A Combination of Blue Light at 460 nm and H2O2 for the Safe and Effective Eradication of Staphylococcus aureus in an Infected Mouse Skin Abrasion Model

Antibiotic-free approaches are more important than ever to address the rapidly growing problem of the antibiotic resistance crisis. The photolysis of the bacterial virulence factor staphyloxanthin using blue light at 460 nm (BL460 nm) has been found to effectively attenuate Staphylococcus aureus to chemical and physical agents. However, phototherapy using BL640 nm still needs to be investigated in detail for its safety in eradicating Staphylococcus aureus in vitro and in vivo. In this study, we employed a 460 nm continuous-wavelength LED source and a low concentration of hydrogen peroxide to treat S. aureus under a culturing condition and a wound abrasion mouse model. The results demonstrated the safety of the combined therapy when it did not modify the bacterial virulence factors or the susceptibility to widely used antibiotics. In addition, the results of the mouse model also showed that the combined therapy was safe to apply to mouse skin since it did not cause adverse skin irritation. More importantly, the therapy can aid in healing S. aureus-infected wounds with an efficacy comparable to that of the topical antibiotic Fucidin. The aforementioned findings indicate that the concurrent application of BL460 nm and hydrogen peroxide can be used safely as an alternative or adjunct to antibiotics in treating S. aureus-infected wounds.

Computational investigation of possible inhibitors of the winged-helix domain of MUS81

The methyl methanesulfonate and ultraviolet sensitive 81 (MUS81) is a structure-specific endonuclease that is highly conserved in eukaryotes and essential for homologous recombination repair. The winged-helix domain at the N-terminus of MUS81 (wMUS81) can bind DNA substrates and regulate the endonuclease activity. The repression of MUS81 activity could enhance the sensitivity to antitumor compounds of different tumour cells. Thus, MUS81 is a potential therapeutic target in cancer therapy. However, specific inhibitors of MUS81 have remained elusive. Here, for the first time, we attempt to discover the compounds disrupting the wMUS81 activity. The binding affinity of available drugs to wMUS81 was first estimated by molecular docking. pK_a values were taken into consideration to eliminate unlikely protonation states of the ligands. Top-lead compounds were then estimated the binding affinity using the fast pulling ligand simulations. Finally, the free energy perturbation method accurately defined the absolute binding free energy of the top four ligands, revealing the most potential inhibitors of wMUS81 including simeprevir and nilotinib. Binding of simeprevir destabilizes the β-hairpin region of wMUS81, likely disturbing the wMUS81 function. The van der Waals free binding energy majorly modulates the ligand-binding mechanism. The two conserved residues Leu189 and Arg196 are likely important in monitoring the interacting process of simeprevir to wMUS81.

Direct colorimetric LAMP assay for rapid detection of African swine fever virus: A validation study during an outbreak in Vietnam

African swine fever (ASF) is a highly infectious viral disease with high mortality. The most recent ASF outbreak in Vietnam began in 2019, posing a threat to spread to the neighbouring Asian countries. Without a commercial vaccine or efficient chemotherapeutics, rapid diagnosis and necessary biosecurity procedures are required to control the disease. While the diagnostic method of ASF recommended by the World Organization of Animal Health is real-time PCR, the ideal diagnosis procedure including master mix setup, template extraction and a high-cost qPCR equipment for many samples being tested simultaneously is not portable. In this study, a colorimetric loop-mediated isothermal amplification (LAMP) assay was modified and evaluated for ASF virus detection using crude serum samples collected from domestic pigs in Vietnam during the 2019 outbreak. The LAMP results can be readily visualized to the naked eye within 30 min without the requirement of DNA extraction and sophisticated equipment. The sensitivity, specificity and limit of detection of direct colorimetric LAMP assay were comparable to a commercial diagnostic real-time PCR kit. Results strongly indicate that the adapted colorimetric LAMP assay has a remarkable potential for the in-field diagnosis of ASF.