ACINETOBACTER

SPECIES

Acinetobacter alcaligenes Acinetobacter baumannii Acinetobacter calcoaceticus Acinetobacter haemolyticus Acinetobacter johnsonii Acinetobacter junii Acinetobacter lwoffii

MICROSCOPIC APPEARANCE

Gram Stain: Negative.
Morphology: Rods.
Size: 0.9 - 1.6 micrometers by 1.5 - 2.5 micrometers.
Motility: Cells exhibit twitching motility due to presence of polar fimbrae.
Capsules: Many strains are encapsulated and can be seen in India ink wet mounts.
Spores: No.

MACROSCOPIC APPEARANCE

Colonies of encapsulated cells are generally non-pigmented and mucoid.

METABOLIC PROPERTIES

Chemoorganoheterotrophic with a respiratory type metabolism. Most strains can grow on minimal salts together with acetate, ethanol, or lactate. Few strains use glucose.

KEY BIOCHEMICAL REACTIONS

HABITAT

Present in soil and sewage, can cause nosocomial infections.

PATHOGENICITY

Although considered to be normally nonpathogenic, Acinetobacters are causative agents of nosocomial infections, particularly in debilitated individuals. Also, evidence has been presented indicating that nosocomial infection with Acinetobacter has a distinct seasonal variation. Infections with Acinetobacter have been shown to result in septicemia, meningitis, endocarditis, brain abscess, lung abscess, pneumonia, empyema and urinary tract infections as well as other clinical manifestations.

RECOMMENDED MEDIA

For culture: Heart Infusion Agar, Brain Heart Infusion Agar (BHIA), Nutrient Agar and Tryptic Soy Agar (TSA).
For selective isolation: MacConkey, EMB.
For maintenance: Tryptic Soy Agar (TSA).

INCUBATION

Temperature: 33 - 35 degrees C.
Time: 24 - 48 hours.
Atmosphere: Aerobic.
pH: Optimum pH for growth 5.5 - 6.0.

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, Volumes 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. Internet: www.hardlink.com /Bacterial Database Search, February, 1997.


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