SURVIVAL OF VIBRIO-PARAHAEMOLYTICUS AT LOW-TEMPERATURES UNDER STARVATION CONDITIONS AND SUBSEQUENT RESUSCITATION OF VIABLE, NONCULTURABLE CELLS

Morphological changes of Vibrio parahaemolyticus from rods to spheres took place after a culture was subjected to starvation at a wide range of temperatures. Scanning electron micrographs revealed that starved spherical cells gradually developed a rippled cell surface with blebs and an extracellular filamentous substance adhesive to the cell surfac e. Cells starved at a low temperature for certain intervals were count ed by various bacterial enumeration methods, including plate count, di rect viable count, and total cell count for both Kanagawa-positive and -negative strains. The results indicated that this species could reac h the nonculturable stage in 50 to similar to 80 days during starvatio n at 3.5 degrees C. Kanagawa-negative strain 38C6 lost culturability m ore slowly than Kanagawa-positive strain 38C1 at low temperature. As d etected by thiosulfate-citrate-bile salts-sucrose plate count, a high percentage of the surviving cells at 3.5 degrees C in starvation mediu m were possibly injured by the low temperature rather than by starvati on. Both addition of nalidixic acid to the starved cultures and the mo st-probable-number method demonstrated that the cells recovered after a temperature upshift probably represented the regrowth of a few survi ving cells. These surviving cells were capable of growth and multiplic ation with limited nutrients at an extraordinary rate when the tempera ture was upshifted.