AEROMONAS

25 plus species including:

SPECIES

Aeromonas allosaccharophila
Aeromonas caviae
Aeromonas hydrophila
Aeromonas jandaei
Aeromonas media
Aeromonas salmonicida
Aeromonas schubertii
Aeromonas sobria
Aeromonas trota
Aeromonas veronii

MICROSCOPIC APPEARANCE

Gram Stain: Negative.
Morphology: Cells straight, rod shaped with rounded ends to coccoid. Occur singly, in pairs or short chains.
Size: 0.3 - 1.0 micrometers by 1.0 - 3.5 micrometers.
Motility: Generally motile by a single polar flagellum. Peritrichous flagella may occur on solid media or in young culture. The Aeromonas salmonicida group is non-motile.
Capsules: No.
Spores: No.

MACROSCOPIC APPEARANCE

Motile aeromonads appear round, raised with an entire edge and a smooth surface. They are translucent and white to buff in color. The non-motile salmonicida group appear round, raised, entire, translucent and friable.

METABOLIC PROPERTIES

Facultatively anaerobic. Chemoorganoheterotrophic having both a respiratory and fermentative type metabolism. Sugars and organic acids are used as carbon sources.

KEY BIOCHEMICAL REACTIONS

HABITAT

Mesophilic motile aeromonads occur widely in water, sludge and sewage. They usually originate from water sources, food, or from the intestinal flora, although the exact source has rarely been identified. Found in marine and fresh waters; Aeromonas salmonicida is parasitic/pathogenic in fish.

PATHOGENICITY

Aeromonads are the causative agents of intestinal and extraintestinal infections. Human disease is usually diarrhea, bacteremia, septicemia. Enteropathogenic potential of motile Aeromonas spp. has come with the finding that some strains produce a heat-stable enterotoxin. Aeromonas spp. may also be involved in nosocomial infections.

Diarrhea is the most frequent infection with Aeromonas spp. The clinical picture of Aeromonas gastroenteritis may vary from acute, profusely watery diarrhea with fever and vomiting to a dysentery-like illness with cramps and abdominal pain, or to mild, chronic diarrhea of more then 10 days' duration (up to several months). The second most prevalent form of disease due to Aeromonas spp. are wound infections, typically occurring after trauma or water contact.

RECOMMENDED MEDIA

For culture: Tryptic Soy Agar, Blood Agar 5%.
Selective pre-enrichment: Alkaline Peptone Water (pH 8.5).
For selective isolation: MacConkey, CIN Agar, HE Agar, Blood Agar with Ampicillin.
For maintenance: Tryptic Soy Agar, Blood Agar 5%.

INCUBATION

Temperature: 20 degrees C., and 35 degrees C.
Time: 18 - 48 hours.
Atmosphere: Aerobic.

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, DC.

5. Internet: www.hardlink.com /Bacterial Database Search, February, 1998.

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


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