TABLE 2 

Summary of T. pallidum subculture experiments

ExperimentStatusStrainNo. of
days in
culture
Passage
no.
Cumulative
fold increase
No. of
generations
Avg
generation
time (h)a
Minimum
generation
time (h)b
1OngoingNichols187261.1 ×10301004533
2OngoingNichols189272.4 ×10311044433
3OngoingNicholsc119172.4 ×1019644336
4OngoingUW231B7092.6 × 109315544
5CompleteUW249Bd4066.5 × 1072654.646
  • a Avg generation time = (time in hours)/(number of generations) for all days in culture, excluding the first culture period.

  • b Minimum generation time = average of the 5 lowest subculture generation times (3 for experiment 5).

  • c Experiment 3 was initiated from frozen stocks of a day 54 culture from experiment 1. All other experiments were initiated from frozen preparations of rabbit-propagated T. pallidum.

  • d Experiment 5 was discontinued after day 40 because of fungal contamination.