Vibrio cholerae is a gram-negative, curved rod-shaped bacteria that is the cause of the disease cholera. It is found in fresh and brackish water throughout the world. There are three pathogenic strains that cause disease in humans. Cholera is transmitted through ingesting contaminated food or water and causes acute, watery diarrhea that can lead to severe dehydration and death if untreated. Diagnosis involves culturing the bacteria from stool samples and identifying its unique biochemical characteristics.

1. Awang Ismawi Bin Awang Ismail
Wan Muhammad Hakimi Bin Wan Zakaria

2.  Gram negative bacteria
 Three members pathogenic to human, other
species are pathogenic for animal and insects
 Lead a commensal existance in numerous
hosts or occur as saprophytes, particularly in
water

3.  Found in fresh and brackish (slighly salt)
water, shellfish and other seafood
 Man is the major reservoir for V.cholerae
 Factor of transmission – inadequate
sanitation, lack of person and food hygiene,
use a polluted water to prepare food,
inadequate cooked shellfish etc

5.  Curved rods with rounded ends
 3 x 0.5µm
 Gram negative – pink stained
 Actively motile with single polar flagellum.
To- and fro- movement (dark-field
micsroscopy)
 Non-capsulated, Non-sporing
 Some strain is lateral flagellum

6.  Produce enterotoxin (exotoxin) that activates
enzyme adenylcyclase
 Causing watery diarrhoea producing ‘rice
water’ stool containing vibrios, epithelial
cells and mucus
 Adherence factor – motility and extracellular
enzymes such as proteases
 Acute cholera – rapid loss of fluid and
electrolytes in stool, vomit leads to muscular
cramps and severe dehydration (fatal),
acidosis, blood urea increase, urine increase
in albumin

7.  Aerobic
 Wide temperature. Optimum 37oC
 Grow in ordinary media but sensitive to acid pH
(alkaline; 8.2)
 2-3 mm in size after 18 – 24 hr incubation in
optimum temp.
 Low convex with an entire edge, whitish and
translucent
 Older colonies develop a light ochre tinta tube of
peptone water with a flake of mucus from stool and
incubating for only 6 – 8 hrs

8.  Ferment glucose, sucrose, mannitol and
maltose without gas production
 Does not utilise lactose or dulcitol
 Positive in indole and nitrites test
 Non-hemolytic in sheep blood agar (Greig
test)
 Can be tested in H2SO4