Methicillin-resistant Staphylococcus Aureus Research Articles

Rational Design of Advanced Gene Delivery Carriers: Macrophage Phenotype Matters.

Nucleic acid delivery in hard-to-transfect macrophages have attracted increasing attention in diverse applications such as defence against bacterial infection. Regulated by microenvironments in specific applications, macrophages have a heterogenous nature and exist in different phenotypes with diverse functions, e.g., pro-inflammatory and anti-inflammatory. However, it is not clear whether macrophage phenotype affects nucleic acid delivery, and which one is harder to transfect, and the design of nucleic acid carriers in harder-to-transfect macrophage phenotypes is largely unexplored. Herein, it is first revealed that nucleic acid delivery efficacy in macrophages is influenced by phenotype: IL-4-treated "M2-like" macrophages with suppressed mammalian target of rapamycin complex 1 (mTORC1) levels are harder-to-transfect than "M1-like" macrophages for mRNA and DNA. This knowledge is then translated to the purpose-design of gene delivery carriers for harder-to-transfect M2 phenotype macrophages dominant upon bacteria immune evasion. By loading chloroquine in tetrasulfide bond-containing organosilica nanoparticles, the resultant composite promotes macrophage M2 polarization to M1 and increases mTORC1 levels for enhanced translation. The design is demonstrated in vitro and in vivo for pathogenic Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) infections. It is expected that the findings may provide new knowledge and gene delivery solutions in other applications where the M2 phenotype macrophage is dominant.

Repurposing Benzbromarone as an Antibacterial Agent against Gram-Positive Bacteria.

The rise of antibiotic-resistant Gram-positive pathogens, particularly methicillin-resistant Staphylococcus aureus (MRSA), presents a significant challenge in clinical settings. There is a critical need for new antibacterial agents to combat these resistant strains. Our study reveals that the uricosuric drug Benzbromarone (Benz) exhibits potent antibacterial activity against Gram-positive pathogens, with minimum inhibitory concentrations (MICs) ranging from 8 to 32 μg/mL and minimum bactericidal concentrations (MBCs) ranging from 32 to 128 μg/mL against clinical isolates of S. aureus, S. epidermidis, Enterococcus faecalis, and Streptococcus agalactiae. Furthermore, Benz significantly inhibits biofilm formation at subinhibitory concentrations and eradicates mature biofilms at higher concentrations. Benz also suppresses the hemolytic activity of S. aureus, indicating its potential to reduce virulence. Proteomic and in vitro induced resistance analyses indicate that Benz inhibits protein synthesis and turnover. Additionally, Benz induces membrane depolarization and increases membrane permeability, likely by targeting the membrane phospholipid phosphatidylethanolamine (PE). In the mouse wound infection model, Benz promotes wound healing and significantly reduces bacterial load. These findings suggest that Benz is a promising candidate for developing new antibacterial therapies against Gram-positive bacterial infections.

Photothermal Nano-Immunotherapy Against Methicillin-Resistant Staphylococcus aureus (MRSA) Biofilm Infections.

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm infections are a prevalent type of biofilm-associated infection with a poor prognosis and antibiotic resistance. The senescence of immune cells in the immune microenvironment contributes to biofilm formation. In this study, Ti₃C₂ MXene-PVA nanosheets loaded with metformin (Met@TiC) are developed for the treatment of MRSA biofilm infections. Nanosheets utilize near-infrared light to induce photothermal effects and provide direct bactericidal activity against biofilm structures. Met, which is known for its anti-inflammatory and anti-senescence properties, modulates immune responses by revitalizing the function of senescent macrophages within the biofilm microenvironment, thereby enhancing their phagocytic and biofilm-eradicating capabilities. The efficacy of this nanoplatform both in vitro and in an MRSA biofilm infection mouse model, demonstrating its potential as a photothermal nanoimmunotherapy for combating MRSA biofilm infections is validated. In summary, the Met@TiC nanoplatform offers a significant alternative to clinical solutions for MRSA biofilm infections.

Evaluation of accuracy of Phenotypic methods in the detection of Methicillin Resistant Staphylococcus aureus

Abstract: Methicillin resistant Staphylococcus aureus (MRSA) is a variant of Staphylococcus aureus; responsible for a significant share of the infectious load. Objective: The current study was conducted to evaluate the accuracy of already in vogue phenotypic methods of identification of MRSA keeping in view the gold standard method of mec-A gene detection using Polymerase chain reaction (PCR) and to compare the sensitivity and specificity of different phenotypic methods (Cefoxitin Disc Diffusion, Oxacillin Disc Diffusion, Oxacillin Screen Agar, and MIC of Oxacillin by Agar Dilution Method) with the genotypic method (PCR). Method: A descriptive cross-sectional study was carried out at Microbiology Lab, Pakistan Railway Hospital, Rawalpindi from October 2021 to September 2022, after attaining the formal approval from Institutional Ethical Review Committee (Riphah/IIMC/IRC/21/73), using non-probability sampling technique. A total of 222 samples of Staphylococcus aureus were isolated from all the clinical specimens received at Microbiology lab at Pakistan Railway Hospital. Among those isolates, 150(67.5%) were Methicillin sensitive Staphylococcus aureus (MSSA) and 72(32.4%) were Methicillin Resistant Staphylococcus aureus (MRSA). The results of Phenotypic methods were compared with the results of PCR by using Chi-square formula. The sensitivity and specificity of Cefoxitin Disc Diffusion method was 62.5% and 96.6%, Oxacillin Disc Diffusion method was 65.3% and 93.3%, Oxacillin Screen Agar technique was 81.9% and 96% while that of Oxacillin MIC by Agar Dilution was 91.6% and 89.3% respectively. Oxacillin screen agar demonstrates the better phenotypic technique for detection of MRSA in routine practice.

Association of Antibiotic Route and Outcomes in Children with Methicillin-Resistant Staphylococcus aureus Bacteremic Osteomyelitis.

There remains uncertainty about whether transitioning to oral antibiotic therapy is appropriate for the management of children with methicillin-resistant Staphylococcus aureus (MRSA) bacteremic osteomyelitis. We compared clinical outcomes for children with MRSA osteomyelitis with associated bacteremia who were transitioned to discharge oral antibiotic therapy to those discharged on outpatient parenteral antibiotic therapy (OPAT). We performed a retrospective, multicenter, cohort study of children ≤ 18 years hospitalized with MRSA bacteremic osteomyelitis across four children's hospitals from 2007 to 2018 discharged on oral antibiotic therapy versus OPAT. The primary outcome was treatment failure within 6 months of discharge, defined as any of the following: diagnosis of chronic osteomyelitis, conversion from oral to IV antibiotic route, an operative procedure after the index hospitalization (abscess drainage, bone biopsy, arthrocentesis, or pathologic fracture) and/or recrudescence of MRSA bacteremia. Outcomes were analyzed in an inverse propensity score weighted (IPW) cohort. A total of 106 cases of MRSA bacteremic osteomyelitis were included; 44 (42%) were discharged in the oral antibiotic therapy group and 62 (59%) patients were discharged in the OPAT group. In the IPW cohort, treatment failure within 6 months of discharge occurred in 3.4% of children in the discharge oral therapy group and 16.3% in the OPAT group (P = 0.03). The odds of 6-month composite treatment failure between discharge oral therapy and OPAT were 0.18 (95% CI 0.05-0.61). Discharge oral therapy was not associated with higher rates of treatment failure compared to OPAT for children with MRSA bacteremic osteomyelitis.

LysSYL-Loaded pH-Switchable Self-Assembling Peptide Hydrogels Promote Methicillin-Resistant Staphylococcus Aureus Elimination and Wound Healing.

Staphylococcus aureus (S. aureus), especially methicillin-resistant S. aureus (MRSA), causes wound infections, whose treatment remains a clinical challenge. Bacterium-infected wounds often create acidic niches with a pH 4.5-6.5. Endolysin LysSYL, which is derived from phage SYL, shows promise as an antistaphylococcal agent. However, endolysins generally exhibit instability and possess low bioavailability in acidic microenvironments. Here, an array of self-assembling peptides is designed, and peptide L5 is screened out based on its gel formation property and bioavailability. L5 exerted a pH-switchable antimicrobial effect (pH 5.5) and formed biocompatible hydrogels at neutral pH (pH 7.4). The LysSYL-loaded L5 can assemble L5@LysSYL hydrogels, increase thermal stability, and exhibit the slow-release effect of LysSYL. Effective elimination of S. aureus is achieved by L5@LysSYL through bacterial membrane disruption and cell separation inhibition. Moreover, L5@LysSYL hydrogels exhibit great potential in promoting wound healing in a mouse wound model infected by MRSA. Furthermore, L5@LysSYL hydrogels are safe and can decrease the cytokine levels and increase the number of key factors for vessel formation, which contribute to wound healing. Overall, the self-assembling L5@LysSYL can effectively clean MRSA and promote wound healing, which suggests its potential as a pH-sensitive wound dressing for the management of wound infections.

Phage-Derived Endolysins Against Resistant Staphylococcus spp.: A Review of Features, Antibacterial Activities, and Recent Applications.

Antimicrobial resistance is a significant global public health issue, and the dissemination of antibiotic resistance in Gram-positive bacterial pathogens has significantly increased morbidity, mortality rates, and healthcare costs. Among them, Staphylococcus, especially methicillin-resistant Staphylococcus aureus (MRSA), causes a wide range of diseases due to its diverse pathogenic factors and infection strategies. These bacteria also present significant issues in veterinary medicine and food safety. Effectively managing staphylococci-related problems necessitates a concerted effort to implement preventive measures, rapidly detect the pathogen, and develop new and safe antimicrobial therapies. In recent years, there has been growing interest in using endolysins to combat bacterial infections. These enzymes, which are also referred to as lysins, are a unique class of hydrolytic enzymes synthesized by double-stranded DNA bacteriophages. They possess glycosidase, lytic transglycosylase, amidase, and endopeptidase activities, effectively destroying the peptidoglycan layer and resulting in bacterial lysis. This unique property makes endolysins powerful antimicrobial agents, particularly against Gram-positive organisms with more accessible peptidoglycan layers. Therefore, considering the potential benefits of endolysins compared to conventional antibiotics, we have endeavored to gather and review the characteristics and uses of endolysins derived from staphylococcal bacteriophages, as well as their antibacterial effectiveness against Staphylococcus spp. based on conducted experiments and trials.

Mycosynthesis of silver nanoparticles from endophytic Aspergillus parasiticus and their antibacterial activity against methicillin-resistant Staphylococcus aureus in vitro and in vivo.

Methicillin-resistant Staphylococcus aureus (MRSA) is a drug-resistant and biofilm-forming pathogenic bacteria with severe morbidity and mortality. MRSA showed resistance against currently available antibiotics. Thus, there is an urgent need to develop novel effective treatments with minimal side effects to eliminate MRSA. In this study, we aimed to mycosynthesize silver nanoparticles (AgNPs) using the endophytic fungus Aspergillus parasiticus isolated from leaves of Reseda Arabica and to examine their antibacterial activity against MRSA. Screening of fungal secondary metabolites using gas chromatography-mass spectroscopy (GC-MS) analysis revealed the presence of high content of bioactive compounds with antibacterial activities. AP-AgNPs were mycosynthesized for the first time using ethyl acetate extract of A. parasiticus and characterized by imaging (transmission electron microscopy (TEM), UV-Vis spectroscopy, zeta potential, X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and Fourier transform infrared spectroscopy (FTIR)). The agar well diffusion method revealed the antibacterial activity of AP-AgNPs against MRSA with 25 μg/mL of minimum inhibitory concentration (MIC). AP-AgNPs were shown to exert antibacterial action via a bactericidal mechanism based on flow cytometry, scanning electron microscopy, and transmission electron microscopy assessment. Our data demonstrated the effective interaction of AP-AgNPs with the bacterial cell membrane, which resulted in cell membrane damage and disruption of cell surface structure. Furthermore, AP-AgNPs successfully prevented the development of MRSA biofilms by disturbing cell adhesion and destructing mature biofilm reaching over 80% clearance rate. Interestingly, topical application of AP-AgNPs to superficial skin infection induced by MRSA in mice effectively promoted wound healing and suppressed bacterial burden. Our results provide a novel green nanoparticle drug design with effective therapeutic potential against MRSA-induced skin infection.

Collateral Sensitivity to β-Lactam Antibiotics in Evolved Apramycin-Resistant MRSA.

Collateral sensitivity is an evolutionary trade-off for bacteria where acquiring resistance to one antibiotic results in an increased sensitivity to another antibiotic. This study was designed to evaluate the collateral sensitivity of methicillin-resistant Staphylococcus aureus (MRSA) to β-lactam antibiotics induced by the evolution of resistance to apramycin. Collateral sensitivity to ampicillin, cephazolin, ceftriaxone, cefotaxime, cefepime and cefquinome occurred after MRSA were exposed to apramycin and induced to acquire resistance. This sensitivity was associated with reduced β-lactamase activity and decreased expression of the mecA gene. We also found a decrease in the proton motive force and decreased efflux activity. These results provide new insights into collateral sensitivity-based strategies for the treatment of MRSA.

From past to present, exploring the applications of mupirocin ointment: A comprehensive review

Mupirocin (MUP), a potent antibacterial agent, has been a cornerstone of topical antimicrobial therapy for several decades. As an older, yet widely used antibiotic, MUP has exhibited efficacy against various bacterial strains, making it a versatile tool in the management of a range of infections. The review synthesizes available literature to highlight the evolution of MUP, from its initial discovery to its current status as a go-to topical antibiotic. In the era of rising antibiotic resistance, MUP is positioned as a valuable therapeutic option due to its broad-spectrum activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Emphasis is placed on its distinctive role in different infections, enhanced efficacy with different additives, and newer drug delivery strategies.In addition to its classical applications in impetigo and other superficial skin infections, this review delves into emerging indications and novel uses of MUP, potentially expanding its clinical utility. The exploration of combination therapies, alternative formulations, and ongoing research endeavors will contribute to a forward-looking perspective on the role of MUP in future antimicrobial strategies.

Metal-phenolic nanoparticles enhance low temperature photothermal therapy for bacterial biofilm in superficial infections

Bacterial infections, especially induced by multidrug-resistant pathogens, have become a significant global health concern. In the infected tissues, biofilms not only serve as a source of nutrients but also act as protective barriers that impede antibiotic penetration. Herein, we developed tea polyphenols epigallocatechin gallate (EGCG) Au nanoparticles (E-Au NPs) through direct one-step self-assembly methods by EGCG chelating with Au ions to eradicate antibiotic-resistant bacteria methicillin-resistant Staphylococcus aureus (MRSA) and prevent the formation of biofilm under near-infrared (NIR) irradiation. The outstanding antibacterial effect involved in mild photothermal therapy, reactive oxygen species production, pathogenicity-related genes regulation, and quinoprotein formation that were specific to the polyphenol-based NPs. The excellent antibacterial and anti-inflammatory therapeutic efficacy of E-Au NPs was validated and topically applied in murine MRSA-infected skin wounds and keratitis model in vivo to kill bacteria, reduce the inflammation response and promote wound healing. Furthermore, the ophthalmic and systemic biosafety profiles were thoroughly evaluated while no significant side effects were revealed achieving a balance between high-efficiency antibacterial properties and biocompatibility. This study provides an effective therapeutic agent of metal-phenolic materials for superficial tissue infection with favorable prognosis and potential in clinical translation.Graphical abstract

Magnetic Field/Ultrasound-Responsive Fe3O4 Microbubbles for Targeted Mechanical/Catalytic Removal of Bacterial Biofilms.

Conventional antibiotics are limited by drug resistance, poor penetration, and inadequate targeting in the treatment of bacterial biofilm-associated infections. Microbubble-based ultrasound (US)-responsive drug delivery systems can disrupt biofilm structures and enhance antibiotic penetration through cavitation effects. However, currently developed US-responsive microbubbles still depend on antibiotics and lack targeting capability. In this work, magnetic field/ultrasound (MF/US)-responsive Fe3O4 microbubbles (FMB) were constructed based on Fe3O4 nanoparticles (NPs) with superparamagnetic and peroxidase-like catalytic properties. In vitro experiments demonstrated that FMB can be targeted to methicillin-resistant Staphylococcus aureus (MRSA) biofilms by the direction of MF. Upon US irradiation, FMB collapse due to inertial cavitation and generate mechanical forces to disrupt the structure of MRSA biofilms and releases Fe3O4 NPs, which catalyze the generation of reactive oxygen species (ROS) from H2O2 in the biofilm microenvironment and kill the bacteria within the biofilm. In a mouse biofilm infection model, FMB efficiently destroyed MRSA biofilms grown in subcutaneous catheters with the MF and US. Magnetic-targeted mechanical/catalytic therapy based on FMB provides a promising strategy for effectively combating bacterial biofilm infection.

Novel isolation and optimization of anti-MRSA bacteriophages using plaque-based biokinetic methods

Background: MRSA (methicillin-resistant Staphylococcus aureus) is a global health problem. Many people are looking for new ways to combat MRSA, for example by using bacteriophages (phages). It has been extremely challenging to isolate a sufficient quantity of lytic anti-MRSA phages. Therefore, new techniques for separating, refining, and reworking anti-MRSA phages were sought in this study. Methods: Of 437 S. aureus isolates, nine clinical MRSA isolates were obtained from three hospitals in Baghdad, Iraq and two ATCC MRSA strains were used to separate wild anti-MRSA phages from sewage, filth, and hospital settings. The wild phage was optimized using plaque-based biokinetic methods. The resulting highly lytic and specific anti-MRSA phages were subjected to novel physico-chemical phage redesign protocols using agents to weaken the bacterial cell wall to allow phages to enter into host bacteria and acquire the specificity of the new host. Three protocols were tested using different combinations of benzethonium chloride (BZT-CH), alkaline ethanol, and chlorhexidine gluconate. Results: Five newly redesigned, transiently stable, anti-MRSA phages were produced using the BZT-CH and ethanol–alkali methods, albeit at varying rates. Conclusion: Although the resulting designed anti-MRSA phages are transiently stable, they represent a rare opportunity and an excellent endless source of lytic anti-MRSA phages from which a large number of permanent phage lysins can be separated and purified.

Isolation, optimization, and redesigning of phages of methicillin-resistant Staphylococcus aureus from clinical hospital isolates in Baghdad

Background: A global health concern is methicillin-resistant Staphylococcus aureus (MRSA). The use of bacteriophages is one of the many novel control strategies against MRSA that are frequently sought. However, it is quite challenging to isolate enough lytic anti-MRSA phages. In order to extract, optimize, and remodel anti-MRSA phages, this study sought novel approaches. Methods: Two ATCC MRSA strains and nine clinical MRSA isolates were used to isolate wild anti-MRSA phages from hospital settings, dirt, and sewage. The wild phages were optimized using plaque-based biokinetic techniques. Using chemicals that weakened bacterial cell walls, the resulting highly lytic and specific anti-MRSA phages were subjected to unique physicochemical phage redesign processes. This allowed the phages to enter host bacteria and acquire the specificity of the new host. Three different protocols were tested using combinations of Tween 20, lysozyme, and nisin A. Results: Nisin A and lysozyme protocols at different rates were found to be successful in producing newly redesigned, transiently stable, anti-MRSA phages. Conclusion: Unlike self-depleting antibiotic-based applications, phage redesign is self-fortifying. In order to address the increasing number of epidemic MRSA strains, this model could prove to be a perfect platform for developing trustworthy control and treatment strategies. Additionally, it is believed to be an infinite supply of anti-MRSA lytic phages from which several permanent phage lysins can be isolated and refined.

Low molecular weight fucoidan induces M2 macrophage polarization to attenuate inflammation through activation of the AMPK/mTOR autophagy pathway

Fucoidan, a sulfated polysaccharide with a complex structure, has gradually become the focus of biomedical research due to its remarkable biological activity and low toxicity. In this research, it was noted that low molecular weight fucoidan (LMWF) exhibited significant antimicrobial effects on Methicillin-resistant Staphylococcus aureus (MRSA) and promoted polarization towards M2 macrophages, leading to a substantial reduction in inflammatory responses within the lipopolysaccharide (LPS)-activated macrophages. We further explored the mechanism underlying the anti-inflammation activity. Our findings indicated that LMWF significantly enhanced the phosphorylation level of AMP-activated protein kinase (AMPK), inhibited the phosphorylation of the mammalian target of rapamycin (mTOR), and enhanced the expression of LC3II. Meanwhile, Compound C (CC) substantially reversed the anti-inflammation effect of LMWF, indicating that the AMPK pathway plays a pivotal role in this effect. In in vivo research, LMWF revealed impressive anti-inflammatory potential. LMWF treatment significantly eliminated MRSA and ameliorated inflammatory symptoms in mice's MRSA-infected skin wound model. Further analysis using Western Blot (WB) indicated significant AMPK/mTOR signaling pathway activation in mice treated with LMWF, which led to accelerated polarization of macrophages from the M1 to the M2 phenotype. In summary, we systematically explored the mechanism by which LMWF exerts anti-inflammatory effects through in vitro and in vivo experiments. It was confirmed that LMWF effectively induced the conversion of macrophages to an anti-inflammatory M2 phenotype by activating the AMPK/mTOR pathway. Simultaneously, LMWF effectively eradicated MRSA and accelerated wound healing in mice. This finding provides an important theoretical basis for further research on fucoidan.

The antibiotic therapy containing contezolid successfully treated methicillin-sensitive Staphylococcus aureus infective endocarditis accompanied with cerebrovascular complications

BackgroundStaphylococcus aureus infective endocarditis (IE) in native valves is associated with high mortality rates and is prone to various complications, including embolic strokes, which often result in poor prognoses. Contezolid, a novel oxazolidinone antibiotic, exhibits superior therapeutic efficacy with a reduced risk of hematologic toxicity. However, there are currently no reports on the treatment of methicillin-susceptible Staphylococcus aureus (MSSA) IE accompanied by cerebrovascular complications.Case PresentationWe reported a young female patient with MSSA IE accompanied by cerebrovascular complications. She was diagnosed through blood culture, transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and cranial imaging, but the therapy using piperacillin-tazobactam and vancomycin failed. Therefore, the combination therapy of cefazolin and linezolid was applied, and her body temperature gradually returned to normal, and the infection symptoms were controlled. However, the platelets (PLT) dropped to 114 × 109/L, so contezolid was used as an alternative therapy. Subsequently, the PLT returned to normal. The patient received contezolid therapy for 3 weeks and was free of adverse events during the 2 years of follow-up.ConclusionThis was the first case of MSSA IE accompanied by cerebrovascular complications in a young woman, who was successfully treated with an antibiotic regimen containing contezolid, without the need for surgical intervention, demonstrating remarkable efficacy and safety.

Assessment of Pelargonium graveolens flower essential oil: Antimicrobial, antioxidant, enzyme inhibition and in vivo topical analgesic and anti-inflammatory efficacy as treatment for atopic dermatitis

Background Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by pruritus and skin barrier dysfunction. This study aims to evaluate the therapeutic potential of Pelargonium graveolens (Geraniaceae) in managing AD symptoms through its essential oil. Methods The chemical composition of Pelargonium graveolens flower essential oil (PFEO) was analyzed using gas chromatography-mass spectrometry (GC-MS). Its antimicrobial, antioxidant, and anti-inflammatory properties were assessed, along with the inhibitory effects of PFEO on key enzymes involved in skin repair: tyrosinase, elastase, and collagenase. An in vivo evaluation of a gel formulation containing PFEO was also conducted to assess its anti-inflammatory and analgesic efficacy. Results GC-MS analysis identified major compounds in PFEO, including Geraniol (22.83%), beta-citronellol (19.51%), naphthalenemethanol (15.36%), and Geranyl tiglate (9.38%), with minor constituents such as linalool (3.81%) and neryl formate (1.31%). PFEO exhibited bacteriostatic activity against various bacterial and fungal strains, including Pseudomonas aeruginosa, Staphylococcus aureus, Methicillin-Resistant Staphylococcus aureus (MRSA), Bacillus anthracis, Streptococcus pyogenes, Staphylococcus epidermidis, Candida albicans, and Malassezia spp. The essential oil also demonstrated significant antioxidant properties and inhibited key enzymes linked to skin alterations in AD. Conclusions PFEO shows promising therapeutic potential for managing symptoms of atopic dermatitis due to its antimicrobial, antioxidant, and anti-inflammatory properties, as well as its analgesic effects. The findings support further exploration of PFEO as a natural alternative in the treatment of AD.

In silico studies on nicotinamide analogs as competitive inhibitors of nicotinamidase in methicillin-resistant Staphylococcus aureus.

Nicotinamidase/PncA is a member of the hydrolase enzyme family, catalyzing the de-amidation of nicotinamide (NM) to nicotinic acid (NA) via salvage pathway. Products are fed into Preiss-Handler pathway for NAD+ biosynthesis which is an important enzyme cofactor and crucial for redox balance in microorganisms. Pathogens like methicillin-resistant Staphylococcus aureus (MRSA) are NAD+ auxotroph and rely on their host environment for NAD+ precursors to synthesize NAD+. Mutations in nicotinamidase/PncA have been reported to be associated with resistance to pyrazinamide (PZA), a front-line anti-tubercular drug, underlying its importance as an important link in NAD+ biosynthesis network in pathogenic organisms such as MRSA. The conserved features of PncA and essentiality of salvage route in MRSA and the absence of this enzyme in humans and other eukaryotes are attractive options to explore therapeutics against this target. In this work, we have screened novel substrate analogs from the PubChem database using virtual screening approaches employing fingerprint tanimoto-based 2D similarity search against Staphylococcus aureus PncA (SaPncA). Identified compounds were further assessed using molecular dynamics simulations to investigate conformational stability and structural integrity. We propose two analogs, namely L28 and L33 with greater stability, favorable binding and strong binding free energies in MM-PBSA calculations. The strategy could provide an important clue in developing similar compound scaffolds as potent drug-like molecules against MRSA and other pathogenic species harboring this enzyme. Smaller scaffolds of these molecules could be attractive options for fragment-based derivatization for inhibitor discovery.

A Target to Combat Antibiotic Resistance: Biochemical and Biophysical Characterization of 3-Dehydroquinate Dehydratase from Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with the acquisition of nosocomial infections, community-acquired infections, and infections related to livestock animals. In the pursuit of molecular targets in the development process of antibacterial drugs, enzymes within the shikimate pathway, such as 3-dehydroquinate dehydratase (DHQD), are regarded as promising targets. Therefore, through biochemical and biophysical techniques, in the present work, the characterization of DHQD from MRSA (SaDHQD) was performed. The kinetic results showed that the enzyme had a Vmax of 107 μmol/min/mg, a Km of 54 μM, a kcat of 48 s−1, and a catalytic efficiency of 0.9 μM−1 s−1. Within the biochemical parameters, the enzyme presented an optimal temperature of 55 °C and was thermostable at temperatures from 10 to 20 °C, being completely inactivated at 60 °C in 10 min. Furthermore, SaDHQD showed an optimal pH of 8.0 and was inactivated at pH 4.0 and 12.0. Moreover, the activity of the enzyme was affected by the presence of ions, surfactants, and chelating agents. The thermodynamic data showed that the rate of inactivation of the enzyme was a temperature-dependent process. Furthermore, the enthalpy change, entropy change, and Gibbs free energy change of inactivation were positive and practically constant, which suggested that the inactivation of SaDHQD by temperature was driven principally by enthalpic contributions. These results provide, for the first time, valuable information that contributes to the knowledge of this enzyme and will be useful in the search of SaDHQD inhibitors that can serve as leads to design a new drug against MRSA to combat antibiotic resistance.

The Influence of COVID-19 on Antimicrobial-Resistance in Gram-Positive Bacteria at a Private Saudi Hospital: A Five-Year Evaluation

Due to the emergence of antimicrobial-resistance (AR) as a public health threat, the Saudi National Action Plan (SNAP) was implemented in 2017, incorporating various strategies to combat AR. To evaluate the effectiveness of SNAP and the impact of COVID-19, the study analyzed pre- and post-pandemic rates of AR, methicillin-resistant Staphylococcus aureus (MRSA), and multidrug resistance (MDR) among Gram-positive bacteria at a private medical center in Saudi Arabia. This study reviewed the cases of all patients who had been diagnosed with Gram-positive bacterial infection between January 2017 and December 2021. Bacterial strain identification was conducted using VITEK-2 ID-GP cards, while AR, MRSA, and MDR were defined using AST-GP 67 and AST-ST02 cards, all adhering to the manufacturer’s recommended protocols. The five-year study from 2017 to 2021 yielded 6,271 Gram-positive bacteria isolates from patients in a Saudi private hospital. Though the rate of AR initially declined between 2017 and 2019, it spiked significantly from 2020 to 2021. Similarly, the MRSA rate exhibited a substantial decrease (p < 0.05) from 2017 to 2019, followed by a significant rise (p < 0.05) between 2020 and 2021. Out of the isolated pathogens, 1,031 (16.44%) exhibited MDR, with all isolates showing a marked increase (p < 0.05) in MDR from 2020 to 2021. The study highlights the aggravating impact of the COVID-19 pandemic on AR, underscoring the need for the SNAP to intensify its efforts in combating AR.