Effects of Temperature and Cell Number on the Production of Hemolysin by Vibrio parahaemolyticus

Abstract

Two strains of Vibrio parahaemolyticus, ATCC 17802 Kanagawa negative (K-) and ATCC 27519, Kanagawa positive (K+) were used in this study. The effect of temperature on the production of hemolysin was studied in trypticase soy broth (TSB) with 3 % NaCl. Maximum hemolysin productions by both strains were obtained at 35°C with little or no production of hemolysin at 4°, 10° and 42°C. The K+ strain consistently produced higher titers of hemolytic activity than its K- counterpart. Hemolysin production at lower temperatures (4° and 10°C) could only be detected after 10 or 12 h in TSB with 3 % NaCl. At 20°, 25°, 30° and 35°C in this medium, production of hemolysin could be detected after 6 or 8 h of incubation. At these same temperatures, both K+ and K- strains produced comparable cell numbers by 12 h; however, the greatest hemolysin production occurred at 35°C. This indicates that temperature, rather than cell numbers, determines the total hemolysin produced during a controlled incubation time period.