Treponema pallidum



Treponema pallidum

Treponema pallidum is the spirochete that is the causative agent of syphilis. Primary syphilis can present with manifestations in the oral region in patients with the risk factor of orogenital contact. The most common finding is an ulcer, and the most common affected site is the lip followed by the tongue and tonsil. Oral involvement during the primary stage is painless, however, and does not present as pharyngitis. If left untreated, a latent period begins, and secondary syphilis subsequently presents up to 6 months later. Secondary syphilis mainly presents with systemic symptoms, but oropharyngeal complaints may also be prominent. Symptoms include headache, malaise, low-grade fever, sore throat, rhinorrhea, neck mass, and rash.
Physical examination of the pharynx reveals oval, red maculopapules and patches. Initially, these lesions are rich in spirochetes and are highly infectious. The tonsils (unilateral or bilateral) may be enlarged and red. Nontender lymphadenopathy can be present in the cervical and other regions. A nonpruritic papular or maculopapular rash that involves the palms and soles is characteristic of secondary syphilis. Symptoms and signs of secondary syphilis can last for 3 to 12 weeks, and then the disease enters another latent phase if it remains untreated. At this point, about one third of patients are cured without any specific treatment, another one third remain latent (no lesions but persistent positive serologic tests), and the remainder progress to the tertiary phase.

Diagnosis during suspected cases of secondary syphilis is made using microscopy or serologic tests. Gram stain cannot detect this bacterium. Spirochetes can be detected by dark-field microscopy, but using this technique, T. pallidum cannot be distinguished from T. microdentium, a commensal in the oral cavity. Warthin-Starry silver stain can detect T. pallidum in tissue specimens, although detection may not be possible late in the course of disease. Nonspecific (RPR) and specific (FTAABS, TPHA) serologic tests are positive, and the treponemalspecific tests remain positive even after adequate treatment.
Treatment for primary or secondary syphilis is with a single intramuscular dose of benzathine penicillin G. Alternative therapy is with doxycycline or ceftriaxone, but longer courses are required to provide a cure.

Source: Cummings Otolaryngology, 6E (2015)

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