INCREASED D-VALUES FOR SALMONELLA-ENTERITIDIS FOLLOWING HEAT-SHOCK

Early stationary-phase cells of Salmonella enteritidis (ATCC 4931) wer e heat shocked at 42 degrees C for 60 min. Following heat shock, the c ells were transferred to casein soymeal peptone-yeast extract broth me dium and experiments were conducted to generate survivor curves and D- values. Survivors were enumerated after heat shock under both aerobic and strict anaerobic conditions. Control cells were not stressed. Heat -shocked cells had significantly (P <0.05) higher D-values than unstre ssed cells at 52, 54, and 56 degrees C, but not at 58 degrees C. Anaer obic enumeration further increased D-values, but not always to a signi ficant extent. Heat shock resulted in the overexpression of seven prot eins, detected by sodium dodecyl sulfate-polyacrylamide gel electropho resis. This study suggests that (i) short-term temperature abuse of fo ods containing S. enteritidis may render these cells more resistant to subsequent heat treatments; (ii) anaerobic microenvironments may enha nce survival of heat-stressed S. enteritidis; and (iii) heat shock res ults in the overexpression of proteins that may be related to increase d thermotolerance.