Background
Cardiobacterium hominis is a member of the HACEK group (Haemophilus paraphrophilus, Haemophilus parainfluenzae, Aggregatibacter actinomycetemcomitans, Aggregatibacter aphrophilus, C hominis, Eikenella corrodens, and Kingella kingae), which are fastidious, gram-negative, aerobic bacilli that normally reside in the respiratory tract. They have been associated with local infection in the mouth and, collectively, cause 5-10% of cases of native valve endocarditis in persons who do not abuse illicit intravenous drugs. [1, 2, 3]
Pathophysiology
C hominis can be isolated from the nose or throat of approximately two thirds of healthy individuals. C hominis is a nonmotile organism that requires 5-10% carbon dioxide for growth. It does not grow on selective media such as MacConkey or eosin methylene blue agar.
In animal studies, C hominis has shown low virulence, with injection of large numbers of organisms failing to produce infection. Nearly all Cardiobacterium infections reported in humans have been in the form of bacteremia or endocarditis. [4] Rare instances of other human infections, including endovascular infections, septic arthritis, ocular infections, and neonatal sepsis, have also been attributed to these organisms. [5, 6, 7, 8]
Epidemiology
Frequency
United States
C hominis endocarditis accounts for 0.1% of all cases of endocarditis. Of these cases, 75% occur in individuals with abnormal valves. The mitral and aortic valves are affected most often.
Mortality/Morbidity
Mycotic aneurysms are an important cause of morbidity and mortality in C hominis endocarditis. Mycotic aneurysm complicates 2.5-10% of cases of C hominis endocarditis. Embolization may occur during the active stages of endocarditis.
Race
Cardiobacterium colonization does not have a race predilection.
Sex
Cardiobacterium colonization does not have a sexual predilection. C hominis is occasionally recovered from uterine, cervical, and vaginal cultures in asymptomatic women.
Age
Cardiobacterium colonization does not have an age predilection.
