Direct Detection of Cardiobacterium hominis in Serum from a Patient with Infective Endocarditis by Broad-
Range Bacterial PCR

Cardiobacterium hominis is a small, gram-negative coccobacillus which is part of the normal human oropharyngeal
flora, but upon disturbance of the mucosal integrity it can become invasive and pathogenic (21, 23). The organism is
a known but rare cause of endocarditis; it is notorious for causing apparently culture-negative endocarditis, as are
the other members of the HACEK group (i.e., Haemophilus species, Actinobacillus actinomycetemcomitans, Eikenella
corrodens, and Kingella kingae), since their growth requires special media and prolonged incubation (2, 3, 4, 5, 13).
J Clin Microbiol. 2006 February; 44(2): 669–672.

Endocarditis Due to a Novel Cardiobacterium Species
TO THE EDITOR: Background: Cardiobacterium hominis, a member
of the HACEK group (
Haemophilus, Actinobacillus, Cardiobacterium,
Eikenella, and
Kingella) of gram-negative rods, is the only Cardiobacterium
species known to cause human disease.

Objective: We describe a case of endocarditis due to a new member
of the Cardiobacterium genus.

Case Report: A previously healthy 46-year-old man gradually developed
anorexia, exertional dyspnea, and fatigue over the course of 1
month. The patient had no significant medical history but had undergone
dental extractions approximately 2 weeks before illness onset.

1 February 2005 Annals of Internal Medicine Volume 142 • Number 3 229

Characterization of oral strains of Cardiobacterium valvarum and emended description of the organism.  
The description of the new species Cardiobacterium valvarum prompted a search for additional strains of the
organism. Here we report characterization of four oral Cardiobacterium strains from the Culture Collection of the
University of Goteborg. The 16S rRNA gene sequences of the organisms exhibited 99.6% to 99.3% homology with
Cardiobacterium valvarum. The cellular fatty acid profiles, electrophoretic patterns of whole-cell proteins, growth rate
and nutritional requirement, colonial and cellular morphology, and biochemical reactions were also similar to those of
C. valvarum. These results thus classify these organisms as oral strains of C. valvarum. All strains were susceptible
to many antibiotics tested. The description of the species was emended. C. valvarum is a rare cause of endocarditis,
and its relationship with periodontal diseases may need investigation.
Journal of Clinical Microbiology, 2005 (Vol. 43) (No. 5) 2370-2374

Late prosthetic valve endocarditis due to Cardiobacterium hominis, an unusual complication


We report a case of prosthetic valve endocarditis caused by Cardiobacterium hominis in a patient who had
undergone atrial septal defect closure and mitral valve replacement of the heart in 1978. He presented with pyrexia
of unknown origin and congestive cardiac failure. Investigations revealed infective endocarditis of prosthetic valve in
mitral portion. Blood culture samples grew C. hominis . The patient was empirically started on vancomycin and
gentamicin intravenously and ceftriaxone was added after isolation of the organism. Though subsequent blood
cultures were negative, patient remained in congestive cardiac failure and died due to complications

The organism is an unusual cause of human disease, notorious for causing culture negative endocarditis.[3] C.
hominis endocarditis has been recorded till date in 81 patients.[4] Only 11 cases of prosthetic valve endocarditis by
C. hominis have been described internationally.
Indian J Med Microbiol 2007;25:64-6

Ruptured Mycotic Aneurysm of the Superior Mesenteric Artery That Was Due to Cardiobacterium

At autopsy, vegetations were present on the aortic and mitral valves. A distal branch of the superior mesenteric
artery was dilated and ruptured. Special stains of specimens from both the aneurysm and vegetations were negative
for microorganisms. Initial blood cultures ultimately yielded Cardiobacterium hominis 15 days after his death. All
cultures following institution of antibiotic therapy, including those of postmortem specimens, were negative.

One group of organisms that cause “culture-negative endocarditis” are those belonging to the Haemophilus,
Actinobacillus, Cardiobacterium, Eikenella, and Kingella group.  Staphylococcus and Streptococcus are the most
commonly isolated organisms from all mycotic aneurysms. In ∼25% of cases, blood cultures remain negative [4].
Clinical Infectious Diseases 1999;29:1573–4


Author: Kerry O Cleveland, MD, Associate Professor of Medicine, University of Tennessee College of Medicine;
Consulting Staff, Department of Internal Medicine, Division of Infectious Diseases, Methodist Healthcare of Memphis
Coauthor(s): Pierre A Dorsainvil, MD, Medical Director, HIV Specialist, Palm Beach County Main Detention Center;
Consulting Staff, Department of Internal Medicine, Division of Infectious Diseases, Lake Ida Medical Center; Burke A
Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious
Disease Division, Winthrop-University Hospital; Michael Gelfand, MD, FACP, Chief, Professor, Department of Internal
Medicine, Division of Infectious Diseases, Methodist Healthcare of Memphis, University of Tennessee
Contributor Information and Disclosures

Updated: Feb 3, 2009

Cardiobacterium hominis is a member of the HACEK group (Haemophilus aphrophilus, Actinobacillus
actinomycetemcomitans, 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.

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

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.

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

Cardiobacterium colonization does not have a sexual predilection. C hominis is occasionally recovered from uterine,
cervical, and vaginal cultures in asymptomatic women.

Cardiobacterium colonization does not have an age predilection.

The clinical course of C hominis endocarditis tends to be subacute. In a published series, the mean duration of
symptoms was 169 days; however, this may reflect the difficulty in growing C hominis in older blood culture systems.
In this same series, 44% of patients had a history of a dental procedure or oral infection.1

Common findings in Cardiobacterium infections include the following:

Fever (86%)
Splenomegaly (59%)
Peripheral embolic phenomenon (44%)
Petechiae (41%)
Clubbing (19%)
Bacteremia with C hominis endocarditis usually occurs in the setting of pre-existing structural heart disease or a
prosthetic heart valve. Many patients have a history of a recent dental procedure or poor dentition