Lab Sixteen:-
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Medical Microbiology
Prepared by: Luma J. Witwit
Vibrio
The genus Vibrio belongs to family Vibrionaceae, they are enteric
pathogens of humans or part of normal flora. Gram negative commashaped, straight or curved rods, motile by means of a single polar
flagellum. Oxidase positive, facultative anaerobic. Most species require
2-3% NaCl or sea water base for optimal growth.
The genus vibrio includes two important human pathogens, Vibrio
cholera causes cholera, While vibrio parahaemolyticus causes a less
severe diarrhoae.
Cholera (frequently called epidemic cholera) is a severe diarrheal
disease caused by the bacterium Vibrio cholera .
Diarrhea occurs-as much as 20-30 L/d-with resulting dehydration,
shock and death.
Vibrio Cholera:
Classification:
Vibrio cholerae
Serogroup produce
cholera toxin
serogroup that do not
produce cholera toxin
serogroups 1 and 139
Biotype
classical
and El Tor
serogroup
Inaba
A and C
non 1 and non 139
serogroups
139 Bengal
139 alcuta
Ogawa
A and B
non toxigenic strain some
time associated with sporadic
diarrhea
Hikojima
A and B and C
Toxigenic strain usually associated
with a large out break
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Lab Sixteen:-
________________
Medical Microbiology
Prepared by: Luma J. Witwit
Pathogenicity:
Rice water diarrhea (through ingestion of food or drink often sea
food). A person with normal gastric acidity may have to ingest as many
as 1010 or more V.cholerae to become infected when the vehicle is water,
because the organisms are susceptible to acid. When the vehicle is food,
as few as 102 - 104 organisms are necessary because of the buffering
capacity of food.
The cells of V.cholereae attach to but do not invade the intestinal
mucosa. Pathogenicity is due to secretion of an enterotoxin, which binds
to ganglioside receptors on mucosal cells. After a large period of 15- 45
min, adenylate cyclase is activated and the cyclic adenosine
monophosphate concentration inside the intestinal cells increases. This in
turn leads to excretion of electrolytes and water and subsequent diarrhea,
leading to severe dehydration.
Specimens:
Rice – water stool contains numerous numbers of vibrio, mucus and
epithelial cells.
Laboratory diagnosis:
1- May be seen directly in stool samples by dark- field microscopy.
a) APW ( Alkaline Peptone Water ): transport media (pH= 8.6 )
b) TCBS (Thiosulfate – Citrate – Bile salt Sucrose agar) for culture
yield yellow colonies.
C) Pepton agar.
2- Indol: positive.
3- TSI: A/A, K/A (due to sucrose fermentation).
4- Blood agar: β-hemolytic colonies.
5- MacConKey agar: colorless (NLF)
6- Gelatinase : positive.
7- Slide agglutination tests using anti- O group 1 or 139 antisera.
Characteristics of ElTor biovar:β- hemolytic on sheep Blood agar
VP: positive.
Polymyxin B (50 IU): resistant.
Resistant to phage group IV.
Classic V.cholera strain give the opposite reactions in these tests.
Non – cholera vibrios
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Lab Sixteen:-
________________
Medical Microbiology
Prepared by: Luma J. Witwit
1. Vibrio mimicus
 Diarrhea after ingestion of under cooked sell fish.
 Ear infection after exposure to marine environment.
2. Halophilic Vibrios
 Vibrio parahemolyticus: diarrhea, wound infection.
 Vibrio alginolyticus:
ear infection, wound infection.
 Vibrio vulnificus:
septicemia, ear infection.
Laboratory diagnosis for Non-cholera vibrios:They do not ferment sucrose (TCBS) green colonies.
Halophilic vibrios require 1 % NaCl in all test media.
Treatment and prevention
-Intravenous administration of fluid and electrolytes .
-Oral administration of a solution contain glucose and electrolytes.
-Antibiotics(Tetracycline).
-Immunization with a whole- cell vaccine(limited use).
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Lab Sixteen:-
________________
Medical Microbiology
Prepared by: Luma J. Witwit
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