AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Cardiobacterium hominis is a member of the HACEK (Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, C hominis, Eikenella corrodens, and Kingella kingae) group, 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.

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 infections reported in humans have been bacteremias or endocarditis.

Frequency

United States

Endocarditis caused by C hominis accounts for 0.1% of all cases of endocarditis. Of these cases, 75% occur in patients 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 endocarditis caused by C hominis. Mycotic aneurysm complicates 2.5-10% of cases of C hominis endocarditis. Embolization may occur during the active stages of endocarditis.

Sex

No difference in colonization rates is observed between males and females. C hominis is occasionally recovered from uterine, cervical, and vaginal cultures in asymptomatic women.

Age

No difference in colonization rates is observed among different age groups.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

The clinical course of endocarditis produced by C hominis 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

Physical

Common findings include the following:

• Fever (86%)
• Splenomegaly (59%)
• Peripheral embolic phenomenon (44%)
• Petechiae (41%)
• Clubbing (19%)

Causes

Bacteremia with endocarditis due to C hominis usually occurs in the setting of preexisting structural heart disease or a prosthetic heart valve. Many patients have a history of a recent dental procedure or poor dentition.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Marantic endocarditis
Carcinoid
Rheumatic heart disease
Eosinophilic heart disease

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Older blood culture systems did not support the growth of HACEK bacteria aerobically or anaerobically; blood cultures needed to be held for up to 2-3 weeks with blind subcultures. Newer blood culture systems support the growth of HACEK bacteria within 5 days. Despite this, some experts continue to recommend holding blood cultures for an extended period (up to one month) when a diagnosis of endocarditis due to this organism is considered.
• In one study, anemia was present in 18 of 23 (78%) patients with C hominis endocarditis
• The erythrocyte sedimentation rate is usually elevated and may exceed 100 mm/h.
• Urinalysis results may show evidence of glomerulonephritis, including hematuria and proteinuria.
• Rheumatoid factor test results may be positive, and this finding is one of the minor criteria for endocarditis.

Imaging Studies

• Transesophageal echocardiogram (TEE) is considerably more sensitive than transthoracic echocardiography (TTE) in helping detect valvular vegetations. TTE is usually performed first, and, if findings are positive, TEE is probably unnecessary.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

• Until recently, the HACEK bacteria were uniformly susceptible to ampicillin. Recently, however, beta-lactamase–producing strains of HACEK have been identified.
• A third-generation cephalosporin (ceftriaxone or cefotaxime) should be considered the drug of choice for HACEK endocarditis.
• Ampicillin plus an aminoglycoside can be used for susceptible isolates.
• In patients unable to take beta-lactams, options include trimethoprim-sulfamethoxazole, fluoroquinolones, or aztreonam.
• Native valve endocarditis should be treated for 3-4 weeks. Prosthetic valve endocarditis requires 6 weeks of treatment.
• The American Heart Association recommends treatment with ceftriaxone, ampicillin-sulbactam, or ciprofloxacin for 4 weeks.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The goals of pharmacotherapy are to eradicate the infection, to reduce morbidity, and to prevent complications.

Drug Category: Antibiotics

Empiric antimicrobial therapy should cover all likely pathogens in the context of the clinical setting.

Drug Name	Ampicillin (Omnipen, Marcillin)
Description	Interferes with bacterial cell wall synthesis during active multiplication, causing bactericidal activity against susceptible organisms.
Adult Dose	12 g/d IV continuously or divided q4h (dose for endocarditis)
Pediatric Dose	100-200 mg/kg/d IV divided q4-6h
Contraindications	Documented hypersensitivity
Interactions	Probenecid and disulfiram elevate levels; allopurinol decreases effects and has additive effects on ampicillin rash; may decrease effects of oral contraceptives; MTX levels may be elevated when coadministered
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Adjust dose in renal failure; evaluate rash and differentiate from hypersensitivity reaction; caution if allergic to cephalosporin

Drug Name	Gentamicin (Garamycin)
Description	Synergistic activity when used with beta-lactam for gram-negative bacteria. Inhibits protein synthesis by binding to the 30S ribosomal subunits.
Adult Dose	1 mg/kg IV q8h; significant adjustment required based on renal function/insufficiency
Pediatric Dose	1.5-2.5 mg/kg IV q8h
Contraindications	Documented hypersensitivity
Interactions	Coadministration with other aminoglycosides, cephalosporins, penicillins, and amphotericin B may increase nephrotoxicity; aminoglycosides enhance effects of neuromuscular blocking agents (thus, prolonged respiratory depression may occur); coadministration with loop diuretics may increase auditory toxicity of aminoglycosides; possible irreversible hearing loss of varying degrees may occur (monitor regularly)
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Narrow therapeutic index; caution in renal failure (not on dialysis), myasthenia gravis, hypocalcemia, and conditions that depress neuromuscular transmission; adjust dose in renal impairment

Drug Name	Ampicillin and sulbactam (Unasyn)
Description	Drug combination of beta-lactamase inhibitor with ampicillin. Interferes with bacterial cell wall synthesis during active replication, causing bactericidal activity against susceptible organisms. Covers skin, enteric flora, and anaerobes. Not ideal for nosocomial pathogens.
Adult Dose	3 g (2 g ampicillin + 1 g sulbactam) IV/IM q6-8h; not to exceed 4 g/d sulbactam or 8 g/d ampicillin
Pediatric Dose	<3 months: Not established 3 months to 12 years: 100-200 mg ampicillin/kg/d (150-300 mg Unasyn) IV divided q6h >12 years: Administer as in adults; not to exceed 4 g/d sulbactam or 8 g/d ampicillin
Contraindications	Documented hypersensitivity
Interactions	Probenecid and disulfiram elevate ampicillin levels; allopurinol decreases ampicillin effects and has additive effects on ampicillin rash; may decrease effects of oral contraceptives
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Adjust dose in renal failure; evaluate rash and differentiate from hypersensitivity reaction

Drug Name	Ciprofloxacin (Cipro)
Description	Fluoroquinolone that inhibits bacterial DNA synthesis and, consequently, growth, by inhibiting DNA gyrase and topoisomerases, which are required for replication, transcription, and translation of genetic material. Quinolones have broad activity against gram-positive and gram-negative aerobic organisms. Has no activity against anaerobes.
Adult Dose	400 mg IV q12h
Pediatric Dose	10-15 mg/kg IV q12h
Contraindications	Documented hypersensitivity
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Adjust dose in renal impairment

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Native valve endocarditis should be treated for 4 weeks, and prosthetic valve endocarditis requires 6 weeks of treatment.

Further Outpatient Care

• Patients can be treated in an outpatient setting but should remain on intravenous antimicrobial therapy for the duration of treatment for endocarditis.
• Risks of embolic complications may arise during therapy.
• Patients should be continuously and carefully monitored and should have prompt access to medical care, including cardiac surgery, in the event of complications.

Deterrence/Prevention

• Antibiotic prophylaxis given prior to dental procedures is primarily directed at Streptococcus viridans but should also help prevent infection due to HACEK bacteria.²

Complications

• Mycotic aneurysm
• Embolization

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Blood culture is the single most important laboratory test performed in a diagnostic workup for infective endocarditis. Echocardiography should also be performed.

Special Concerns

• Embolization or mycotic aneurysm may occur, even during appropriate treatment.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Wormser GP, Bottone EJ. Cardiobacterium hominis: review of microbiologic and clinical features. Rev Infect Dis. Jul-Aug 1983;5(4):680-91. [Medline].
2. Wilson W, Taubert KA, Gewitz M, Lockhart PB, Baddour LM, Levison M, et al. Prevention of Infective Endocarditis. Guidelines From the American Heart Association. A Guideline From the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. Apr 19 2007;[Medline].
3. Baddour LM, Wilson WR, Bayer AS, Fowler VG Jr, Bolger AF, Levison ME, et al. Infective endocarditis: diagnosis, antimicrobial therapy, and management of complications: a statement for healthcare professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young, and the Councils on Clinical Cardiology, Stroke, and Cardiovascular Surgery and Anesthesia, American Heart Association: endorsed by the Infectious Diseases Society of America. Circulation. Jun 14 2005;111(23):e394-434. [Medline].
4. Berbari EF, Cockerill FR 3rd, Steckelberg JM. Infective endocarditis due to unusual or fastidious microorganisms. Mayo Clin Proc. Jun 1997;72(6):532-42. [Medline].
5. Elliott TS, Foweraker J, Gould FK, Perry JD, Sandoe JA. Guidelines for the antibiotic treatment of endocarditis in adults: report of the Working Party of the British Society for Antimicrobial Chemotherapy. J Antimicrob Chemother. Dec 2004;54(6):971-81. [Medline].
6. Horstkotte D, Follath F, Gutschik E, Lengyel M, Oto A, Pavie A, et al. Guidelines on prevention, diagnosis and treatment of infective endocarditis executive summary; the task force on infective endocarditis of the European society of cardiology. Eur Heart J. Feb 2004;25(3):267-76. [Medline].
7. Le Quellec A, Bessis D, Perez C, Ciurana AJ. Endocarditis due to beta-lactamase-producing Cardiobacterium hominis. Clin Infect Dis. Nov 1994;19(5):994-5. [Medline].
8. Nerard JL, Snydman DR. Miscellaneous gram-negative bacilli: Acinetobacter, Cardiobacterium, Actinobacillus, Chromobacterium, Capnocytophaga, and others. In: Gorbach SL, Bartlett JG, Blacklow NR. Infectious Diseases. Philadelphia, Pa: WB Saunders; 1992:1543-55.
9. Nurnberger M, Treadwell T, Lin B, Weintraub A. Pacemaker lead infection and vertebral osteomyelitis presumed due to Cardiobacterium hominis. Clin Infect Dis. Oct 1998;27(4):890-1. [Medline].
10. Silver SE. Ruptured mycotic aneurysm of the superior mesenteric artery that was due to cardiobacterium endocarditis. Clin Infect Dis. Dec 1999;29(6):1573-4. [Medline].
11. Wilson WR, Karchmer AW, Dajani AS, Taubert KA, Bayer A, Kaye D, et al. Antibiotic treatment of adults with infective endocarditis due to streptococci, enterococci, staphylococci, and HACEK microorganisms. American Heart Association. JAMA. Dec 6 1995;274(21):1706-13. [Medline].

Article Last Updated: Jul 2, 2007