Influence of the sigB gene on the cold stress survival and subsequent recovery of two Listeria monocytogenes serotypes.

The influence of serotype and the role of the sigB gene of Listeria monocytogenes during the survival and recovery on different substrates were determined. Wild-type and sigB mutants of two serotypes of L. monocytogenes were inoculated into buffer and onto beef steaks, and incubated at 4 degrees C for 8 weeks during which samples were removed and Listeria numbers determined. Growth kinetics of stationary phase wild-type and sigB mutant cells were compared, without prechilling and after prechilling at 4 degrees C. The two serotypes had similar survival capabilities under the conditions examined, and the sigB gene was influential in survival of chill stress, but was dependent upon additional nutritional factors. Prechilling cells prior to growth extended the lag phase of both strains, and this lag phase extension was compounded by the absence of a functional sigB gene. In conclusion, the sigB gene is involved in the survival and recovery from chill stress by the two serotypes tested. Additional factors such as previous growth conditions, nutritional requirements and serotype susceptibility are also contributory. This study adds relevant information regarding the influence of the sigB gene, in conjunction with the historical growth conditions and serotype differences. Understanding the significance of these factors may be useful in creating improved recovery systems for the detection of L. monocytogenes from at-risk foods.