Inhibitory activity of the liquid fase of Copahue Thermal mud (Neuquén, Argentina) on strains of "Staphylococcus aureus"

Abstract

The Copahue Thermal Complex is located at 1,980 m above sea level, at 18 km from the Copahue Volcano, on the Andes mountain range, in Neuquén, Argentina, where Lake Madre, whose temperature ranges from 70°C to 90° C is found. Grey fango composed of sulfur, silicon, oxygen and aluminum is found at the bottom of this lake. Empirically, mineral fango is known to have antiflogistic and antibacterial properties, which are currently used for treating skin conditions, rheumatic diseases and surgical wound infections and for cosmetic purposes. Staphylococcus aureus is a microorganism which forms part of the human microbiota, and as a skin and mucous membranes colonizer, it is involved in several infectious processes. Its presence in the human microbiota increases the risk of invasive infections. Antimicrobial resistance is a consequence arising from the treatment of this type of infections. The purpose of this work was to analyze the antimicrobial properties of the liquid phase of Copahue thermal fango by means of in vitro assays using skin and mucous membranes colonizer strains of S. aureus, isolated from community and hospital patients. The fango was obtained from the perimeter edge of the lake at a depth of 70 cm. Agar diffusion and bactericidal effect tests were conducted. The agar diffusion test showed an inhibition zones for six assayed strains of S. aureus. The estimated inhibitory effect for all the strains showed a fast decline in the viable colony count before 4 hs. ( 3 log order), visualizing a microbial regrowth at 24 hs. The Killing Curve technique allowed to establish the optimum contact time to achieve bacterial growth inhibition among microorganisms and the fango liquid phase. This work shows the antimicrobial properties of the liquid phase of fango from the Copahue Volcano against colonizer strains of S. aureus.