Differentiation of Listeria Isolates by PCR Amplicon Profiling and Sequence Analysis of 16S-23S RRNA Internal Transcribed Spacer Loci

The 16S-23S rRNA internal transcribed spacer region (ITS) in genomic DNA from Listeria species was amplified and sequenced so as to find sequence differences that would allow rapid species and strain differentiation. Agarose gel profiles of amplicons generated with primers designed to amplify ITS loci indicated that Listeria DNA can contain at least two distinct ITS regions. The direct sequencing of the smaller of these ITS amplicons (330 bp) was found useful for the rapid and accurate differentiation of various Listeria species. On the other hand analysis of ITS amplicons generated from a total of 27 L. monocytogenes strains indicated that 4/27 of these strains could be distinguished on the basis of their ITS profile (the presence of a unique 350 bp amplicon). The lack of sequence heterogeneity in the small 333 bp amplicon did not permit rapid strain differentiation.