Objective To perform single-molecule, real-time sequencing of ceftazidime-avibactam (CAZ-AVI)-resistant Pseudomonas aeruginosa and to investigate the mechanism underlying ceftazidime-avibactam resistance in P. aeruginosa. Methods The susceptibility of 89 P. aeruginosa isolates randomly sampled from clinical specimens in Sanming First Hospital Affiliated to Fujian Medical University from November 2021 through July 2023 to common antimicrobial agents was tested, and the minimum inhibitory concentration (MIC) of CAZ-AVI was determined against P. aeruginosa with a broth microdilution assay, with CAZ-AVI MICs of 8 mg/L and lower defined as susceptible and 16 mg/L and higher as resistant. The expression of drug-resistant genes ampC, oxa-488, oprD, mexA, oxa-10, oxa-14, vim and tem was quantified in P. aeruginosa using a real-time quantitative reverse transcription PCR (qPCR) assay. CAZ-AVI-susceptible and -resistant P. aeruginosa isolates from the same case were selected for PacBio single-molecule, real-time sequencing, and sequencing results were subjected to genome structure and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional annotations. Results The 89 P. aeruginosa isolates showed a relatively high level of resistance to meropenem (75.28%) and imipenem (74.16%) and the highest susceptibility to amikacin (91.01%). There were 49 CAZ-AVI-resistant P. aeruginosa isolates and 40 susceptible isolates. qPCR assay detected lower oprD gene expression in CAZ-AVI-resistant P. aeruginosa isolates [0.104 (2.385)] than in susceptible isolates [0.551 (17.885)] (Z = -2.958, P < 0.01), and there were no significant differences between CAZ-AVI-susceptible and -resistant P. aeruginosa isolates in terms of ampC, oxa-488, mexA or tem gene expression (all P values > 0.05), while oxa-10, oxa-14 and vim gene was expressed in few P. aeruginosa isolates. There were 1 729, 3 936, 3 737 and 3 955 genes in CAZ-AVI-resistant P. aeruginosa isolates PA-762 and PA-M174 and susceptible isolates PA-885 and PA-808 that were annotated to GO terms, with the highest numbers of genes enriched in the molecular function of catalytic activity, high numbers of genes enriched in biological processes of metabolic process, single-organism process and cellular process, and high numbers of genes enriched in cellular components of cell and cell membranes. There were 1 803, 4 084, 3 915 and 4 066 genes in the PA-762, PA-M174, PA-885 and PA-808 isolates enriched in the KEGG signaling pathway, and the majority of genes were enriched in four primary signaling pathways of metabolism, genetic information processing, environmental information processing and cellular process, with the highest number of genes associated with metabolic pathways. Both CAZ-AVI-resistant P. aeruginosa isolates PA-762 and PA-M174 carried multiple efflux pumps systems, including MexAB-OprM, MexCD-OprJ, MexEF-OprN and MexXY-OprM. Single nucleotide substitution was found at position 169 in the DNA sequence of the PA-762 isolate, leading to substitution of serine for glycine at position 57 in the protein sequence, and there are deletions of two bases at positions 307 and 308 in the DNA sequence of the PA-M174 isolate, leading to substitution of threonine for arginine at position 103 in the protein sequence. Conclusion Mutation or downregulation of oprD gene may lead to CAZ-AVI resistance in P. aeruginosa.

Exosomes are cell-derived nanovesicles with diameters from 30 to 150 nm, released upon fusion of multivesicular bodies with the cell surface. They can transport nucleic acids, proteins, and lipids for intercellular communication and activate signaling pathways in target cells. In cancers, exosomes may participate in growth and metastasis of tumors by regulating the immune response, blocking the epithelial-mesenchymal transition, and promoting angiogenesis. They are also involved in the development of resistance to chemotherapeutic drugs. Exosomes in liquid biopsies can be used as non-invasive biomarkers for early detection and diagnosis of cancers. Because of their amphipathic structure, exosomes are natural drug delivery vehicles for cancer therapy.

To investigate the role of ET 1 in the pathogenesis of SU, a model was established by cold restraint stress(CRS) inducing rat ulcer, immunohistochemistry(IHC)ABC method and radioimmunoassay(RIA) methods were used to determine ET 1 content and to study the expression and location of ET 1 in stomach of normal and CRS rats,and to evaluate the ulcer index(UI). IHC showed that ET 1 was stained as brownish grains,localized in the cytoplasm of vascular endothelial cells, stomach smooth muscle cells, gastric epithelial and vascular smooth muscule cells around lamina muscularis mucosae in stomach. The proportion of ET 1 positive cells was significantly higher in 3h poststress gastric mucosa than in normal gastric mucosa in rats by IHC( P