The combined effect of low pH (5.0), low salinity (0.5%) and temperatu
re (5 and 20 degrees C) on the survival of Vibrio vulnificus cells was
studied. The effect of the combined stress was examined on the basis
of the decrease in cell counts throughout 6 h of incubation in brain-h
eart infusion broth pH 5. Combined stress had an immediate effect that
did not produce cellular lysis but a marked loss of culturability on
thiosulphate citrate-bile salts-sucrose agar. However, a large number
of cells remained viable, as determined both by direct viable counts a
nd by colony forming units on non-selective medium. Cell injury affect
ed a great number of cells but the survival fraction of non-injured ce
lls remained above 20% of the initial number. The inactivation of a si
gnificant number of cells was examined in terms of the D-10-values. Th
ey varied depending on the parameter examined but in general D-10 valu
es were obtained more rapidly at 20 than at 5 degrees C. However, afte
r 24 h of incubation, when no cells could be detected onto non-selecti
ve medium, viable cells were defected by direct viable counts, both at
5 and 20 degrees C. (C) 1996 Academic Press Limited