Question

A 10-year-old girl is brought to the office because of fever and chills for 3 days. She had been complaining of a headache and feeling tired for 10 days before she developed fever. The parents had tried giving her acetaminophen, but the child's condition was not improving. Her past medical history is significant for frequent streptococcal throat infections over the past 2 years and a new onset heart murmur detected at her last well child visit 2 months earlier. She is on no medication currently, except for acetaminophen. Otherwise, she has been wearing dental braces for the past year and had a primary tooth extracted 2 weeks earlier in the attempt of liberating space for permanent teeth. On physical examination, the patient is diaphoretic, in moderate distress with a temperature of 39.0° C (102.2° F), blood pressure of 90/60 mm Hg, pulse of 110/min, and respirations of 24/min. On her fingernails, you note several splinter hemorrhages. Auscultation confirms a grade 2/6 high-pitched, blowing, systolic ejection murmur, best heard at the apex that radiates to the left axilla. A chest radiograph is unremarkable, but the electrocardiogram shows signs of left ventricular strain. An echocardiogram reveals vegetations on the mitral valve.

Which of the following microorganisms is the most likely cause of this patient's current condition? a. Candida species
b. Pseudomonas aeruginosa
c. Serratia marcescens
d. Staphylococcus aureus
e. Streptococcus viridans

Answer 1

The likely cause of the patient's condition, infective endocarditis, is Streptococcus viridans, due to her history of streptococcal infections and recent dental work. The correct option is E.

Step-by-step explanation:

The patient with a history of frequent streptococcal throat infections, a new onset heart murmur, and vegetations on the mitral valve is most likely suffering from infective endocarditis.

Given the constellation of symptoms including fever, chills, headache, fatigue, and the clinical findings of splinter hemorrhages, a murmur suggestive of valvular damage, and echocardiographic evidence of vegetations, along with the history of recent dental procedure, the most likely causative microorganism is Streptococcus viridans.

This group of bacteria is a common cause of subacute infective endocarditis, especially in patients with pre-existing valvular heart disease or recent dental procedures, which may provide the entry point for the bacteria to enter the bloodstream and infect the heart valves.