16S to 23S rRNA spacer fragment length polymorphism of Salmonella entericaat subspecies and serotype levels

The variation in the lengths of the internal transcribed spacer (ITS) betwe en 16S and 23S rRNA genes of 101 strains representing 58 serotypes of Salmo nella enterica (used for Salm. choleraesuis) subsp. enterica (I), salamae ( II), arizonae (IIIa), diarizonae (IIIb), houtenae (IV) and indica (VI) was used for typing by PCR amplification. Ten fragment lengths were observed by denaturing polyacrylamide gel electrophoresis on an automatic DNA sequence r resulting in 21 unique fragment patterns. Ten out of the 58 serotypes sho wed specific patterns but 48 serotypes were not fully differentiated. More than one ITS pattern was observed in seven serotypes. Five of the 21 fragme nt patterns contained representatives of more than one subspecies. Under no n-denaturing electrophoresis conditions, serotype specificity was obtained but precise ITS fragment length determination was not possible. DNA sequenc e comparison between ITSs of individual rrn operons is needed to further in terpret ITS diversity within Salm. enterica at serotype and subspecies leve ls.