Isolation of Vibrio parahaemolyticus from fecal specimens on mannitol salt agar

Vibrio parahaemolyticus and related halophilic Vibrios

Approximately 30 years have elapsed since Dr. Fujino's original discovery that Vibrio parahaemolyticus (then termed Pasteurella parahemolytica) was the cause of "summer diarrhea" in Japan. Since that finding, V. parahaemolyticus has been established as a cause of gastroenteritis in numbers and places approaching global proportions. It has been isolated in marine and estuarine areas almost worldwide and despite its halophilic nature, V. parahaemolyticus has been isolated from saline-free waters. The relationship of this organism to the environment reveals a close association with other marine organisms especially copepods on which the Vibrios depend for survival in winter months and growth in summer months. There is a uniquely provocative disparity between human strains of V. parahaemolyticus which are Kanagawa phenomenon (KP) positive and the environmental strains which to a large extent are KP negative, the significance being that pathogenicity is measured according to the Kanagawa phenomenon (hemolytic activity) reaction. The hemolysin of the pathogenic strains is a thermostable, cardiotoxic protein, which thus far has not been implicated in the mechanism(s) which causes human gastroenteritis. The interest in this organism has been widened in recent years by the finding that similar organisms, V. alginolyticus, lactose positive vibrios and group F vibrios also cause serious disease in humans.

Salt-starch xylose lysine deoxycholate agar. A single medium for the isolation of sodium and non-sodium dependent enteric gram-negative bacilli

Salt dependent gram-negative bacilli responsible for gastroenteritis and tissue infections are often not recovered because proper media for isolation are not used. A salt-starch XLD agar with 1.5% NaC1 and 0.5% starch medium has been found to permit the isolation of pathogenic Enterobacteriaceae, non-Enterobacteriaceae gram-negative bacilli, and salt-dependent gram-negative bacilli, among which is Vibrio parahemolyticus. As far as the Enterobacteriaceae are concerned, the selectivity and sensitivity of the medium are the same as with standard media with the added advantage of isolating salt-dependent organisms, thereby saving time and money. It can be used for routine blood cultures, investigation of sea water, seafood and tissue infections related to marine activities.