AimsSalmonella enterica serovar Enteritidis (Salm.Enteritidis) encounters mild ethanol stress during its life cycle. However, adaptation to a stressful condition may affect bacterial resistance to subsequent stresses. Hence, this work was undertaken to investigate the influences of ethanol adaptation on stress tolerance of Salm.Enteritidis. Methods and ResultsSalmonella Enteritidis was subjected to different ethanol adaptation treatments (25-10% ethanol for 1h). Cellular morphology and tolerance to subsequent environmental stresses (15% ethanol, -20 degrees C, 4 degrees C, 50 degrees C and 10% NaCl) were evaluated. It was found that 10% was the maximum ethanol concentration that allowed growth of the target bacteria. Ethanol adaptation did not cause cell-surface damage in Salm.Enteritidis as revealed by membrane permeability measurements and electron micrograph analysis. Salmonella Enteritidis adapted with 25-10% ethanol displayed an enhanced resistance to a 15%-ethanol challenge compared with an unchallenged control. The maximum ethanol resistance was observed when ethanol concentration used for ethanol adaptation was increased to 50%. Additionally, pre-adaptation to 50% ethanol cross-protected Salm.Enteritidis against -20 degrees C, but not against 4 degrees C, 50 degrees C or 10% NaCl. ConclusionsEthanol adaptation provided Salm.Enteritidis direct protection from a high level ethanol challenge and cross-protection from freezing, but not other stresses tested (low temperature, high salinity or high temperature). Significance and Impact of the StudyThe results are valuable in developing adequate and efficient control measures for Salm.Enteritidis in foods.