CARDIOBACTERIUM

SPECIES

Cardiobacterium hominis

MICROSCOPIC APPEARANCE

Gram Stains: Gram-negative. The cells are arranged singly, in pairs, chains and rosette clusters.
Morphology: Pleomorphic rods (Pleomorphism disappears when yeast extract is present in the medium). One or both ends of the cells are frequently enlarged, and the crystal violet of the gram stain may be retained in these areas.
Size: 0.5-0.75 micrometers by 1.0-3.0 micrometers in length with rounded ends. Occasionally long filaments are seen that range from 7.0-35.0 micrometers in length.
Motility: Cardiobacterium hominis is non-motile.
Capsules: None.
Spores: None.

MACROSCOPIC APPEARANCE

At 24 hours, Cardiobacterium hominis colonies are minute but at 48 hours the colonies are 1-2 millimeters in diameter, opaque, smooth, moist and butyrous. The colonies of some strains may pit the agar.

METABOLIC PROPERTIES

Facultatively anaerobic but may require CO 2 on primary isolation. Growth requires a capnophilic atmosphere. Aerobic growth is scant unless humidity is elevated. Chemoorganotrophic, with a fermentative type of metabolism.

KEY BIOCHEMICAL REACTIONS

HABITAT

Cardiobacterium hominis is part of the nasal pharyngeal and upper respiratory tract flora of humans. The organism has also been found in the genitourinary and gastroinstestinal tracts.

PATHOGENICITY

Cardiobacterium hominis is an etiologic agent of bacterial endocarditis in patients with preexisting cardiovascular defects, but has also been involved in a case of fatal septicemia in an immunocompromised patient with no known preexisting heart disease. (5)

Also, Cardiobacterium spp. are considered causative agents of abdominal abscesses.

RECOMMENDED MEDIA

For culture: Plated media: Blood Agar(may be poor on primary isolation) or Chocolate Agar.

Blood culture bottles: Recovered from most blood culture media with the exception of Thioglycollate and Schaedler Broth where there are some reports of poor growth.

For selective isolation: No specific media described.
For maintenance: -70 degrees C.
Optimum pH: 7.0-7.2.

INCUBATION

Temperature: 35 degrees C.
Time: Plated media: 48 hours.

Blood culture bottles: 5-8 days, but may take as long as 23 days.

Atmosphere: 10% CO 2 best (4+).
Anaerobic poor (1+).

REFERENCES

1. Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology , 9th ed. Williams & Wilkins, Baltimore, MD.

2. Holt, J.G., et al. 1986. Bergey's Manual of Systemic Bacteriology , Vol. I & II. Williams & Wilkins, Baltimore, MD.

3. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.

4. Murray, P.R., et al. 1995. Manual of Clinical Microbiology , 6th ed. American Society of Microbiology, Washington, D.C.

5. Howard, B.J., et al. 1994. Clinical and Pathogenic Microbiology , 2nd ed. Mosby, St. Louis, IL.

6. Savage, D.D., et al. 1977. Cardiobacterium hominis Endocarditis: Descripiton of Two Patients and Characterization of the Organism. Jour. Clin. Microbiol. ; 5:75-80.

7. Standards Unit, Department for Evaluations, Standards and Training Centre for Infections, Reference no. BSOP ID 12i2. 2009. Identification of Haemophilus species and the HACEK Group of Organisms. Issue no. 2.
www.hpa-standardmethods.org.uk/documents/bsopid/pdf/bsopid12.pdf.


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