R factor in Enterobacter cloacae resistant to silver sulfadiazine

A strain of Enterobacter cloacae resistant to silver sulfadiazine was recovered from a unit in which this antimicrobial agent was in use. This strain was found to harbor an R factor responsible for resistance to carbenicillin, kanamycin and ampicillin. These antibiotic resistances were transferable to Escherichia coli by mating. Resistance to silver sulfadiazine was not, however, transmissible.