Studies on the mechanism of zinc pyrithione resistance in Pseudomonas aeruginosa PAO1

  • Suzanne Abdel-Malek

    Student thesis: Doctoral Thesis


    Previous workers have suggested that it is possible to passage Pseudomonas aeruginosa towards resistance against selected antimicrobial agents (Isothiazolone biocides). These passages in sub-minimal inhibitory concentrations (sub-MIC) of antimicrobial agents also exhibited corresponding shifts in outer membrane protein profiles. The aim of this project was to elucidate whether or not such adaptive resistance was evidenced with consecutive passages in sub-MIC of the Pyrithione group of antimicrobial agents and whether or not such passages yielded comparable outer membrane protein shifts.

    Pseudomonas aeruginosa, an opportunistic Gram-negative bacteria known for its resistance to a wide range of antimicrobials was found to develop an adaptive resistanceto the biocides Zinc Pyrithione (ZnPT) and Sodium Pyrithione (NaPT) and Cetrimide. Investigation of the mechanism of resistance involved SDS-PAGE analysis of outer membranes of biocide-sensitive and biocide-resistant cells, SDS-PAGE LPS analysis,changes in cell surface hydrophobicity, cross resistance, multiple antibiotic resistance, efflux systems and stress response.

    Results indicate that the ZnPT-resistant phenotype exhibited an increase in cell surface hydrophobicity and LPS changes. When outer membrane protein profiles of ZnPT-resistant cells and ZnPT-sensitive cells were compared, a 26.30 kDa protein was observed to be missing from the outer membranes of the former but was expressed inthe latter. Furthermore, this protein was observed to reappear when the ZnPT-resistant cells were grown in a ZnPT-free media. The ZnPT-resistant phenotype exhibited resistance towards NaPT and Cetrimide but did not show resistance towards a selection of antibiotics, which indicates that ZnPT is not an inducer of the mar regulon in P.aeruginosa. Experiments using efflux pump inhibitors suggested the possible involvement of an efflux mechanism in the resistance developed towards ZnPT.

    SDS-PAGE of cell lysates of ZnPT-resistant and ZnPT-sensitive cells has shown that resistant cells expresses cytoplasmic proteins that were not expressed in sensitive cells. Using western blot analysis these proteins were found to be dissimilar to P.aeruginosa heat shock proteins, suggesting that they could be ZnPT-specific stress proteins or molecular chaperones that assist the cells in recovering from ZnPT-induced cellular damage.
    Date of AwardApr 2002
    Original languageEnglish
    SponsorsUniversity of Petra
    SupervisorPhillip J. Collier (Supervisor)

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