Detailed information on Vibrio cholerae

2. Domain : Bacteria
Phylum : Proteobacteria
Class : Gammaproteobacteria
Order : Vibrionales
Family : Vibrionaceae
Genus : Vibrio
Species : V.cholerae
Fig.1: V.cholerae

3. Characterisitcs
1. V.cholerae is a Gram-negative, comma-shaped bacterium. The
bacterium's natural habitat is brackish or saltwater where they attach
themselves easily to the chitin-containing shells of crabs, shrimps, and
other shellfish.
2.Some strains of V.cholerae cause the disease cholera, which can
be derived from the consumption of undercooked or raw marine life
species. V.cholerae is a facultative anaerobe and has a flagellum at
one cell pole as well as pili.
3. V.cholerae can undergo respiratory and fermentative metabolism.
When ingested, V.cholerae can cause diarrhea and vomiting in a host
within several hours to 2–3 days of ingestion. V.cholerae is a highly
motile and halophilic. Initial isolates are slightly curved, whereas they
can appear as straight rods upon laboratory culturing.
4.The Vibrios tolerate alkaline media that kill most intestinal
commensals, but they are sensitive to acid. It measures 0.3 micron in
diameter and 1.3 micron in length with average swimming velocity of
around 75.4 +/- 9.4 microns/sec.

4. Fig.1.1: Structure of Vibrio Cholerae

5. History
1.V.cholerae was first isolated as the cause of Cholera in 1854 by
Italian anatomist Filippo Pacini and by the Catalan Joaquim Balcells i
Pascual in the same year, but their discovery was not widely known until
Robert Koch, working independently 30 years later, publicized the knowledge
and the means of fighting the disease.
2.Pacini published a paper in 1854 entitled, “Microscopical
observations and pathological deductions on cholera” in which he
described the organism and its relation to the disease. His microscopic slides
of the organism were clearly labeled, identifying the date and nature of his
investigations.
Fig.2.1: This microscope slide, prepared By Pacini in 1854, was clearly Fig.2.2: Fillippo
Pacini
identified as containing the cholera bacterium.

6. Pathogenesis
1. Vibrio cholerae is the causative agent of the diarrheal
disease Cholera.
2.The disease is characterized by sudden effortless
vomiting, profuse rice water stool followed by rapid
dehydration.
3.Incubation occurs in human via oral route by ingestion of
contaminated food or water.
4.Incubation period is 6 hours to 3 days.
5.The ingested micro organism reaches to the stomach and
the multiplication occurs in the small intestine.
6.After the growth and multiplication it starts to produce
toxins namely, “Cholera toxin” or “Cholera enterotoxin” or
“Choleragen”

7. 7.This toxins cause the of Hyper secretion of glands in
the intestine and resulting in large amount of intestinal
fluids in the intestinal lumens.
8.The toxin also increases the capillary permeability
leading to edema.
9.On the same hand it produces proteolytic enzymes,
which help the organism to penetrate the covering of GI tract
and causes the diarrheal disease among humans.
10.The stools are rice water similar which containing
mucous, epithelial cells and large number of vibrios.
11.The massive loss of electrolytes from the body leads to
metabolic acidosis, muscle cramps, anuria, acute
tubular necrosis, shock and some times death.
12.This disease may last for 4-5 days with an average
fluid loss of 15-20 liters per day.

8. Fig.3: Mechanism of the Cholera Toxin.

9. Cultural Characteristics
1. Vibrio is aerobic, growth being scanty and slow anaerobically
2.Temp range 16-40 degree Celsius (optimum 37oC)
3.Growth better in alkaline medium, pH range 6.4-9.6 (optimum 8.2)
4. NaCl (0.5-1%) is required for optimal growth though high concentration (6%
and above) are inhibitory halotolerant.
5.Vibrios while halophilic vibrios like parahaemolyticus needs a higher
concentration of NaCl
6.Grows well in ordinary culture media
1. Nutrient Agar medium: Overnight growth colonies are moist, translucent,
round discs about 1-2 mm in diameter, with a bluish tinge in transmitted light.
2. Macconkey Agar medium: Colorless at first but become reddish on
prolonged incubation due to late lactose fermentation
3.Blood Agar medium: Colonies are surrounded by the zone of greening, later
becomes clear due to hemodigestion.

10. 7.In gelatin stab culture, infundibuliform (funnelshaped) or
napiform (turnip-shaped) liquefaction occurs in 3 days at 22oC
8.Peptone water: Growth occurs in six hours as a fine surface
pellicle, which on shaking breaks down into membranous pieces.
Turbidity and a powdery deposit develop on continued
incubation.
Special Media
Holding or transport media:
1.Modified form of VR medium: 1 ml of stool is added to each
bottle.Vibrio remain viable for several weeks
2.Cary Blair medium
3.Autoclaved Seawater
Enrichment Media:
Alkaline Peptone Water (Transport as well as enrichment media)
TCBA Media:
In this medium large colonies will be formed in yellow color. Later the
yellow color will be changed to green color.

11. Fig.4.1: Blood Agar medium Fig.4.2: TCBS cholera medium

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