ENTEROCOCCUS

19 plus species including:

SPECIES

Enterococcus avium
Enterococcus casseliflavus
Enterococcus cecorum
Enterococcus columbae
Enterococcus dispar
Enterococcus durans
Enterococcus faecalis
Enterococcus flavescens
Enterococcus faecium
Enterococcus gallinarum
Enterococcus hirae
Enterococcus malodoratus
Enterococcus mundtii
Enterococcus pseudoavium
Enterococcus raffinosus
Enterococcus saccharolyticus
Enterococcus seriolicida
Enterococcus solitarius
Enterococcus sulfureus

MICROSCOPIC APPEARANCE

Gram Stains: Gram-positive.
Morphology: Cocci that are spherical or ovoid.
Size: 0.6-2.0 micrometers by 0.6-2.5 micrometers.
Motility: Enterococcus is sometimes motile by scanty flagella.
Capsules: They lack obvious capsules.
Spores: None.
Other: They usually appear in pairs or short chains in liquid media.

MACROSCOPIC APPEARANCE

On solid media, Enterococcus spp. appear as smooth, cream or white colonies with entire edges. E. faecalis are non-hemolytic on sheep blood agars but are beta-hemolytic on media containing rabbit, horse and human blood.

METABOLIC PROPERTIES

Chemoorganoheterotrophic; facultatively anaerobic; can grow in 6.5% NaCl at pH 9.6; fermentative, some respiratory when provided with hemin under aerobic conditions.

KEY BIOCHEMICAL REACTIONS

HABITAT

Enterococci can be found in soil food, water animals and birds. They can survive in harsh environments and persist almost everywhere. E. faecalis is one of the most common isolates of the human gastrointestinal tract.

PATHOGENICITY

Enterococci are opportunistic pathogens in the urinary tract and blood stream. Because of the proximity of their habitat, the normal gastrointestinal tract flora of humans, enterococci are frequent causes of urinary tract infections, especially in hospitalized patients who have urinary tract infections and hospitalized patients who have urinary tract abnormalities or those undergoing urinary tract manipulation. They are commonly present in polymicrobial abdominal and pelvic infections, although their clinical significance in that setting is sometimes doubtful. (5) They are implicated in approximately 10% of all urinary tract infections and 16% of nosocomial urinary tract infections. Enterococci are also the third leading cause of nosocomial bacteremia. Most infections involving nosocomial infections by enterococci occur in patients with underlying conditions or are immunocompromised. Enterococcal infections of the respiratory tract or the central nervous system can occur but they are rare.

RECOMMENDED MEDIA

For culture: TSA Agar, Blood Agar 5%, Chocolate Agar, Nutrient Agar.
For selective isolation: Bile Esculin Azide (BEA) Media, 6.5% NaCl Broth, 6.5% NaCl Agar, Columbia CNA, Mannitol Salt Agar, Mannitol Salt Broth.
For maintenance: TSA Agar, Blood Agar 5%. Media containing cryoprotectants such as glycerol or serum may be used for long-term storage at -70 degrees C. (i.e. Brucella with Glycerol, TSB with Glycerol).

INCUBATION

Temperature: 35 degrees C.
Time: 18-24 hours
Atmosphere: Aerobic (Facultative anaerobe)

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 for Microbiology, Washington, D.C.

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


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