Enzyme linked immunoassay with diffusion rate limiting medium

A method for detecting a target organism in a sample, the method comprising

• a. optionally immobilizing the target organism to a solid phase;
• b. incubating the target organism with one or more reporter enzyme detection probes to form one or more target organism-enzyme detection probe complexes;
• c. removing any unbound reporter enzyme detection probes;
• d. contacting the one or more target organism-enzyme detection probe complexes with a diffusion rate limiting medium containing one or more substrates and incubating the one or more target organism—enzyme detection probe complexes with the one or more substrates in the diffusion rate limiting medium to generate one or more detectable products;
• and
• e. detecting the one or more detectable products by detecting visible spots;
• wherein the diffusion rate limiting medium is any suitable medium that decreases diffusion rate of the one or more detectable products and thereby allowing formation of the visible spots.