June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Mode-of-action evaluation of the antimycotic effect of a tetracycline-chloramphenicol-colistimethate sodium fixed-dose combination
Author Affiliations & Notes
  • Anna Rita Blanco
    SIFI SpA, Aci S. Antonio, Catania, Italy
  • Manuela D'Arrigo
    Scienze Chimiche, Biologiche, Farmaceutiche e Ambientali, Università Messina, Messina, Messina, Italy
  • Maria Grazia Mazzone
    SIFI SpA, Aci S. Antonio, Catania, Italy
  • Andreana Marino
    Scienze Chimiche, Biologiche, Farmaceutiche e Ambientali, Università Messina, Messina, Messina, Italy
  • Footnotes
    Commercial Relationships   Anna Rita Blanco, SIFI SpA (E); Manuela D'Arrigo, None; Maria Grazia Mazzone, SIFI SpA (E); Andreana Marino, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 1086. doi:
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      Anna Rita Blanco, Manuela D'Arrigo, Maria Grazia Mazzone, Andreana Marino; Mode-of-action evaluation of the antimycotic effect of a tetracycline-chloramphenicol-colistimethate sodium fixed-dose combination. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1086.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Previous our studies showed that the commercially available ophthalmic product, as fixed antibiotic combination (Colbiocin®), containing tetracycline, chloramphenicol and colistimethate sodium, had a good efficacy against Candida spp., including resistant strains (Marino et al., ARVO 2016). The aim of this work was to study the mode-of-action of this antibacterial product against yeasts.

Methods : C. albicans ATCC and clinical isolated treated with sub-MIC concentrations of Colbiocin eye drop or with antibiotics of the formulation, alone and in combination each other, were examined by propidium iodide staning and MitoTracker red staining to determine cell permeability and mitochondrial function, respectively. Observations under the fluorescence microscope were performed.

Results : Microscopic examination using propidium staining demonstrated that the C. albicans cells treated with colistimethate sodium were stained red because they lost in cell membrane integrity. Propidium iodide, a red-fluorescent nuclear stain, is a membrane impermeant dye that is generally excluded from viable cells. Microscopic examination using MitoTracker demonstrated that untreated yeast cells showed intense and definite staining of mitochondria, whereas a diffused staining was observed in the yeast cells treated with tetracycline or chloramphenicol, as result of an altered mitochondrial membrane potential. MitoTracker, fluorescent dye, labels mitochondria within live cells utilizing the mitochondrial membrane potential. The yeast cells treated with the fixed combination Colbiocin® demonstrated both effects, the membrane permeabilization and the change in mithocondrial structure.

Conclusions : The additive mechanism of the fixed combination against Candida spp., previously shown, can be explained as follows: the colistimethate sodium binds with anionic lipids disrupting membrane integrity thus allowing to tetracycline and chloramphenicol to penetrate through the lipid bilayer and promote mitochondrial dysfunction. These new results on the mode-of-action, support previously published data and the use of the fixed combination Colbiocin® in the treatment of yeast infections.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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