EFFECTS OF TEMPERATURE AND SALINITY ON SURVIVAL OF TOXIGENIC VIBRIO-CHOLERAE O1 IN SEAWATER

In 1991 and 1992, the Latin American epidemic strain of Vibrio cholera e 01 was isolated from ballast water, bilge water, and sewage taken fr om cargo ships docked in Mobile Bay, Alabama. The findings raised ques tions regarding the organism's ability to survive long-term aboard shi ps and to withstand the exchange of ballast at sea. The effects of tem perature (6, 18, and 30 degrees C) and salinity (8, 16, and 32 ppt) on survival of V. cholerae 01 strains C6706 and C6707 and a ballast wate r isolate in sterile seawater were determined. The ballast water isola te, which had a D-value (number of days required to produce a 1 log(10 ) reduction in colony-forming units per milliliter) of 240 days at 18 degrees C, 32 ppt salinity, had the longest survival time. The range o f D-values was 36-240 days at 18 degrees C, 60-120 days at 30 degrees C, and 5-20 days at 6 degrees C. In sterile seawater short-term surviv al was temperature dependent, whereas long-term survival was salinity dependent. In raw seawater, survival time of the ballast water isolate was reduced to 12-27 days, implying the existence of biological influ ences. As also shown in our previous work, the organism appeared to be able to survive for several months under relatively stable conditions in ballast water aboard ships; however, viability may be reduced to o nly a few weeks after the organism is introduced into estuarine or mar ine environments.