Evaluation of repetitive extragenic palindromic-polymerase chain reaction and denatured gradient gel electrophoresis in identifying Salmonella serotypes isolated from processed turkeys

The current study was conducted to determine the usefulness of 2 molecular techniques, automated repetitive extragenic palindromic-PCR (REP-PCR) and denaturing gradient gel electrophoresis (DGGE), to identify Salmonella serotypes of poultry origin. Salmonella continues to be a foodborne pathogen of principal concern in the United States. The interspersed conserved repetitive sequence of the bacterial genome and the 16-23S rDNA intergenic spacer region were amplified for REP-PCR and DGGE, respectively. Fifty-four Salmonella isolates from 2 turkey processing plants (A and B) were used for this comparison. Serotypes consisted of Brandenburg, Derby, Hadar, and Typhimurium, with n = 6, 21, 12, and 15, respectively. The REP-PCR was fully automated, whereas DGGE was run on an acrylamide gel and the image was captured digitally. Both dendrograms were created using the unweighted pair group method with arithmetic average. There were more variations in percentage similarity in DGGE when compared with REP-PCR. The banding patterns were more distinct and uniform in the REP-PCR group than with DGGE. The results from the REP-PCR were generated within 1 h, whereas the DGGE required approximately 1 d to run. These data suggest that DGGE and REP-PCR are useful tools for identifying Salmonella serotypes isolated from poultry production or processing environments. In addition, REP-PCR is more rapid, may have a higher discriminatory power, but may be less cost-effective than DGGE. However, more research may be needed to validate this argument. Both DGGE and REP-PCR displayed high sensitivity in discriminating among Salmonella serotypes and either method could be considered as an alternative to more expensive and time-consuming conventional antibody-based serotyping methodologies.