During the early 1940s, rabbit models in combination with the drug penicillin allowed for a long term drug treatment. These experiments establish the ground work that modern scientists use for syphilis therapy. Penicillin can inhibit<unk>  in 6–8 hours though the cells still remain in lymph nodes and regenerate. Penicillin is not the only drug that can be used to inhibit<unk> ; it has been found that any β-lactam antibiotics or macrolides can be used. The<unk>  strain 14 has built resistance to some macrolides, including erythromycin and azithromycin. Resistance to macrolides in<unk>  strain 14 is believed to derive from a single point mutation that increased the organism's livability. Many of the syphilis treatment therapies only lead to bacteriostatic results, unless larger concentrations of penicillin are used for bactericidal effects. Penicillin overall is the most recommended antibiotic by the CDC as it shows the best results with prolonged usage. It can inhibit and may even kill<unk>  at low to high doses with each increase in concentration being more effective.
Treponema pallidum
Haemophilus ducreyi
Chlamydia trachomatis
Herpes simplex virus
Mycoplasma genitalium
Veillonella parvula
Toxoplasma gondii
Cryptosporidium parvum