3. Epidemiology of Vibrio cholerae
Cholera recognized for more than two millennia
with sporadic disease and epidemics
Endemic in communities with poor sanitation
Seven pandemics (possible beginning of 8th)
since 1817
Human carriers and environmental reservoirs
4. Historical Perspective:
1817-1820
First Pandemic
spread out of India to
Europe
spread from India -> Middle
East (reaching Turkey &
Persia) -> Far East
(Singapore, Japan,
Philippines)
1829-1851
Second pandemic
Entered US through NY
and New Orleans ->
proceeded through
entire country
5. Historical Perspective: Identification
1854 - Filippo Pacini identified curved or comma shaped
bacterium associated with this disease, which he called
Vibrio cholerae
1883- Rober Koch isolated the bacteria
6. Historical Perspective:
1854- John Snow hypothesized
water as primary reservoir for
transmission
– Broad Street pump incident
– 56 deaths in 2 days
7. Recent Cholera Pandemics
7th pandemic:
V. cholerae O1 biotype El Tor
Began in Asia in 1961
8th pandemic (??)
V. cholerae O139 Bengal
Began in India in 1992 and spread to Asia, Europe
and U.S.
11. Comma-shaped bacilli
pH range for growth on media
pH 7.0 - 9.0
V. cholerae grow without salt, Most other
vibrios are halophilic
General Characteristics of Vibrio
12. Taxonomy of Vibrio cholerae
>200 serogroups based on somatic O-antigen
O1 and O139 serogroups are responsible for
epidemic cholera
O1 serogroup subdivided into
Two biotypes: El Tor and classical
Three serotypes: ogawa, inaba, hikojima
Non-cholera vibrio (NCV) or non-
agglutinating vibrios (NAG) or non-O1
vibrio cholerae)
15. Pathogenesis of V.cholerae
Incubation period: 2-3 days
High infectious dose
Abrupt onset of life-threatening watery
diarrhea
Rice-water stools:
Colorless
Odorless
Speckled with mucus
16. Pathogenesis of V. cholerae
Cholera toxin leads to profuse loss of fluids
and electrolytes (Na, K HCO3)
A-B type of toxin, receptor GM1, increase
intracellular cAMP
Death attributable to:
Hypovolemic shock
Metabolic acidosis
17. Laboratory Identification of Vibrios
Transport medium or holding medium
- Cary-Blair
- Venkatraman Ramakrishnan medium- liquid
Enrichment medium - alkaline peptone broth
18. Yellow colonies on TCBS
Selective/differential
culture medium -
TCBS agar
– V. cholerae grow as
yellow colonies
– Gram stain
– Biochemical and
serological tests
– Motility- Darting
motility on hanging
drop preparation
20. Summary
General characters of vibrio, history
Vibrio cholerae
Cholera: mode of spread, clinical features
Laboratory diagnosis
Treatment/prevention