Project description:Polymyxin B is considered as a last-resort antibiotic for multidrug-resistant or extensively drug-resistant gram-negative bacterial infections. Addressing Salmonella resistance to polymyxin B is crucial for global public health. In this study, transcriptomic detection and analysis were used to clarify the mechanisms by which CpxA-deleted S.typhimurium is involved in resistance to polymyxin B stress, which may be related to processes such as increased assembly of bacterial flagella.
2024-11-07 | GSE281216 | GEO
Project description:Multidrug resistant Salmonella serovars isolated from poultry
Project description:Salmonella enterica serotype Typhimurium produces a variety of fimbrial appendages, among which the type 1 fimbriae is the most common type. In vitro static broth culture favors S. Typhimurium to produce type 1 fimbriae, while solid agar inhibits its expression. A transposon inserted in the stbC gene, which would encode an usher protein for Stb fimbriae of a non-flagellar S. Typhimurium LB5010 strain, conferred it to agglutinate yeast cells on both cultures, and was mannose-sensitive. Reverse transcription polymerase chain reaction (RT-PCR) revealed that the expression of the fimbrial major subunit gene fimA, and fimZ, a positive regulator gene of fimA, were both increased in the stbC mutant strain when grown on LB agar; fimW, a repressor gene of fimA, exhibited lower expression. Flagella were observed in the stbC mutant and this phenotype was correlated with the motile phenotype detected by MSRV agar medium and reaction with flagella antiserum. Microarray data and RT-PCR also indicated that the expression of three genes, motA, motB, and cheM, was enhanced in the stbC mutant. The S. Typhimurium stbC mutant was resistant to a variety of antibiotics, consistent with the finding that expression of yhcQ and ramA, two genes involved in multidrug resistance, was enhanced. A complementation test revealed that transforming a recombinant plasmid possessing the coding sequence of the stbC gene restored the mannose-sensitive agglutination phenotype to the stbC mutant much as that in the parental S. Typhimurium LB5010 strain, indicating the possibility of an interplay of different fimbrial systems in coordinating their expression. Key Words: Salmonella enterica serotype Typhimurium, fimbriae, type 1 fimbriae, stbC, transposon, multidrug resistant, flagella RNA transcript of Salmonella Typhimurium LB5010 strain comparing wild-type with stbC mutant. Two-cindition experiment, wild-type vs. stbC mutant strain.
Project description:Through releasing virulence molecules into host cells, intracellular bacteria interfere with host cellular functions and grow in the cells that engulf them. To ensure survival and virulence, these pathogens also manipulate host factors, but this process is not fully understood. In this study, we investigated the host molecular mechanisms required for intracellular bacterial growth in macrophages using Salmonella typhimurium (Salmonella) infection model and bacterial division reporter system. Upon Salmonella infection, Protein Phosphatase 6 (Pp6) was significantly reduced in macrophages containing growing bacteria. Conditional knockout of Pp6 increased host susceptibility to Salmonella-mediated killing, which was attributed to the poor resistance in Pp6-deficient macrophages. MicroRNA-31 (miR-31) was identified as a negative regulator of Pp6, and its conditional deletion promoted Salmonella clearance. Moreover, a yeast two-hybrid screening identified 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 1 (Pfkfb1), a key metabolic regulator, as a substrate of Pp6. Pp6-deficient macrophages exhibited elevated Pfkfb1 expression. Furthermore, we found that macrophages containing growing Salmonella exclusively exhibited high Pfkfb1 expression. Pfkfb1 deletion reduced bacterial growth, likely due to increased NO levels, while also downregulating arginase-1 (Arg-1) expression and impairing arginine biosynthesis and metabolism in macrophages. Together, we investigated the role of Pp6-Pfkfb1 axis in orchestrating host metabolic adaptions and intracellular bacterial survival, which may provide therapeutic targets for infectious diseases against intracellular multidrug-resistant bacteria.
Project description:Multidrug-resistant (MDR; resistance to >3 antimicrobial classes) Salmonella enterica serovar I 4,[5],12:i:- strains were linked to a 2015 foodborne outbreak from pork. Strain USDA15WA-1, associated with the outbreak, harbors an MDR module and the metal tolerance element Salmonella Genomic Island 4 (SGI-4). Characterization of SGI-4 revealed that conjugational transfer of SGI-4 resulted in the mobile genetic element (MGE) replicating as a plasmid or integrating into the chromosome. Tolerance to copper, arsenic, and antimony compounds was increased in Salmonella strains containing SGI-4 compared to strains lacking the MGE. Following Salmonella exposure to copper, RNA-seq transcriptional analysis demonstrated significant differential expression of diverse genes and pathways, including induction of numerous metal tolerance genes (copper, arsenic, silver, and mercury). Evaluation of swine administered elevated concentrations of zinc oxide (2,000 mg/kg) and copper sulfate (200 mg/kg) as an antimicrobial feed additive (Zn+Cu) in their diet for 4 weeks prior to and 3 weeks post-inoculation with serovar I 4,[5],12:i:- indicated that Salmonella shedding levels declined at a slower rate in pigs receiving in-feed Zn+Cu compared to control pigs (no Zn+Cu). The presence of metal tolerance genes in MDR Salmonella serovar I 4,[5],12:i:- may provide benefits for environmental survival or swine colonization in metal-containing settings.
Project description:Objectives: Colistin remains a last-line treatment for multidrug-resistant Acinetobacter baumannii and combined use of colistin and carbapenems has shown synergistic effects against multidrug-resistant strains. In order to understand the bacterial responses to these antibiotics we analysed the transcriptome of A. baumannii following exposure to each.