Levine M M, Kaper J B, Lockman H, Black R E, Clements M L, Falkow S
J Infect Dis. 1983 Oct;148(4):699-709. doi: 10.1093/infdis/148.4.699.
Recombinant DNA risk assessment studies quantitated the mobilizability of "safe" plasmid pBR325, in comparison with readily mobilizable plasmid pJBK5 (chloramphenicol and tetracycline resistant). Of 15 volunteers who became colonized after ingestion of 5 X 10(10) Escherichia coli HS-4, a normal human flora strain containing pJBK5 and daily oral tetracycline, nine manifested transfer of pJBK5 to normal flora by means of triparental mating. In contrast, none of 12 other volunteers cocolonized with HS-4 bearing "safe" pBR325 and normal flora showed transfer (P = 0.001), despite ingestion of tetracycline. To accomplish transfer directly, E coli HS-4 containing both pBR325 and a derepressed, conjugative plasmid (F-amp) was fed to two groups of volunteers. Transfer of pBR325 to normal flora occurred in 13 of 18 volunteers taking daily tetracycline but in none of eight who did not (P less than 0.002). Nor were transconjugants detected, despite tetracycline ingestion, in five volunteers who ingested and excreted E coli K12 (pBR325 plus F-amp).
重组DNA风险评估研究对“安全”质粒pBR325的可转移性进行了定量分析，并与易于转移的质粒pJBK5（对氯霉素和四环素耐药）进行了比较。在15名志愿者摄入含有pJBK5的正常人肠道菌群菌株大肠杆菌HS - 4（5×10¹⁰个）并每日口服四环素后发生定殖，其中9人通过三亲本杂交将pJBK5转移至正常菌群。相比之下，在另外12名与携带“安全”pBR325的HS - 4和正常菌群共同定殖的志愿者中，尽管摄入了四环素，但无一例显示转移（P = 0.001）。为了直接实现转移，将同时含有pBR325和去阻遏的接合性质粒（F - amp）的大肠杆菌HS - 4喂给两组志愿者。在每日服用四环素的18名志愿者中，有13人发生了pBR325向正常菌群的转移，但在未服用四环素的8名志愿者中无一例发生转移（P＜0.002）。在5名摄入并排泄大肠杆菌K12（pBR325加F - amp）的志愿者中，尽管摄入了四环素，但也未检测到转接合子。
