Actividad bactericida del agua de plata coloidal sobre indicadores de calidad microbiológicaun estudio a partir de muestras ambientales

Resumen

The aim of this study was to evaluate the bactericidal activity of colloidal silver on microorganisms classified as indicators of microbiological quality which were isolated from samples of: (i) water of 16 irrigation canals in the province of Tungurahua – Ecuador and (ii) utensils and supplies from the kitchen in a cafe located in Quito – Ecuador. For this, silver water with a concentration of 4 ppm, 10 ppm, or 15 ppm was applied during 15, 30 or 60 minutes on cell suspensions equivalent to A625 between 0,08 – 0,1 of the strains: Escherichia coli ATCC 11229, Salmonella Choleraesuis ATCC 10708, Staphylococcus aureus ATCC 6538 and Pseudomonas aeruginosa ATCC 15442. After the standardization of the technique, we compared the population density of: aerobic mesophilic bacteria, E. coli – coliform and Enterobacteriaceae in 16 samples of irrigation canal water and 11 samples of food preparation surfaces, before and after exposure to 4 ppm, 10 ppm or 15 ppm of colloidal silver. Regarding the irrigation canal water, the treatments inhibited the growth of all the evaluated microbial groups except in 31,3% (n=5) of the cases where exposure to 4 ppm of colloidal silver resulted in aerobic mesophilic bacteria counts ranging between 10 x 102 CFU/mL and  40 x 102 CFU/mL. In the case of samples collected in the cafe, the mesophilic bacteria counts decreased in 64,3% (n=9) of the total sampled surfaces, whereas counting of E. coli – coliform decreased in 93% (n=13) of the sampled areas after 5 minutes of exposure to 4ppm of colloidal silver.