Since 1969, strains of S. wien resistant to multiple anti-bacterial drugs caused widespread epidemics of enteritis in Europe and North Africa. Of 113 British strains examined between Jan. 1970 and Jan. 1977, 67 were multi-resistant. These strains and 22 strains from 6 other countries were examined to determine their plasmid content. Two plasmids were found in the vast majority of strains: an FIme factor, conferring resistance to ampicillin, chloramphenicol, kanamycin, streptomycin, spectinomycin, sulfonamides and tetracyclines (ACKSSpSuT), and a non-autotransferring plasmid of resistance type ASSu. The FIme plasmids have dual incompatibility: they are incompatible with group FI factors and with the MP10 plasmid of S. typhimurium, which belongs to a separate group. Other plasmids found in S. wien included principally a ColIa factor and an autotransferring plasmid that codes for ampicillin resistance and belongs to compatibility group I2. The similarity in plasmid content of strains isolated in widely spearated areas suggests that they have a clonal origin.
