Abstract：
OBJECTIVE: Linezolid-resistant opportunistic human pathogens Enterococcus faecalis and Enterococcus faecium are emerging health threats as limited therapeutic options remain. The aim of this study was to investigate the epidemiology, resistance mechanisms, and genetic diversity of linezolid-resistant enterococci (LRE) isolated between 2013 and 2021 and received at the Belgian National Reference Centre (NRC) for Enterococci.
METHODS: Linezolid susceptibility testing was performed upon request on 2458 submitted enterococci strains. Whole-genome sequencing was performed on all LRE strains.
RESULTS: Seventy-eight LRE human isolates, of which 63 (81%) E. faecalis and 15 (19%) E. faecium strains, were submitted to the Belgian NRC for Enterococci. Of the linezolid-resistant E. faecalis strains, 97% harboured the optrA gene (56% wild-type pE349) and 3% the poxtA gene. Of the linezolid-resistant E. faecium strains, 54% harboured the G2576T point mutation in the V domain of the 23S rRNA genes, 23% the poxtA, and 23% the optrA gene. Furthermore, two E. faecium strains were identified with a combination of two resistance mechanisms ([i] optrA and poxtA, and [ii] cfr(B) and G2576T point mutation, respectively). Vancomycin resistance was observed in 15% (n = 12) of the LRE. ST480 (n = 42/63 typed strains, 67%) was the most frequently detected sequence type (ST) in linezolid-resistant E. faecalis strains, while ST203 (n = 5/15 typed strains, 33%) was the most frequently detected ST in linezolid-resistant E. faecium strains.
CONCLUSIONS: E. faecalis isolates harbouring optrA were the predominant LRE in Belgium, with ST480 as the most prominent multilocus sequence typing. Linezolid resistance in E. faecium could be attributed to either chromosomal mutations or transferable resistance determinants.
METHODS: Linezolid susceptibility testing was performed upon request on 2458 submitted enterococci strains. Whole-genome sequencing was performed on all LRE strains.
RESULTS: Seventy-eight LRE human isolates, of which 63 (81%) E. faecalis and 15 (19%) E. faecium strains, were submitted to the Belgian NRC for Enterococci. Of the linezolid-resistant E. faecalis strains, 97% harboured the optrA gene (56% wild-type pE349) and 3% the poxtA gene. Of the linezolid-resistant E. faecium strains, 54% harboured the G2576T point mutation in the V domain of the 23S rRNA genes, 23% the poxtA, and 23% the optrA gene. Furthermore, two E. faecium strains were identified with a combination of two resistance mechanisms ([i] optrA and poxtA, and [ii] cfr(B) and G2576T point mutation, respectively). Vancomycin resistance was observed in 15% (n = 12) of the LRE. ST480 (n = 42/63 typed strains, 67%) was the most frequently detected sequence type (ST) in linezolid-resistant E. faecalis strains, while ST203 (n = 5/15 typed strains, 33%) was the most frequently detected ST in linezolid-resistant E. faecium strains.
CONCLUSIONS: E. faecalis isolates harbouring optrA were the predominant LRE in Belgium, with ST480 as the most prominent multilocus sequence typing. Linezolid resistance in E. faecium could be attributed to either chromosomal mutations or transferable resistance determinants.
摘要：
目的：利奈唑胺耐药的机会性人类病原体粪肠球菌和屎肠球菌是一种新兴的健康威胁，因为治疗选择有限。目的是调查流行病学，2013年至2021年间分离的比利时利奈唑胺耐药肠球菌（LRE）的耐药机制和遗传多样性在比利时国家肠球菌参考中心（NRC）收到。
方法：应要求对2458株提交的肠球菌进行利奈唑胺药敏试验。对所有LRE菌株进行全基因组测序。
结果：78个LRE人类分离株，其中粪肠球菌63株(81%)和屎肠球菌15株(19%)，已将肠球菌提交比利时NRC。在利奈唑胺耐药粪肠球菌菌株中，97％的人携带optrA（56％的野生型pE349）和3％的poxtA基因。在耐利奈唑胺的屎肠球菌菌株中，54％的人在23SrRNA基因的V域中具有G2576T点突变，23%的poxtA和23%的optrA基因。此外,用两种抗性机制((i)optrA和poxtA和(ii)cfr(B)和G2576T点突变)的组合鉴定了两种屎肠球菌菌株。在15%(n=12)的LRE中观察到万古霉素抗性。ST480(n=42/63型菌株，67%)是利奈唑胺耐药粪肠球菌菌株中最常见的序列类型(STs)，而ST203(n=5/15分型菌株，33%)是耐利奈唑胺的屎肠球菌菌株中最经常检测到的STs。
结论：E.在比利时，包含optrA的粪菌是主要的LRE，而ST480是最突出的MLST。屎肠球菌中的利奈唑胺抗性可归因于染色体突变或可转移抗性决定子。
方法：应要求对2458株提交的肠球菌进行利奈唑胺药敏试验。对所有LRE菌株进行全基因组测序。
结果：78个LRE人类分离株，其中粪肠球菌63株(81%)和屎肠球菌15株(19%)，已将肠球菌提交比利时NRC。在利奈唑胺耐药粪肠球菌菌株中，97％的人携带optrA（56％的野生型pE349）和3％的poxtA基因。在耐利奈唑胺的屎肠球菌菌株中，54％的人在23SrRNA基因的V域中具有G2576T点突变，23%的poxtA和23%的optrA基因。此外,用两种抗性机制((i)optrA和poxtA和(ii)cfr(B)和G2576T点突变)的组合鉴定了两种屎肠球菌菌株。在15%(n=12)的LRE中观察到万古霉素抗性。ST480(n=42/63型菌株，67%)是利奈唑胺耐药粪肠球菌菌株中最常见的序列类型(STs)，而ST203(n=5/15分型菌株，33%)是耐利奈唑胺的屎肠球菌菌株中最经常检测到的STs。
结论：E.在比利时，包含optrA的粪菌是主要的LRE，而ST480是最突出的MLST。屎肠球菌中的利奈唑胺抗性可归因于染色体突变或可转移抗性决定子。
