VIBRIO
Genus Vibrio
Most important species, V. cholerae, causes cholera. V. parahaemolyticus also causes diarrheal disease.
Characteristics:
Curved Gram-negative rods, highly motile by means of single polar flagellum. Capable of aerobic and anaerobic respiration. Many species salt tolerant; some salt requiring.
Classification:
Transmission:
V. cholerae is a human pathogen; no animal reservoir, but El Tor biotype survives better in the inanimate environment than classical V. cholerae. Infection is acquired from contaminated water or food. V. parahaemolyticus infection acquired from consumption of contaminated fish and seafood.
Diseases:
Cholera caused by V. cholerae. V. parahaemolyticus causes diarrheal disease.
Other species may cause wound infections.
LABORATORY DIAGNOSIS:
Sample Collection:
Stool or Rectal swab if stool sample is difficult to obtain e.g. children
Transportation of sample:
Sample should be transported in any of media mention below:
- Alkaline peptone water
- Cary-Blair medium
- Taurocholate-tellurite peptone water
Methods for Identification of Organism:
- Microscopy : Vibrio are Gram negative, curved, motile bacilli
- Hanging Drop Method : Darting motility seen.
- Culture: Nutrient agar, MacConkey agar, Thiosulphate Citrate Bile Sucrose (TCBS)
- Nutrient agar : 1 to 2 mm translucent,convex colonies.
- MacConkey agar: Colonies are colorless.
- T.C.B.S. medium (Selective Medium): Colonies are yellow due to fermentation of sucrose.
- Biochemical Reactions: Important which help in diagnosis of Cholera
- Oxidase test – Positive
- TSI agar slant: Acid/Acid no gas
- Cholera red reaction – Positive
- String test – Positive
- V. cholerae is claffified into two biotypes Classical and El Tor, based on certain biochemical properties.
- Antisera Testing:
- Confirmation of V. choleare is done by agglutination reaction with O1 and O139 antiserum.
- V. cholerae is subclassified in to Inaba, Ogawa and Hikojima serotypes using Inaba and Ogawa antisera.
5. Antibiotic sensitivity test.
