Control of Shigella sonnei and adhesive invasive Escherichia coli infections with a natural product which inhibits the bacterial oxidoreductase DsbA

  • Z Zainulabedeen R M H Mirza

Student thesis: Doctoral Thesis


Many Gram-negative bacterial pathogens such as Shigella and adhesive invasive Escherichia coli (AIEC) cause infections characteristic of hyperinflammation. These infections require antimicrobial therapy. However, due to the widespread emergence of multiple drug-resistant strains, alternative strategies must be sought to combating infectious diseases. It has been shown that natural compounds such as propolin D are able to control Shigella growth inside host cells. Geraniol is another natural product which has a chemical structure similar to the side chain of propolin D, which possesses properties potentially useful for antimicrobial therapy. qPCR analysis revealed that propolin D caused extensive bacterial envelopE stress, as indicated by a changed expression of key bacterial genes involved in stress responses. Propolin D also enhanced the autophagy activity of the host cells; the intracellular growth of S. sonnei was significantly reduced in wild type HEK293 cells but not changed in ATG5 knockout cells. Propolin D was unable to enhance septin cage as intracellular S. sonnei formed actin tails in the presence of propolin D; septin cage would restrict formation of actin tails. Geraniol has been shown to target the major virulence regulator, DsbA, which is vital for Shigella's survival in the reducing host cell cytosol. Geraniol and geranylxvacetate inhibited DsbA function in vitro; wild type DsbA efficiently reduced fluorescently labelled Di-E-GSSG whereas a mutant protein, DsbA33G, was less potent in this in vitro assay. By supplementing acidic and nutrient-poor medium with geraniol the growth of S. sonnei and AIEC strains was severely inhibited. Geraniol was effective in protecting of Galleria. mellonella larva from S. sonnei and AIEC infection. The Galleria mellonella larvae were highly tolerant to geraniol - indicating the great potential of geraniol for future in vivo and clinical studies. In light of previous reports that geraniol synergistically works with antibiotics and induces IL-10 from macrophages, it was concluded that geraniol holds great potential in treating Shigella and AIEC infections.
Date of Award27 Jul 2017
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorJun Yu (Supervisor) & Christine Duf├Ęs (Supervisor)

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