INTER-PHAGE AND INTRA-PHAGE TYPE DIFFERENTIATION OF SALMONELLA-ENTERICA SUBSP ENTERICA SEROVAR ENTERITIDIS ISOLATES USING MOLECULAR TYPING METHODS

Seventy-six Salmonella enterica subsp. enterica serovar Enteritidis (S . Enteritidis) isolates which represented 14 phage types and RDNC isol ates were investigated by several independent molecular methods. Eleve n different plasmid profiles were detected. Plasmid-encoded virulence genes of the spy gene cluster were shown by hybridization with a spvB/ C gene probe to be located on plasmids of either 55 kbp or 95 kbp. Rib otyping as performed with gene probes that recognized either the entir e rrn operon or 16S rRNA genes allowed no differentiation between the S. Enteritidis isolates. Three different hybridization patterns could be observed by IS200-typing. Macrorestriction analysis of XbaI-, SpeI- and NotI-digested whole cell DNA proved to be the most discriminatory method as confirmed by the calculation of discriminatory indices. Bas ed on the data obtained from plasmid analysis and macrorestriction ana lyses with three suitable restriction endonucleases, the 76 S. Enterit idis isolates were assigned to 26 different genomic groups. The observ ation that several genomic groups included isolates of different phage types has suggested that a combination of suitable molecular methods and phage typing is most useful for tracing S. Enteritidis isolates in epidemiological investigations.