Bioactivities and Structure-Activity Relationships of Fusidic Acid Derivatives: A Review

Novel Crown Ether-Functionalized Fusidic Acid Butyl Ester: Synthesis, Biological Evaluation, In Silico ADMET, and Molecular Docking Studies

Crown ethers have gained importance in the field of medicine because of their resemblance to natural ionophores like valinomycin. With the goal of developing new pharmacologically important crown ethers, a novel series of crown ethers linked with Fusidic acid butyl ester 10a-d were synthesized and characterized by means of their 1H NMR, 13C NMR DEPT-135, FT-IR, and mass spectrometry. In vitro antioxidant and α-glucosidase inhibition activities of all crown ethers along with the precursor Fusidic acid butyl ester were examined and compared to the standard butylated hydroxyanisole and acarbose, respectively. Compounds (FABE-16-crown-4) 10b and (FABE-19-crown-5) 10c showed high antioxidant potential with the IC50 = 22.5 ± 0.2 μM and 32.1 ± 0.3 μM, respectively, when compared to the standard BHA (IC50 = 44.2 ± 0.34 μM). To understand the binding mode of the compounds, molecular docking investigations were performed using human antioxidant protein, peroxiredoxin 5. Molecular docking studies revealed higher docking scores (-6.5 and -6.7 kcal/mol) for the highly active compounds 10c and 10b, respectively, than standard BHA (-5.3 kcal/mol). Synthesized crown ethers exhibited moderate α-glucosidase inhibition with (IC50 = 23.5 ± 0.2 to 76.5 ± 0.1 μM) when compared to acarbose as standard (IC50 = 5.2 ± 0.8 μM). The in silico ADMET predictions indicated that the prepared compounds obeyed (bRO5) and Veber's rule for the acceptance as orally administered drugs and indicated that all the prepared crown ethers exhibited calculated values of drug likeness parameters in acceptable ranges that showed good potential of these molecules for further drug development investigations.

Topical administration of mupirocin ointment and fusidic acid in bacterial infection-induced skin diseases

Introduction

Bacterial skin diseases have strong virulence to penetrate deep into the skin.

Aim

To evaluate the therapeutic effects of 2% mupirocin ointment and 2% fusidic acid cream on bacterial skin diseases and their safety.

Material and methods

One-hundred patients with bacterial skin diseases treated from May 2021 to May 2024 were randomly divided into a control group and a treatment group (n = 50) and they were given 2% mupirocin ointment and 2% fusidic acid cream, respectively. The skin injury areas, eczema area and severity index (EASI) scores, therapeutic effects and adverse reactions were compared before and after two courses of medication. The antibacterial activities of these two drugs against Staphylococcus epidermidis and Propionibacterium acnes were detected by the agar diffusion method.

Results

After treatment, the EASI and itching scores of both groups significantly decreased compared with those before treatment (t = 30.804, 19.018, p < 0.001; t = 24.594, 12.680, p < 0.001), and the treatment group had significantly lower scores than those of the control group (p < 0.05). The overall effective rate of the treatment group (96.00%) was higher than that of the control group (90.00%) (p > 0.05), and the distribution of therapeutic effects of the treatment group was significantly better (p < 0.05). The two groups had similar incidence rates of adverse reactions (χ2 = 1.0147, p = 0.3074) that were remitted without additional therapy. Both mupirocin ointment and fusidic acid cream had clear inhibition zones for S. epidermidis, with similar diameters (31.69 ±7.12 mm vs. 31.78 ±6.54 mm, t = 0.0949, p = 0.9245). However, only fusidic acid cream had an obvious inhibition zone for P. acnes on reinforced Brucella agar plate.

Conclusions

The therapeutic effects of fusidic acid cream on bacterial skin diseases were superior to those of mupirocin ointment.

Fusidic Acid and Lidocaine-Loaded Electrospun Nanofibers as a Dressing for Accelerated Healing of Infected Wounds

Introduction

Wound treatment is a significant health burden in any healthcare system, which requires proper management to minimize pain and prevent bacterial infections that can complicate the wound healing process.

Rationale

There is a need to develop innovative therapies to accelerate wound healing cost-effectively. Herein, two polymer-based nanofibrous systems were developed using poly-lactic-co-glycolic-acid (PLGA) and polyvinylpyrrolidone (PVP) loaded with a combination of an antibiotic (Fusidic acid, FA) and a local anesthetic (Lidocaine, LDC) via electrospinning technique for an expedited healing process by preventing bacterial infections while reducing the pain sensation.

Results

The fabricated nanofibers showed an excellent morphology with an average fiber diameter of 556 ± 71 nm and 291 ± 87 nm for the dual drug-loaded PLGA/PVP and PVP nanofibers, respectively. The encapsulation efficiency (EE%) and drug loading (DL) studies revealed that PLGA/PVP loaded with FA and LDC exhibited EE% of 92% and 75%, respectively, while the DL was measured at 40 ± 8 µg/mg for FA and 32 ± 7 µg/mg for LDC. Furthermore, both drugs were fully released from the nanofibers within 48 hours. In contrast, FA/LDC-loaded PVP nanofibers exhibited EE% of 100% for FA and 84% for LDC; DL was measured at 85 ± 3 µg/mg for FA and 70 ± 3 µg/mg for LDC, while both drugs were completely released within 24 hours. The in vitro cytotoxicity study demonstrated a safe concentration of FA and LDC at ≤ 125 μg/mL. The prepared nanofibers were tested in vivo in an S. aureus-infected wound mice model to assess their efficacy, and the results showed that the FA/LDC-PVP had a faster wound closure and the lowest bacterial counts compared to other groups.

Conclusion

These findings showed the potential application of the fabricated dual drug-loaded nanofibers as a wound-healing plaster against infected acute wounds.

Metabolic analysis of the mode of action and mode of resistance of fusidic acid against Staphylococcus aureus

Understanding bacterial responses to antibiotics is essential for identifying resistance mechanisms and developing novel therapies. This study evaluated the resistance of Staphylococcus aureus (S. aureus) to fusidic acid (FD) in 100 patients with skin and soft tissue infections (SSTIs), revealing susceptibility to FD despite resistance to other antibiotics. Through adaptive laboratory evolution, we developed a highly FD-resistant strain, E10, and identified three gene mutations (fusA, BPENGOFF-00211, and rplF) using whole-genome sequencing. The fusA mutation was the primary contributor to resistance. Furthermore, the evolved fusA mutant strain (H457Y) displayed impaired coagulation function and reduced growth rates. We also analyzed the metabolomic profiles of ancestral ATCC 25923 and evolved E10 strains, both treated and untreated with FD, revealing that the fusA gene can independently induce metabolic reprogramming. These changes primarily impacted pathways involved in central carbon metabolism, nucleotide metabolism, and amino acid synthesis. This study highlights the complexity of FD resistance in S. aureus and offers insights into the metabolic pathways associated with antibiotic resistance.

The fungal natural product fusidic acid demonstrates potent activity against Mycoplasma genitalium

Antimicrobial resistance is extremely common in Mycoplasma genitalium, a frequent cause of urethritis in men and cervicitis, vaginitis, and pelvic inflammatory disease in women. Treatment of M. genitalium infections is difficult due to intrinsic and acquired resistance to many antibiotic classes. We undertook a program to identify novel antimicrobials with activity against M. genitalium from fungal natural products. Extracts of Ramularia coccinea contained a molecule with potent activity that was subsequently identified as fusidic acid, a fusidane-type antibiotic that has been in clinical use for decades outside the United States. We found that minimum inhibitory concentrations of fusidic acid ranged from 0.31 to 4 µg/mL among 17 M. genitalium strains including laboratory-passaged and low-passage clinical isolates. Time-kill data indicate that bactericidal killing occurs when M. genitalium is exposed to ≥10 µg/mL for 48 h, comparing favorably to serum concentrations obtained from typical loading dose regimens. Resistance to fusidic acid was associated with mutations in fusA consistent with the known mechanism of action in which fusidic acid inhibits protein synthesis by binding to elongation factor G. Interestingly, no mutants resistant to >10 µg/mL fusidic acid were obtained and a resistant strain containing a F435Y mutation in FusA was impaired for growth in vitro. These data suggest that fusidic acid may be a promising option for the treatment of M. genitalium infections.

Albumin as a functional carrier solubilizing and facilitating fusidic acid transmembrane delivery into Gram-negative bacteria

Reversing the bacterial resistance is of great significance and importance. Fusidic acid (FA) is commonly effective against Gram-positive bacterial infections, but most Gram-negative bacteria have intrinsic resistance to FA, primarily due to the strong cell membrane-FA interactions, which highly inhibit the intracellular transport of FA. Herein, we use albumin (bovine serum albumin, BSA) as a bifunctional carrier to solubilize FA and facilitate its transmembrane delivery into Gram-negative bacterial cells. The water solubility of FA is significantly enhanced from 11.87 to 442.20 μg/mL by 5 mg/mL BSA after forming FA-BSA complex. Furthermore, FA-BSA (200 μg/mL) causes 99.96 % viability loss to the model pathogen E. coli upon incubation for 3 h, while free FA or BSA alone shows little activity. Elongation of E. coli cells after treated by FA-BSA is demonstrated by SEM, and the transmembrane transport of FA-BSA is demonstrated by CLSM. Interestingly, increasing the BSA amount substantially reduce the antibacterial activity of FA-BSA, implying an albumin-based transmembrane delivery mechanism may exist. This is the first report regarding successfully reversing the intrinsic resistance of Gram-negative bacteria to FA in the form of FA-BSA. The ready availability of albumin and the simple preparation allows FA-BSA to have great potentials for clinical use.

Structures of the Staphylococcus aureus ribosome inhibited by fusidic acid and fusidic acid cyclopentane

The antibiotic fusidic acid (FA) is used to treat Staphylococcus aureus infections. It inhibits protein synthesis by binding to elongation factor G (EF-G) and preventing its release from the ribosome after translocation. While FA, due to permeability issues, is only effective against gram-positive bacteria, the available structures of FA-inhibited complexes are from gram-negative model organisms. To fill this knowledge gap, we solved cryo-EM structures of the S. aureus ribosome in complex with mRNA, tRNA, EF-G and FA to 2.5 Å resolution and the corresponding complex structures with the recently developed FA derivative FA-cyclopentane (FA-CP) to 2.0 Å resolution. With both FA variants, the majority of the ribosomal particles are observed in chimeric state and only a minor population in post-translocational state. As expected, FA binds in a pocket between domains I, II and III of EF-G and the sarcin-ricin loop of 23S rRNA. FA-CP binds in an identical position, but its cyclopentane moiety provides additional contacts to EF-G and 23S rRNA, suggesting that its improved resistance profile towards mutations in EF-G is due to higher-affinity binding. These high-resolution structures reveal new details about the S. aureus ribosome, including confirmation of many rRNA modifications, and provide an optimal starting point for future structure-based drug discovery on an important clinical drug target.

The Structural and Molecular Mechanisms of Mycobacterium tuberculosis Translational Elongation Factor Proteins

Targeting translation factor proteins holds promise for developing innovative anti-tuberculosis drugs. During protein translation, many factors cause ribosomes to stall at messenger RNA (mRNA). To maintain protein homeostasis, bacteria have evolved various ribosome rescue mechanisms, including the predominant trans-translation process, to release stalled ribosomes and remove aberrant mRNAs. The rescue systems require the participation of translation elongation factor proteins (EFs) and are essential for bacterial physiology and reproduction. However, they disappear during eukaryotic evolution, which makes the essential proteins and translation elongation factors promising antimicrobial drug targets. Here, we review the structural and molecular mechanisms of the translation elongation factors EF-Tu, EF-Ts, and EF-G, which play essential roles in the normal translation and ribosome rescue mechanisms of Mycobacterium tuberculosis (Mtb). We also briefly describe the structure-based, computer-assisted study of anti-tuberculosis drugs.

Unlocking translational machinery for antitubercular drug development

Targeting translational factor proteins (TFPs) presents significant promise for the development of innovative antitubercular drugs. Previous insights from antibiotic binding mechanisms and recently solved 3D crystal structures of Mycobacterium tuberculosis (Mtb) elongation factor thermo unstable-GDP (EF-Tu-GDP), elongation factor thermo stable-EF-Tu (EF-Ts-EF-Tu), and elongation factor G-GDP (EF-G-GDP) have opened up new avenues for the design and development of potent antituberculosis (anti-TB) therapies.

Antistaphylococcal discovery pipeline; where are we now?

The serious spread of antibiotic-resistant Staphylococcal aureus strains is alarming. This is reflected by the measures governments and health-related bodies are offering to ease antibiotic drug development. Finding new active agents, preferably with novel mechanism of action, or even finding new targets for drug development are essential. In this review, we summarize the current status of novel antistaphylococcal agents undergoing clinical trials. We mainly discuss antistaphylococcal small molecules and peptides in the text with a special focus on their chemistry, while antistaphylococcal immunotherapy (antibodies) are mentioned in a summative table. This review shall serve as a summary that influences future synthetic efforts in the antistaphyloccocals development field.

Reversing the Natural Drug Resistance of Gram-Negative Bacteria to Fusidic Acid via Forming Drug-Phospholipid Complex

Drug resistance substantially compromises antibiotic therapy and poses a serious threat to public health. Fusidic acid (FA) is commonly used to treat staphylococcal infections, such as pneumonia, osteomyelitis and skin infections. However, Gram-negative bacteria have natural resistance to FA, which is almost restrained in cell membranes due to the strong interactions between FA and phospholipids. Herein, we aim to utilize the strong FA-phospholipid interaction to pre-form a complex of FA with the exogenous phospholipid. The FA, in the form of an FA-phospholipid complex (FA-PC), no longer interacts with the endogenous membrane phospholipids and thus can be delivered into bacteria cells successfully. We found that the water solubility of FA (5 µg/mL) was improved to 133 µg/mL by forming the FA-PC (molar ratio 1:1). Furthermore, upon incubation for 6 h, the FA-PC (20 µg/mL) caused a 99.9% viability loss of E. coli and 99.1% loss of P. aeruginosa, while free FA did not work. The morphology of the elongated bacteria cells after treatment with the FA-PC was demonstrated by SEM. The successful intracellular delivery was shown by confocal laser scanning microscopy in the form of coumarin 6-PC (C6-PC), where C6 served as a fluorescent probe. Interestingly, the antibacterial effect of the FA-PC was significantly compromised by adding extra phospholipid in the medium, indicating that there may be a phospholipid-based transmembrane transport mechanism underlying the intracellular delivery of the FA-PC. This is the first report regarding FA-PC formation and its successful reversing of Gram-negative bacteria resistance to FA, and it provides a platform to reverse transmembrane delivery-related drug resistance. The ready availability of phospholipid and the simple preparation allow it to have great potential for clinical use.

The anti-staphylococcal fusidic acid as an efflux pump inhibitor combined with fluconazole against vaginal candidiasis in mouse model

BACKGROUND

Candida albicans is the most common fungus that causes vaginal candidiasis in immunocompetent women and catastrophic infections in immunocompromised patients. The treatment of such infections is hindered due to the increasing emergence of resistance to azoles in C. albicans. New treatment approaches are needed to combat candidiasis especially in the dwindled supply of new effective and safe antifungals. The resistance to azoles is mainly attributed to export of azoles outside the cells by means of the efflux pump that confers cross resistance to all azoles including fluconazole (FLC).

OBJECTIVES

This study aimed to investigate the possible efflux pump inhibiting activity of fusidic acid (FA) in C. albicans resistant isolates and the potential use of Fusidic acid in combination with fluconazole to potentiate the antifungal activity of fluconazole to restore its activity in the resistant C. albicans isolates.

METHODS

The resistance of C. albicans isolates was assessed by determination of minimum inhibitory concentration. The effect of Fusidic acid at sub-inhibitory concentration on efflux activity was assayed by rhodamine 6G efflux assay and intracellular accumulation. Mice model studies were conducted to evaluate the anti-efflux activity of Fusidic acid and its synergistic effects in combination with fluconazole. Impact of Fusidic acid on ergosterol biosynthesis was quantified. The synergy of fluconazole when combined with Fusidic acid was investigated by determination of minimum inhibitory concentration. The cytotoxicity of Fusidic acid was tested against erythrocytes. The effect of Fusidic acid on efflux pumps was tested at the molecular level by real-time PCR and in silico study. In vivo vulvovaginitis mice model was used to confirm the activity of the combination in treating vulvovaginal candidiasis.

RESULTS

Fusidic acid showed efflux inhibiting activity as it increased the accumulation of rhodamine 6G, a substrate for ABC-efflux transporter, and decreased its efflux in C. albicans cells. The antifungal activity of fluconazole was synergized when combined with Fusidic acid. Fusidic acid exerted only minimal cytotoxicity on human erythrocytes indicating its safety. The FA efflux inhibitory activity could be owed to its ability to interfere with efflux protein transporters as revealed by docking studies and downregulation of the efflux-encoding genes of both ABC transporters and MFS superfamily. Moreover, in vivo mice model showed that using fluconazole-fusidic acid combination by vaginal route enhanced fluconazole antifungal activity as shown by lowered fungal burden and a negligible histopathological change in vaginal tissue.

CONCLUSION

The current findings highlight FA's potential as a potential adjuvant to FLC in the treatment of vulvovaginal candidiasis.

Chemical Constituents and Bioactivities of the Plant-Derived Fungus Aspergillus fumigatus

A new bergamotane sesquiterpenoid, named xylariterpenoid H (1), along with fourteen known compounds (2-15), were isolated from the crude extract of Aspergillus fumigatus, an endophytic fungus isolated from Delphinium grandiflorum L. Their structures were elucidated mainly by extensive analyses of NMR and MS spectroscopic data. In addition, the screening results of antibacterial and cytotoxic activities of compounds 1-15 showed that compound 4 displayed antibacterial activities against Staphylococcus aureus and MRSA (methicillin-resistant S. aureus) with an MIC value of 3.12 µg/mL.

Neutrophil-targeted combinatorial nanosystems for suppressing bacteremia-associated hyperinflammation and MRSA infection to improve survival rates

There is currently no specific and effective treatment for bacteremia-mediated sepsis. Hence, this study engineered a combinatorial nanosystem containing neutrophil-targeted roflumilast-loaded nanocarriers and non-targeted fusidic acid-loaded nanoparticles to enable the dual mitigation of bacteremia-associated inflammation and methicillin-resistant Staphylococcus aureus (MRSA) infection. The targeted nanoparticles were developed by conjugating anti-lymphocyte antigen 6 complex locus G6D (Ly6G) antibody fragment on the nanoparticulate surface. The particle size and zeta potential of the as-prepared nanosystem were about 200 nm and -25 mV, respectively. The antibody-conjugated nanoparticles showed a three-fold increase in neutrophil internalization compared to the unfunctionalized nanoparticles. As a selective phosphodiesterase (PDE) 4 inhibitor, the roflumilast in the nanocarriers largely inhibited cytokine/chemokine release from the activated neutrophils. The fusidic acid-loaded nanocarriers were vital to eliminate biofilm MRSA colony by 3 log units. The nanoparticles drastically decreased the intracellular bacterial count compared to the free antibiotic. The in vivo mouse bioimaging demonstrated prolonged retention of the nanosystem in the circulation with limited organ distribution and liver metabolism. In the mouse bacteremia model, the multifunctional nanosystem produced a 1‒2 log reduction of MRSA burden in peripheral organs and blood. The functionalized nanosystem arrested the cytokine/chemokine overexpression greater than the unfunctionalized nanocarriers and free drugs. The combinatory nanosystem also extended the median survival time from 50 to 103 h. No toxicity from the nanoformulation was found based on histology and serum biochemistry. Furthermore, our data proved that the active neutrophil targeting by the versatile nanosystem efficiently alleviated MRSA infection and organ dysfunction caused by bacteremia. STATEMENT OF SIGNIFICANCE: Bacteremia-mediated sepsis poses a significant challenge in clinical practice, as there is currently no specific and effective treatment available. In our study, we have developed a novel combinatorial nanosystem to address this issue. Our nanosystem consists of neutrophil-targeted roflumilast-loaded nanocarriers and non-targeted fusidic acid-loaded nanoparticles, enabling the simultaneous mitigation of bacteremia-associated inflammation and MRSA infection. Our nanosystem demonstrated the decreased neutrophil activation, effective inhibition of cytokine release, elimination of MRSA biofilm colonies, and reduced intracellular bacterial counts. In vivo experiments showed prolonged circulation, limited organ distribution, and increased survival rates in a mouse bacteremia model. Importantly, our nanosystem exhibited no toxicity based on comprehensive assessments.

Natural Compounds of Fungal Origin with Antimicrobial Activity-Potential Cosmetics Applications

The phenomenon of drug resistance in micro-organisms necessitates the search for new compounds capable of combating them. Fungi emerge as a promising source of such compounds as they produce a wide range of secondary metabolites with bacteriostatic or fungistatic activity. These compounds can serve as alternatives for commonly used antibiotics. Furthermore, fungi also accumulate compounds with antiviral activity. This review focuses on filamentous fungi and macrofungi as sources of antimicrobial compounds. The article describes both individual isolated compounds and extracts that exhibit antibacterial, antifungal, and antiviral activity. These compounds are produced by the fruiting bodies and mycelium, as well as the biomass of mycelial cultures. Additionally, this review characterizes the chemical compounds extracted from mushrooms used in the realm of cosmetology; specifically, their antimicrobial activity.

Roles of Virtual Screening and Molecular Dynamics Simulations in Discovering and Understanding Antimalarial Drugs

Malaria continues to be a global health threat, with approximately 247 million cases worldwide. Despite therapeutic interventions being available, patient compliance is a problem due to the length of treatment. Moreover, drug-resistant strains have emerged over the years, necessitating urgent identification of novel and more potent treatments. Given that traditional drug discovery often requires a great deal of time and resources, most drug discovery efforts now use computational methods. In silico techniques such as quantitative structure-activity relationship (QSAR), docking, and molecular dynamics (MD) can be used to study protein-ligand interactions and determine the potency and safety profile of a set of candidate compounds to help prioritize those tested using assays and animal models. This paper provides an overview of antimalarial drug discovery and the application of computational methods in identifying candidate inhibitors and elucidating their potential mechanisms of action. We conclude with the continued challenges and future perspectives in the field of antimalarial drug discovery.

Bacterial GTPases as druggable targets to tackle antimicrobial resistance

Small molecules as antibacterial agents have contributed immensely to the growth of modern medicine over the last several decades. However, the emergence of drug resistance among bacterial pathogens has undermined the effectiveness of the existing antibiotics. Thus, there is an exigency to address the antibiotic crisis by developing new antibacterial agents and identifying novel drug targets in bacteria. In this review, we summarize the importance of guanosine triphosphate hydrolyzing proteins (GTPases) as key agents for bacterial survival. We also discuss representative examples of small molecules that target bacterial GTPases as novel antibacterial agents, and highlight areas that are ripe for exploration. Given their vital roles in cell viability, virulence, and antibiotic resistance, bacterial GTPases are highly attractive antibacterial targets that will likely play a vital role in the fight against antimicrobial resistance.

Access to dialkylated allylic stereogenic centers by Ni-catalysed enantioselective hydrovinylation of unactivated alkenes

Tertiary dialkylated allylic stereogenic centers are widespread substructures in bioactive molecules and natural products. However, enantioselective access to dialkyl substituted allylic motifs remains a long-term challenge. Herein, a straightforward protocol to build allylic dialkylated stereogenic centers enabled by nickel-catalysed regio- and enantioselective hydrovinylation of isolated unactivated alkenes facilitated by a weakly coordinating group with vinyl bromides was developed, affording dialkylated allylic species in good yields with excellent enantioselectivities. The reaction distinguishes distinct alkenes and works for both terminal and internal aliphatic alkenes. The reaction proceeds under mild conditions and tolerates a wide range of functional groups.