THERMOSENSITIVE TRANSFER OF ANTIMICROBIAL RESISTANCES AND CITRATE UTILIZATION AND COTRANSFER OF HYDROGEN-SULFIDE PRODUCTION FROM AN ESCHERICHIA-COLI ISOLATE

A hydrogen-sulfide producing, citrate-positive strain of Escherichia c oli isolated from urinary tract infection was found to be resistant to chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm), trimethop rim (Tmp), sulfamethoxazole (Smx), and cotrimoxazole (Tmp/Smx). The st rain contained 7 plasmids of molecular sizes 120, 35, 5.0, 3.2, 3.0, 2 .6, and 2.4 megadaltons (Md), as detected by agarose gel electrophores is of plasmid DNA. Thermosensitive transfer of Cm, Tc, and citrate uti lization occurred conjugally to E. coli K-12 recipient strains at a fr equency of approximately 10(-6) per donor cell after an 18 hour incuba tion. The transconjugants were also resistant to Sm and Smx and produc ed hydrogen-sulfide. Two plasmids of about 120 Mel, pNH222, and 35 Md, pNH223, were detected in these transconjugants. Transformation or 1-h our conjugal transfer experiments at 26 degrees C with selection for C m or Tc yielded only the 120 Md species. Plasmid pNH222 showed one way incompatibility with F plasmids, a characteristic shown previously to be typical of Inc HI1 plasmids. Transformation experiments with selec tion for Sm yielded transformants with one plasmid species, (pNH223), 35 Md in size, which carried the gene(s) for H2S production but not fo r raffinose fermentation. The fact that characteristics such as citrat e utilization and hydrogen sulfide production, used in the identificat ion of enteric bacteria, can be transmitted to E. coli by plasmids is of important taxonomic significance.