title: Antibacterial activity of silver and zinc nanoparticles against Vibrio cholerae and enterotoxic Escherichia coli.
abstract: Vibrio cholerae and enterotoxic Escherichia coli (ETEC) remain two dominant bacterial causes of severe secretory diarrhea and still a significant cause of death, especially in developing countries. In order to investigate new effective and inexpensive therapeutic approaches, we analyzed nanoparticles synthesized by a green approach using corresponding salt (silver or zinc nitrate) with aqueous extract of Caltropis procera fruit or leaves. We characterized the quantity and quality of nanoparticles by UV-visible wavelength scans and nanoparticle tracking analysis. Nanoparticles could be synthesized in reproducible yields of approximately 10(8) particles/ml with mode particles sizes of approx. 90-100 nm. Antibacterial activity against two pathogens was assessed by minimal inhibitory concentration assays and survival curves. Both pathogens exhibited similar resistance profiles with minimal inhibitory concentrations ranging between 5×10(5) and 10(7) particles/ml. Interestingly, zinc nanoparticles showed a slightly higher efficacy, but sublethal concentrations caused adverse effects and resulted in increased biofilm formation of V. cholerae. Using the expression levels of the outer membrane porin OmpT as an indicator for cAMP levels, our results suggest that zinc nanoparticles inhibit adenylyl cyclase activity. This consequently deceases the levels of this second messenger, which is a known inhibitor of biofilm formation. Finally, we demonstrated that a single oral administration of silver nanoparticles to infant mice colonized with V. cholerae or ETEC significantly reduces the colonization rates of the pathogens by 75- or 100-fold, respectively.
authors.affiliation: University of Graz, Institute of Molecular Biosciences, BioTechMed-Graz, Humboldtstrasse 50, A-8010 Graz, Austria; South Valley University, Faculty of Science, Qena, Egypt.
authors.forename: Wesam
authors.initials: W
authors.lastname: Salem
authors.affiliation: University of Graz, Institute of Molecular Biosciences, BioTechMed-Graz, Humboldtstrasse 50, A-8010 Graz, Austria.
authors.forename: Deborah R
authors.initials: DR
authors.lastname: Leitner
authors.affiliation: University of Graz, Institute of Molecular Biosciences, BioTechMed-Graz, Humboldtstrasse 50, A-8010 Graz, Austria.
authors.forename: Franz G
authors.initials: FG
authors.lastname: Zingl
authors.affiliation: Institute of Biophysics, Medical University of Graz, BioTechMed-Graz, Schmiedlstraße 6, 8042 Graz, Austria.
authors.forename: Gebhart
authors.initials: G
authors.lastname: Schratter
authors.affiliation: Institute of Biophysics, Medical University of Graz, BioTechMed-Graz, Schmiedlstraße 6, 8042 Graz, Austria.
authors.forename: Ruth
authors.initials: R
authors.lastname: Prassl
authors.affiliation: Institute for Chemistry, Analytical Chemistry, University of Graz, BioTechMed-Graz, 8010 Graz, Austria.
authors.forename: Walter
authors.initials: W
authors.lastname: Goessler
authors.affiliation: University of Graz, Institute of Molecular Biosciences, BioTechMed-Graz, Humboldtstrasse 50, A-8010 Graz, Austria.
authors.forename: Joachim
authors.initials: J
authors.lastname: Reidl
authors.affiliation: University of Graz, Institute of Molecular Biosciences, BioTechMed-Graz, Humboldtstrasse 50, A-8010 Graz, Austria. Electronic address: stefan.schild@uni-graz.at.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schild
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D031107:Calotropis / Q000737:chemistry; D002771:Cholera / Q000517:prevention & control; D004195:Disease Models, Animal; D054307:Enterotoxigenic Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000517:prevention & control; D051379:Mice; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D053758:Nanoparticles / Q000378:metabolism* / Q000627:therapeutic use; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology; D012834:Silver / Q000302:isolation & purification / Q000494:pharmacology* / Q000627:therapeutic use; D016896:Treatment Outcome; D014734:Vibrio cholerae / Q000187:drug effects*; D015032:Zinc / Q000302:isolation & purification / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts; D012834:Silver; D015032:Zinc
keywords: Antimicrobial activity; Biofilm; Caltropis procera; Colonization; In vivo; Infant mouse model; Minimal inhibitory concentration; Nanoparticles; Survival curve; Therapeutic agent