A FRAMEWORK FOR IS200, 16S RIBOSOMAL-RNA GENE AND PLASMID-PROFILE ANALYSIS IN SALMONELLA SEROGROUP D1

Chromosomal fingerprinting of the type strains of serotypes of Salmone lla O-serogroup D1 with the DNA insertion sequence IS200 generated pat terns which were either serotype-specific (e.g., Typhi), or conserved among groups of related serotypes (e.g., Dublin, Restock and certain p hage types of Enteritidis). The number of IS200 copies varied consider ably, and the IS200 patterns of type strains of serotypes associated w ith systemic infections in man were specific and suitable for identify ing strains within those serotypes. Polymorphism at 16S rRNA gene loci was examined among type strains and 11 16S rRNA gene profiles were ch aracterised. The most prevalent of these was conserved among type stra ins of 11 serotypes, and the next most prevalent among type strains of nine serotypes; together, they encompassed 15 unique IS200 profiles. The distribution and mol. wts of plasmids carrying spvBC (virulence) g enes could be directly related to certain chromosomal genotypes define d by IS200 patterns. The presence of virulence plasmids in serotypes L omalinda, Antarctica and Wangata is reported for the first time. Compa rison of 16S rRNA gene profiles and IS200 patterns provides a definiti on of genotype that is applicable to epidemiological studies of variou s group D1 serotypes and should prove particularly useful for those la cking plasmid DNA.