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)

What causes rickettsial pox?

Answer: Rickettsia akari carried by mites that causes an initial red papule at the bite site, and eventually chickenpox-like vesicles over the body

What is endemic typhus, and how is it spread?

Answer: Fever, headache, rash from Rickettsia typhi (less severe than epidemic typhus) spread by rodent-fleas from a rodent reservoir.

Note that found in urban areas in the United States

What is epidemic typhus, and how is it spread?

Answer: Fever, headache, rash due to Rickettsia prowazekii. Transmitted at times of overcrowding (poverty, war) by human body lice. Characteristic rash consists of pink macules; starts centrally and spreads outward sparing the palms and soles.

Where does the rash related to RMSF start? Where does it spread to?

Answer: On the ankles and wrists and palms and soles and then spreads to the trunk, and face (centripetal spread)

What is Rocky Mountain spotted fever (RMSF)?

Answer: Fever, headache, conjunctival redness, and petechial rash on palms and soles due to Rickettsia rickettsii. RMSF is transmitted by wood tick bites and is actually more common in the eastern United States.

What is the Weil-Felix reaction?

Answer: A test for antibodies to Proteus vulgaris antigens used to diagnose rickettsial infection based on the coincidental cross-reactivity with Rickettsia (except C. burnetii)

What symptoms are associated with most rickettsial infections?

Answer: Rash (vasculitis), high fever, severe headache

How are rickettsiae transmitted?

Answer: Through arthropod vectors (except Q fever, Coxiella burnetii was previously classified as a Rickettsia)

What is the appropriate therapy for chlamydial neonatal conjunctivitis?

Answer: Erythromycin eye drops

How are Chlamydia infections treated?

Answer: Tetracycline, doxycycline, erythromycin, azithromycin, or a fluoroquinolone

How are C. pneumoniae and C. psittaci transmitted?

Answer: Aerosol transmission

What vascular changes may Chlamydia pneumoniae elicit?

Answer: Intimal changes with deposition of lipid-laden macrophages, resulting in a fatty streak.

Note that the significance of C. pneumoniae in the pathogenesis of atherosclerosis remains unclear.

What disease is caused by Chlamydia pneumoniae?

Answer: Atypical pneumonia (gradual onset of fever and nonproductive cough, eosinophilia, history of conjunctivitis)