A low-cost, innovative and non-invasive colorimetric test, which can be universally used, is proposed to detect pathogen bacteria via the simple and fast detection of volatile metabolites released by enzymatic hydrolysis. The proof of 10 concept is shown via three sets of experiments studying the release of the p-nitrophenol metabolite in solution in the E. coli cultures containing 4-nitrophenyl-β-D-glucuronide, the trapping efficiency of the gaseous metabolite by various tailored and functionalized xerogels, and the trapping and 15 detection of gaseous p-nitrophenol released by E. coli bacteria.