Camiolo S M, Beck M E, Reynard A M
Antimicrob Agents Chemother. 1975 Oct;8(4):488-94. doi: 10.1128/AAC.8.4.488.
Hospital isolates of Escherichia coli resistant to tetracycline (TC) were studied to identify mechanisms which regulate TC resistance levels and ability to transfer TC resistance. Antibiotic resistance patterns, resistance levels to TC, and ability to transfer TC resistance were determined for the isolates. Similar data were obtained for the transferable plasmids after transfer to several new host strains of E. coli. Of the 110 isolates, 50% were able to transfer TC resistance by conjugation. There was a nearly linear relationship between the minimum inhibitory concentration (MIC) of TC for the hospital strains and the percentage of strains at a given MIC that could transfer TC resistance. The strains that were simultaneously resistant to tetracycline, streptomycin, and ampicillin had relatively high MICs of TC and high ability to transfer TC resistance. These results and surveys of TC-resistant E. coli by others suggest that TC resistance levels and transmissibility may be influenced by other resistance markers. The isolates which did not transfer TC resistance by conjugation were tested for the presence of TC resistance plasmids by mobilization or by transformation with deoxyribonucleic acid from the isolates. Evidence for plasmid-mediated TC resistance was found in 92 (84%) of the 110 hospital strains.
对医院分离出的耐四环素（TC）大肠杆菌进行了研究，以确定调节TC耐药水平和TC耐药转移能力的机制。测定了分离株的抗生素耐药模式、对TC的耐药水平以及转移TC耐药的能力。将可转移质粒转移到几种新的大肠杆菌宿主菌株后，获得了类似的数据。在110株分离株中，50%能够通过接合转移TC耐药性。医院菌株对TC的最低抑菌浓度（MIC）与在给定MIC下能够转移TC耐药性的菌株百分比之间存在近乎线性的关系。同时对四环素、链霉素和氨苄青霉素耐药的菌株具有相对较高的TC MIC和较高的转移TC耐药性的能力。这些结果以及其他人对耐TC大肠杆菌的调查表明，TC耐药水平和传播性可能受其他耐药标记的影响。通过接合不转移TC耐药性的分离株，通过从分离株中动员或用脱氧核糖核酸转化来检测TC耐药质粒的存在。在110株医院菌株中的92株（84%）中发现了质粒介导的TC耐药证据。
