A clinical isolate of Proteus sp., resistant to ampicillin, carbenicillin, cephaloridine, chloramphenicol, cotrimoxazole, gentamicin,
kanamycin and tetracycline, was examined for the presence of conjugative R plasmids. Results from conjugation, agarose gel
electrophoresis and transformation experiments showed that it harboured a large self-transmissible R plasmid which coded for all
the resistance traits.