The paper aims to emphasis the specific detection of bacterial strains using enzyme-linked immunosorbent assay. The assay is based on the specific binding of polyclonal antibody anti E.coli tagged with FITC to E.coli and monoclonal antibody anti Ps. aeruginosa tagged with Alexa Fluor 647 tagged to Ps. aeruginosa and on subsequent enzymatic immunological demonstration of the conjugated enzyme. In this experiment the negative control was the Salmonella enterica strain. The two antibodies had no interaction with the negative control, instead they were specific for E . coli and Ps. aeruginosa strains. When both strains were in the same well, the fluorescence intensity given by the presence of E. coli was 2.3 times higher than that given by Ps . aeruginosa, and the intensity of fluorescence decreased if there are both bacterial strains in the wells.