The invention concerns a culture medium for isolating Vibrio bacteria, characterised in that it comprises, in a Vibrio culture medium, at least a chromogenic agent selected among the β-glucosidase substrates and the β-galactosidase substrates.
1. A culture medium comprising (per liter);
Agar
15 g
Peptone
15 g
Yeast extract
3 g
NaCl
10 g
5-Bromo-6-chloro-3-indoxyl-β-glucoside
0.1 g
5-Bromo-4-chloro-3-indoxyl-β-galactoside
0.1 g
Sucrose
20 g
Glucose
1 g
Lactose
0.1 g
IPTG
0.04 g
Trizma base
5 g
Sodium citrate
10 g
Sodium thiosulfate
10 g
Sodium cholate
3 g.
2. A method for differentiating V. parahaemolyticus from V. alginolyticus in a sample of bacteria of the Vibrio genus, comprising the following steps:
a. inoculating a Vibrio culture medium comprising at least one chromogenic agent that is a substrate for β-glucosidase and sucrose at a concentration of greater than 5 g/l with a sample of bacteria of the Vibrio genus or an inoculum derived from said sample, and
b. detecting enzyme activity for V. parahaemolyticus and an absence of β-glucosidase activity for V. alginolyticus in said culture medium, thereby differentiating V. parahaemolyticus from V. alginolyticus.
3. The method of claim 2 , wherein in said Vibrio culture medium, said at least one chromogenic agent releases, by hydrolysis, a chromophore selected from the group consisting of an indoxyl, haloindoxyl, methylindoxyl and hydroxyquinoline.
4. The method of claim 2 , wherein in said Vibrio culture medium said β-glucosidase substrate is indoxyl glucoside.
5. The method of claim 4 , wherein said β-glucosidase substrate is 5-bromo-6-chloro-3-indoxyl-β-glucoside.
6. The method of claim 2 , wherein said Vibrio culture medium further comprises a β-galactosidase substrate that is indoxyl galactoside.
7. The method of claim 2 , wherein said Vibrio culture medium further comprises a β-galactosidase substrate that is 5-bromo-4-chloro-3-indoxyl-β-galactoside.
8. The method of claim 3 , wherein said haloindoxyl is selected from the group consisting of bromoindoxyl, chloroindoxyl, fluoroindoxyl, iodoindoxyl, dichloroindoxyl, chlorobromoindoxyl, and trichloroindoxyl.
9. The method of claim 8 , wherein said haloindoxyl is selected from the group consisting of: 6-chloroindoxyl, 5-bromoindoxyl, 3-bromoindoxyl, 6-fluoroindoxyl, 5-iodoindoxyl, 4,6-dichloroindoxyl, 6,7-dichloroindoxyl, 5-bromo-4-chloroindoxyl, 5-bromo-6-chloroindoxyl and 4,6,7-trichloroindoxyl.
10. The method of claim 3 , wherein said hydroxyquinoline is 8-hydroxyquinoline.
11. The method of claim 3 , wherein said methylindoxyl is N-methylindoxyl.