Effects of anaerobic and microaerophilic conditions of extraction and incubation on the survival of Treponema pallidum in vitro.

Treponema pallidum extracted from infected rabbit testes under anaerobic conditions survived longer in vitro than those extracted under aerobic conditions. Anaerobically extracted treponemes were incubated anaerobically for 0, 12, 24, 36, or 48 hours and then exposed to microaerophilic conditions (3% oxygen) for further incubation. Treponemes transferred to microaerophilic conditions after 36 or 48 hours' anaerobic incubation maintained significantly greater viability compared with those kept under constant microaerophilic conditions, although there was no difference after 12 or 24 hours. T pallidum incubated under constant anaerobic conditions, however, usually maintained greater viability than those kept under constant microaerophilic conditions. These results suggest that T pallidum is sensitive to oxygen toxicity both during initial extraction from orchitic rabbit testes and subsequent incubation in vitro. In the latter case, it can be partially protected by a period of anaerobic incubation in vitro, before exposure to microaerophilic conditions.