Abstract
Seventy-two Salmonella strains including eight serovars isolated from 12 outbreaks of human enteritis during the period from 1980 through 1990 were characterized on the basis of their plasmid profiles and antibiotic resistance. Out of 72 isolates, a total of 42 including four serovars from six outbreaks carried plasmids; however, no plasmid was found in any of the isolates from the remaining six outbreaks. The plasmid profiles of the isolates carrying plasmids showed the identical or similar patterns except those from two outbreaks. In these two outbreaks, one gave some isolates not carrying any plasmid and the other caused by S. Litchfield gave two different plasmid profiles, although all the isolates demonstrated the same antibiotic resistance. Thus, we concluded that the isolates in the latter outbreak belong to different bacterial clones. In these results, plamid analysis proved to be a useful tool for epidemiological investigation. Among the 72 isolates, twenty strains were resistant to two or more antibiotics, although the antibiotic resistance was not transferable by conjugation among these strains.
