Tolerance evaluation in Salmonella enterica serovar Typhimurium challenged with sublethal amounts of Rosmarinus officinalis L. essential oil or 1,8-cineole in meat model

The induction of direct bacterial tolerance and cross-tolerance (NaCl, acid pH, high temperature) in Salmonella Typhimurium ATTC 14028 following the exposure to sublethal amounts of the essential oil from Rosmarinus officinalis L. (ROEO), and its major component 1,8-cineole (CIN) was evaluated in this study. Direct protection was not induced when cells were exposed to 1/2 MIC and 1/4 MIC of ROEO or CIN in meat broth and in previously irradiated meat ground-beef. Cells exposed to ROEO or CIN at sublethal amounts did not present cross-protection to high temperature, lactic acid and NaCl. Likewise, cells progressively subcultured in meat broth containing increasing amounts of ROEO or CIN were able to survive only up to 1/4 MIC for both tested substances. From these results, S. Typhimurium ATCC 14028 was not capable to develop direct or cross-tolerance when exposed to ROEO or CIN in a meat-based growth media and was not able to develop direct tolerance in a meat-based model.