An estimated 3-5 million cases and
over 100,000 deaths occur each year
around the world.
 Since October 2010, over 470,000
Haitians have been sickened and
nearly 7,000 have died.


In 2011-2012-cholera outbreak in
multiple African nations in all regions
except north African regions-Ghana –due
to intense hand washing campaign

30 May 2014-cholera outbreak –in sudan
CURRENT SITUATION
From October 2010 - Jan 2014,the govt. of
Haiti has reported 698,304 suspected
cholera cases and 8562 cholera related
deaths
 Of these,58,505 cases and 610 fatalities
were recorded from Jan- december 2013
 Only 1396 cases and 16 fatalities have so
far been registered in jan 2014 - reflecting
significant reduction in number of cases

Situation in India
CHOLERA
V.Cholerae - cholera
Name vibrio from latin as these bacteria possess
single polar flagellum and appear to vibrate
 Italian doctor Fillippo Pacini first discovered
cholera bacillus in 1854
 Robert Koch first isolated in pure culture in 1883
 Causes cholera, acute watery diarrhea due to a
potent Enterotoxin, disease of poor water
sanitation

Epidemiology

Worldwide with epidemic, sporadic and
pandemic nature

Poor sanitation, unsafe drinking water, natural
calamities, overcrowding predispose.

7 pandemics thus far

6 originated in India - V.cholerae biotype
classical, confined to Asia (1817 – 1923)
Epidemiology contd….)
7th and current pandemic started outside
India, 1961, in Indonesia by El Tor biotype
 Humans are only sources of infection
 Between periods of epidemics, bacteria
survive in marine and estuarine water,
zooplanktons

Genus Vibrio
Comprised of many species inhabiting
fresh or marine water
 Sensitive to acid pH but tolerate alkaline
pH ( 8-9.6) very well
 Curved Gram negative bacilli
 Most important members are V.cholerae,
V.parahemolyticus and V.vulnificus

Bacteriology







Curved Gram negative bacilli
Motile with single polar flagellum – DARTING
MOTILITY
Facultative anaerobe and fermenter
Oxidase positive
Sensitive to acid pH but grows better at alkaline
pH.
Humans are the natural hosts
Also found in marine and estuarine water
V.cholerae
Antigens and classification





Possess somatic O antigen, flagellar H antigen
and fimbrial antigen
O antigen and biochemical reactions are the
basis of classification
139 serovars ( O1 – O139), 2 biotypes( Classical
and El Tor), 3 serotypes( Ogawa, Inaba,
Hikojima)
V.cholerae O1 biotype ElTor is the common
isolate now.
O139 isolation is also increasing
Classification- Gardner &
Venkatraman
V. cholerae
O1
Classical
ogawa
non O1 (O 2-139)
El Tor
inaba
hikojima
Virulence factors
Eneterotoxin – choleragen, an exotoxin
84kD protein with 2 domains. Resembles
toxin of ETEC
A domain is active, B domain for binding to
intestinal epithelial cells(GM1 receptors)
 Adhesins – fimbriae
 Flagella
 Mucinase & other proteolytic enzymes

Pathogenesis
Source: Patients and carriers
 Vehicle of transmission: contaminated
water and food, flies, fingers…
 Mode of transmission: feco oral, ingestion
 Incubation period : 1 – 5 days
 Gastric acidity offers protection

Pathogenesis contd…)
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Ingestion ( >106 bacilli)
Escape gastric acidity
Reach small intestine
Adhesion, colonisation, production of enterotoxin
Activation of adenyl cyclase
Overproduction of cAMP.
Outpouring of water & electrolytes into lumen
Watery diarrhea
Can secrete > 20L/Day
Dehydration
Pathogenesis cont..

Addition ,multiplication, entrotoxin production
(choleragen)

Choleragen (consists –A (active subunit) &
B(binding subunit)

B subunit binds to ganglioside receptors-on
surface of entrocytes

A subunit is inserted into cytosol
Catalyzes the addition of ADP-ribose to Gs
protien (stimulatory G –protien)
Locks the Gs protein in “ON” position
Causes persistent stimulation of Adenylate
cyclase
Overproduction of CAMP stimulation-secretion
of chlorine ion and water
Leading-massive watery diarrhea- dehydration
& electrolyte imbalance-death
Genes for cholera toxin and other
virulence factor-carried on single stranded
DNA bacteriophage –CTX
 Lysogenic conversion of non toxic
producing strains to toxin producing one
can occur-when CTX transduces these
genes

Mechanism
of Action of
Cholera Toxin
NOTE: In step #4,
uptake of Na+ and Clfrom the lumen is also
blocked.
HCO3- = bicarbonate
which provides
buffering capacity.
1
2
3
4
Mechanism of Action of Cholera Toxin
Pathology
Mucosa hyperemic, mild inflammation
 NO INVASION, MUCOSA INTACT
 Nature of stool: dilute , watery with mucus
flakes – RICE WATER STOOL

Clinical features
Profuse watery diarrhea
 May be upto 20L/day
 Vomiting
 Dehydration
 No fever

Carrier state

Cholera is exclusively human disease

Infection mainly spreads from patient and
carriers via contaminated water & food

There are’ NO’ known animal reservoirs and
anthropod vectors

El Tor strain has got higher carriage state
3 types
Incubator
Carrier
convalescent
Carrier
chronic
Carrier
Incubatory carrier -shed vibrio only during
brief period of incubation of cholera
Convalescent carrier-in few cases bacilli may
survive in gallbladder & excretion of vibrios
may continue during convalescence -4-5 weeks
Chronic carrier-short , asymptomatic
infection of gall bladder
 Found in endemic areas & vibrios are
excreted in faeces intermittently from gall
bladder
 El Tor cholera –greater incidence of casual
carrier
 incidence rates- 7.3% in west bengal,
21.7% in philippines

Complications
Dehydration
 Electrolyte imbalance
 Hypovolemic shock
 Death
 Mortality 60% if untreated
 1% if adequately treated

LAB DIAGNOSIS
Specimen - Stool; Rectal swab.
 Transport - VR medium; Cary Blair medium
 Microscopy -For clinical purposes: darkfield or
phase microscopic visualization of vibrios moving like‚
shooting stars‘, inhibited by serotype-specific
antiserum
 Gram stain- Comma shaped GNB
 Culture - BA - small round moist colnies with
heamodigestion
 MA - late lactose fermenting
 TCBS (selective ) - Yellow colored colonies ( Sucrose
fermenter)

TCBS (thiosulphate citrate bile
sucrose agar
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Identification:
String test +ve
Oxidase +ve; Catalase +ve
Cholera red reaction
Fermentation - Glucose, Sucrose, Mannitol
Confirmation: isolation of V. cholerae
(serogroup 01 or 0139) from faeces, in nonepidemic areas final confirmation by
biochemical and serologic reactions and
detection of cholera toxin
Differences - Classical & El Tor
Haemolysis of sheep
RBC
-
+
Haemagglutination
Of Chick RBC
-
+
VP test
-
+
Polymyin B
Sensitive
Resistant
Phage V
Sensitive
Resistant
Vibrio cholerae El Tor
 1st
isolated in Celebes (Indonesia) in
1937-1938.
 7th Pandemic in 1960 – Honkong
 1963 – South west Pacific countries
 1970 – Africa
 1991 – South America
Treatment

Rehydration is essential: in severe cases,
intravenous electrolyte solutions with alkali is used
for initial stage, followed by oral rehydration; oral
rehydration only may be used for mild cases

Formulation of ORS-
Sodium chloride
-
Potassium chloride
-
Sodium citrate
Glucose
3.5g
-
1.5g
2.9g
20.0g
To be dissolved in 1 liter of clean drinking water
Appropriate antibiotics should be
administered until the vibrio disappears
from the stool
 Tetracycline or doxycyclineis useful –in
reducing stool output in cholera &
shortens period of excretion of vibrios

Preventive Measures
Public Health Strategies
Prevention comprises:

Basic sanitary and hygiene measures including
– treated water supplies, improving water delivery and sewage
control
– adequate food hygiene
– supplying handwashing facilities, latrines, boiled water

Prevention through immunization - considered as
complementary to basic sanitary and hygiene
measures
Vaccines - Complementary to
sanitary and hygiene
measures

Parenteral killed cholera vaccine, providing only partial
protection (50%) of short duration (3-6 months), is not
longer recommended

2 newly developed oral vaccines have shown to be safe,
immunogenic and effective, are licensed in some countries
and are currently under consideration for use in public
health:
– Killed vaccine consisting of whole-cell V. cholerae O1 with purified
recombinant B-subunit of cholera toxoid (WC/rBS)
– Attenuated live vaccine based on the genetically modified
V.cholera O1 strain‚ CVD 103-HgR‘
Cholera - Summary

Cholera no longer poses a threat to countries with
minimum standards of healthy living but remains a
threat for countries without access to safe drinking water
and adequate sanitation

Proper treatment (rehydration!), reduces CFR <2%

Prevention is mainly based on basic sanitary and hygiene
measures; newly developed oral vaccines are under
consideration for their use in public health
NAG Vibrios
No agglutination with O 1 antisera
 Can cause cholera like illness
 O 139 Bengal - 1992 -1993; caused
epidemic in Bangladesh & South east
Asian countries

HALOPHILIC VIBRIOS

V.parahaemolyticus, V.alginolyticus,
V.vulnifucus – marine habitat

V.parahaemolyticus:
– Food poisoning due to ingestion of sea food
– Vomiting, diarrhea, fever
– Wound, eye & ear infections.
– Kanagawa phenomenon – hemolysis in blood
agar containing 7% NaCl and rabbit blood

V.alginolyticus:
– grows in 10% NaCl
– Otitis externa, marine wound infection
– cellulitis

V.vulnifucus:
– Ferments lactose, capsulated, invasive
– Fatal wound infections & septicemia
– Gastroenteritis due to consumption of raw
oysters
Aeromonas (Family Aeromonadaceae)
 Gram-negative facultatively anaerobic bacillus
resembling members of the Enterobacteriaceae
 Motile species have single polar flagellum
(nonmotile species apparently not associated with
human disease)
 16 phenospecies: Most significant human
pathogens A. hydrophila, A. caviae, A. veronii
biovar sobria
 Ubiquitous in fresh and brackish water
 Acquired by ingestion of or exposure to
contaminated water or food
Clinical Syndromes of Aeromonas
 Associated with gastrointestinal disease
 Chronic diarrhea in adults
 Self-limited acute, severe disease in children
resembling shigellosis with blood and leukocytes
in the stool
 3% carriage rate
 Wound infections
 Opportunistic systemic disease in immunocompromised
 Putative virulence factors include: endotoxin;
hemolysins; eneterotoxin; proteases; siderophores;
adhesins
REVIEW
 Formerly Plesiomonadaceae
 Closely related to Proteus & now classified as
Enterobacteriaceae despite differences:
 Oxidase positive
 Multiple polar flagella (lophotrichous)
 Single species: Plesiomonas shigelloides
 Isolated from aquatic environment (fresh or
estuarine)
 Acquired by ingestion of or exposure to
contaminated water or seafood or by exposure to
amphibians or reptiles
 Self-limited gastroenteritis: secretory, colitis or
chronic forms
 Variety of uncommon extra-intestinal infections
REVIEW
Plesiomonas