Microbiology: Antibiotics right under our nose

Bacteria-targeted magnolol-loaded multifunctional nanocomplexes for antibacterial and anti-inflammatory treatment

Natural plant-derived small molecules have shown great potential for their antimicrobial and anti-inflammatory properties. In this study, we successfully developed a nanocomplex consisting of magnolol (Mag), a surfactant with an 18 carbon hydrocarbon chain and multi-amine head groups (C18N3), and a peptide (cyclic 9-amino acid peptide (CARG)) with targeting capabilities forStaphylococcus aureus(S. aureus). The obtained Mag/C18N3/CARG nanocomplexes exhibited strong antibacterial activity againstS. aureus. Furthermore, they demonstrated anti-inflammatory effects by reducing the secretion of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1βfrom macrophage inflammatory cells. This was achieved through downregulating the activation of NF-κB, KEAP1, and NRF2 signaling pathways. In a murine skin infection model, the Mag/C18N3/CARG nanocomplexes effectively suppressed the growth ofS. aureusin the infected area and promoted wound healing. Additionally, in a mouse model of acute kidney injury (AKI), the nanocomplexes significantly reduced the levels of blood urea nitrogen and creatinine, leading to a decrease in mortality rate. These findings demonstrate the potential of combining natural plant-derived small molecules with C18N3/CARG assemblies as a novel approach for the development of effective and safe antibacterial agents.

Chromophore-Targeting Precision Antimicrobial Phototherapy

Phototherapy, encompassing the utilization of both natural and artificial light, has emerged as a dependable and non-invasive strategy for addressing a diverse range of illnesses, diseases, and infections. This therapeutic approach, primarily known for its efficacy in treating skin infections, such as herpes and acne lesions, involves the synergistic use of specific light wavelengths and photosensitizers, like methylene blue. Photodynamic therapy, as it is termed, relies on the generation of antimicrobial reactive oxygen species (ROS) through the interaction between light and externally applied photosensitizers. Recent research, however, has highlighted the intrinsic antimicrobial properties of light itself, marking a paradigm shift in focus from exogenous agents to the inherent photosensitivity of molecules found naturally within pathogens. Chemical analyses have identified specific organic molecular structures and systems, including protoporphyrins and conjugated C=C bonds, as pivotal components in molecular photosensitivity. Given the prevalence of these systems in organic life forms, there is an urgent need to investigate the potential impact of phototherapy on individual molecules expressed within pathogens and discern their contributions to the antimicrobial effects of light. This review delves into the recently unveiled key molecular targets of phototherapy, offering insights into their potential downstream implications and therapeutic applications. By shedding light on these fundamental molecular mechanisms, we aim to advance our understanding of phototherapy's broader therapeutic potential and contribute to the development of innovative treatments for a wide array of microbial infections and diseases.

Photolysis of methicillin-resistant Staphylococcus aureus using Cu-doped carbon spheres

Developing alternative treatment strategies against methicillin-resistant Staphylococcus aureus (MRSA) infections is a challenge but could have many potential applications. In this paper, we developed a novel approach to eradicate MRSA through photolysis of the staphyloxanthin (STX) pigment found within the MRSA membranes and intracellular molecules (e.g. genomic DNA and proteins). Specifically, Cu-doped hollow carbon spheres (Cu-HCSs) were employed here for antibacterial treatment. Unlike blue-light treatment alone, which only "injured" MRSA, Cu-HCSs in combination with blue-light irradiation promoted photobleaching of STX to destroy membrane integrity, and further caused oxidative cleavage of DNA and proteins inside MRSA, working as a nuclease/protease mimicking nanozyme, resulting in efficient killing of MRSA. Mechanism analysis showed that the cleavage activity resulted from the elevated levels of singlet oxygen (1O2) generated from the photosensitized oxidation of Cu-HCSs. Further animal studies demonstrated that the photolysis activity of Cu-HCSs could be used to treat subcutaneous abscesses and bacteremia caused by MRSA. Thus, this photolysis-based antibacterial platform may help avoid bacterial resistance, with the potential to kill multidrug resistant bacteria.

Multidrug Resistance (MDR) and Collateral Sensitivity in Bacteria, with Special Attention to Genetic and Evolutionary Aspects and to the Perspectives of Antimicrobial Peptides-A Review

Antibiotic poly-resistance (multidrug-, extreme-, and pan-drug resistance) is controlled by adaptive evolution. Darwinian and Lamarckian interpretations of resistance evolution are discussed. Arguments for, and against, pessimistic forecasts on a fatal “post-antibiotic era” are evaluated. In commensal niches, the appearance of a new antibiotic resistance often reduces fitness, but compensatory mutations may counteract this tendency. The appearance of new antibiotic resistance is frequently accompanied by a collateral sensitivity to other resistances. Organisms with an expanding open pan-genome, such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae, can withstand an increased number of resistances by exploiting their evolutionary plasticity and disseminating clonally or poly-clonally. Multidrug-resistant pathogen clones can become predominant under antibiotic stress conditions but, under the influence of negative frequency-dependent selection, are prevented from rising to dominance in a population in a commensal niche. Antimicrobial peptides have a great potential to combat multidrug resistance, since antibiotic-resistant bacteria have shown a high frequency of collateral sensitivity to antimicrobial peptides. In addition, the mobility patterns of antibiotic resistance, and antimicrobial peptide resistance, genes are completely different. The integron trade in commensal niches is fortunately limited by the species-specificity of resistance genes. Hence, we theorize that the suggested post-antibiotic era has not yet come, and indeed might never come.

Photolysis of Staphyloxanthin in Methicillin-Resistant Staphylococcus aureus Potentiates Killing by Reactive Oxygen Species

Confronted with the severe situation that the pace of resistance acquisition is faster than the clinical introduction of new antibiotics, health organizations are calling for effective approaches to combat methicillin-resistant Staphylococcus aureus (MRSA) infections. Here, an approach to treat MRSA through photolysis of staphyloxanthin, an antioxidant residing in the microdomain of S. aureus membrane, is reported. This photochemistry process is uncovered through transient absorption imaging and quantitated by absorption spectroscopy, Raman spectroscopy, and mass spectrometry. Photolysis of staphyloxanthin transiently elevates the membrane permeability and renders MRSA highly susceptible to hydrogen peroxide attack. Consequently, staphyloxanthin photolysis by low-level 460 nm light eradicates MRSA synergistically with hydrogen peroxide and other reactive oxygen species. The effectiveness of this synergistic therapy is well validated in MRSA planktonic culture, MRSA-infected macrophage cells, stationary-phase MRSA, persisters, S. aureus biofilms, and two mice wound infection models. Collectively, the work demonstrates that staphyloxanthin photolysis is a new therapeutic platform to treat MRSA infections.

Hollow Au loaded with kanamycin for pharmacological and laser-triggered photothermal sterilization

Anti-E. coli-conjugated and kanamycin-loaded hAuNPs (hAuNPs-anti-E. coli-kana) were prepared for sterilization.