetration due to the cleavage of disulfide bonds in the presence of GSH. Thereafter, Van is then detached from the NPs because the Schiff base bonds are broken at low pH when SP@IR780 NPs penetrate into the interior of biofilm. The released Van and IR780 exhibit a robust synergistic effect of chemotherapy and phototherapy, strongly eliminate the biofilm both in vitro and in vivo. Therefore, these biocompatible SP-Van@IR780 NPs provide a new outlook for the therapy of bacterial biofilm infection.

Host-defense piscidin peptides as antibiotic adjuvants against Clostridioides difficile.

The spore-forming intestinal pathogen Clostridioides difficile causes multidrug resistant infection with a high rate of recurrence after treatment. Piscidins 1 (p1) and 3 (p3), cationic host defense peptides with micromolar cytotoxicity against C. difficile, sensitize C. difficile to clinically relevant antibiotics tested at sublethal concentrations. Both peptides bind to Cu2+ using an amino terminal copper and nickel binding motif. Here, we investigate the two peptides in the apo and holo states as antibiotic adjuvants against an epidemic strain of C. difficile. We find that the presence of the peptides leads to lower doses of metronidazole, vancomycin, and fidaxomicin to kill C. difficile. The activity of metronidazole, which targets DNA, is enhanced by a factor of 32 when combined with p3, previously shown to bind and condense DNA. Conversely, the activity of vancomycin, which acts at bacterial cell walls, is enhanced 64-fold when combined with membrane-active p1-Cu2+. As shown through microscopy monitoring the permeabilization of membranes of C. difficile cells and vesicle mimics of their membranes, the adjuvant effect of p1 and p3 in the apo and holo states is consistent with a mechanism of action where the peptides enable greater antibiotic penetration through the cell membrane to increase their bioavailability. The variations in effects obtained with the different forms of the peptides reveal that while all piscidins generally sensitize C. difficile to antibiotics, co-treatments can be optimized in accordance with the underlying mechanism of action of the peptides and antibiotics. Overall, this study highlights the potential of antimicrobial peptides as antibiotic adjuvants to increase the lethality of currently approved antibiotic dosages, reducing the risk of incomplete treatments and ensuing drug resistance.

Structural Element of Vitamin U-Mimicking Antibacterial Polypeptide with Ultrahigh Selectivity for Effectively Treating MRSA Infections.

Antimicrobial peptides (AMPs) exhibit mighty antibacterial properties without inducing drug resistance. Achieving much higher selectivity of AMPs towards bacteria and normal cells has always been a continuous goal to be pursued. Herein, a series of sulfonium-based polypeptides with different degrees of branching and polymerization were synthesized by mimicking the structure of vitamin U. The polypeptide, G2 -PM-1H+ , shows both potent antibacterial activity and the highest selectivity index of 16000 among the reported AMPs or peptoids (e.g., the known index of 9600 for recorded peptoid in "Angew. Chem. Int. Ed., 2020, 59, 6412."), which can be attributed to the high positive charge density of sulfonium and the regulation of hydrophobic chains in the structure. The antibacterial mechanisms of G2 -PM-1H+ are primarily ascribed to the interaction with the membrane, production of reactive oxygen species (ROS), and disfunction of ribosomes. Meanwhile, altering the degree of alkylation leads to selective antibacteria against either gram-positive or gram-negative bacteria in a mixed-bacteria model. Additionally, both in vitro and in vivo experiments demonstrated that G2 -PM-1H+ exhibited superior efficacy against methicillin-resistant Staphylococcus aureus (MRSA) compared to vancomycin. Together, these results show that G2 -PM-1H+ possesses high biocompatibility and is a potential pharmaceutical candidate in combating bacteria significantly threatening human health.

Emergence of vancomycin-resistant enterococci from vancomycin-susceptible enterococci in hospitalized patients under antimicrobial therapy.

OBJECTIVES: Enterococci are opportunistic pathogens with plastic genomes that evolve, acquire, and transmit antimicrobial-resistant determinants such as vancomycin resistance clusters. While vancomycin-resistant enterococci (VRE) have emerged as successful nosocomial pathogens, the mechanism by which vancomycin-susceptible enterococci (VSE) transform to VRE in hospitalized patients remains understudied. METHODS: Genomes of Enterococcus faecium from two critically ill hospitalized patients subjected to multiple antibiotic therapies, including broad-spectrum antibiotics, were investigated. To identify mechanisms of resistance evolution, genomes of vancomycin-susceptible and -resistant isolates were compared. RESULTS: While VSE isolates were initially identified, VRE strains emerged post-vancomycin therapy. Comparative genomics revealed horizontal transmission of mobile genetic elements containing the Tn1549 transposon, which harbours the vanB-type vancomycin resistance gene cluster. This suggests that broad-spectrum antibiotic stress promoted the transfer of resistance-conferring elements, presumably from another gut inhabitant. CONCLUSION: This is one of the first studies investigating VSE and VRE isolates from the same patient. The mechanism of transmission and the within-patient evolution of vancomycin resistance via mobile genetic elements under antibiotic stress is illustrated. Our findings serve as a foundation for future studies building on this knowledge which can further elucidate the dynamics of antibiotic stress, resistance determinant transmission, and interactions within the gut microbiota.

Synergistic effects of polymyxin and vancomycin combinations on carbapenem- and polymyxin-resistant Klebsiella pneumoniae and their molecular characteristics.

IMPORTANCE: This study provides insights into the mechanisms of polymyxin resistance in K. pneumoniae clinical isolates and demonstrates potential strategies of polymyxin and vancomycin combinations for combating this resistance. We also identified possible mechanisms that might be associated with the treatment of these combinations against carbapenem- and polymyxin-resistant K. pneumoniae clinical isolates. The findings have significant implications for the development of alternative therapies and the effective management of infections caused by these pathogens.

Chemical composition and antibacterial activity of bee venom against multi-drug resistant pathogens.

Bee venom with an antimicrobial effect is a powerful natural product. One of the most important areas where new antimicrobials are needed is in the prevention and control of multi-drug resistant pathogens. Today, antibacterial products used to treat multi-drug resistant pathogen infections in hospitals and healthcare facilities are insufficient to prevent colonisation and spread, and new products are needed. The aim of the study is to investigate the antibacterial effect of the bee venom (BV), a natural substance, on the species of Methicillin resistant Staphylococcus aureus, Vancomycin resistant Enterococcus faecalis, Carbapenem resistant Escherichia coli, Carbapenem resistant Klebsiella pneumoniae and Carbapenem resistant Acinetobacter baumannii. As a result of this study, it was found that MIC90 and MBC90 values ranged from 6.25 µg/mL - 12.5 µg/mL and numbers of bacteria decreased by 4-6 logs within 1-24 h for multi-drug resistant pathogens. In particular, Vancomycin resistant Enterococcus faecalis isolate decreased 6 log cfu/mL at 50 µg/mL and 100 µg/mL concentrations in the first hour. The effective bacterial inhibition rate of bee venom suggests that it could be a potential antibacterial agent for multi-drug resistant pathogens.Contribution: The treatment options of antibiotic-resistant pathogens are a major problem in both veterinary and human medicine fields. We have detected a high antibacterial effect against these agents in this bee venom study, which is a natural product. Apitherapy is a fashionable treatment method all over the world and is used in many areas of health. Bee venom is also a product that can be used as a drug or disinfectant raw material and can fill the natural product gap that can be used against resistant bacteria.

Characteristics of Gram-positive cocci infection and the therapeutic effect after liver transplantation. / è‚ç§»æ¤æœ¯åŽé©å °æ°é˜³æ€§çƒèŒçš„æ„ŸæŸ“ç‰¹ç‚¹åŠé˜²æ²»æ•ˆæžœ.

OBJECTIVES: Gram-positive cocci is the main pathogen responsible for early infection after liver transplantation (LT), posing a huge threat to the prognosis of liver transplant recipients. This study aims to analyze the distribution and drug resistance of Gram-positive cocci, the risk factors for infections and efficacy of antibiotics within 2 months after LT, and to guide the prevention and treatment of these infections. METHODS: In this study, data of pathogenic bacteria distribution, drug resistance and therapeutic efficacy were collected from 39 Gram-positive cocci infections among 256 patients who received liver transplantation from donation after citizens' death in the Third Xiangya Hospital of Central South University from January 2019 to July 2022, and risk factors for Gram-positive cocci infection were analyzed. RESULTS: Enterococcus faecium was the dominant pathogenic bacteria (33/51, 64.7%), followed by Enterococcus faecalis (11/51, 21.6%). The most common sites of infection were abdominal cavity/biliary tract (13/256, 5.1%) and urinary tract (10/256, 3.9%). Fifty (98%) of the 51 Gram-positive cocci infections occurred within 1 month after LT. The most sensitive drugs to Gram-positive cocci were teicoplanin, tigecycline, linezolid and vancomycin. Vancomycin was not used in all patients, considering its nephrotoxicity. Vancomycin was not administered to all patients in view of its nephrotoxicity.There was no significant difference between the efficacy of daptomycin and teicoplanin in the prevention of cocci infection (P>0.05). Univariate analysis indicated that preoperative Model for End-Stage Liver Disease (MELD) score >25 (P=0.005), intraoperative red blood cell infusion ≥12 U (P=0.013) and exposure to more than 2 intravenous antibiotics post-LT (P=0.003) were related to Gram-positive cocci infections. Multivariate logistic regression analysis revealed that preoperative MELD score >25 (OR=2.378, 95% CI 1.124 to 5.032, P=0.024) and intraoperative red blood cell transfusion ≥ 12 U (OR=2.757, 95% CI 1.227 to 6.195, P=0.014) were independent risk factors for Gram-positive cocci infections after LT. Postoperative Gram-positive cocci infections were reduced in LT recipients exposing to more than two intravenous antibiotics post-LT (OR=0.269, 95% CI 0.121 to 0.598, P=0.001). CONCLUSIONS: Gram-positive cocci infections occurring early after liver transplantation were dominated by Enterococcus faecalis infections at the abdominal/biliary tract and urinary tract. Teicoplanin, tigecycline and linezolid were anti-cocci sensitive drugs. Daptomycin and teicoplanin were equally effective in preventing cocci infections due to Gram-positive cocci. Patients with high preoperative MELD score and massive intraoperative red blood cell transfusion were more likely to suffer Gram-positive cocci infection after surgery. Postoperative Gram-positive cocci infections were reduced in recipients exposing to more than two intravenous antibiotics post-LT.

Short-Chain Fatty Acids Alleviate Vancomycin-Caused Humoral Immunity Attenuation in Rabies-Vaccinated Mice by Promoting the Generation of Plasma Cells via Akt-mTOR Pathway.

Mounting evidence suggests that gut microbial composition and its metabolites, including short-chain fatty acids (SCFAs), have beneficial effects in regulating host immunogenicity to vaccines. However, it remains unknown whether and how SCFAs improve the immunogenicity of the rabies vaccine. In this study, we investigated the effect of SCFAs on the immune response to rabies vaccine in vancomycin (Vanco)-treated mice and found that oral gavage with butyrate-producing bacteria (C. butyricum) and butyrate supplementation elevated RABV-specific IgM, IgG, and virus-neutralizing antibodies (VNAs) in Vanco-treated mice. Supplementation with butyrate expanded antigen-specific CD4+ T cells and IFN-γ-secreting cells, augmented germinal center (GC) B cell recruitment, promoted plasma cells (PCs) and RABV-specific antibody-secreting cells (ASCs) generation in Vanco-treated mice. Mechanistically, butyrate enhanced mitochondrial function and activated the Akt-mTOR pathway in primary B cells isolated from Vanco-treated mice, ultimately promoting B lymphocyte-induced maturation protein-1 (Blimp-1) expression and CD138+ PCs generation. These results highlight the important role of butyrate in alleviating Vanco-caused humoral immunity attenuation in rabies-vaccinated mice and maintaining host immune homeostasis. IMPORTANCE The gut microbiome plays many crucial roles in the maintenance of immune homeostasis. Alteration of the gut microbiome and metabolites has been shown to impact vaccine efficacy. SCFAs can act as an energy source for B-cells, thereby promoting both mucosal and systemic immunity in the host by inhibiting HDACs and activation of GPR receptors. This study investigates the impact of orally administered butyrate, an SCFA, on the immunogenicity of rabies vaccines in Vanco-treated mice. The results showed that butyrate ameliorated humoral immunity by facilitating the generation of plasma cells via the Akt-mTOR in Vanco-treated mice. These findings unveil the impact of SCFAs on the immune response of the rabies vaccine and confirm the crucial role of butyrate in regulating immunogenicity to rabies vaccines in antibiotic-treated mice. This study provides a fresh insight into the relationship of microbial metabolites and rabies vaccination.

Nano-antibiotic based on silver nanoparticles functionalized to the vancomycin-cysteamine complex for treating Staphylococcus aureus and Enterococcus faecalis.

BACKGROUND: Bacterial resistance is defined as a microorganism's capacity to develop mechanisms for resisting a determined antimicrobial. Gram-positive bacteria, such as Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis), are internationally recognized among the isolates with this resistance profile. In this context, the demand for new medicines has risen, and silver nanoparticles (AgNPs) have been highlighted, especially for their anti-bacterial effects. To develop a nano-antibiotic for treating these Gram-positive strains, we herein report synthesizing and characterizing a nano-antibiotic based on AgNPs functionalized with the complex vancomycin-cysteamine. METHODS: AgNPs were produced using the bottom-up methodology and functionalized with vancomycin modified by the carbodiimide chemistry, forming Ag@vancomycin. Susceptibility tests were performed using S. aureus and E. faecalis strains to assess the bacteriostatic and bactericidal potential of the developed nano-antibiotic. RESULTS: Fourier transform infrared spectroscopy measurements showed the efficacy of vancomycin chemical modification, and the characteristic bands of AgNPs functionalization with the antibiotic. The increase in the nano-antibiotic average hydrodynamic diameter observed by dynamic light scattering proved the presence of vancomycin at the surface of AgNPs. The data from the minimum inhibitory concentration and minimal bactericidal concentration assays tested on standard and clinical planktonic strains of S. aureus and E. faecalis presented excellent performance. CONCLUSION: The results indicate the promising development of a new nano-antibiotic in which the functionalization potentiates the bacteriostatic action of AgNPs and vancomycin with greater efficacy against Gram-positive strains.

Differential response to antibiotic therapy in staphylococcal infective endocarditis: contribution of an ex vivo model.

OBJECTIVES: Staphylococcal infective endocarditis (IE) remains a hard-to-treat infection with high mortality. Both the evaluation of new innovative therapies and research on alternative models mimicking human IE are therefore urgently needed to improve the prognosis of patients with diagnosed IE. Dalbavancin is a novel anti-staphylococcal lipoglycopeptide but there are limited data supporting its efficacy on biofilm infections. This antibiotic could be an alternative to current therapies for the medical treatment of IE but it needs to be further evaluated. METHODS: Here we developed an original ex vivo model of Staphylococcus aureus IE on human heart valves and assessed biofilm formation on them. After validating the model, the efficacy of two antistaphylococcal antibiotics, vancomycin and dalbavancin, was compared by measuring and visualizing their respective ability to inhibit and eradicate late-formed biofilm. RESULTS: Determination of the minimum biofilm inhibitory (MbIC) and eradicating (MbEC) concentrations in our ex vivo model identified dalbavancin as a promising drug with much lower MbIC and MBEC than vancomycin (respectively <0.01 versus 28 mg/L and 0.03 versus 32 mg/L). CONCLUSIONS: These data highlight a strong bactericidal effect of dalbavancin, particularly on an infected heart valve compared with vancomycin. Dalbavancin could be a realistic alternative treatment for the management of staphylococcal IE.

A Clinically Selected Staphylococcus aureus clpP Mutant Survives Daptomycin Treatment by Reducing Binding of the Antibiotic and Adapting a Rod-Shaped Morphology.

Daptomycin is a last-resort antibiotic used for the treatment of infections caused by Gram-positive antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA). Treatment failure is commonly linked to accumulation of point mutations; however, the contribution of single mutations to resistance and the mechanisms underlying resistance remain incompletely understood. Here, we show that a single nucleotide polymorphism (SNP) selected during daptomycin therapy inactivates the highly conserved ClpP protease and is causing reduced susceptibility of MRSA to daptomycin, vancomycin, and ß-lactam antibiotics as well as decreased expression of virulence factors. Super-resolution microscopy demonstrated that inactivation of ClpP reduced binding of daptomycin to the septal site and diminished membrane damage. In both the parental strain and the clpP strain, daptomycin inhibited the inward progression of septum synthesis, eventually leading to lysis and death of the parental strain while surviving clpP cells were able to continue synthesis of the peripheral cell wall in the presence of 10× MIC daptomycin, resulting in a rod-shaped morphology. To our knowledge, this is the first demonstration that synthesis of the outer cell wall continues in the presence of daptomycin. Collectively, our data provide novel insight into the mechanisms behind bacterial killing and resistance to this important antibiotic. Also, the study emphasizes that treatment with last-line antibiotics is selective for mutations that, like the SNP in clpP, favor antibiotic resistance over virulence gene expression.

In vitro evaluation of multiple antibacterial agents for the treatment of chronic staphylococcal anterior blepharitis.

OBJECTIVE: To evaluate the bactericidal efficacy of several compounds used in the treatment of chronic staphylococcal anterior blepharitis through an in vitro study. MATERIALS AND METHODS: Standard commercial strains of Staphylococcus aureus (SAu) (ATCC 25923 Culti-Loops) and coagulase-negative Staphylococcus (CoNS) (ATCC 12228 Culti-Loops) were cultured. Susceptibility tests were performed to vancomycin 30 µg, netilmicin 30 µg, hypochlorous acid (HOCl) 0.01% (Ocudox™, Brill®), Melaleuca alternifolia leaf oil (MeAl) (Navyblef® Daily Care, NOVAX®) and 1% chlorhexidine digluconate (DGCH) (Cristalmina™, Salvat®) using the agar disk diffusion method (Rosco Neo-Sensitabs®). After 24 h, the induced halos were measured with automatic calipers. The results were analyzed using the EUCAST- and CLSI potency Neo-Sensitabs® guidelines. RESULTS: Vancomycin induced a halo of 22.37 mm and 21.81 mm in SAu and CoNS, respectively. Netilmicin produced halos of 24.45 mm in SAu and 32.49 mm in CoNS. MeAl induced halos of 12.65 mm in SAu and 15.83 mm in CoNS. A 12.11 mm halo was found in SAu and an 18.38 mm halo in CoNS using HOCl. DGCH produced halos of 26.55 mm and 23.12 mm in SAu and CoNS, respectively. CONCLUSION: Netilmicin and vancomycin demonstrated antibiotic activity against both pathogens, so they can be alternative rescue therapies to treat chronic staphylococcal blepharitis. DGCH has efficacy against both comparable to antibiotics, while HOCl and MeAl show less efficacy.

Antibiotic-induced accumulation of lipid II synergizes with antimicrobial fatty acids to eradicate bacterial populations.

Antibiotic tolerance and antibiotic resistance are the two major obstacles to the efficient and reliable treatment of bacterial infections. Identifying antibiotic adjuvants that sensitize resistant and tolerant bacteria to antibiotic killing may lead to the development of superior treatments with improved outcomes. Vancomycin, a lipid II inhibitor, is a frontline antibiotic for treating methicillin-resistant Staphylococcus aureus and other Gram-positive bacterial infections. However, vancomycin use has led to the increasing prevalence of bacterial strains with reduced susceptibility to vancomycin. Here, we show that unsaturated fatty acids act as potent vancomycin adjuvants to rapidly kill a range of Gram-positive bacteria, including vancomycin-tolerant and resistant populations. The synergistic bactericidal activity relies on the accumulation of membrane-bound cell wall intermediates that generate large fluid patches in the membrane leading to protein delocalization, aberrant septal formation, and loss of membrane integrity. Our findings provide a natural therapeutic option that enhances vancomycin activity against difficult-to-treat pathogens, and the underlying mechanism may be further exploited to develop antimicrobials that target recalcitrant infection.

Antimicrobial Isoflavans and Other Metabolites of Dalea jamesii.

The phytochemical investigation of extracts of Dalea jamesii root and aerial portions led to the isolation of ten phenolic compounds. Six previously undescribed prenylated isoflavans, summarily named ormegans A - F (1 - 6: ), were characterized, along with two new arylbenzofurans (7, 8: ), a known flavone (9: ), and a known chroman (10: ). The structures of the new compounds were deduced by NMR spectroscopy, supported by HRESI mass spectrometry. The absolute configurations of 1 - 6: were determined by circular dichroism spectroscopy. Compounds 1 - 9: exhibited in vitro antimicrobial activities, causing 98% or greater growth inhibition at concentrations as low as 2.5 - 5.1 µM against methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, and Cryptococcus neoformans. Interestingly, the most active compound was the dimeric arylbenzofuran 8: (> 90% growth inhibition at 2.5 µM) against both methicillin-resistant S. aureus and vancomycin-resistant E. faecalis, tenfold more active than its corresponding monomer (7: ).

Pangenome profiling of novel drug target against vancomycin-resistant Enterococcus faecium.

Enterococcus faecium is a frequent causative agent of nosocomial infection mainly acquired from outgoing hospital patients (Hospital Acquired Infection-HAIs). They are largely involved in the outbreaks of bacteremia, UTI, and endocarditis with a high transmissibility rate. The recent emergence of VRE strain (i.e. vancomycin resistant enterococcus) turned it into high priority pathogen for which new drug research is of dire need. Therefore, in current study, pangenome and resistome analyses were performed for available antibiotic-resistant genomes (n = 216) of E. faecium. It resulted in the prediction of around 5,059 genes as an accessory gene, 1,076 genes as core and 1,558 genes made up a unique genome fraction. Core genes common to all strains were further used for the identification of potent drug targets by applying subtractive genomics approach. Moreover, the COG functional analysis showed that these genomes are highly enriched in metabolic pathways such as in translational, ribosomal, proteins, carbohydrates and nucleotide transport metabolism. Through subtractive genomics it was observed that 431 proteins were non-homologous to the human proteome, 166 identified as essential for pathogen survival while 26 as potential and unique therapeutic targets. Finally, 3-dehydroquinate dehydrogenase was proposed as a potent drug target for further therapeutic candidate identification. Moreover, the molecular docking and dynamic simulation technique were applied to performed a virtual screening of natural product libraries (i.e., TCM and Ayurvedic compounds) along with 3-amino-4,5-dihydroxy-cyclohex-1-enecarboxylate (DHS) as a standard compound to validate the study. Consequently, Argeloside I, Apigenin-7-O-gentiobioside (from Ayurvedic library), ZINC85571062, and ZINC85570908 (TCM library) compounds were identified as potential inhibitors of 3-dehydroquinate dehydrogenase. The study proposed new compounds as novel therapeutics, however, further experimental validation is needed as a follow-up.Communicated by Ramaswamy H. Sarma.

Antibiotic Tolerance and Treatment Outcomes in Cystic Fibrosis Methicillin-Resistant Staphylococcus aureus Infections.

Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent in U.S. cystic fibrosis (CF) patients and is associated with worse clinical outcomes in CF. These infections often become chronic despite repeated antibiotic therapy. Here, we assessed whether bacterial phenotypes, including antibiotic tolerance, can predict the clinical outcomes of MRSA infections. MRSA isolates (n = 90) collected at the incident (i.e., acute) and early infection states from 57 patients were characterized for growth rates, biofilm formation, hemolysis, pigmentation, and vancomycin tolerance. The resistance profiles were consistent with those in prior studies. Isolates from the early stage of infection were found to produce biofilms, and 70% of the isolates exhibited delta-hemolysis, an indicator of agr activity. Strong vancomycin tolerance was present in 24% of the isolates but was not associated with intermediate vancomycin susceptibility. There were no associations between these phenotypic measures, antibiotic tolerance, and MRSA clearance. Our research suggests that additional factors may be relevant for predicting the clearance of MRSA. IMPORTANCE Chronic MRSA infections remain challenging to treat in patients with cystic fibrosis (CF). The ability of the bacterial population to survive high concentrations of bactericidal antibiotics, including vancomycin, despite lacking resistance is considered one of the main reasons for treatment failures. The connection between antibiotic tolerance and treatment outcomes remains unexplored and can be crucial for prognosis and regimen design toward eradication. In this study, we measured the capacity of 90 MRSA isolates from CF patients to form vancomycin-tolerant persister cells and evaluated their correlation with the clinical outcomes. Additionally, various traits that could reflect the metabolism and/or virulence of those MRSA isolates were systematically phenotyped and included for their predictive power. Our research highlights that despite the importance of antibiotic tolerance, additional factors need to be considered for predicting the clearance of MRSA.

Herbal Products and Their Active Constituents Used Alone and in Combination with Antibiotics against Multidrug-Resistant Bacteria.

The purpose of this review is to summarize the current knowledge acquired on herbal products and their active constituents with antimicrobial activity used alone and in combination with antibiotics against multidrug-resistant bacteria. The most promising herbal products and active constituents used alone against multidrug-resistant bacteria are Piper betle (methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, extended-spectrum beta-lactamase, Acinetobacter baumannii, Pseudomonas aeruginosa), Glycyrrhiza glabra (methicillin-resistant S. aureus, vancomycin-resistant Enterococcus, P. aeruginosa), and berberine (methicillin-resistant S. aureus, A. baumannii, P. aeruginosa), respectively. The synergistic effect of the combination of herbal products and their active constituents with antibiotics against multidrug-resistant bacteria are also described. These natural antibacterial agents can be promising sources of inhibitors, which can modulate antibiotic activity against multidrug-resistant bacteria, especially as efflux pump inhibitors. Other possible mechanisms of action of herbal therapy against multidrug-resistant bacteria including modification of the bacterial cell wall and/or membrane, inhibition of the cell division protein filamenting temperature sensitive Z-ring, and inhibition of protein synthesis and gene expression, all of which will also be discussed. Our review suggests that combination herbal therapy and antibiotics can be effectively used to expand the spectrum of their antimicrobial action. Therefore, combination therapy against multidrug-resistant bacteria may enable new choices for the treatment of infectious diseases and represents a potential area for future research.

The Medium Composition Impacts Staphylococcus aureus Biofilm Formation and Susceptibility to Antibiotics Applied in the Treatment of Bone Infections.

The biofilm-associated infections of bones are life-threatening diseases, requiring application of dedicated antibiotics in order to counteract the tissue damage and spread of microorganisms. The in vitro analyses on biofilm formation and susceptibility to antibiotics are frequently carried out using methods that do not reflect conditions at the site of infection. To evaluate the influence of nutrient accessibility on Staphylococcus aureus biofilm development in vitro, a cohesive set of analyses in three different compositional media was performed. Next, the efficacy of four antibiotics used in bone infection treatment, including gentamycin, ciprofloxacin, levofloxacin, and vancomycin, against staphylococcal biofilm, was also assessed. The results show a significant reduction in the ability of biofilm to grow in a medium containing elements occurring in the serum, which also translated into the diversified changes in the efficacy of used antibiotics, compared to the setting in which conventional media were applied. The differences indicate the need for implementation of adequate in vitro models that closely mimic the infection site. The results of the present research may be considered an essential step toward the development of in vitro analyses aiming to accurately indicate the most suitable antibiotic to be applied against biofilm-related infections of bones.