Syphilis

Syphilis is a sexually transmitted infection caused by the spirochete bacteriumTreponema pallidum subspecies pallidum.

The primary route of transmission is through sexual contact; it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis.

Other human diseases caused by related Treponema pallidum include yaws (subspeciespertenue), pinta (subspecies carateum), and bejel (subspecies endemicum).

The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, and tertiary). The primary stage classically presents with a single chancre (a firm, painless, non-itchy skin ulceration), secondary syphilis with a diffuse rash which frequently involves the palms of the hands and soles of the feet, latent syphilis with little to no symptoms, and tertiary syphilis with gummas, neurological, or cardiac symptoms. It has, however, been known as "the great imitator" due to its frequent atypical presentations. Diagnosis is usually made by using blood tests; however, the bacteria can also be detected using dark field microscopy. Syphilis can be effectively treated with antibiotics, specifically the preferred intramuscular benzathine penicillin G (or penicillin G potassium given intravenously for neurosyphilis), or else ceftriaxone, and in those who have a severe penicillin allergy, oral doxycycline or azithromycin.

Penicillin

The drug of choice is parenteral penicillin G for all stages of syphilis. According to the 2010 CDC STD treatment guidelines, penicillin G is the only therapy that is clinically documented to be effective against syphilis during pregnancy.^[18] Since the dividing time of T pallidum is slow (days), penicillin G benzathine is the only penicillin effective for single-dose therapy because it is in depo form and levels remain therapeutic in the blood for up to 30 days. Avoiding Bicillin C-R (combination procaine and benzathine), which remains in blood for only 7 days, is essential.

On rare occasions, T pallidum has been found to persist after adequate penicillin therapy; however, no indication exists that T pallidum has acquired resistance to the drug.