Procedure Preparation of food homogenate Prepare as described above Dilution Prepare as described above Inoculation Inoculate three 10 ml portions of 1:10 dilutions into 10 ml each of double strength GSTB, and then inoculate three 1ml portions of 1:10, 1:100, 1:1000 and 1:10000 dilutions into single strength GSTB. Incubation Incubate broth tubes overnight at 350C. Confirmation a) After incubation, streak a loopful of the culture from the three highest dilutions of GSTB showing growth onto TCBS agar plates.
Incubate the plates for 18 hours at 350C.
The colonies of V.parahaemolyticus on TCBS appear
round, 2-3mm in diameter with green or blue centres. V.alginolyticus colonies are larger and yellow. Coliforms, proteus and enterococci colonies are small and translucent.
TSI: Streak the slant and stab the butt and incubate overnight at 350C.
parahaemolyticus produces alkaline slant and acid butt, no gas and no H2S (typical shigella-like reaction). 369