Solvatochromic dyes are used herein to indicate the presence of bacteria by incorporating them into various substrates such as films, woven and nonwoven fabrics, paper towels, coform and airlaid materials and bonded carded webs. These dyes change color in response to a change in polarity of the environment. Since water is a polar solvent and most bacteria are made from non-polar substances, the presence of bacteria changes the polarity of the environment, triggering a change visible by the unaided eye. A lateral flow device incorporating solvatochromic dyes and a method of detecting bacteria are also included.