wcb22
07-06-2006, 12:11 PM
A 22-year-old man comes to the emergency department with a 3-day history of fever, chills, a cough, pleuritic chest pain, and low-back pain. He says that the symptoms came on "out of the blue". He is the son of a wealthy local businesswoman and still lives at home, which he says "is cool because my parents are never around". His temperature is 39 C (102.2 F), blood pressure is 120/80 mm Hg, pulse is 70/min, and respirations are 16/min. Physical examination shows oval, retinal hemorrhages with a clear, pale center and pinpoint lesions between his toes. Blood cultures are drawn. A chest x-ray film shows multiple patchy infiltrates. Laboratory studies show:
Hemoglobin...................................11 g/dL
Hematocrit....................................39%
Erythrocyte sedimentation rate.......39 mm/hr
Which of the following is the most likely pathogen?
A. Candida albicans
B. Pseudomonas aeruginosa
C. Serratia marcescens
D. Staphylococcus aureus
E. Streptococcus viridans
Explanation:
The correct answer is
D. This patient has acute bacterial endocarditis, most likely due to Staphylococcus aureus, the most common organism causing endocarditis in intravenous drug abusers. The "pinpoint lesions" between his toes are signs of injection drug abuse. Acute endocarditis in drug abusers typically presents with a high fever, pleuritic chest pain, and a cough. The tricuspid valve is commonly affected in these patients. A murmur may not be present in early acute endocarditis or in injection drug abusers with tricuspid valve disease. The retinal lesions are called Roth spots. Other findings include anemia and an elevated erythrocyte sedimentation rate. Diagnosis is with blood cultures, which are typically positive for S. aureus, and with echocardiography. Treatment is with antibiotics.
Candida albicans(choice A), Pseudomonas aeruginosa(choice B), and Serratia marcescens(choice C) are infrequent causes of endocarditis.
Streptococcus viridans(choice E) is a common cause of endocarditis in individuals who are not injection drug abusers. The onset of symptoms is usually more gradual, patients present with a low-grade fever, new cardiac murmur, splenomegaly, hematuria, proteinuria, and an elevated erythrocyte sedimentation rate.
Hemoglobin...................................11 g/dL
Hematocrit....................................39%
Erythrocyte sedimentation rate.......39 mm/hr
Which of the following is the most likely pathogen?
A. Candida albicans
B. Pseudomonas aeruginosa
C. Serratia marcescens
D. Staphylococcus aureus
E. Streptococcus viridans
Explanation:
The correct answer is
D. This patient has acute bacterial endocarditis, most likely due to Staphylococcus aureus, the most common organism causing endocarditis in intravenous drug abusers. The "pinpoint lesions" between his toes are signs of injection drug abuse. Acute endocarditis in drug abusers typically presents with a high fever, pleuritic chest pain, and a cough. The tricuspid valve is commonly affected in these patients. A murmur may not be present in early acute endocarditis or in injection drug abusers with tricuspid valve disease. The retinal lesions are called Roth spots. Other findings include anemia and an elevated erythrocyte sedimentation rate. Diagnosis is with blood cultures, which are typically positive for S. aureus, and with echocardiography. Treatment is with antibiotics.
Candida albicans(choice A), Pseudomonas aeruginosa(choice B), and Serratia marcescens(choice C) are infrequent causes of endocarditis.
Streptococcus viridans(choice E) is a common cause of endocarditis in individuals who are not injection drug abusers. The onset of symptoms is usually more gradual, patients present with a low-grade fever, new cardiac murmur, splenomegaly, hematuria, proteinuria, and an elevated erythrocyte sedimentation rate.