Cervoni Matteo, Lo Sciuto Alessandra, Bianchini Chiara, Mancone Carmine, Imperi Francesco
Department of Science, Roma Tre University, Rome, Italy.
Department of Molecular Medicine, Sapienza University of Rome, Rome, Italy.
Front Microbiol. 2021 Oct 27;12:778968. doi: 10.3389/fmicb.2021.778968. eCollection 2021.
Colistin represents a last-line treatment option for infections caused by multidrug resistant Gram-negative pathogens, including . Colistin resistance generally involves the modification of the lipid A moiety of lipopolysaccharide (LPS) with positively charged molecules, namely phosphoethanolamine (PEtN) or 4-amino-4-deoxy-L-arabinose (Ara4N), that reduce colistin affinity for its target. Several lines of evidence highlighted lipid A aminoarabinosylation as the primary colistin resistance mechanism in , while the contribution of phosphoethanolamination remains elusive. PEtN modification can be due to either endogenous (chromosomally encoded) PEtN transferase(s) (e.g., EptA in ) or plasmid borne MCR enzymes, commonly found in enterobacteria. By individually cloning and into a plasmid for inducible gene expression, we demonstrated that MCR-1 and EptA have comparable PEtN transferase activity in and confer colistin resistance levels similar to those provided by lipid A aminoarabinosylation. Notably, EptA, but not MCR-1, negatively affects growth and, to a lesser extent, cell envelope integrity when expressed at high levels. Mutagenesis experiments revealed that PEtN transferase activity does not account for the noxious effects of EptA overexpression, that instead requires a C-terminal tail unique to EptA, whose function remains unknown. Overall, this study shows that both endogenous and exogenous PEtN transferases can promote colistin resistance in , and that PEtN and MCR-1 mediated resistance has no impact on growth and cell envelope homeostasis, suggesting that there may be no fitness barriers to the spread of in .
黏菌素是治疗由多重耐药革兰氏阴性病原体引起的感染的最后一线治疗选择，包括……。黏菌素耐药性通常涉及用带正电荷的分子，即磷酸乙醇胺（PEtN）或4-氨基-4-脱氧-L-阿拉伯糖（Ara4N）修饰脂多糖（LPS）的脂质A部分，这会降低黏菌素对其靶标的亲和力。多项证据表明脂质A氨基阿拉伯糖基化是……中主要的黏菌素耐药机制，而磷酸乙醇胺化的作用仍不明确。PEtN修饰可能是由于内源性（染色体编码）的PEtN转移酶（如……中的EptA）或通常在肠杆菌中发现的质粒携带的MCR酶。通过将……和……分别克隆到用于诱导基因表达的质粒中，我们证明MCR-1和EptA在……中具有相当的PEtN转移酶活性，并赋予与脂质A氨基阿拉伯糖基化相似的黏菌素耐药水平。值得注意的是，EptA而非MCR-1在高水平表达时会对……生长产生负面影响，并在较小程度上影响细胞包膜完整性。诱变实验表明，PEtN转移酶活性并不能解释EptA过表达的有害作用，相反，这需要EptA特有的C末端尾巴，其功能尚不清楚。总体而言，这项研究表明内源性和外源性PEtN转移酶都可以促进……中的黏菌素耐药性，并且PEtN和MCR-1介导的耐药性对生长和细胞包膜稳态没有影响，这表明……在……中的传播可能不存在适应性障碍。
