THE COMPLEX CHARACTERIZATION OF SALMONELL A STRAINS USED IN LIVE VACCINES, DEMONSTRATED ON A SALMONELLA-TYPHIMURIUM MUTANT

A complex characterization of salmonella live vaccine strains was demo nstrated for the auxotrophic S. Typhimurium mutant Zoosaloral H. Aviru lence and auxotrophy remained stable after five passages in day-old ch icks, The molecular techniques plasmid analysis, ribotyping, IS200 typ ing and macrorestriction analysis provided a reliable differentiation of the vaccine strain from wild type strains of the same serovar and p roved to be suitable for monitoring the genetic stability of the vacci ne strain. Macrorestriction analyses revealed differences in the chrom osomal DNA between the vaccine strain and its parent strain, The Zoosa loral H strain carries a virulence plasmid of approximately 90 kbp whi ch has structural differences compared with that found in both the par ent strain and the wild type S. Typhimurium strains, The virulence-ass ociated spy gene cluster was located on HindIII fragments of different sizes in the virulence plasmid of the vaccine strain on one hand and in those of the parent strain and the S, Typhimurium wild type strains on the other hand, The detection of a characteristic restriction endo nuclease pattern of the the virulence plasmid of the vaccine strain pr ovides the basis for investigations to exclude the transfer of the Zoo saloral II-specific virulence plasmid from the vaccine strain to field isolates. Gas chromatographic analysis of the whole cell fatty acid p atterns also differentiated the Zoosaloral H strain from its parent st rain and from a representative pool of S. Typhimurium field isolates. The investigation of S. Dublin vaccine, parent and wild type strains y ielded similar results. All methods used provided useful information f or the reliable identification and characterization of the vaccine str ains and confirmed their genetic stability.