Oviedo, DumasRojas, Jesús MaríaBorda, Ricardo AlbertoDurango, Mónica María2014-10-212014-10-2120132256-3903http://hdl.handle.net/10567/1188Introduction. The germicidal effect UV-C light has is regarded as an effective tool to inactivate and eliminate harmful contaminating agents, such as Escherichia coli and Salmonella typhimurium. Objective. evaluating the effectiveness of UV-C light for reducing Escherichia coli and Salmonella typhimorium populations from cultures that had the microorganisms, combining factors like concentration, time and distance. Methodology. A UV-C lamp, with a 254 nm and 8 volts power, was used; the microbial strains used were Escherichia coli and Salmonella typhimurium of ATCC references. The factors to be measured were the concentration of the microorganism 1x103 and 1x105 ufc/g, time 5-10 and 15 min, distance 5-10 and 20 cm. The data were finally analyzed by the use of descriptive statistics and variance analysis. Results. a higher germicidal effect was observed in the 1x105 concentration for both microorganisms, thus demonstrating significant differences of the microbial reduction of Escherichia coli. The time with the highest reduction of the growth rate for both microorganisms was 15 minutes and the distance with the highest microbial reduction was 5cm. There were not, nevertheless, significant differences of the microbial reduction in the time and distance factors. Besides, Salmonella typhimorium had a higher sensibility to the exposition than that of Escherichia coli. Conclusion. the microbial concentration is a crucial factor for the Escherichia coli`s survival. After being exposed to the UV-C light, Salmonella typhimorium is more sensible to that exposition than Escherichia coli.esCorporación Universitaria LasallistaFacultad de IngenieríasEscherichia coliSalmonella typhimuriumLuz ultravioleta uv-cDesinfecciónArticle