Development of a broth medium for Bacteroides forsythus.

Bacteriodes forsythus has been implicated as a possible pathogen in certain destructive periodontal diseases. This species has been extremely difficult to grow in broth, thus hampering its characterization and identification. A broth medium was developed consisting of 30 g of phytone, 10 g of NaCl, and 1 g of filter-sterilized L-cysteine per liter. The medium supported the growth of 23 fresh isolates of B. forsythus from six subjects to optical densities averaging 0.71 +/- 0.20 (standard deviation) at 550 nm after 48 to 72 h of anaerobic incubation.