Procedure for Isolation and Enumeration of Vibrio parahaemolyticus ,

An evaluation of criteria used in the identification ofVibrio parahaemolyticus showed that cultural responses varied with respect to growth in broth with 10% NaCl, type of hemolysis, reactions in triple sugar-iron-agar, and serological reactions. With few or no exceptions, cultures were positive for cytochrome oxidase, utilized glucose fermentatively, were sensitive to pteridine (0/129) and novobiocin, and failed to grow in Trypticase soy broth (TSB) without NaCl. A procedure employing a direct plating technique, with or without prior enrichment, was designed for the isolation and enumeration ofV. parahaemolyticus . The plating medium consisted of 2.0% peptone, 0.2% yeast extract, 1.0% corn starch, 7% NaCl, and 1.5% agar, with thep H adjusted to 8.0. The enrichment broth was TSB with 7% NaCl. Dilutions of food homogenates were either spread directly on the plates or inoculated into enrichment broth. TSB enrichments were incubated at 42 C for 18 hr. A loopful of the TSB tubes then was streaked onto the direct plating medium. Incubation of plates was at 42 C for 24 to 48 hr. Smooth, white to creamy, circular, amylase-positive colonies were then picked as suspectV. parahaemolyticus . Confirmation of gram-negative, fermentative, oxidase-positive, pleomorphic rods sensitive to pteridine 0/129 was made by a fluorescent-antibody technique. With this procedure, a satisfactory quantitative recovery of knownV. parahaemolyticus from inoculated seafoods was made possible.V. parahaemolyticus was nto isolated from other salted foods.