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Saint-Christol-lès-Alès, France

Tartanson M.-A.,Montpellier University | Tartanson M.-A.,CARDPool SAS | Soussan L.,Montpellier University | Rivallin M.,Montpellier University | And 5 more authors.
Applied and Environmental Microbiology | Year: 2015

The bactericidal activity of an Al2O3-TiO2-Ag granular material against an Escherichia coli strain was confirmed by a culturebased method. In particular, 100% of microorganisms were permanently inactivated in 30 to 45 min. The present work aimed to investigate the mechanisms of the bactericidal action of this material and their dynamics on Escherichia coli using different techniques. Observations by transmission electron microscopy (TEM) at different times of disinfection revealed morphological changes in the bacteria as soon as they were put in contact with the material. Notably highlighted were cell membrane damage; cytoplasm detachment; formation of vacuoles, possibly due to DNA condensation, in association with regions exhibiting different levels of electron density; and membrane lysis. PCR and flow cytometry analyses were used to confirm and quantify the observations of cell integrity. The direct exposure of cells to silver, combined with the oxidative stress induced by the reactive oxygen species (ROS) generated, was identified to be responsible for these morphological alterations. From the first 5 min of treatment with the Al2O3-TiO2-Ag material, 98% of E. coli isolates were lysed. From 30 min, cell viability decreased to reach total inactivation, although approximately 1% of permeable E. coli cells and 1% of intact cells (105 genomic units · ml-1) were evidenced. This study demonstrates that the bactericidal effect of the material results from a synergic action of desorbed and supported silver. Supported silver was shown to generate the ROS evidenced. © 2015, American Society for Microbiology.

Tartanson M.A.,Montpellier University | Tartanson M.A.,CARDPool SAS | Soussan L.,Montpellier University | Rivallin M.,Montpellier University | And 5 more authors.
Water Research | Year: 2014

A new composite material based on alumina (Al2O3) modified by two surface nanocoatings - titanium dioxide (TiO2) and silver (Ag) - was studied for spa water disinfection. Regarding the most common microorganisms in bathing waters, two non-pathogenic bacteria Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram positive) were selected as surrogates for bacterial contamination. The bactericidal properties of the Al2O3-TiO2-Ag material were demonstrated under various operating conditions encountered in spa water (temperature: 22-37°C, presence of salt: CaCO3 or CaCl2, high oxygen content, etc.). Total removal of 108CFUmL-1 of bacteria was obtained in less than 10min with 16gL-1 of material. Best results were observed for both conditions: a temperature of 37°C and under aerobic condition; this latest favouring Reactive Oxygen Species (ROS) generation. TheCaCO3 salt had no impact on the bactericidal activity of the composite material and CaCl2 considerably stabilized the silver desorption from the material surface thanks to theformation of AgCl precipitate. Preliminary tests of the Al2O3-TiO2-Ag bactericidal behaviour in a continuous water flow confirmed that 2gL-1 of material eliminated more than 90% of a 2.0×108CFUmL-1 bacterial mixture after one water treatment recycle andreached the disinfection standard recommended by EPA (coliform removal=6 log) within 22h. © 2014 Elsevier Ltd.

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