A sensitive photometric pyrogen assay.

One of the biocompatibility criteria for implants and invasive devices is the absence of pyrogens at their surface. Currently the assay to measure such surface contaminations is the printing of these surface-attached microorganisms onto culture plates, and, after prolonged incubation, counting of the number of colonies that develop on a particular growth medium. For small parts such as needles or tubes etc. this is difficult to carry out. Mixed contaminations or fragments of bacteria can be detected with a pyrogen assay which utilizes the coagulation of a limulus hemolysate in the presence of small numbers of gram negative bacteria. In the course of developing a very sensititve assay for detection of microorganisms in highly purified water we have improved a commercially available pyrogen test procedure. With the kinetic evaluation of photometric long term incubations we can reach a detection limit of