The stability of R plasmids in Vibrio cholerae.

We examined the stability of various R plasmids in Vivrio cholerae, and found that many of the R plasmids detected in the bacteria isolated from human and domestic animals were very unstable in this bacterium, but a few of them as well as most of the R plasmids detected in the bacteria from marine as well as fresh water fish were stably maintained in this bacterium. Chloramphenicol, tetracycline and sulfonamides resistances mediated by these R plasmids were lower in V. cholerae than in Escherichia coli, streptomycin resistance mediated by these R plasmids was far higher in V. cholerae than in E. coli, and ampicillin resistance mediated by these R plasmids was almost same in both V. cholerae and E. coli.