A 55-year-old woman comes to the emergency department due to a 3-week history of fatigue and exertional shortness of breath. She feels "exhausted" all the time and takes several naps during the day. The patient had rheumatic fever as a child and was diagnosed with mild mitral stenosis as an adult. Her last cardiology follow-up was 6 months ago, and she reported no symptoms. The patient's other medical problems include hypercholesterolemia and diet-controlled type 2 diabetes mellitus. She has progressive dental caries requiring several tooth extractions; the last was 4 weeks ago. The patient does not smoke and drinks alcohol occasionally. Temperature is 37.8 C (100.0 F), blood pressure is 120/70 mm Hg, and pulse is 92/min and regular. Cardiac examination shows a 3/6 holosystolic murmur at the apex as well as a diastolic rumble. The lungs are clear on auscultation. Abdominal examination is unremarkable. A linear hemorrhage is present under the right index nail. Laboratory results are as follows: Urinalysis reveals 1+ protein. Blood cultures are sent. Which of the following organisms is most likely to be isolated in this patient?

Question

A 55-year-old woman comes to the emergency department due to a 3-week history of fatigue and exertional shortness of breath.  She feels "exhausted" all the time and takes several naps during the day.  The patient had rheumatic fever as a child and was diagnosed with mild mitral stenosis as an adult.  Her last cardiology follow-up was 6 months ago, and she reported no symptoms.  The patient's other medical problems include hypercholesterolemia and diet-controlled type 2 diabetes mellitus.  She has progressive dental caries requiring several tooth extractions; the last was 4 weeks ago.  The patient does not smoke and drinks alcohol occasionally.  Temperature is 37.8 C (100.0 F), blood pressure is 120/70 mm Hg, and pulse is 92/min and regular.  Cardiac examination shows a 3/6 holosystolic murmur at the apex as well as a diastolic rumble.  The lungs are clear on auscultation.  Abdominal examination is unremarkable.  A linear hemorrhage is present under the right index nail.  Laboratory results are as follows:  Urinalysis reveals 1+ protein.  Blood cultures are sent.  Which of the following organisms is most likely to be isolated in this patient?

Quizplus · Accepted Answer

11ec25c8_d1b0_e2b2_bc81_51c4d2461877_MD0003_00 This patient most likely has infective endocarditis (IE) caused by viridans group streptococci (eg, Streptococcus mutans, S mitis, S oralis, S sanguinis). Viridans group streptococci typically colonize the oral mucosa and are the most common cause of IE following dental procedures. Gingival manipulation causes transient bacteremia that can lead to IE in patients with an underlying valvular defect (eg, mitral stenosis). The presentation of IE due to viridans group streptococci is typically subacute with several weeks of fatigue and low-grade fever. Patients with IE typically have a new regurgitant murmur (systolic when the mitral valve is affected), and splinter hemorrhages due to microemboli may be present under the fingernails. Leukocytosis and anemia of chronic disease are common, and proteinuria is present in over half of cases. IE is diagnosed using the modified Duke criteria. modified Duke criteria Overall, the risk of IE following dental procedures in patients with acquired valvular defects due to rheumatic fever is low, and antibiotic prophylaxis is not indicated. However, prophylaxis is indicated in patients with a history of IE. (Choice A) Group B streptococcus (Streptococcus agalactiae) is a common cause of skin and soft-tissue infections (eg, pyoderma, cellulitis). IE is rare, and when it does occur, typically affects immunosuppressed patients. (Choice B) The enterococci species (eg, Enterococcus faecalis) are common causes of IE and are associated with IE following procedural manipulation of the urinary tract. (Choice C) Staphylococcus aureus can infect structurally normal heart valves and is the most common cause of IE. Intravenous drug users and patients with prosthetic valves or implanted devices (eg, pacemaker, defibrillator) are at increased risk. The presentation is typically acute with high fever and rapidly progressive cardiac dysfunction. (Choice D) Staphylococcus epidermidis (coagulase-negative staphylococcus) is a common cause of IE. Patients typically have an indwelling intravascular catheter or an implanted prosthetic valve. (Choice E) Streptococcus gallolyticus (S bovis) characteristically causes IE in patients with ulcerative lesions of the colon due to colon cancer or inflammatory bowel disease. (Choice G) Streptococcus pneumoniae is a rare cause of IE. When it does occur, it typically involves the aortic valve and has an acute presentation following an episode of pneumonia. Educational objective: Viridans group streptococci colonize the oral mucosa and can cause infective endocarditis of a structurally abnormal heart valve following dental procedures. Patients typically have a subacute presentation with several weeks of fatigue and low-grade fever. References: Infective endocarditis in adults: diagnosis, antimicrobial therapy, and management of complications: a scientific statement for healthcare professionals from the American Heart Association. (http://www.ncbi.nlm.nih.gov/pubmed/26373316)

A 55-Year-Old Woman Comes to the Emergency Department Due to a 3-Week