Fig. 1: Scheme of the natural in vitro mutagenesis of the TPA SS14 strain.

The mixture of TP0705 PCR products, containing A1873G and G2122A mutations present in TPA from a ceftriaxone failure case, was added to an in vitro culture of the SS14 strain. From day 7, ceftriaxone (2.5 ng/ml of culture medium) was used for the selection of recombinants. At day 140, the A1873G mutation was fixed in the SS14 culture. At day 212, this mutation was not detected in the control treponemal cultures without the PCR mixture and ceftriaxone. The treponemal culture without the PCR mixture was eliminated in the ceftriaxone-supplemented control. The arrows indicate position 1873 of the TP0705 gene. As G2122A recombinants were not found during the experiment, this position is not shown. The scheme contains real sequences from the experiment at relevant time points after mutagenesis.