Scavenging of reactive oxygen species effectively reduces Pseudomonas aeruginosa biofilms through disrupting policing

Inhibition of quorum sensing serves as an effective strategy to mitigate the risks of human bacterial pathogens in soil

The coexistence of antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and virulence factor genes (VFGs) in human bacterial pathogens (HBPs) increases their risks to ecological security and human health and no effective strategy is available. Herein, we demonstrated two typical quorum sensing (QS) interfering agents, 4-nitropyridine-N-oxide (4-NPO, a QS inhibitor) and Acylase Ⅰ (a quorum quenching (QQ) enzyme), effectively decreased the abundance of HBPs by 48.30% and 72.54%, respectively, which was accompanied by the reduction of VFGs, ARGs, and MGEs. The decrease in QS signals mediated by QS interfering agents disturbed bacterial communication and inhibited biofilm formation. More importantly, QS interfering agents reduced the intra-species and inter-species conjugation frequencies among bacteria, considerably inhibiting the dissemination of ARGs and VFGs via horizontal gene transfer. Furthermore, the QS interfering agents did not significantly affect the metabolic function of other nonpathogenic microorganisms in the soil. Collectively, our study provides an effective and eco-friendly strategy to mitigate the risks of HBPs in soil.

Nanostructured N/S doped carbon dots/mesoporous silica nanoparticles and PVA composite hydrogel fabrication for anti-microbial and anti-biofilm application

Regarding the convergence of the worldwide epidemic, the appearance of bacterial infection has occasioned in a melodramatic upsurge in bacterial pathogens with confrontation against one or numerous antibiotics. The implementation of engineered nanostructured particles as a delivery vehicle for antimicrobial agent is one promising approach that could theoretically battle the setbacks mentioned. Among all nanoparticles, silica nanoparticles have been found to provide functional features that are advantageous for combatting bacterial contagion. Apart from that, carbon dots, a zero-dimension nanomaterial, have recently exhibited their photo-responsive property to generate reactive oxygen species facilitating to enhance microorganism suppression and inactivation ability. In this study, potentials of core/shell mesoporous silica nanostructures (MSN) in conjugation with carbon dots (CDs) toward antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli have been investigated. Nitrogen and sulfur doped CDs (NS/CDs) conjugated with MSN which were cost effective nanoparticles exhibited much superior antimicrobial activity for 4 times as much as silver nanoparticles against all bacteria tested. Among all nanoparticles tested, 0.40 M NS/CDs@MSN showed the greatest minimal biofilm inhibitory at very low concentration (< 0.125 mg mL-1), followed by 0.20 M NS/CDs@MSN (0.5 mg mL-1), CD@MSN (25 mg mL-1), and MSN (50 mg mL-1), respectively. Immobilization of NS/CDs@MSN in polyvinyl alcohol (PVA) hydrogel was performed and its effect on antimicrobial activity, biofilm controlling efficiency, and cytotoxicity toward fibroblast (NIH/3 T3 and L-929) cells was additionally studied for further biomedical applications. The results demonstrated that 0.40 M NS/CDs-MSN@PVA hydrogel exhibited the highest inhibitory effect on S. aureus > P. aeruginosa > E. coli. In addition, MTT assay revealed some degree of toxicity of 0.40 M NS/CDs-MSN@PVA hydrogel against L-929 cells by a slight reduction of cell viability from 100% to 81.6% when incubated in the extract from 0.40 M NS/CDs-MSN@PVA hydrogel, while no toxicity of the same hydrogel extract was detected toward NIH/3 T3 cells.