Teng L J, Liaw S J, Hsueh P R, Ho S W, Luh K T
School of Medical Technology, College of Medicine, National Taiwan University, Taipei.
J Formos Med Assoc. 1998 Dec;97(12):855-9.
High-level resistance (minimum inhibitory concentration, MIC > 1,000 micrograms/ml) to gentamicin (HLGR) in enterococci is common in Taiwan. In this study, we investigated the distribution of gentamicin resistance elements in enterococci isolated at National Taiwan University Hospital in a 1-year period, and also examined the transfer and the genetic variability of the resistance elements of different isolates. Among 109 isolates tested, 43 (39%) HLGR isolates were identified. HLGR was most common in Enterococcus faecium isolates (7/15, 47%), followed by Enterococcus faecalis (34/80, 43%), Enterococcus avium (1/5, 20%), and Enterococcus casseliflavus (1/9, 11%). To understand the mechanism of resistance transfer, four isolates of E. faecalis and five isolates of E. faecium showing HLGR were studied. Transfer of resistance markers to a plasmid-free recipient strain of E. faecalis JH2-7 was observed, with transfer frequencies ranging from 10(-2) to 10(-8). All of the transconjugants contained plasmids, with sizes ranging from 45 kb to larger than 70 kb. At least three plasmid patterns were observed on digestion with HaeIII. Hybridization with a probe specific for the aac6'aph2" gentamicin resistance gene confirmed that all of these HLGR isolates carried a Gm(r) determinant, though the hybridization patterns of the plasmids from E. faecalis and E. faecium were different. Although many similarities exist among enterococcal Gm(r) determinants, the results suggest heterogeneity may occur in the flanking regions of resistance elements.
在台湾，肠球菌对庆大霉素的高水平耐药（最低抑菌浓度，MIC＞1000微克/毫升）情况很常见。在本研究中，我们调查了台湾大学医院一年内分离出的肠球菌中庆大霉素耐药元件的分布情况，还检测了不同分离株耐药元件的转移及遗传变异性。在所检测的109株分离株中，鉴定出43株（39%）高水平庆大霉素耐药株。高水平庆大霉素耐药在屎肠球菌分离株中最为常见（7/15，47%），其次是粪肠球菌（34/80，43%）、鸟肠球菌（1/5，20%）和卡氏肠球菌（1/9，11%）。为了解耐药转移机制，对4株粪肠球菌和5株屎肠球菌的高水平庆大霉素耐药株进行了研究。观察到耐药标记向粪肠球菌JH2 - 7无质粒受体菌株的转移，转移频率范围为10⁻²至10⁻⁸。所有转接合子都含有质粒，大小范围从45 kb到大于70 kb。用HaeIII消化后观察到至少三种质粒图谱。用对aac6′aph2″庆大霉素耐药基因特异的探针进行杂交证实，所有这些高水平庆大霉素耐药株都携带一个庆大霉素耐药决定簇，尽管粪肠球菌和屎肠球菌质粒的杂交图谱不同。虽然肠球菌庆大霉素耐药决定簇之间存在许多相似之处，但结果表明耐药元件侧翼区域可能存在异质性。
