Giving antibiotics an assist

Synergistic antimicrobial efficacy of glabrol and colistin through micelle-based co-delivery against multidrug-resistant bacterial pathogens

BACKGROUND

Widespread bacterial infection and the spread of multidrug resistance (MDR) exhibit increasing threats to the public and thus require new antibacterial strategies. Coupled with the current slow pace of antibiotic development, the use of antibiotic adjuvants to revitalize existing antibiotics offers great potential.

PURPOSE

We aim to explore the synergistic antimicrobial mechanism of glabrol (GLA) and colistin (COL) while developing an innovative multifunctional micelle-based drug delivery system to enhance therapeutic efficacy.

METHODS

The synergy between GLA and COL was assessed through a combination of high-throughput screening and checkerboard analysis techniques. Moreover, we performed fluorescence-based assays to investigate the underlying mechanisms of action of the GLA and COL combination. We also developed a multifunctional drug delivery platform that integrates GLA and COL into co-loaded composite micelles, aimed at improving antibacterial efficacy against peritoneal sepsis and chronic bacterial wound infections caused by diverse microbial pathogens.

RESULTS

We have discovered that natural flavonoids found in plants act synergistically with colistin against MDR bacterial infections, effectively improving its efficacy through a co-delivery strategy. The combination therapy consisting of GLA and COL exhibits enhanced antibacterial efficacy and is capable of clearing 99% of MDR Gram-positive and Gram-negative bacteria in 4 h. Mechanistic studies showed that COL increases the outer membrane permeability, which promotes the adhesion of GLA to the inner membrane, disrupting bacterial metabolism, and ultimately leading to bacterial death. Furthermore, a novel pH-responsive hydrogel system was developed and dispersed with GLA and COL co-loaded composite micelles to mitigate the selective pressure of antibiotics with fewer side effects. Lastly, such a system showed high efficacy in two animal models.

CONCLUSION

Our findings provide a potential therapeutic option using a co-delivery system functionalized with combination therapy, to address the prevalent infections caused by complex bacterial infections and even MDR bacterial infections.

Methods for Rapid Evaluation of Microbial Antibiotics Resistance

Antibiotic resistance is a major challenge for public health systems worldwide. Rapid and effective identification of bacterial strains is critical for reducing the use of antibiotics and restricting the spread of antibiotic-resistant microorganisms. Various approaches have been developed in recent years for rapid bacterial identification and antibiotic susceptibility testing (AST), such as Raman spectroscopy, single cell image analysis, microfluidic techniques, mass spectrometry analysis, use of high-sensitive luminescent and fluorescent tags, impedance-based detection, and others. This review describes the methods developed for rapid bacterial identification and assessment of their antibiotic susceptibility, including general principles, specific problems, and future prospects.

Atmospheric Pressure Enhanced Self-Sealing Rotation-SlipChip with Programmable Concentration Gradient Generation for Microbiological Applications

In microbiological research, traditional methods for bacterial screening and antibiotic susceptibility testing are resource-intensive. Microfluidics offers an efficient alternative with rapid results and minimal sample consumption, but the demand for cost-effective, user-friendly platforms persists in communities and hospitals. Inspired by the Magdeburg hemispheres, the strategy adapts to local conditions, leveraging omnipresent atmospheric pressure for self-sealing of Rotation-SlipChip (RSC) equipped with a 3D circular Christmas tree-like microfluidic concentration gradient generator. This innovative approach provides an accessible and adaptable platform for microbiological research and testing in diverse settings. The RSC can avoid leakage concerns during multiple concentration gradient generation, chip-rotating, and final long-term incubation reaction (≥24 h). Furtherly, RSC subtypes adapted to different reactions can be fabricated in less than 15 min with cost less than $1, the result can be read through designated observational windows by naked-eye. Moreover, the RSC demonstrates its capability for evaluating bacterial biomarker activity, enabling the rapid assessment of β-galactosidase concentration and enzyme activity within 30 min, and the limit of detection can be reduced by 10-fold. It also rapidly determines the minimum antibiotic inhibitory concentration and antibiotic combined medications results within 4 h. Overall, these low-cost and user-friendly RSC make them invaluable tools in determinations at previously impractical environment.

Development of Phloroglucinol-Linked Tris-Quaternary Ammonium Salt Antimicrobial Peptide Mimics with Low Cytotoxicity and Broad-Spectrum Antibacterial Activity

Encouraged by the significantly different toxicities and antibacterial activities of diverse linkers, such as alkyl and aromatic nuclei linkers, and the unique structure of phloroglucinol, we synthesized a series of tris-quaternary ammonium salt (tris-QAS) antibacterial peptide mimics based on the marketed drug phloroglucinol. Among them, 2f displayed excellent activity against Staphylococcus aureus (MIC = 0.5 μg/mL) and high selectivity (SI > 2560). Surprisingly, the cytotoxicity of 2f (CC50 = 152.7 μg/mL) was dramatically better than those of alkyl QAS I and hydroquinone QAS II. Additionally, 2f possessed rapid bactericidal capability, was not prone to inducing bacterial resistance, and also exhibited excellent activity against S. aureus biofilms and persistent bacteria. Mechanistic research and transcriptome analysis revealed that 2f can interfere with the normal metabolism of bacterial cells, and it can specifically bind with phosphatidylglycerol to destroy the cell membrane. Importantly, 2f exhibited potent in vivo antibacterial activity in a mouse subcutaneous methicillin-resistant S. aureus (MRSA) infection model.

Strategically Engineered Ru(II) Complexes with Enhanced ROS Activity Enabling Potent Sonodynamic Effect against Multidrug-Resistant Biofilms

Sonodynamic therapy (SDT) can generate reactive oxygen species (ROS) to combat multidrug-resistant biofilms, which pose significant challenges to human health. As the key to producing ROS in SDT, the design of sonosensitizers with optimal molecular structures for sufficient ROS generation and activity in complex biofilm matrix is essential. In this study, we propose a π-expansion strategy and synthesize a series of small-molecule metal Ru(II) complexes (Ru1-Ru4) as sonosensitizers (Ru1-Ru4) to enhance the efficacy of SDT. Among these complexes, Ru4 demonstrates remarkable ROS generation capability (∼65.5-fold) that surpasses most commercial sonosensitizers (1.3- to 6.7-fold). Through catalyzing endogenous H2O2 decomposition, Ru4 facilitates the production of abundant O2 as a resource for 1O2 and the generation of new ROS (i.e., •OH) for improving SDT. Furthermore, Ru4 maintains the sustained ROS activity via consuming the interferences (e.g., glutathione) that react with ROS. Due to these unique advantages, Ru4 exhibits potent biofilm eradication ability against methicillin-resistant Staphylococcus aureus (MRSA) both in vitro and in vivo, underscoring its potential use in clinical settings. This work introduces a new approach for designing effective sonosensitizers to eliminate biofilm infections, addressing a critical need in healthcare management.

Emerging contaminants: A One Health perspective

Environmental pollution is escalating due to rapid global development that often prioritizes human needs over planetary health. Despite global efforts to mitigate legacy pollutants, the continuous introduction of new substances remains a major threat to both people and the planet. In response, global initiatives are focusing on risk assessment and regulation of emerging contaminants, as demonstrated by the ongoing efforts to establish the UN's Intergovernmental Science-Policy Panel on Chemicals, Waste, and Pollution Prevention. This review identifies the sources and impacts of emerging contaminants on planetary health, emphasizing the importance of adopting a One Health approach. Strategies for monitoring and addressing these pollutants are discussed, underscoring the need for robust and socially equitable environmental policies at both regional and international levels. Urgent actions are needed to transition toward sustainable pollution management practices to safeguard our planet for future generations.

Rapid and Accurate Antimicrobial Susceptibility Testing Using Label-Free Electrical Impedance-Based Microfluidic Platform

Antimicrobial resistance has become a serious threat to the global public health. Accurate and rapid antimicrobial susceptibility testing (AST) allows evidence-based prescribing of antibiotics to improve patient care and clinical outcomes. Current culture-based AST assays are inherently limited by the doubling time of bacterial reproduction, which require at least 24 h to have a decisive result. Herein, a label-free electrical impedance-based microfluidic platform designed to expedite and streamline AST procedure for clinical practice is presented. Following a 30-min exposure of bacterial samples to antibiotics, the presented high-throughput, single-bacterium level impedance characterization platform enables a rapid 2-min AST assay. The platform facilitates accurate analysis of individual bacterial viability, as indicated by changes in electrical characteristics, thereby enabling the determination of antimicrobial resistance. Moreover, the potential clinical applicability of this platform is demonstrated by testing different E. coli strains against five antibiotics, yielding 100% categorical agreements compared to standard culture methods.

Down-Regulation of HSP by Pd-Cu Nanozymes for NIR Light Triggered Mild-Temperature Photothermal Therapy Against Wound Bacterial Infection: In vitro and in vivo Assessments

Purpose

We aimed to develop an oxidative-stress-activated palladium-copper nanozyme to reduce bacterial's heat sensitivity by down-regulating heat shock proteins to overcome the shortcomings of conventional photothermal antimicrobial therapy and achieve mild photothermal bactericidal efficacy.

Methods

We first synthesized palladium-copper nanozymes (PC-NPs) by hydration and used transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy to demonstrate their successful preparation. Their photothermal therapy (PTT) and chemo-dynamic therapy (CDT) activities were then determined by a series of photothermal performance tests and peroxidase-like performance tests, and the destruction of heat shock proteins by reactive oxygen species (ROS) was verified at the protein level by Western Blotting tests, providing a basis for the effective bacteria-killing by the mild-temperature photothermal treatment subsequently applied. We also validated this promising programmed and controlled antimicrobial treatment with palladium-copper nanozymes by in vivo/in vitro antimicrobial assays. A hemolysis assay, MTT cytotoxicity test and histopathological analysis were also performed to assess the in vivo safety of PC-NPs.

Results

In the micro-acidic environment of bacterial infection, PC-NPs showed peroxidase-like activity that broke down the H2O2 at the wound into hydroxyl radicals and down-regulated bacterial heat shock proteins. The application of PC-NPs increased bacteria's sensitivity to subsequent photothermal treatment, enabling the elimination of bacteria via mild photothermal treatment.

Conclusion

The programmed synergistic catalytic enhancement of CDT and mild photothermal therapy achieves the most efficient killing of bacteria and their biofilms, which brings future thinking in the relationship between heat shock proteins and oxidative stress damage in bacteria.

A New Discovery of Unique 13-(Benzimidazolylmethyl)berberines as Promising Broad-Spectrum Antibacterial Agents

A new hybridization of berberine and benzimidazoles was performed to produce 13-(benzimidazolylmethyl)berberines (BMB) as potentially broad-spectrum antibacterial agents with the hope of confronting multidrug-resistant bacterial infections in the livestock industry. Some of the newly prepared hybrids showed obvious antibacterial effects against tested strains. Particularly, 13-((1-octyl-benzimidazolyl)methyl)berberine 6f (OBMB-6f) was found to be the most promising compound that not only exerted a strong activity (MIC = 0.25-2 μg/mL) and low cytotoxicity but also possessed a fast bactericidal capacity and low propensity to develop resistance toward Staphylococcus aureus and Escherichia coli even after 26 serial passages. Moreover, OBMB-6f displayed the ability to prevent bacterial biofilm formation at low and high temperatures. The mechanistic exploration revealed that OBMB-6f could significantly disintegrate bacterial membranes, markedly facilitate intracellular ROS generation, and efficiently intercalate into DNA. These results provided a profound insight into BMB against multidrug-resistant bacterial infections in the livestock industry.

Sea urchin-like Bi2S3/curcumin heterojunction rapidly kills bacteria and promotes wound healing under near-infrared light

Bacterial infection is an urgent public health problem. We design a novel photo-responsive hybrid material by growing small molecules of curcumin (Cur) in situ on a sea urchin-like Bi₂S₃ surface by a one-step hydrothermal reaction method, thus forming an organic-inorganic hybrid material with interfacial contact. The Bi₂S₃/Cur hybrid material has good antibacterial effect under 808 nm near-infrared (NIR) light irradiation. The antibacterial mechanism is that the electron redistribution at the interface of Bi₂S₃/Cur excited by 808 nm NIR light will cause a large number of electrons to gather on the side of Bi₂S₃, forming an internal electric field to drive the excited electrons from Bi₂S₃ to Cur, which accelerates the separation of photoexcited electron-hole pairs and enhances the production of reactive oxygen species (ROS). In conclusion, due to these synergistic effects of the photothermal properties of Bi₂S₃, the production of more ROS and the release of small molecules of Cur from traditional Chinese medicine in Bi₂S₃/Cur, the antibacterial efficacy against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) is 99.96% and 99.03%, respectively. In vivo experiments in animals show that Bi₂S₃/Cur can reduce the inflammatory response and promote wound healing. This paper presents a simple, rapid and safe strategy for the treatment of wound infections with near-infrared light.

Photodegradable Antimicrobial Agents: Synthesis and Mechanism of Degradation

As a strategy to inactivate antimicrobial agents after use, we designed a range of ethanolamine derivatives where four of them possessed interesting activity. The ethanolamine moiety facilitates photodecomposition, which in a potential drug will take place after use. Herein, the synthetic preparation of these compounds and the mechanism of photoinactivation are described.