A 23-year-old woman comes to the hospital due to fever, chills, dyspnea, and cough for the past several days. She also has sharp right-sided chest pain exacerbated by breathing. Her temperature is 39 C (102 F), blood pressure is 115/70 mm Hg, and pulse is 108/min. On examination, the patient has several needle track marks on both arms. There is a 3/6 holosystolic murmur heard best at the lower sternal border that increases on inspiration. Chest imaging reveals scattered bilateral peripheral lung opacities. HIV testing is negative. This patient's blood cultures are most likely to grow which of the following organisms?

Question

A 23-year-old woman comes to the hospital due to fever, chills, dyspnea, and cough for the past several days.  She also has sharp right-sided chest pain exacerbated by breathing.  Her temperature is 39 C (102 F), blood pressure is 115/70 mm Hg, and pulse is 108/min.  On examination, the patient has several needle track marks on both arms.  There is a 3/6 holosystolic murmur heard best at the lower sternal border that increases on inspiration.  Chest imaging reveals scattered bilateral peripheral lung opacities.  HIV testing is negative.  This patient's blood cultures are most likely to grow which of the following organisms?

Quizplus · Accepted Answer

Staphylococcus aureus can cause right-sided endocarditis in intravenous drug users (IVDUs). In patients other than IVDUs, S aureus disseminates from a primary disease process (eg, abscess, infected central line) and moves by hematogenous spread to the endocardium. S aureus settles on the valve leaflets due to blood flow turbulence at these sites. S aureus can cause perforations in the heart valves, rupture the chordae tendineae, and send septic emboli to the lung (with right heart endocarditis) or to the brain and systemic circulation (with left heart endocarditis). This patient with fever is an IVDU with a holosystolic murmur that increases with inspiration (likely tricuspid regurgitation) and multiple lung opacities (likely septic emboli). She likely has S aureus endocarditis. (Choice A) Candida endocarditis (rare) is typically a severe manifestation of candidemia, with septic emboli to the brain, extremities, and gastrointestinal tract. Patients who are IVDUs, have prosthetic heart valves, or have indwelling lines are at increased risk of infection. (Choice B) Culture-negative endocarditis - due to Bartonella, Coxiella, Mycoplasma, Histoplasma, Chlamydia, or the HACEK organisms (Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella), among others - would be much less likely than S aureus endocarditis. (Choices C, D, E, and H) Streptococcus pneumoniae and Klebsiella pneumoniae typically cause pneumonia; Klebsiella can also lead to urinary tract infections. Nocardiosis typically affects the lungs (cavitary lesions), brain (brain abscess), or skin and is seen mostly in immunocompromised patients. Peptostreptococcus causes anaerobic infections (dental, cutaneous, intraabdominal). (Choice G) Streptococcus gallolyticus (formerly S bovis) is a part of the normal flora of the colon, and bacteremia or endocarditis caused by S bovis is associated with colon cancer (~25% of cases). (Choice I) Streptococcus viridans is the most common etiologic agent in subacute bacterial endocarditis (SBE) following dental work. SBE occurs most frequently in patients with a preexisting valvular abnormality (eg, rheumatic heart disease, congenital heart malformations). The presentation is typically subacute (over weeks rather than days). Educational objective: Staphylococcus aureus causes acute bacterial endocarditis with rapid onset of symptoms, including shaking chills (rigors), high fever, dyspnea on exertion, and malaise. In intravenous drug users, it can cause right-sided endocarditis with septic embolization into the lungs.

A 23-Year-Old Woman Comes to the Hospital Due to Fever