A 77-year-old man comes to the physician with a 2-week history of fevers and generalized weakness. His other medical history includes a hospitalization for pyelonephritis requiring intravenous antibiotics 3 months ago, an episode of rheumatic fever as a child, and Hodgkin's lymphoma treated with chemotherapy 15 years ago. He also recently underwent cystoscopy for evaluation of persistent dysuria. His temperature is 37.8 C (100 F), blood pressure is 150/86 mm Hg, pulse is 98/min, and respirations are 16/min. The patient appears slightly diaphoretic. There is a new II/VI holosystolic murmur at the apex and tender erythematous lesions affecting several fingertips. The remainder of the physical examination is unremarkable. Which of the following bacteria is most likely responsible for this patient's present illness?
Culture-positive infective endocarditis | |
Staphylococcus aureus |
|
Viridans streptococci |
|
Staphylococcus epidermidis |
|
Enterococci |
|
Streptococcus gallolyticus |
|
Fungi |
|
This patient has low-grade fever, generalized weakness, a new holosystolic murmur, and several tender erythematous lesions affecting the fingertips (Osler's nodes). These findings, along with a prior history of rheumatic fever, are suggestive of infective endocarditis (IE).
A variety of microorganisms can cause IE, and certain bacteria are more frequently associated with specific clinical conditions. Staphylococcal infection is the most common cause of healthcare-associated IE. The enterococci species (eg, Enterococcus faecalis) are another common (30%) cause of nosocomial-acquired endocarditis, particularly in those with associated nosocomial urinary tract infections. Given this patient's history of pyelonephritis and persistent dysuria, he likely has urinary tract colonization of enterococci species. The bacteremia in this patient likely occurred through urinary tract manipulation from the recent cystoscopy, leading to IE.
(Choice A) Coxiella burnetii is a rickettsial bacterium that causes Q fever via inhalation of contaminated aerosols from infected livestock or consumption of unpasteurized milk. It is seen rarely in endocarditis in immunocompromised patients with underlying valvular disease.
(Choice C) Staphylococcus epidermidis (coagulase-negative staphylococci) is a major constituent of normal skin flora and is commonly seen in hospital-acquired endocarditis associated with intravascular catheters. This patient had intravenous antibiotics 3 months ago and would likely have had symptoms sooner if the bacteremia had occurred then.
(Choice D) Group A Streptococcus (Streptococcus pyogenes) causes pharyngitis, cutaneous infections (eg, pyoderma, cellulitis), and complications associated with streptococcal infection (eg, acute rheumatic fever, glomerulonephritis). It is not a common cause of IE.
(Choice E) IE associated with viridans group streptococci is usually related to dental or upper respiratory source of infection. It is not associated with genitourinary tract manipulation/infections.
Educational objective:
Enterococci, especially Enterococcus faecalis, are a common cause of endocarditis associated with nosocomial urinary tract infections.