A method for the detection of bacterial load comprising the phases of adding a sample to be analysed to an analysis reagent in a suitable reaction container (12) appropriately sterilised, thermos tatting the reaction container at a temperature of between 25 and 450C, and verifying the change in colouring of the analysis reagent. The analysis reagent is an aqueous solution comprising from 1 to 100 g/1 of a source of amino acids chosen from the group consisting of meat peptones, vegetable peptones, casein hydrolysates, tryptose, tryptones and yeast extract; from 0 to 50 g/1 of a source of glucides chosen from monometric or oligomeric glucides metabolisable by micro-organisms/ 0 to 200 g/1 of a buffer system suitable for maintaining the pH between 5.5 and 8.5; 0.03 to 3 g/1 of a redox indicator with potential between -250 and +250 mV and/or a pH indicator with colour change interval between pH 4.0 and pH 9.0; and an organic liquid compound not miscible with water and with lower density than the water itself and suitable for separating the aqueous phase from a gaseous phase existing prior to the analysis or formed during the reaction.