A 50-year-old man presented to his family doctor complaining of flu-like symptoms. The doctor gave him a shot of penicillin and sent him home. The man came back a week later and in fact, felt worse. The man was a rancher and raised a lot of cattle. He told the doctor that he had congenital heart disease and an attack of rheumatic fever when he was young. The man now complained of fever, night sweats, continual coughing, weight loss, and lethargy. The doctor had the man hospitalized because he now suspected subacute bacterial endocarditis (SBE). A culture of his blood did not show any bacterial growth, but a serum analysis for antibodies against a certain bacterium was positive. As a result of finding antibodies to this organism, treatment with doxycycline was begun and the patient improved and was released from the hospital. What was the name of the organism with which the man was infected?
Correct Answer: Coxiella burnetii
Description: The man had Q-fever. This disease is caused by infection with Coxiella burnetii. This organism is extremely stable and can survive in milk and soil for a very long time. Infections in man occur when the organisms become airborne from a contaminated source such as soil or milk from a farm. Man can also become infected by drinking contaminated milk. That is why it is a good idea to drink only pasteurized milk. Most of the people exposed to Coxiella burnetii suffer an asymptomatic infection and most symptoms that people do experience are flu-like. Q-fever can occur a long time after the original exposure to the organism and this occurs primarily in people with congenital heart disease. In this case, SBE is most commonly seen. The two Chlamydophila organisms (psittaci and pneumoniae) are incorrect. The man got his infection working on his cattle ranch. The Chlamydophila are not extremely stable and do not survive in dust. Chlamydia trachomatis is incorrect because this organism is not extremely stable and does not survive in dust. While the viridans streptococci do cause SBE, they did not cause this man's infection because they are sensitive to penicillin and they would have grown out in his blood culture had they been present.
Category:
Microbiology
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