Survival Estimation of Pathogenic Vibrio cholerae after Invasion from Ballast Water Discharged into Tokyo Bay

Abstract

 The authors used the isolate, Vibrio sp., as a model strain to estimate the survivability of pathogenic V. cholerae after invasion from ballast water discharged into Tokyo Bay. The seawater samples taken from Tokyo Bay were also examined for V. cholerae contamination. All samples tested negative for V. cholerae. As for the survivability of Vibrio sp., the initial number of the cells, in the order of 10³ to 10⁴ colony-forming units (CFU) ml^-1, was drastically reduced in vitro within 2 weeks of incubation under competition with 10^3.5 to 10^6.1 CFU ml^-1 of the indigenous population. On the other hand, Vibrio sp. cells could grow in the seawater previously autoclaved. The indigenous population was not affected at all even in the presence of Vibrio sp. cells. These results indicate that V. cholerae cells have less potential to survive after invasion. The utilization of H₂O₂, with a final concentration of 0.3% in seawater, was shown to be effective for the pasteurization of seawater taken from busy ports in the vicinity of southeastern Japan.