Department of Clinical Microbiology, Christian Medical College, Vellore, India.
Department of Microbiology, Jai Prakash Narayan Apex Trauma Centre, All India Institute of Medical Sciences, New Delhi, India.
J Glob Antimicrob Resist. 2022 Jun;29:168-172. doi: 10.1016/j.jgar.2022.03.013. Epub 2022 Mar 23.
The genetic basis for the spread of vancomycin resistance in Enterococcus faecium is largely unexplored in India. The present study aimed to investigate the plasmid diversity and variation of Tn1546 associated with vanA harbouring VREfm isolates.
A total of 122 VREfm isolates collected from blood cultures were included in this study. MLST analysis was performed on all isolates, and they were also screened for the presence of vanA and vanB genes. Whole genome sequencing was performed for a subset of fifteen VREfm isolates belonging to ST1643.
All of the 122 VREfm isolates carried the vanA gene. Twenty-four different sequence types were seen; of these, ST1643, ST80 and ST17 were predominant. Whole genome sequencing was performed on 15 VREfm isolates belonging to ST1643. For eight isolates the vanA gene was found on pRUM-like circular plasmids, and for the remaining seven isolates, the vanA gene was found on the linear plasmids. Novel Tn1546 variants carrying vanA were found on both circular and linear plasmids. Interestingly, co-presence of vanA and optrA were seen in the backbone of three linear plasmids.
Multiple vanA-carrying plasmids and Tn1546-like elements were involved in the dissemination of vancomycin resistance in VREfm. The co-occurrence of Tn1546 carrying vanA and Tn554 family transposon carrying optrA on the backbone of plasmids is worrisome. The dissemination of such plasmids may pose treatment and infection control challenges.
肠球菌中万古霉素耐药性传播的遗传基础在印度很大程度上尚未得到探索。本研究旨在调查与携带 vanA 的 VREfm 分离株相关的 Tn1546 质粒多样性和变异。
本研究纳入了从血液培养物中收集的 122 株 VREfm 分离株。对所有分离株进行 MLST 分析，并筛选 vanA 和 vanB 基因的存在。对属于 ST1643 的 15 株 VREfm 分离株的子集进行全基因组测序。
122 株 VREfm 分离株均携带 vanA 基因。共观察到 24 种不同的序列类型；其中，ST1643、ST80 和 ST17 占优势。对属于 ST1643 的 15 株 VREfm 分离株进行了全基因组测序。在 8 株分离株中，vanA 基因位于 pRUM 样环状质粒上，而在其余 7 株分离株中，vanA 基因位于线性质粒上。在环状和线性质粒上均发现了携带 vanA 的新型 Tn1546 变体。有趣的是，在 3 个线性质粒的骨架上同时存在 vanA 和 optrA。
在 VREfm 中，多种携带 vanA 的质粒和 Tn1546 样元件参与了万古霉素耐药性的传播。在质粒骨架上同时存在携带 vanA 的 Tn1546 和携带 optrA 的 Tn554 家族转座子令人担忧。这些质粒的传播可能会对治疗和感染控制带来挑战。
