Detection of the induction of Salmonella enterotoxin gene expression by contact with epithelial cells with RT-PCR.

All strains of Salmonella enterica investigated were found to carry the Salmonella enterotoxin gene (stn) as determined by PCR and hybridization studies. However, when using CHO-K1 cells for testing the toxicity of the strains, not all strains showed a toxic effect (cell elongation) on the cells or did so only at a low level. The cultivation of Salmonella in contact with epithelial cells (IEC-6) led to an increase in the production of toxin. The stn gene expression was detectable with the help of the RT-PCR after 3 h of incubation. The RNA of the strains was isolated, transcribed into cDNA (with MMLV-reverse transcriptase) and amplified using PCR. The PCR products were separated electrophoretically using a polyacrylamide gel and detected by silver staining.