Case Presentation: A 62 year old female with a past medical history of hypertension and diabetes presented to the emergency department with two days of fevers and lethargy. She was hypotensive despite fluid resuscitation and admitted to the intensive care unit for septic shock. Both urine cultures and initial blood cultures grew E. coli resistant to ampicillin and otherwise pan-sensitive.Within 24 hours, she required intubation for respiratory failure. On hospital day two, she developed atrial fibrillation of which she had no prior history. A transthorathoracic echocardiogram at that time was unremarkable. The patient continued to remain altered and neurologic examination showed new hemiparesis; an MRI was performed demonstrating multiple emboli throughout the brain. Our patient’s clinical picture met three minor Duke criteria (fever, positive blood culture, and vascular phenomena) consistent with infective endocarditis (IE). A transesophageal echocardiogram demonstrated a 0.8 by 1.4 cm vegetation on the mitral valve. After discussion with cardiothoracic surgery, she was transferred to a tertiary care hospital for evaluation and consideration of surgery. Given high risk of mortality, the patient’s family opted to delay surgery pending improved neurologic status. She initially demonstrated clinical improvement, however, within a few days, she began to acutely worsen. As a result, she was transitioned to comfort care and expired.
Discussion: Historically, gram negative IE is likely be caused by HACEK group organisms (Haemophilus species, Aggregatibacter species, Cardiobacterium hominis, Eikenella corrodens, and Kingella species) and account for 5 to 10% of community acquired IE (1). More recently, Escherichia coli (E. coli) has been an emerging causative agent in IE, especially in older, diabetic, and female patients like ours. Gram-negative bacteria generally lack the surface proteins that bind to host matrix molecules with which to adhere to endocardium, so it is unclear why E. coli is emerging as a causative organism in IE (2). An increase in the number of immunocompromised and elderly patients may play a role in the changing virulence of E. coli. Extra-intestinal pathogenic E. coli (ExPEC) has been proposed as a designation for new strains of E. Coli with particular virulence factors that enable them to adhere to cardiac valves, but there is not one strain of E. coli that seems to be more prevalent in IE isolates (3) To date there are less than 40 cases of E. coli IE in the literature, accounting for approximately 0.51% of cases of IE (4,3). The majority of these cases (52%) derive from genitourinary infections, as noted in our patient. While E. coli IE is more common in patients with prosthetic valves, in patients with native valve endocarditis (NVE), as in our patient, 68% had no history of valvular abnormalities. The mortality rate of E. coli IE tends to be higher (21%) as well as the rate of need of surgical intervention (42%) (2).
Conclusions: Currently over 90% of patients with non-HACEK gram-negative endocarditis take more than one month from onset of symptoms to clinical diagnosis. The high mortality rate as well as high likelihood for needing surgical intervention in E. coli IE makes timely diagnosis a priority. Clinicians should have a high degree of suspicion for E. coli endocarditis in patients with positive blood cultures who do not clinically improve so that appropriate evaluation and treatment are not delayed.