In vitro and in vivo transfer of drug resistance for Salmonella and Escherichia coli strains in turkeys.

In vitro and in vivo transfers of antibiotic drug resistance were observed when isolates of multi-resistant Salmonella saint-paul and Escherichia coli donors were mated with multi-sensitive E coli and Salmonella typhimurium recipients, respectively. For in vivo studies, day-old turkey poults were used. Drug resistances were transferred either alone or in various combinations. In vitro, transfer was more frequent from E coli to S typhimurium; in vivo, transfer was more often observed from S saint-paul to E coli. Transfer occurred in vivo within 3 or 6 days after the recipient strain was given to poults previously infected with donor bacteria. In some instances, phage typing of S typhimurium indicated a change after transfer of drug resistance from E coli to S typhimurium. The criteria for in vivo transfer of drug resistance were discussed, and the implications of a change in phage type were noted.