Background: The threat of drug-resistant Pseudomonas aeruginosa requires great efforts to develop highly effective and safe bactericide. Objective: This study aimed to investigate the antibacterial activity and mechanism of silver nanoparticles (AgNPs) against multidrug-resistant P. aeruginosa. Methods: The antimicrobial effect of AgNPs on clinical isolates of resistant P. aeruginosa was assessed by minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). In multidrug-resistant P. aeruginosa, the alterations of morphology and structure were observed by the transmission electron microscopy (TEM); the differentially expressed proteins were analyzed by quantitative proteomics; the production of reactive oxygen species (ROS) was assayed by H 2 DCF-DA staining; the activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was chemically measured and the apoptosis-like effect was determined by flow cytometry. Results: Antimicrobial tests revealed that AgNPs had highly bactericidal effect on the drug-resistant or multidrug-resistant P. aeruginosa with the MIC range of 1.406-5.625 µg/mL and the MBC range of 2.813-5.625 µg/mL. TEM showed that AgNPs could enter the multidrug-resistant bacteria and impair their morphology and structure. The proteomics quantified that, in the AgNP-treated bacteria, the levels of SOD, CAT, and POD, such as alkyl hydroperoxide reductase and organic hydroperoxide resistance protein, were obviously high, as well as the significant upregulation of low oxygen regulatory oxidases, including cbb3-type cytochrome c oxidase subunit P2, N2, and O2. Further results confirmed the excessive production of ROS. The antioxidants, reduced glutathione and ascorbic acid, partially antagonized the antibacterial action of AgNPs. The apoptosis-like rate of AgNP-treated bacteria was remarkably higher than that of the untreated bacteria (P,0.01). Conclusion: This study proved that AgNPs could play antimicrobial roles on the multidrug-resistant P. aeruginosa in a concentration-and time-dependent manner. The main mechanism involves the disequilibrium of oxidation and antioxidation processes and the failure to eliminate the excessive ROS.

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Background: Chronic kidney disease (CKD) is the end point of a number of renal and systemic diseases. The metabolomics with a highly multiplexed and efficient manner is a challenging goal in nephrology. Methods: A 1H‐NMR based metabolomics approach was applied to establish a human CKD serum metabolic profile. Serum samples were obtained from CKD patients with four stages (N= 80) and healthy controls (N= 28). The data acquired by CMPG spectrum were further processed by pattern recognition (PR) analysis. Principal components analysis (PCA) and partial least‐squares‐discriminant analysis (PLS‐DA) was capable of clustering the disease groups and establishing disease‐specific metabolites profile. Results: The classification models could grade CKD patients with considerably high value of Q2 and R2. The significant endogenous metabolites that contributed to distinguish CKD in different stages included the products of glycolysis (glucose, lactate), amino acids (valine, alanine, glutamate, glycine), organic osmolytes (betaine, myo‐inositol, taurine, glycerophosphcholine), and so on. Based on these metabolites, the model for diagnosing patients with CKD achieved the sensitivity and specificity of 100%. Conclusion: The study illustrated that serum metabolic profile was altered in response to renal dysfunction and the progression of CKD. The identified metabolic biomarkers may provide useful information for the diagnosis of CKD, especially in early stages. Clin Trans Sci 2012; Volume 5: 379–385

The decline of clinically effective antibiotics has made it necessary to develop more effective antimicrobial agents, especially for refractory biofilm-related infections. Silver nanoparticles (AgNPs) are a new type of antimicrobial agent that can eradicate biofilms and reduce bacterial resistance, but its anti-biofilm mechanism has not been elucidated. In this study, we investigated the molecular mechanism of AgNPs against multidrug-resistant Pseudomonas aeruginosa by means of anti-biofilm tests, scanning electron microscopy (SEM), and tandem mass tag (TMT)-labeled quantitative proteomics. The results of anti-biofilm tests demonstrated that AgNPs inhibited the formation of P. aeruginosa biofilm and disrupted its preformed biofilm. SEM showed that when exposed to AgNPs, the structure of the P. aeruginosa biofilm was destroyed, along with significant reduction of its biomass. TMT-labeled quantitative proteomic analysis revealed that AgNPs could defeat the P. aeruginosa biofilm in multiple ways by inhibiting its adhesion and motility, stimulating strong oxidative stress response, destroying iron homeostasis, blocking aerobic and anaerobic respiration, and affecting quorum sensing systems. Our findings offer a new insight into clarifying the mechanism of AgNPs against biofilms, thus providing a theoretical basis for its clinical application.