Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany.
German Center for Infection Research (DZIF), Partner Site Bonn-Cologne, Cologne, Germany.
J Antimicrob Chemother. 2021 Mar 12;76(4):883-886. doi: 10.1093/jac/dkaa532.
To characterize two Enterococcus faecium isolates with different resistance phenotypes obtained from the same blood culture.
The isolates were identified by MALDI-TOF MS and antimicrobial susceptibility testing (AST) was performed using a VITEK® 2 AST P592 card and Etest. WGS was performed on the MiSeq and MinION sequencer platforms. Core-genome MLST (cgMLST) and seven-loci MLST were performed. Plasmid analysis was performed using S1-PFGE followed by Southern-blot hybridization.
Both E. faecium isolates were ST203. AST revealed that one was a vancomycin-resistant E. faecium (VREfm) isolate and the other was a vancomycin-susceptible E. faecium (VSEfm) isolate. The VREfm isolate harboured the vanA gene cluster as part of a Tn1546-type transposon encoded on a 49 kb multireplicon (rep1, rep2 and rep7a) plasmid (pAML0157.1). On the same plasmid, ant(6)-Ia, cat-like and erm(B) were encoded. The VSEfm isolate harboured a rep2 plasmid (pAML0158.1), 12 kb in size, which was present in full length as part of pAML0157.1 from the VREfm isolate. The vanA-encoding pAML0157.1 was a chimera of the rep2 pAML0158.1 and a second DNA segment harbouring vanA, ant(6)-Ia, erm(B) and cat-like, as well as the replicons rep1 and rep7a. By cgMLST analysis, the VREfm and VSEfm isolates were identical.
Our results demonstrate that the VREfm and VSEfm blood culture isolates represented ST203 and were identical. The investigated heterogeneous resistance phenotypes resulted from the acquisition or loss of plasmid segments in the enterococcal isolates. These data illustrate that mobile genetic elements may contribute to the spread of vancomycin resistance among enterococci and to the genotypic and phenotypic variation within clonal isolates.
从同一血培养物中分离出具有不同耐药表型的 2 株屎肠球菌。
采用 MALDI-TOF MS 对分离株进行鉴定，并采用 VITEK® 2 AST P592 卡和 Etest 进行药敏试验（AST）。采用 MiSeq 和 MinION 测序仪平台进行 WGS。进行核心基因组 MLST（cgMLST）和 7 个基因座 MLST。采用 S1-PFGE 进行质粒分析，然后进行 Southern 印迹杂交。
2 株屎肠球菌均为 ST203。AST 显示，一株为万古霉素耐药屎肠球菌（VREfm）分离株，另一株为万古霉素敏感屎肠球菌（VSEfm）分离株。VREfm 分离株携带 vanA 基因簇，该基因簇为 Tn1546 型转座子的一部分，编码在一个 49kb 的多复制子（rep1、rep2 和 rep7a）质粒（pAML0157.1）上。在同一质粒上，编码 ant（6）-Ia、cat-like 和 erm（B）。VSEfm 分离株携带 rep2 质粒（pAML0158.1），大小为 12kb，作为 VREfm 分离株中 pAML0157.1 的全长部分存在。编码 vanA 的 pAML0157.1 是 rep2 pAML0158.1 和第二个 DNA 片段的嵌合体，该片段还携带 vanA、ant（6）-Ia、erm（B）和 cat-like 以及复制子 rep1 和 rep7a。通过 cgMLST 分析，VREfm 和 VSEfm 分离株完全相同。
本研究结果表明，VREfm 和 VSEfm 血培养分离株均为 ST203，且完全相同。所研究的异质耐药表型是由于肠球菌分离株中质粒片段的获得或丢失所致。这些数据表明，移动遗传元件可能导致万古霉素耐药在肠球菌中的传播，并导致克隆分离株的基因型和表型变异。
