Microtemperature gradient gel electrophoresis (-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 -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 -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 -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.Listeria monocytogenes is considered one of the most dangerous food-borne pathogens because it causes approximately 2,500 cases of listeriosis per year in the United States, with a mortality rate of ϳ20% (22). Listeriosis outbreaks have been associated with L. monocytogenes contamination of foods such as coleslaw, cheese, and milk (8). Therefore, it is critical for food producers and administrators to be able to quickly trace the route of contamination when L. monocytogenes is detected in the final food product (42). Such field tests, however, can be complicated by the existence of L. monocytogenes in the natural environment.L. monocytogenes strains comprise 13 serovars grouped into three lineages (lineages I, II, and III) (14,31,43). Among these, serovars 1/2a, 1/2b, and, especially, 4b are implicated in many cases of human listeriosis (38). Various molecular typing methods beyond serovar typing have been investigated, including ribotyping (26), pulsed-field gel electrophoresis (PFGE) (34, 44), randomly amplified polymorphic DNA (RAPD) analysis (21), PCR-electrophoresis-based methods (15, 36), microarrays (4), esterase typing (9), amplified fragment length polymorphism analysis (1, 17), and multilocus enzyme electrophoresis (11). Among these, ribotyping and PFGE have better discriminatory powers and have been widely used (16). Recently, sequence typing (ST) and its extension, multilocus sequence typing (MLST), have been applied for analysis of L. monocytogenes (5,23,29,32,33,45). These methods have the benefit of delivering relatively standardized data, allowing easy comparisons between laboratories or against databases. In addition, MLST has been shown to be superior to ribotyping and PFGE in terms of discrimination power (32, 45). Unfortunately, ST and MLST are relatively laborious and time-consuming for analyses of large numbers of samples, limiting their usefulness in larger contexts.Temperature gradient gel electrophoresis (TGGE) and denaturing gradient gel electrophoresis (DGGE) are methods for the...