Defect in small millipore filters disclosed by new technique for isolating oral treponemes.

Three Millipore filters (100, 50, and 10 mmicro) can effectively and easily be used to isolate oral spirochetes from a mixed oral inoculum. The spirochetes appear pure in the underlying agar, owing to their ability to grow through the filter. Their passage through the 10-mmicro filters may be attributed to the instability of this pore size on storage.