Guardabassi L, Dalsgaard A
Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University, 1870 Frederiksberg, Denmark.
Appl Environ Microbiol. 2004 Feb;70(2):984-90. doi: 10.1128/AEM.70.2.984-990.2004.
The occurrence, structure, and mobility of Tn1546-like elements were studied in environmental vancomycin-resistant enterococci (VRE) isolated from municipal sewage, activated sludge, pharmaceutical waste derived from antibiotic production, seawater, blue mussels, and soil. Of 200 presumptive VRE isolates tested, 71 (35%) harbored vanA. Pulsed-field gel electrophoresis analysis allowed the detection of 26 subtypes, which were identified as Enterococcus faecium (n = 13), E. casseliflavus (n = 6), E. mundtii (n = 3), E. faecalis (n = 3), and E. durans (n = 1) by phenotypic tests and 16S ribosomal DNA sequencing. Long PCR-restriction fragment length polymorphism (L-PCR-RFLP) analysis of Tn1546-like elements and PCR analysis of internal regions revealed the presence of seven groups among the 29 strains studied. The most common group (group 1) corresponded to the structure of Tn1546 in the prototype strain E. faecium BM4147. Two novel L-PCR-RFLP patterns (groups 3 and 4) were found for E. casseliflavus strains. Indistinguishable Tn1546-like elements occurred in VRE strains belonging to different species or originating from different sources. Interspecies plasmid-mediated transfer of vancomycin resistance to E. faecium BM4105 was demonstrated for E. faecalis, E. mundtii, and E. durans. This study indicates that VRE, including species other than E. faecium and E. faecalis, are widespread in nature and in environments that are not exposed to vancomycin selection and not heavily contaminated with feces, such as seawater, blue mussels, and nonagricultural soil. Tn1546-like elements can readily transfer between enterococci of different species and ecological origins, therefore raising questions about the origin of these transposable elements and their possible transfer between environmental and clinical settings.
对从城市污水、活性污泥、抗生素生产产生的制药废料、海水、蓝贻贝和土壤中分离出的耐万古霉素肠球菌（VRE）中的Tn1546样元件的发生情况、结构和移动性进行了研究。在测试的200株疑似VRE分离株中，71株（35%）携带vanA。脉冲场凝胶电泳分析检测到26个亚型，通过表型试验和16S核糖体DNA测序鉴定为粪肠球菌（n = 13）、格氏肠球菌（n = 6）、蒙氏肠球菌（n = 3）、屎肠球菌（n = 3）和耐久肠球菌（n = 1）。对Tn1546样元件进行长PCR-限制性片段长度多态性（L-PCR-RFLP）分析，并对内部区域进行PCR分析，结果显示在所研究的29株菌株中存在7个组。最常见的组（第1组）与原型菌株粪肠球菌BM4147中的Tn1546结构相对应。发现格氏肠球菌菌株有两种新的L-PCR-RFLP模式（第3组和第4组）。属于不同物种或源自不同来源的VRE菌株中出现了无法区分的Tn1546样元件。粪肠球菌、蒙氏肠球菌和耐久肠球菌对屎肠球菌BM4105进行了种间质粒介导的万古霉素耐药性转移。这项研究表明，包括粪肠球菌和屎肠球菌以外的其他物种在内的VRE在自然环境以及未接触万古霉素选择且未被粪便严重污染的环境中广泛存在，如海水、蓝贻贝和非农业土壤。Tn1546样元件可在不同物种和生态来源的肠球菌之间轻易转移，因此引发了关于这些转座元件的起源及其在环境和临床环境之间可能转移的问题。
