A case of infectious endocarditis caused by Cardiobacterium hominis identified by confirming the bottle graph of the Bact/ALERT 3D

Abstract

Cardiobacterium hominis is a resident of the oropharynx and rarely causes infectious endocarditis. We experienced treating a case of C. hominis-infected endocarditis in which Bact/ALERT 3D did not show positive results. The patient was a 57-year-old male. He consulted the emergency department presenting with fever and dyspnea on exertion, and a blood culture test was conducted. Later, transesophageal echocardiography revealed bacterial vegetations at two mitral valve cusps. He was diagnosed with infectious endocarditis and received ceftriaxone at home. He was hospitalized two days later and received ceftriaxone and sulbactam/ampicillin. A mitral valve replacement was performed on the 6th day of hospitalization. A large number of Gram-negative bacilli were detected by Gram staining of mitral valve tissue samples. However, a tissue culture test showed negative results. We confirmed these negative test results using the blood samples collected for culture at the time of his outpatient visit using Bact/ALERT 3D, whose automatic judgment was also negative. However, a slight increase was observed in one of the four bottle graphs. Gram staining was performed on this bottle graph, and Gram-negative bacilli were found. After culturing, colonies grew and were identified as C. hominis. Mitral valve tissue culture could not confirm the growth of bacteria, probably because the test was conducted after the administration of antibiotics. Although the automatic blood culture device did not give a positive result, we could identify C. hominis by searching blood culture bottles.