Coxiella

CASE 1

• A 43 year old man came to the hospital with a 5-day history of increasing fever with chills and dry cough. He also complained of increasing malaise and generalized body aches. He was otherwise healthy and had no known underlying chronic diseases.

• The patient is a kente weaver. No one in his family has been ill, but he did report that three of his adult male friends from his village have similar symptoms. His most recent contact with these friends was during a game of draughts. This meeting was particularly memorable, because he recalls that a stray cat gave birth to kittens beneath the game table while the friends were assembled together. Three other adult males were present at the draughts game but had not become ill.

• The patient's chest xray showed a bilateral bronchopneumonia.

• His WBC count was 10,800 with no left shift. The rest of his laboratory evaluation was normal. There was no sputum produced for examination or culture.

• He was treated with ceftriaxone intravenously and oral doxycycline, and his symptoms improved over the next three days. A serology for Coxiella burnetii turned positive during the convalescent phase of his illness. A diagnosis of Q fever pneumonia was made.

Questions:

1. How was this infection acquired in this case?
2. How else can Q fever (Coxiella burnetii infection) be acquired?
3. What role did the parturient cat play in this episode? What other animals are frequently implicated in cases of Q fever? Why does birthing of infected animals present a special risk?
4. Can you grow Coxiella on routine laboratory media? If not, why not?
5. The diagnosis was made clinically and confirmed by retrospective serology. If you possessed the materials to cultivate this pathogen at the time of the patient's acute illness, would you have attempted it? Why or why not?
6. How does this obligate intracellular pathogen survive in the environment between mammalian hosts? How does it survive and grow when taken up by mammlian mononuclear phagocytes?
7. Forgetting the critical history of the cat exposure, and going solely by the clinical symptoms, blood count, and chest xray, what other infectious pneumonias could this patient have had?
8. Which antibiotic was most helpful in this case, ceftriaxone or doxycycline?

CASE 2

• A 65 year old woman has low grade fever, night sweats, malaise, loss of appetite, and weight loss for the past 2 months. These symptoms persisted after a more severe "flu-like" illness that occurred 2 months earlier but resolved (partially) after ~ 10 days. In recent weeks the patient has noted that she is awakened by cough in the night and frequently has to sit upright to catch her breath. She has also noted increased swelling of her ankles. (The later two signs are indicative of fluid overload due to mild congestive heart failure.)

• The patient is married to a farmer. She tends the household as well as the household animals, including chickens, goats, and sheep.

• On physical examination, her temperature is 38.2 degrees. The heart rate is 108/minute. The blood pressure is 130/60mmHg. There are basilar crackles heard at both lung bases. There is a loud cardiac murmur heard throughout systole at the apex of the heart and radiating into the axilla (suggesting incompetancy of the mitral valve). The liver is felt 2 cm below the right costal margin and is slightly tender. There is pitting edema of both ankles. There were numerous hemorrhages of the nails and a conjunctival petechial hemorrhage noted.

• A complete blood count shows a mild anemia. The hepatic transaminases were three times the upper limit of normal, and the total bilirubin was twice normal.

• An echocardiogram showed a large vegetation on the mitral valve, consistent with infective endocarditis (see below). However, three blood cultures taken on three successive days were negative. Serology for Coxiella was sent and was positive at an extremely high titer (1:2560).

Questions:

1. If the patient has endocarditis with a mitral valve vegetation and mild congestive heart failure, why are the blood cultures negative?
2. What is the significance of the liver test abnormalities?
3. What was the most most likely source of infection in this case?
4. What can be done to help this woman?