Mitral valve endocarditis caused by a serum-resistant strain of Escherichia coli

Endocarditis due to Escherichia coli is rare. The case of a 79-year-old woman with E. coli bacteremia and multiple hemorrhagic cerebral infarcts is reported. A two-dimensional echocardiogram showed no evidence of a vegetation. While she was receiving antimicrobial therapy, bacteremia, hematuria, conjunctival petechiae, and a mitral regurgitant murmur occurred. The patient died, and at autopsy a large (2.2 x 2.0 x 0.7 cm) necrotic vegetation on the anterior leaflet of the mitral valve and several hemorrhagic infarcts of the brain were noted. An in vitro study with use of pooled human serum was performed and demonstrated that the patient's infecting strain of E. coli was serum resistant, in contrast to a serum-sensitive control strain of E. coli that was isolated from the cultures of blood from a patient with pyelonephritis. Including our case, 19 well-described cases of E. coli endocarditis from 1945 to 1990 have been reported. E. coli can cause endocarditis of both sides of the heart. More cases of endocarditis of host valves than of prosthetic valves have been documented.