Cervoni Matteo, Ferriero Antonio Maria, Lo Sciuto Alessandra, Guidi Francesca, Babić Jordamović Naida, Piazza Silvano, Jousson Olivier, Esposito Alfonso, Imperi Francesco
Department of Science, University Roma Tre, 00146 Rome, Italy.
International Centre for Genetic Engineering and Biotechnology, 34149 Trieste, Italy.
Antibiotics (Basel). 2025 Jun 13;14(6):601. doi: 10.3390/antibiotics14060601.
Colistin is a last-resort treatment for multidrug-resistant infections, but resistance to it is emerging. While colistin resistance in is typically associated with chromosomal mutations inducing lipopolysaccharide (LPS) aminoarabinosylation, other mutations unrelated to LPS modifications have been proposed to influence the extent of colistin resistance. Here, we examined whether the genetic background and culture conditions affect the evolution of high-level colistin resistance in this bacterium. : We performed in vitro evolution experiments in the presence or absence of increasing colistin concentrations with two phylogenetically distant reference strains in a standard laboratory medium and in two media mimicking growth during lung or systemic infections. Resistance-associated mutations were identified by comparative genomics, and the role of selected mutated genes was validated by allele replacement, deletion, or conditional mutagenesis. : Most colistin-resistant mutants carried mutations in genes belonging to four functional groups: two-component systems controlling LPS aminoarabinosylation (PmrAB, PhoPQ), LPS biosynthesis, the production of the polyamine norspermidine, and fatty acid metabolism. No mutation was exclusively and invariably associated with a specific strain or medium. We demonstrated that norspermidine is detrimental to the acquisition of colistin resistance upon PmrAB activation and that impaired fatty acid biosynthesis can promote colistin resistance, even if it increases susceptibility to other antibiotics. : The evolution of colistin resistance in appeared to be only marginally affected by the genetic background and culture conditions. Notably, mutations in fatty acid biosynthetic genes represent a newly identified genetic determinant of colistin resistance, warranting further investigation in clinical isolates.
黏菌素是治疗多重耐药感染的最后手段，但对其的耐药性正在出现。虽然鲍曼不动杆菌中的黏菌素耐药性通常与诱导脂多糖（LPS）氨基阿拉伯糖基化的染色体突变有关，但也有其他与LPS修饰无关的突变被认为会影响黏菌素耐药的程度。在此，我们研究了遗传背景和培养条件是否会影响该菌高水平黏菌素耐药性的演变。：我们在有或没有增加黏菌素浓度的情况下，用两种系统发育距离较远的参考菌株在标准实验室培养基以及两种模拟肺部或全身感染期间生长的培养基中进行了体外进化实验。通过比较基因组学鉴定出与耐药相关的突变，并通过等位基因替换、缺失或条件诱变验证了所选突变基因的作用。：大多数黏菌素耐药突变体在属于四个功能组的基因中发生了突变：控制LPS氨基阿拉伯糖基化的双组分系统（PmrAB、PhoPQ）、LPS生物合成、多胺亚精胺的产生以及脂肪酸代谢。没有突变与特定菌株或培养基完全且始终相关。我们证明，亚精胺在PmrAB激活时对获得黏菌素耐药性不利，并且脂肪酸生物合成受损可促进黏菌素耐药性，即使这会增加对其他抗生素的敏感性。：鲍曼不动杆菌中黏菌素耐药性的演变似乎仅受到遗传背景和培养条件的轻微影响。值得注意的是，脂肪酸生物合成基因中的突变代表了新发现的鲍曼不动杆菌黏菌素耐药的遗传决定因素，值得在临床分离株中进一步研究。
