Use of ribotyping, IS200 typing and plasmid analysis for the identification of Salmonella enterica subsp. enterica serovar Typhimurium vaccine strain Zoosaloral H and its differentiation from wild type stains of the same serovar

Fifty Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) isolates obtained from one vaccinated and three non-vaccinated poultry herds as well as the commercially available vaccine strain Zoosaloral H and a S. Typhimurium reference strain were characterized genotypically to differentiate between S. Typhimurium live vaccine strain Zoosaloral H and wild type strains of the same sarovar. Ribotyping revealed five different patterns of which one exclusively occured in the vaccine strain. Seven different hybridization patterns could be observed by IS200-typing of the S. Typhimurium isolates including the vaccine strain harboured large plasmids of approximately 60 MDa. Hybridizaiton with a virulence gene probe identified only 48 % of these large plasmids, including that of the vaccine strain, to carry this virulence-associated gene. However, restriction endonuclease analysis of the hybridizing plasmids showed that the virulence gene was located on HindIII fragments of dif