A 19-year-old man who recently went camping in the northeast United States presents to the student health clinic at his college with fever, headache, and a rash around both his ankles and wrists. What is the most likely pathogen, how is it transmitted, and what would the treatment of choice be?

Answer: Rickettsia rickettsii, tick bite, doxycycline

A 29-year-old woman and her husband seek your consultation for an inability to conceive. After a thorough workup, you believe the cause to be an undiagnosed infection in the woman. Examination reveals mild cervical motion tenderness; Gram stain of cervical secretions shows neutrophils but no organisms. The inability of the causal bacteria to produce what substance causes it to be an obligate intracellular parasite?

Answer: The patient here has pelvic inflammatory disease (PID). The causal organism is C. trachomatis, an intracellular parasite that is unable to make adenosine triphosphate (ATP). PID includes endometritis, salpingitis, tubo-ovarian abscess, and pelvic peritonitis. PID increases the risk of infertility as well as ectopic pregnancies.

A 24-year-old sexually active man presents with dysuria and urethral discharge. Gram stain of the discharge reveals neutrophils but no gram-negative diplococci. What is the diagnosis and treatment?

Answer: Most likely nongonococcal urethritis caused by C. tmchomatis serotypes D-K. However, treat for all likely causes of urethritis—either doxycycline or azithromycin for C. trachomatis and Ureaplasma urealyticum, and ceftriaxone for N. gonorrhoeae.

How does C. bumetii differ from other rickettsiae?

Answer: It is transmitted by aerosols rather than an arthropod vector, is not associated with a rash, and the Weil-Felix reaction is negative.

What are the symptoms of Q fever?

Answer: Self-limited flu-like illness, soaking sweats, pneumonia, and can cause hepatitis and endocarditis. Note that there is no rash

What disease does C. burnetii cause? How does C. bumetii spread?

Answer: Q fever. Spreads by inhalation of endospores from placental products of animals

What class of antibiotic can be used for all rickettsial infections?

Answer: Tetracyclines (eg, doxycycline)