A 55-year-old woman comes to the physician with a 3-week history of low-grade fever, weight loss of 4.5 kg (10 lb), and malaise. She is known to have mitral valve prolapse but is otherwise healthy. She underwent a tooth extraction a month ago. The patient does not use tobacco, alcohol, or illicit drugs. Her temperature is 38.5 C (101.3 F), blood pressure is 145/76 mm Hg, pulse is 90/min, and respirations are 18/min. The chest is clear to auscultation and percussion. A 3/6 holosystolic murmur is present at the apex. Chest x-ray is normal. Urinalysis is unremarkable. Blood cultures are drawn and empiric antibiotics are started. Echocardiogram shows moderate mitral regurgitation with a 6-mm mobile mass attached to the mitral valve. Which of the following organisms is the most likely cause of this patient's condition?

Question

A 55-year-old woman comes to the physician with a 3-week history of low-grade fever, weight loss of 4.5 kg (10 lb), and malaise.  She is known to have mitral valve prolapse but is otherwise healthy.  She underwent a tooth extraction a month ago.  The patient does not use tobacco, alcohol, or illicit drugs.  Her temperature is 38.5 C (101.3 F), blood pressure is 145/76 mm Hg, pulse is 90/min, and respirations are 18/min.  The chest is clear to auscultation and percussion.  A 3/6 holosystolic murmur is present at the apex.  Chest x-ray is normal.  Urinalysis is unremarkable.  Blood cultures are drawn and empiric antibiotics are started.  Echocardiogram shows moderate mitral regurgitation with a 6-mm mobile mass attached to the mitral valve.  Which of the following organisms is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

11ec25c8_d131_c713_bc81_197c896162f8_MD0003_00 This patient's clinical presentation and echocardiographic findings are suggestive of infective endocarditis (IE) involving the mitral valve. A possible transient bacteremia in the presence of mitral valve prolapse most likely predisposed her to IE. Staphylococcal infection is the most common cause of healthcare-associated IE; streptococcal infection is a common cause of community-acquired IE. Streptococcus sanguinis belongs to the viridans group of streptococci, which also includes S mitis, S oralis, S mutans, S sobrinus, and the S milleri group. IE with viridans group streptococci is commonly encountered after dental procedures involving manipulation of the gingival tissue or oral mucosa and procedures involving incision and biopsy of the respiratory tract. (Choice A) The enterococci species, especially Enterococcus faecalis, are a common cause of healthcare-associated endocarditis associated with nosocomial urinary tract infections. (Choices B and C) Staphylococcus aureus and coagulase-negative staphylococci (eg, S epidermidis) are the most common causes of healthcare-associated IE. They are usually seen in patients with indwelling intravascular catheters or implanted prosthetic valves or devices and in intravenous drug users. S epidermidis (Choice D) S saprophyticus usually causes urinary tract infections in young women. (Choice E) IE due to S bovis (S gallolyticus) is seen in patients with ulcerative lesions of the colon due to colon cancer or inflammatory bowel disease. Educational objective: Staphylococcal infection is the most common cause of healthcare-associated infective endocarditis (IE); streptococcal infection is a common cause of community-acquired IE. IE with viridans group streptococci is commonly encountered after dental procedures involving manipulation of the gingival tissue or oral mucosa and with procedures involving incision and biopsy of the respiratory tract. References: Preeminence of Staphylococcus aureus in infective endocarditis: a 1-year population-based survey. (http://www.ncbi.nlm.nih.gov/pubmed/22492317)

A 55-Year-Old Woman Comes to the Physician with a 3-Week