Discovery of Furanoquinone Derivatives as a Novel Class of DNA Polymerase and Gyrase Inhibitors for MRSA Eradication in Cutaneous Infection

Small Schiff Base Molecules-A Possible Strategy to Combat Biofilm-Related Infections

Microorganisms participating in the development of biofilms exhibit heightened resistance to antibiotic treatment, therefore infections involving biofilms have become a problem in recent years as they are more difficult to treat. Consequently, research efforts are directed towards identifying novel molecules that not only possess antimicrobial properties but also demonstrate efficacy against biofilms. While numerous investigations have focused on antimicrobial capabilities of Schiff bases, their potential as antibiofilm agents remains largely unexplored. Thus, the objective of this article is to present a comprehensive overview of the existing scientific literature pertaining to small molecules categorized as Schiff bases with antibiofilm properties. The survey involved querying four databases (Web of Science, ScienceDirect, Scopus and Reaxys). Relevant articles published in the last 10 years were selected and categorized based on the molecular structure into two groups: classical Schiff bases and oximes and hydrazones. Despite the majority of studies indicating a moderate antibiofilm potential of Schiff bases, certain compounds exhibited a noteworthy effect, underscoring the significance of considering this type of molecular modeling when seeking to develop new molecules with antibiofilm effects.

Therapeutic Strategies To Counteract Antibiotic Resistance in MRSA Biofilm-Associated Infections

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the leading causes of persistent human infections. This pathogen is widespread and is able to colonize asymptomatically about a third of the population, causing moderate to severe infections. It is currently considered the most common cause of nosocomial infections and one of the main causes of death in hospitalized patients. Due to its high morbidity and mortality rate and its ability to resist most antibiotics on the market, it has been termed a "superbug". Its ability to form biofilms on biotic and abiotic surfaces seems to be the primarily means of MRSA antibiotic resistance and pervasiveness. Importantly, more than 80 % of bacterial infections are biofilm-mediated. Biofilm formation on indwelling catheters, prosthetic devices and implants is recognized as the cause of serious chronic infections in hospital environments. In this review we discuss the most relevant literature of the last five years concerning the development of synthetic small molecules able to inhibit biofilm formation or to eradicate or disperse pre-formed biofilms in the fight against MRSA diseases. The aim is to provide guidelines for the development of new anti-virulence strategies based on the knowledge so far acquired, and, to identify the main flaws of this research field, which have hindered the generation of new market-approved anti-MRSA drugs that are able to act against biofilm-associated infections.

Synthetic Naphthofuranquinone Derivatives Are Effective in Eliminating Drug-Resistant Candida albicans in Hyphal, Biofilm, and Intracellular Forms: An Application for Skin-Infection Treatment

Candida albicans is the most common cause of fungal infection. The emergence of drug resistance leads to the need for novel antifungal agents. We aimed to design naphthofuranquinone analogs to treat drug-resistant C. albicans for topical application on cutaneous candidiasis. The time-killing response, agar diffusion, and live/dead assay of the antifungal activity were estimated against 5-fluorocytosine (5-FC)- or fluconazole-resistant strains. A total of 14 naphthofuranquinones were compared for their antifungal potency. The lead compounds with hydroxyimino (TCH-1140) or O-acetyl oxime (TCH-1142) moieties were the most active agents identified, showing a minimum inhibitory concentration (MIC) of 1.5 and 1.2 μM, respectively. Both compounds were superior to 5-FC and fluconazole for killing planktonic fungi. Naphthofuranquinones efficiently diminished the microbes inside and outside the biofilm. TCH-1140 and TCH-1142 were delivered into C. albicans-infected keratinocytes to eradicate intracellular fungi. The compounds did not reduce the C. albicans burden inside the macrophages, but the naphthofuranquinones promoted the transition of fungi from the virulent hypha form to the yeast form. In the in vivo skin mycosis mouse model, topically applied 5-FC and TCH-1140 reduced the C. albicans load from 1.5 × 10⁶ to 5.4 × 10⁵ and 1.4 × 10⁵ CFU, respectively. The infected abscess diameter was significantly decreased by TCH-1140 (3-4 mm) as compared to the control (8 mm). The disintegrated skin-barrier function induced by the fungi was recovered to the baseline by the compound. The data support the potential of TCH-1140 as a topical agent for treating drug-resistant C. albicans infection without causing skin irritation.

Coenzyme Q0 From Antrodia cinnamomea Exhibits Drug-Resistant Bacteria Eradication and Keratinocyte Inflammation Mitigation to Ameliorate Infected Atopic Dermatitis in Mouse

Atopic dermatitis (AD) is an inflammatory skin disease that is usually accompanied by Staphylococcus aureus infection due to cutaneous barrier-function damage. Benzenoid compounds from Antrodia cinnamomea are known to exhibit antibacterial and anti-inflammatory activities. This study sought to investigate the potential of benzenoids for treating bacteria-infected AD. The compounds were screened against methicillin-resistant S. aureus (MRSA). Coenzyme Q₀ (CoQ₀), a key ingredient in A. cinnamomea, showed the strongest MRSA growth inhibition. We further tested the inhibitory effect of CoQ₀ on planktonic and biofilm MRSA. The work was also performed to explore the potential effectiveness of CoQ₀ on AD using activated keratinocytes and in vivo experimental AD mice as the models. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CoQ₀ against MRSA were 7.81 μg/ml. CoQ₀ was found to eradicate biofilm MRSA efficiently and reduce the biofilm thickness. CoQ₀ killed MRSA by inhibiting DNA polymerase and topoisomerases. A proteomic assay showed that CoQ₀ also reduced the ribosomal proteins. In the anti-inflammation study, CoQ₀ was found to downregulate the expression of interleukin (IL)-6, chemokine (C-C motif) ligand (CCL)5, and CCL17 in HaCaT cells. CoQ₀ at 0.5 μg/ml could recover the filaggrin decreased by HaCaT activation to the normal control. We established a bacteria-infected AD-like model in mice using ovalbumin (OVA) and topically applied MRSA. Topical CoQ₀ delivery lessened the MRSA presence in the AD-like lesions by >90%. The erythema, barrier function, and epidermal thickness of the AD-like wounds were improved by CoQ₀ through the reduction of IL-1β, IL-4, IL-6, IL-10, interferon (IFN)-γ, and by neutrophil infiltration in the lesional skin. CoQ₀ is therefore regarded as effective in mitigating AD symptoms associated with bacterial load.

Design, Synthesis, and Anti-Bacterial Evaluation of Triazolyl-Pterostilbene Derivatives

Staphylococcus aureus resistance to current antibiotics has become the greatest global challenge facing public health. The development of new antimicrobial agents is urgent and important and is needed to provide additional therapeutic options. In our previous study, we found out that pterostilbene exhibited potent antibacterial activity, especially against methicillin-resistant Staphylococcus aureus (MRSA). According to previous studies, 1,2,3-triazole, with the characteristic of increasing the interaction with the target readily and enhancing water solubility, were widely used in the approved anti-bacterial drugs. Therefore, these results attract our interest to use the structure of pterostilbene as a scaffold for the hybrid 1,2,3-triazole moiety to develop a novel anti-MRSA infection agent. In this study, we demonstrated the design and synthesis of a series of triazolylpterostilbene derivatives. Among these compounds, compound 4d exhibited the most potent anti-MRSA activity with a minimum inhibitory concentration (MIC) value of 1.2–2.4 μg/mL and a minimum bactericidal concentration (MBC) value of 19.5–39 μg/mL. The structure–activity relationship and antibacterial mechanism were investigated in this study. Molecular docking studies were carried out to verify and rationalize the biological results. In this study, the results confirmed that our design could successfully increase the inhibitory activity and specificity against MRSA. Compound 4d could be used as a candidate for anti-bacterial agents and in depth vivo studies should be further investigated.