Survival of Salmonella serovars on beef carcasses and molecular mechanisms to survive low temperature stress and desiccation

We have investigated survival of Salmonella serotypes on beef cuts over a 14-days period at 3°C. A reduction in the colony forming (CFU) units were found for all the tested serotypes. The reductions varied from a 30-fold reduction for S. Typhimurium DT104 to a more than 1000-fold reduction for S. Infantis and S.

Newport. This experiment indicates that storage at low temperature of beef carcasses can be used as a reduction strategy for Salmonella spp. in beef. In addition molecular mechanisms to resist low temperature stress and desiccation have been investigated. Mutants in the otsA, rpoS and clpP genes of the S.

Typhimurium C5 wildtype are under investigation. The mutants and the wildtype have been tested for growth and survival at low temperature and desiccation. No differences were observed between wildtype and mutants after 20 days at fridge temperature (~4°C) on LB agar plates. However, both at 10°C and 15°C, the ¿clpP mutant was severely affected in ability to form colonies compared to the wildtype.

Neither the ¿otsA nor the ¿rpoS were affected in growth or survival at low temperature. In a desiccation model, both the ¿rpoS and ¿clpP mutant were more sensitive than the C5 wildtype. No difference was found between the ¿otsA mutant and the wildtype, which was unexpected.