Dr. Jyotsna AgarwalDr. Jyotsna Agarwal

Dept. MicrobiologyDept. Microbiology

Vibrio choleraeVibrio cholerae

Cholera: IntroductionCholera: Introduction

Transmitted to humans via Transmitted to humans via contaminated food and watercontaminated food and water

Part of normal flora of brackish water Part of normal flora of brackish water and estuariesand estuaries

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

Historical PerspectiveHistorical Perspective::

1817-1820 1817-1820 First PandemicFirst Pandemic

spread out of India tospread out of India to

Europe Europe

spread from India -> spread from India -> MiddleMiddle

East (reaching Turkey & East (reaching Turkey &

Persia) -> Far EastPersia) -> Far East

(Singapore, Japan, (Singapore, Japan, PhilippinesPhilippines)

1829-1851 1829-1851

Second Second pandemicpandemicEntered US through Entered US through NY and New Orleans -NY and New Orleans -> proceeded through > proceeded through entire countryentire country

Historical Perspective: IdentificationHistorical Perspective: Identification

1854 - Filippo Pacini identified curved or comma 1854 - Filippo Pacini identified curved or comma shaped bacterium associated with this disease, shaped bacterium associated with this disease, which he called which he called Vibrio choleraeVibrio cholerae

1883- Rober Koch isolated the bacteria1883- Rober Koch isolated the bacteria

Historical Perspective:Historical Perspective:

1854- 1854- John SnowJohn Snow hypothesized water as hypothesized water as primary reservoir for primary reservoir for transmissiontransmission– Broad Street pump incidentBroad Street pump incident– 56 deaths in 2 days56 deaths in 2 days

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.

Cholera affected countriesCholera affected countries

Similarities to Enterobacteriaceae Gram-negativeFacultative anaerobesFermentative bacilli

Differences from EnterobacteriaceaePolar flagella Oxidase positive

General Characteristics of Vibrio

Vibrio spp. (Family Vibrionaceae) Associated with Human Disease

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

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 classicalThree serotypes: ogawa, inaba,

hikojimaNon-cholera vibrio (NCV) or non-agglutinating vibrios (NAG) or non-O1 vibrio cholerae)

Difference between El Tor & Difference between El Tor & classical Vibrio choleraeclassical Vibrio cholerae

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

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

Laboratory Identification of Vibrios

Transport medium or holding medium

- Cary-Blair-Venkatraman Ramakrishnan medium- liquid

Enrichment medium - alkaline peptone broth

Yellow colonies on TCBSYellow 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

Treatment & Prevention of cholera

Untreated: 60% fatality Treated: <1% fatality Rehydration & supportive

therapy Oral Intravenous

Doxycycline or tetracycline

Water purification, sanitation & sewage treatment

Vaccines

SummarySummary

General characters of vibrio, historyGeneral characters of vibrio, history Vibrio choleraeVibrio cholerae Cholera: mode of spread, clinical Cholera: mode of spread, clinical

featuresfeatures Laboratory diagnosisLaboratory diagnosis Treatment/preventionTreatment/prevention