Antibiotic Resistance Determinants and Virulence Factors of Hypervirulent and Carbapenem Non-Susceptible Pseudomonas aeruginosa.

BACKGROUND: The aim was to investigate the distribution of antibiotic resistance determinants and virulence factors in a group of carbapenem non-susceptible Pseudomonas aeruginosa (P. aeruginosa). METHODS: From March 2018 to May 2019, a total of 98 P. aeruginosa samples were collected from 6 hospitals in Ningbo and Hangzhou, Zhejiang Province, China. Drug susceptibility tests to 13 antimicrobial agents were conducted. The presence of antibiotic resistance determinants and virulence factors were investigated by PCR, including 39 ß-lactamase genes, 14 aminoglycoside modifying enzyme genes, 10 16SrRNA methylase genes, and 11 virulence genes. Phylogenetics of 98 P. aeruginosa was analyzed by sample cluster analysis (UPGMA). RESULTS: PCR revealed the presence of 7 ß-lactamase genes, 5 aminoglycoside modifying enzymes, 1 16S rRNA methylase gene, and 8 virulence genes in total, at least 2 ß-lactamase genes and 4 virulence genes were positive in every isolate. In addition, regional differences in distributions of resistance and virulence genes remained between 2 cities. Sample cluster analysis showed that the strains had obvious aggregation and were divided into several clusters, strains in the same cluster were isolated from different hospitals, even from different cities. CONCLUSIONS: Carrying resistance genes blaPDC and blaOXA-50 group and virulence genes plcH, aprA, and algD were the important epidemiological characteristics of this group of P. aeruginosa. The present findings provide insights into the mechanisms of hypervirulence as well as resistance to ß-lactams and aminoglycosides. To the best of our knowledge, this is the first report of blaPDC, blaOXA-50, and aph(3')-XV in P. aeruginosa in China.

Metformin attenuates motility, contraction, and fibrogenic response of hepatic stellate cells in vivo and in vitro by activating AMP-activated protein kinase.

AIM: To investigate the effect of metformin on activated hepatic stellate cells (HSCs) and the possible signaling pathways involved. METHODS: A fibrotic mouse model was generated by intraperitoneal injection of carbon tetrachloride (CCl4) and subsequent treatment with or without metformin. The level of fibrosis was detected by hematoxylin-eosin staining, Sirius Red staining, and immunohistochemistry. The HSC cell line LX-2 was used for in vitro studies. The effect of metformin on cell proliferation (CCK8 assay), motility (scratch test and Transwell assay), contraction (collagen gel contraction assay), extracellular matrix (ECM) secretion (Western blot), and angiogenesis (ELISA and tube formation assay) was investigated. We also analyzed the possible signaling pathways involved by Western blot analysis. RESULTS: Mice developed marked liver fibrosis after intraperitoneal injection with CCl4 for 6 wk. Metformin decreased the activation of HSCs, reduced the deposition of ECM, and inhibited angiogenesis in CCl4-treated mice. Platelet-derived growth factor (PDGF) promoted the fibrogenic response of HSCs in vitro, while metformin inhibited the activation, proliferation, migration, and contraction of HSCs, and reduced the secretion of ECM. Metformin decreased the expression of vascular endothelial growth factor (VEGF) in HSCs through inhibition of hypoxia inducible factor (HIF)-1α in both PDGF-BB treatment and hypoxic conditions, and it down-regulated VEGF secretion by HSCs and inhibited HSC-based angiogenesis in hypoxic conditions in vitro. The inhibitory effects of metformin on activated HSCs were mediated by inhibiting the Akt/mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK) pathways via the activation of adenosine monophosphate-activated protein kinase (AMPK). CONCLUSION: Metformin attenuates the fibrogenic response of HSCs in vivo and in vitro, and may therefore be useful for the treatment of chronic liver diseases.