Biosensor for detecting the presence of bacteria

A biosensor for detecting the presence and/or measuring the concentration of at least one biological agent, comprising a support on which a barcode is placed, at least one area of which is functionalized by at least one aptamer capable of selectively immobilizing said biological agent, said aptamer itself being linked, directly or indirectly, to a coloring molecule, wherein:

• said coloring molecule is linked via a labile bond to the aptamer and is able to produce color following an enzyme attack causing a break of said labile bond;
• or, alternatively,
• said coloring molecule is an antibiotic covalently bonded to the aptamer and is able to produce color or to change color following the immobilization of the biological agent by said aptamer.