iTRAQ-based quantitative proteomic analysis of the antibacterial mechanism of silver nanoparticles against multidrug-resistant Streptococcus suis

Background: The increase in antibiotic resistance of bacteria has become a major concern in clinical treatment. Silver nanoparticles (AgNPs) have significant antibacterial effects against Streptococcus suis. Therefore, this study aimed to investigate the antibacterial activity and mechanism of action of AgNPs against multidrug-resistant S. suis.

Methods: The effect of AgNPs on the morphology of multidrug-resistant S. suis was observed using scanning electron microscopy (SEM). Differentially expressed proteins were analyzed by iTRAQ quantitative proteomics, and the production of reactive oxygen species (ROS) was assayed by H2DCF-DA staining.

Results: SEM showed that AgNPs disrupted the normal morphology of multidrug-resistant S. suis and the integrity of the biofilm structure. Quantitative proteomic analysis revealed that a large number of cell wall synthesis-related proteins, such as penicillin-binding protein and some cell cycle proteins, such as the cell division protein FtsZ and chromosomal replication initiator protein DnaA, were downregulated after treatment with 25 μg/mL AgNPs. Significant changes were also observed in the expression of the antioxidant enzymes glutathione reductase, alkyl hydroperoxides-like protein, α/β superfamily hydrolases/acyltransferases, and glutathione disulfide reductases. ROS production in S. suis positively correlated with AgNP concentration.

Conclusion: The potential antibacterial mechanism of AgNPs may involve disrupting the normal morphology of bacteria by inhibiting the synthesis of cell wall peptidoglycans and inhibiting the growth of bacteria by inhibiting the cell division protein FtsZ and Chromosomal replication initiator protein DnaA. High oxidative stress may be a significant cause of bacterial death. The potential mechanism by which AgNPs inhibit S. suis biofilm formation may involve affecting bacterial adhesion and interfering with the quorum sensing system.

 

Comments:

This study on silver nanoparticles (AgNPs) and their effects on multidrug-resistant Streptococcus suis is quite intriguing! The findings suggest a multifaceted mechanism of action for AgNPs against these bacteria.

1. **Morphological Disruption:** AgNPs visibly disrupted the normal morphology of the bacteria and compromised the integrity of the biofilm structure. This is an essential observation indicating the physical impact of AgNPs on S. suis.

2. **Proteomic Analysis:** The quantitative proteomic analysis revealed a multitude of affected proteins. Downregulation of cell wall synthesis-related proteins, such as penicillin-binding protein, hints at the disruption of peptidoglycan synthesis, a crucial component of bacterial cell walls. Additionally, the inhibition of cell cycle proteins like FtsZ and DnaA suggests interference with bacterial growth and division.

3. **Antioxidant Enzymes and ROS Production:** The alterations in antioxidant enzymes and the correlation between ROS production and AgNP concentration are significant. High oxidative stress appears to contribute to bacterial death, indicating a potential route for AgNP-induced antibacterial effects.

4. **Biofilm Formation Inhibition:** AgNPs seem to affect biofilm formation by potentially interfering with bacterial adhesion and disrupting the quorum sensing system, a crucial communication method for bacteria within biofilms.

The comprehensive understanding of AgNP action against multidrug-resistant S. suis outlined in this study could offer promising insights into combating antibiotic resistance. It's a fascinating approach to exploring alternative strategies to tackle bacterial infections.

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