Welcome and thanks for posting your query to HCM.
First and fore most I would like to thank you for asking the last part of query in question, which actually made me and my other Professor colleagues to read twice in our books and journals.
Now there are three parts of the question:
1. Transmission of syphilis
from person to person: Yes it is definitely quite possible by direct contact with the person as the syphilitic sore is having high concentration of treponema pallidum
(organism causing syphilis). So if the non infected person is having some cuts or abrasions the chances are quite high. As for any of the STD's the chances are highest in anal then vaginal and lastly oral sexual contact because of grade of trauma in all three. This also depends on the stage of the infection as it is highest in secondary stage of syphilis.
2. Transmission from infected other to fetus: Yes there is high chance of transmission from infected mother to the fetus because the organism can pass through the placental barrier.
3. Transmission from infected person by nonliving things such as toothbrush:This part of question actually made us to read and review the things from various books, journals and studies. Now the conclusion is that treponema pallidum is not transmissible by nonliving things such as toothbrush etc. This is because of the reason that treponema pallidum is a very delicate organism which dies quite early in unfavorable environment. Even Dark field microscopy (test to deonstrate treponema pallidum) is done bed side because of its delicate nature. The same thing applies for any nonliving material on which treponema pallidum is present. Even if we think of high infectivity during secondary stage of syphilis then also the infective dose (ID50) is not sufficient to cause infection. Nevertheless toothpastes present on the brush also contains certain chemicals which actually kills even the most of the microorganisms. Een if somebody has used the brush immediately after the use of an infected person and has sores in oral mucosa
then also theoretically the chances of infection are minimal.
Hope to have given you the best of knowledge regarding the query,
Dr Sanjay K Kanodia
MD ( Dermatology and STD/ Venereology)