USE OF HOMODUPLEX RIBOSOMAL DNA SPACER AMPLIFICATION PRODUCTS AND HETERODUPLEX CROSS-HYBRIDIZATION PRODUCTS IN THE IDENTIFICATION OF SALMONELLA SEROVARS

When the hypervariable 16S-23S intergenic spacer regions found in prok aryotic ribosomal DNA (rDNA) are amplified from conserved adjacent Seq uences, homoduplex double-stranded DNA structures and heteroduplex str uctures containing substantial regions of single-stranded DNA are gene rated, The electrophoretic separation of these structures results in p roduct profile patterns, which may be organized into highly correlated pattern groups of ribosomal spacer and heteroduplex polymorphism (RS/ HP) types, In a test panel of 380 Salmonella strains that were analyze d by this procedure, 36 unique RS/HP types were observed, Of the 28 se rovars in the test group, 21 showed single characteristic RS/HP types, The remaining seven serovars each contained multiple RS/HP types, whi ch were also unique to individual serovars, Formation of heteroduplex structures with a substantially reduced electrophoretic mobility was o bserved in 29 of the 36 RS/HP pattern types, Because the mobility of t hese heteroduplex structures is sensitive to intergenic spacer sequenc e composition, the presence of these structures adds an additional dia gnostic feature that is extremely useful in the differentiation of Sal monella serovars, The RS/HP types show sufficient diversity to be usef ul in the identification of many commonly observed Salmonella serovars , This analytical procedure is simple to perform and is well suited to rapid and inexpensive screening of large numbers of Salmonella strain s.