- Vibrio are Gram-negative, curved rods or comma-shaped bacteria that are highly motile due to single polar flagella. They are found worldwide in marine and coastal environments. - The most important species is Vibrio cholerae, which causes the disease cholera. Other medically important species include V. paraheamolyticus and V. vulnificus. - V. cholerae produces a heat-labile enterotoxin that causes a massive loss of water and electrolytes from the intestines, leading to dehydration and cholera's severe diarrhea symptoms.

1. Vibrio
Dr. Rakesh Prasad Sah
Assistant Professor, Microbiology

2.  Gram-negative, oxidase positive,
short, rigid
 Curved rods or comma shaped
 Highly motile-single polar flagella
 Vibrios  Vibrare  Vibrate
 present in marine environments &
surface waters worlwide.
 The most important member of the
genus is Vibrio cholerae
Dr. Rakesh
 Gram-negative, oxidase positive,
short, rigid
 Curved rods or comma shaped
 Highly motile-single polar flagella
 Vibrios  Vibrare  Vibrate
 present in marine environments &
surface waters worlwide.
 The most important member of the
genus is Vibrio cholerae

3. Classification
Dr. Rakesh

4. Non-Halophilic Vibrios
- V. cholerae  O1 classical and El Tor biotype
- Non O1 V. cholerae  Non cholera vibrio (NCV) or non-
agglutinating vibrio (NAG)
Halophilic Vibrios
- V. parahaemolyticus
- V. alginolyticus
- V. vulnificus
Dr. Rakesh

5. Dr. Rakesh

6. Robert Koch Isolates V.cholrae 1883
It was first isolated by
Koch (1883) from
cholera patients in
Egypt.
Dr. Rakesh

7. Medically important species
Vibrio cholerae
Vibirio paraheamolyticus
Vibrio vulnificus
Dr. Rakesh

8. Vibrio cholerae
Morphology
 Gram negative
 rigid, curved rods
 actively motile
 Comma shaped
 Sheathed, polar flagellum
Dr. Rakesh

9. Physiology
 Facultative anaerobic
 Asporogenous & noncapsulated.
 Growth stimulated by NaCl
 pH 6.4 – 9.6 (optimum 8.2).
Acid labile
 Temperature 16 - 400
C
(Optimum 370
C)
 It grows well on ordinary media.
Dr. Rakesh

10.  Ordinary media
- Nutrient Agar
- MacConkeys agar
- Blood Agar
- Peptone water
- Gelatin stab culture
 Special Media
- Transport media  VR medium, Cary blair medium
- Enrichment media  Alkaline peptone water,
Monsur’s taurocholate tellurite peptone water,
- Plating media  Alkaline bile salt agar, GTTA, TCBS
Dr. Rakesh

11.  Peptone Water:
Incubated at 37°C, it forms a fine surface pellicle in 6-9 hrs.
 Nutrient Agar:
moist and translucent colonies, 1-2 mm in diameter after 18-
24 hrs, bluish tinge in transmitted light.
 Blood Agar:
non hemolytic, but some strains may produce zones of
haemolysis
 MacConkey’s Agar:
Most strains grow well giving pale i.e., non lactose fermenting
colonies in 24-36 hrs. but later on pink on prolonged
incubation
Dr. Rakesh

12.  VR medium
pH 8.6 to 8.8, do not multiply but remains viable for several
weeks.
 Cary-Blair medium
Disodium phosphate, sod thioglycolate, NaCl, CaCl2,
pH 8.4, Salmonella, Shigella, Vibrio
 Monsur’s gelatin taurocholate trypticase tellurite agar
(GTTA) medium, pH 8.5
small, transulcent with greyish black centre and a tubid halo
around colonies  hydrolysis of gelatin.
Dr. Rakesh

13. Selective Medium – TCBS
V. cholerae grows well on
Thiosulphate citrate
Bile salts sucrose (TCBS )
agar, on which it
produces yellow
colonies that are readily
visible against the dark
green background of
the agar.
Dr. Rakesh

14. Biochemical Reactions
Dr. Rakesh

15. Antigenic Structure & Properties
 Many vibrios show a single heat labile, flagellar (H) antigen.
 Antibodies to H antigen not protective in susceptible hosts.
 The somatic polysaccharide (O) antigen used to subdivide Vibrio
species into serogroups is of fundamental importance in the identification
of this organism.
 There are > 140 serotypes of V. cholerae, (O1 – 140),
 7 - O groups of V. vulnificus and 13 O serogroups of V.
parahaemolyticus.
 V. cholerae O1, or O139 (Bengal strain) are the causative agents of
cholera epidemics.
 Most of the other serotypes are harmless.
 Antigenic variation plays an important role in the epidemiology and
virulence of cholera.
Dr. Rakesh

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19. Vibrio cholerae - Enterotoxin
 V.cholrae produce heat labile enterotoxin with a Moll wt. of about
84,000 consisting of sub units A ( MW 28,000 ) and B
 Ganglioside GM1 serves as a mucosal receptor for subunit B,
which promotes entry of subunit A into the cell
 Activation of subunit A1 yields increased levels of intracellular
cAMP and results in prolonged hyper secretion of water and
electrolytes
 There is increased sodium dependent chloride secretion, and
absorption of sodium and chloride is inhibited
 The genes for V.cholrae Enterotoxin are on the bacterial
chromosome
 Cholerae Enterotoxin is antigenically related to LT of Escherichia
Dr. Rakesh

20. Modes of Transmission
Water (infectious dose = 109
)
Food (infectious dose = 103
)
Person-to-person
Dr. Rakesh

21. Dr. Rakesh

22. Pathogenesis
Dr. Rakesh
The ingested organisms pass through the acid barrier of the stomach
multiply in the alkaline medium of the small intestine.
Produces Enterotoxin and the disease
Do not penetrate deep into the gut and there is no bacteraemia
Adhere with the epithelium by special fimbriae such as the toxin co-
regulated pilus (TCP)
Enterotoxin and TCP are regulated by the Tox R gene product, Tox R
protein

23. Dr. Rakesh

24.  Massive loss of water & electrolytes (Sodium and bicarbonate)
by action of enterotoxin leads to :
- Dehydration 
- haemoconcentration,
- anuria,
- hypovolemic shock
- Base deficit acidosis & muscle cramps due to hypokalaemia
 In untreated cases mortality rate 60-70% due to renal failure.
Dr. Rakesh

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27. Laboratory Identification of Vibrios
Transport medium or holding medium
- Cary-Blair
-Venkatraman Ramakrishnan medium- liquid
Direct Microscopy  Hanging drop  darting
motility
Enrichment medium - alkaline peptone broth

28. Dr. Rakesh

29. 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

30. String Test
 The string test may be performed
on a glass microscope slide or
plastic petri dish by suspending
18 to 24 hour growth from Heart
Infusion Agar (HIA) or other non-
inhibitory medium in a drop of
0.5% aqueous solution of sodium
deoxycholate.
Dr. Rakesh

31. Dr. Rakesh

32. Vaccination
Killed parenteral vaccine
- 12,000 million V. cholera per ml
- Equal no. of Inba & Ogwa strains
- 2 inj intramuscularly at interval of 4 weeks
- 50-60%
Dr. Rakesh

33. Killed Oral Vaccine
- B subunit whole cell (BS-WS) vaccine
- Heat killed classical vibrio (both Inba & Ogwa)
- Formalin killed EL Tor Vibrio (both Inba & Ogwa)
- 85% for 1 yr
- 60% for 2 yrs
Dr. Rakesh

34. Halophilic Vibrios
 Can not grow in media lacking sodium choride.
 Natural habitat is sea water and marine life.
 E.g. V. parahaemolyticus, V. alginolyticus, V. vulnificus.
Dr. Rakesh

35. Vibrio parahaemolyticus
 First isolated in Japan in 1951 as causative agent of food poisoning due to
consumption of seafood.
 Isolated from shell fish, shrimps, crabs and mulluscs.
 Optimum NaCl concentration 2-4%, (tolerate upto 8%).
 Do not ferment sucrose so yellow colour colonies on TCBS medium.
 All strains are not pathogenic for man.
 strains  environment  non hemolytic  high salt agar
(Wagatsuma agar)
 Strains  humans  hemolytic  Kanagawa phenomenon
 Causes food poisioning, acute diarrhoea, abdominal pain vomiting and
dehydration
Dr. Rakesh

36. Vibrio alginolyticus
 Frequently found in sea fish
 Role in human lesion is uncertain.
 Resembles parahaemolyticus
- Higher salt tolerance (up to 10%)
Dr. Rakesh

37. Vibrio vulnificus
 Designated as L+ vibrio for its ability to ferment lactose.
 It resembles V. parahaemolyticus but ferments lactose and
has salt tolerance of less than 8%.
 Cuses wound infection and cellulitis following exposure to
seawater.
 Ingestion of under-cooked or raw seafood  penetrates the
gut mucosa  without causing GIT manifestations 
blood stream  septicemia  high mortality rate.
Dr. Rakesh