A 29 year old patient presents with a diffuse rash and fever. A painless genital ulcer occurred weeks earlier. A skin lesion is cultured and fluorescent staining shows thin spiral spirochetes. What organism are you suspecting and what additional testing would you perform for confirmation?

Prepare for the CAMLPR Microbiology Test. Utilize flashcards and engaging multiple-choice questions, each equipped with descriptions and explanations. Ready yourself for an excellent performance!

The key idea is recognizing syphilis from the presentation and the appearance of a thin spiral spirochete. A painless genital ulcer followed weeks later by a diffuse rash and fever fits secondary syphilis, and seeing spirochetes that are Treponema on fluorescence supports Treponema pallidum as the culprit. In practice, the confirmation strategy starts with a non-treponemal screening test, such as VDRL or RPR, which detects antibodies against cardiolipin and is inexpensive and useful for monitoring treatment response. Because these tests can yield false positives, a treponemal-specific test is then performed to confirm the infection, with examples like FTA-ABS or TP-PA. This combination—Treponema pallidum as the organism and a non-treponemal screen followed by a treponemal confirmatory test—is the standard approach for diagnosing syphilis. Direct PCR or culture aren’t routinely used for confirmation, and serology for Borrelia burgdorferi would not fit the clinical picture.