Rapid discrimination of Listeria monocytogenes strains by microtemperature gradient gel electrophoresis

Microtemperature gradient gel electrophoresis (mu-TGGE) was examined for use for the rapid subtyping of Listeria monocytogenes strains. Comparison of genomes between L. monocytogenes strains F2365 and H7858 identified a sequence encoding a portion of the PRT/PTS system IIA 2 protein domain as appropriate for mu-TGGE analysis. Thirty-one strains belonging to 10 different serovar types were tested by PCR, and sequence analysis of the amplified products revealed that the strains comprise 11 groups. All 55 possible pairs within the 11 groups were examined by mu-TGGE analysis. Of these, 47 pairs could be successfully discriminated, with a total electrophoresis time of only 7 min. Moreover, Cy3/Cy5 labeling allowed rapid identification of the sequence type in unknown strains of L. monocytogenes isolated from meat. These findings collectively indicate that mu-TGGE can be used for the rapid analysis of L. monocytogenes strains, facilitating determination of routes of contamination when these bacteria are found in food products.