[Plasmid patterns of Salmonella typhimurium lysotype n.c. 1/72/n.c. strains from East Germany]

Salmonella typhimurium strains isolated in the German Democratic Republic between 1972 and 1980 mainly belong to phage type n.c.1/72/n.c. and biochemotype b. Nearly all of these strains are characterized by an identical basic plasmid pattern. Thus, they may be considered to be independent isolates of the same epidemic strain. Moreover, some multiple drug resistant offsprings of that epidemic strain have been characterized by their carriage of an additional IncH-1 R plasmid. However, a few strains of phage type n.c.1/72/n.c. were found to differ fundamentally in their plasmid patterns from that of the epidemic strain. The phage pattern of these strains is determined by a conjugative R plasmid belonging to the incompatibility group IncI4. Despite of the same phage- and biochemotype these strains must be considered non-related with the epidemic strain, therefore. The analysing of the plasmid pattern of bacterial strains turns out to be an important contribution to the investigation of epidemic processes.