Vibrio

Lab Sixteen:- ________________ Medical Microbiology
Prepared by: Luma J. Witwit


Vibrio

The genus Vibrio belongs to family Vibrionaceae, consists of Gram negative comma-shaped, 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.
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:

1- V. Cholera serogroup O1 and O139 .

a) Biovar Classic.
b) Biovar El Tor

2- Non – O1 and O139 Vibrio.

V. Cholera serogroup O1 can sub divided into three serogroup:
-Serogroup Ogawa
-Serogroup Inaba
-Serogroup HiKojima

Antigenic variation plays an important role in the epidemiology and virulence of cholera. The flagellar antigens of V.cholera are shared with many water vibrios,
There are three distinct O1 biotypes named Ogawa, Inaba and Hikojima and each biotype may display the classical or El Tor phenotype.

Table : Antigenic Determinates of Vibrio cholera.

(O) Antigens Serotype
A,B
A,C
A,B,C Ogawa
Inaba
Hikojima



Disease:
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.

Specimens:
Rice – water stool contains enormous numbers of vibrio, mucus and epithelial cells.

Laboratory diagnosis:
1- Isolation
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: ?-hemolytic colonies.
5- MacConKey agar: colorless (NLF)
6- Gelatinase : positive.

Culture:
V cholerae produces convex, smooth, round colonies that are opaque and granular in transmitted light.

Specific test:
V cholerae organisms are further identified by slide agglutination tests using anti- O group 1 or 139 antisera and by biochemical reaction patterns.

Characteristics of El Tor biovar:-
?- 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
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.