Department of Bacteriology and Food Safety, Animal Health and Veterinary Laboratories Agency, Addlestone, Surrey, United Kingdom.
School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom.
PLoS One. 2013 Dec 27;8(12):e84142. doi: 10.1371/journal.pone.0084142. eCollection 2013.
In this study 6 CTX-M positive E. coli isolates collected during a clinical study examining the effect of antibiotic use in a human trial were analysed. The aim of the study was to analyse these isolates and assess the effect of full or partial loss of plasmid genes on bacterial fitness and pathogenicity. A DNA array was utilised to assess resistance and virulence gene carriage. Plasmids were characterised by PCR-based replicon typing and addiction system multiplex PCR. A phenotypic array and insect virulence model were utilised to assess the effect of plasmid-loss in E. coli of a large multi-resistance plasmid. All six E. coli carrying bla CTX-M-14 were detected from a single participant and were identical by pulse field gel electrophoresis and MLST. Plasmid profiling and arrays indicated absence of a large multi-drug resistance (MDR) F-replicon plasmid carrying blaTEM, aadA4, strA, strB, dfrA17/19, sul1, and tetB from one isolate. Although this isolate partially retained the plasmid it showed altered fitness characteristics e.g. inability to respire in presence of antiseptics, similar to a plasmid-cured strain. However, unlike the plasmid-cured or plasmid harbouring strains, the survival rate for Galleria mellonella infected by the former strain was approximately 5-times lower, indicating other possible changes accompanying partial plasmid loss. In conclusion, our results demonstrated that an apparently healthy individual can harbour bla CTX-M-14 E. coli strains. In one such strain, isolated from the same individual, partial absence of a large MDR plasmid resulted in altered fitness and virulence characteristics, which may have implications in the ability of this strain to infect and any subsequent treatment.
在这项研究中，分析了在一项人类临床试验中检查抗生素使用效果的临床研究中收集的 6 株 CTX-M 阳性大肠杆菌分离株。该研究的目的是分析这些分离株，并评估质粒基因完全或部分缺失对细菌适应性和致病性的影响。利用 DNA 芯片评估耐药性和毒力基因携带情况。通过基于 PCR 的复制子分型和加性系统多重 PCR 对质粒进行特征分析。利用表型芯片和昆虫致病模型评估大多重耐药质粒大肠杆菌中质粒缺失的影响。从一名参与者中检测到携带 blaCTX-M-14 的 6 株大肠杆菌均通过脉冲场凝胶电泳和 MLST 鉴定为相同。质粒图谱和芯片表明，从一个分离株中不存在携带 blaTEM、aadA4、strA、strB、dfrA17/19、sul1 和 tetB 的大型多药耐药 (MDR) F 复制子质粒。尽管该分离株部分保留了质粒，但显示出适应性特征的改变，例如在防腐剂存在下无法呼吸，类似于质粒消除菌株。然而，与质粒消除或携带质粒的菌株不同，前者感染的家蚕幼虫的存活率约低 5 倍，表明伴随部分质粒缺失的其他可能变化。总之，我们的研究结果表明，一个看似健康的个体可以携带 blaCTX-M-14 大肠杆菌菌株。在从同一个体中分离的一株菌中，大型 MDR 质粒的部分缺失导致适应性和毒力特征发生改变，这可能影响该菌株的感染能力和任何后续治疗。
