PCR amplification of the Salmonella typhimurium fimY gene sequence to detect the Salmonella species.

This study evaluated the suitability of fimY gene amplification by PCR as an effective means of detecting Salmonella species. Although fimY gene of Salmonella typhimurium is involved in regulating type 1 fimbrial expression, the amino acid sequence of FimY shares very little homology with other known prokaryotic proteins in the GenBank database. Therefore, fimY is a promising target gene to detect the presence of Salmonella species. Herein, two primers internal to the fimY gene of S. typhimurium are used to investigate the distribution of the fimY homologous sequence among 45 Salmonella serovars and 20 non-Salmonella species by using PCR. Experimental results indicated that only Salmonella species possessed the fimY homologous sequence, subsequently generating the specific 526-bp DNA fragments. The sensitivity of the fmY-specific primer set was demonstrated on a Salmonella-free swab sample from a pork carcass surface, which was then artificially contaminated with different concentrations of S. typhimurium. A combining of pre-enrichment step in buffered peptone water and PCR amplification of fimY allowed the detection of S. typhimurium at the concentration of 3.4 x 10(0) CFU/ml from the swab sample. With an additional enrichment step in Rappaport-Vassiliadis (RV) broth, this procedure can also detect pork carcass surface naturally contaminated with Salmonella species in a slaughterhouse. Results in this study demonstrate that fimY is unique to Salmonella species and is an appropriate PCR target for detecting these microorganisms.