Acid and Thermal Resistance of a Salmonella Enteritidis Strain Involved in Several Foodborne Outbreaks

Acid and thermal resistances of a Salmonella enteritidis strain involved in several foodborne outbreaks in southern Brazil were compared with other two Salmonella serovars. Strains were cultivated in Nutrient Broth supplemented with 1% glucose for acid adaptation, and then cells were exposed to different pH and temperatures. Survivors were enumerated and cellular proteins were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). S. enteritidis presented better acid adaptation than S. typhimurium and S. bredeney after exposure to pH 3.5 and 4.0, but all serovars demonstrated a similar behavior at pH 4.5. At 52C, nonadapted and acid‐adapted S. bredeney presented enhanced survivor rates when compared to the other serovars, although acid adaptation protected S. enteritidis. At 56C and 60C, nonadapted and acid‐adapted S. enteritidis was more thermally resistant than other serovars. Differences in protein profiles of nonadapted and acid‐adapted cells of all serovars were observed by SDS‐PAGE. S. enteritidis demonstrated greater acid adaptation and thermal resistance after acid adaptation than other serovars. PRACTICAL APPLICATIONS These results could be related to the frequent involvement of this strain with salmonellosis in southern Brazil. Information on the thermal resistance of pathogenic microorganisms is an important step toward the optimization of the thermal processing of foods. Underestimation of thermal resistance increases the risk that a sufficient portion of an initial pathogen population may persist after thermal treatments, which could result in a foodborne outbreak.