The present invention provides a sialidaseactivity detection kit or device, comprising: (i) an indicator molecule, the indicator molecule comprising a sialylated peptide and a capture site; (ii) a capture zone, the capture zone comprising a capture molecule; and (iii) a binding molecule, the binding molecule being capable of binding to a desialylated derivative of the indicator molecule. Also provided are a method for using the kit or device, a specific indicator molecule, and a specific binding molecule.
Provided are: a biomarker for determining the stress level, which is for determining the stress level suffered by a subject by a non-invasive and simple method; a method for detecting the biomarker; a method for collecting data including the detection method; and a kit for determining the stress level. The above-mentioned purpose can be achieved by using, as a biomarker, sialidase activity of bacteria from a sample obtained from a subject. The sample is preferably excrement and / or the subject is preferably human.