Identification of a novel tedizolid resistance mutation in rpoB of MRSA after in vitro serial passage.
Identification of a novel tedizolid resistance mutation in rpoB of MRSA after in vitro serial passage.
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DOI：
10.1093/jac/dkaa422
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
Tianwei Shen;K. Penewit;A. Waalkes;Libin Xu;S. Salipante;Abhinav Nath;Brian J. Werth
中科院分区：
文献类型：
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作者：
Tianwei Shen;K. Penewit;A. Waalkes;Libin Xu;S. Salipante;Abhinav Nath;Brian J. Werth
泰地唑胺是一种恶唑烷酮类抗菌剂，对革兰氏阳性菌（包括MRSA）具有活性。替地唑胺耐药是罕见的，替地唑胺选择其他抗菌药物交叉耐药的能力尚不完全清楚。本研究的目的是进一步探讨耐甲氧西林金黄色葡萄球菌对替地唑胺耐药的表型和遗传基础。方法：我们通过连续传代选择耐替地唑胺的MRSA实验室菌株N315，直到回收到MIC ≥1 log 2稀释度高于耐药折点（≥2 mg/L）的分离株。对该分离株进行WGS，并检测对一组相关和不相关抗菌剂的敏感性，以确定交叉耐药性。进行同源性建模以评价突变对靶蛋白功能的潜在影响。结果连续传代10天后，我们回收了一个表型稳定的突变体，其替地唑胺MIC为4 mg/L。WGS结果显示rpoB中只有一个单核苷酸变异（A1345 G），对应于氨基酸取代D449 N。利奈唑胺、氯霉素、瑞他帕林和奎奴普汀/达福普汀的MIC增加≥2 log 2稀释度，表明出现了所谓的“PhLOPSa”耐药表型。对其他药物的敏感性，包括利福平，基本上没有变化。同源性模型显示，RNA聚合酶的突变残基不太可能直接影响恶唑烷酮的作用。结论：据我们所知，这是第一次rpoB突变与PhLOPSa抗菌剂耐药性有关。耐药机制尚不清楚，但可能是间接的，涉及σ-因子结合或转录调控的其他改变。
OBJECTIVES Tedizolid is an oxazolidinone antimicrobial with activity against Gram-positive bacteria, including MRSA. Tedizolid resistance is uncommon and tedizolid's capacity to select for cross-resistance to other antimicrobials is incompletely understood. The objective of this study was to further explore the phenotypic and genetic basis of tedizolid resistance in MRSA. METHODS We selected for tedizolid resistance in an MRSA laboratory strain, N315, by serial passage until an isolate with an MIC ≥1 log2 dilution above the breakpoint for resistance (≥2 mg/L) was recovered. This isolate was subjected to WGS and susceptibility to a panel of related and unrelated antimicrobials was tested in order to determine cross-resistance. Homology modelling was performed to evaluate the potential impact of the mutation on target protein function. RESULTS After 10 days of serial passage we recovered a phenotypically stable mutant with a tedizolid MIC of 4 mg/L. WGS revealed only one single nucleotide variant (A1345G) in rpoB, corresponding to amino acid substitution D449N. MICs of linezolid, chloramphenicol, retapamulin and quinupristin/dalfopristin increased by ≥2 log2 dilutions, suggesting the emergence of the so-called 'PhLOPSa' resistance phenotype. Susceptibility to other drugs, including rifampicin, was largely unchanged. Homology models revealed that the mutated residue of RNA polymerase would be unlikely to directly affect oxazolidinone action. CONCLUSIONS To the best of our knowledge, this is the first time that an rpoB mutation has been implicated in resistance to PhLOPSa antimicrobials. The mechanism of resistance remains unclear, but is likely indirect, involving σ-factor binding or other alterations in transcriptional regulation.