Krogstad D J, Korfhagen T R, Moellering R C, Wennersten C, Swartz M N
J Clin Invest. 1978 Jun;61(6):1645-53. doi: 10.1172/JCI109085.
Mating experiments have shown that high-level resistance (minimal inhibitory concentration greater than 2,000 microgram/ml) to streptomycin and kanamycin, and resistance to penicillin-streptomycin and penicillin-kanamycin synergism are transferable by conjugation from resistant clinical isolates of enterococci to a sensitive recipient strain. Cesium chloride-ethidium bromide ultracentrifugation revealed a satellite (plasmid) band in resistant clinical isolates and the transconjugant strains but not in the sensitive recipient. Examination of these satellite bands by agarose gel electrophoresis and electron microscopy demonstrated a common plasmid with a weight of 45 megadaltons. Novobiocin treatment of a resistant clinical isolate produced simultaneous loss of high-level resistance to streptomycin and kanamycin, and of resistance to penicillin-aminoglycoside synergism. These results suggest that (a) high-level resistance to streptomycin and kanamycin among some clinical isolates of enterococci is associated with a 45 megadalton plasmid, and (b) the same plasmid is also responsible for the resistance to penicillin-aminoglycoside synergism observed in these strains.
交配实验表明，肠球菌临床耐药菌株对链霉素和卡那霉素的高水平耐药性（最低抑菌浓度大于2000微克/毫升）以及对青霉素-链霉素和青霉素-卡那霉素协同作用的耐药性可通过接合作用从耐药临床分离株转移至敏感受体菌株。氯化铯-溴化乙锭超速离心显示，耐药临床分离株和接合子菌株中有一条卫星（质粒）带，而敏感受体菌株中没有。通过琼脂糖凝胶电泳和电子显微镜对这些卫星带进行检测，发现了一种分子量为45兆道尔顿的常见质粒。用新生霉素处理一株耐药临床分离株，可同时导致对链霉素和卡那霉素的高水平耐药性以及对青霉素-氨基糖苷类协同作用的耐药性丧失。这些结果表明：（a）一些肠球菌临床分离株对链霉素和卡那霉素的高水平耐药性与一个45兆道尔顿的质粒有关；（b）同一质粒也导致了这些菌株中观察到的对青霉素-氨基糖苷类协同作用的耐药性。
