Resistance Nodulation cell Division (RND) efflux pumps are known to contribute to the tolerance of Pseudomonas putida to aromatic hydrocarbons, but their role in antibiotic resistance has not been fully elucidated. In this study, two types of single‐step multidrug‐resistant (MDR) mutants were selected in vitro from reference strain KT2440. Mutants of the first type were more resistant to fluoroquinolones and β‐lactams except imipenem, and overproduced the efflux system TtgABC as a result of mutations occurring in regulator TtgR. In addition to TtgABC, mutants of the second type such as HPG‐5 were found to upregulate a novel RND pump, dubbed ParXY/TtgC, which accommodates cefepim, fluoroquinolones and aminoglycosides. As demonstrated by gene deletion experiments, TtgABC and ParXY/TtgC are both under the positive control of a two‐component system, PpeRS. Whole‐genome sequence analyses revealed that mutant HPG‐5 harbours a mutation inactivating the gene (sucD) of succinyl‐CoA synthetase, an enzyme of the tricarboxylic cycle. Disruption of sucD in strain KT2440 reproduced the resistance phenotype of HPG‐5, and activated the glyoxylate shunt. Finally, identification of two MDR clinical strains of P. putida that jointly overexpress TtgABC and ParXY/TtgC, of which one is a sucD mutant, highlights the role of these efflux systems as determinants of antibiotic resistance.

中文翻译：

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两个RND外排系统ParXY和TtgABC的坐标过表达导致恶臭假单胞菌的多药耐药性。

已知耐药结节细胞分裂（RND）外排泵有助于恶臭假单胞菌对芳香烃的耐受性，但尚未充分阐明它们在抗生素耐药性中的作用。在这项研究中，选择了两种类型的单步耐多药（MDR）突变体来自参考菌株KT2440。除亚胺培南外，第一类突变体对氟喹诺酮类和β-内酰胺类的耐药性更高，并且由于调节剂TtgR中发生突变而导致外排系统TtgABC过量产生。除TtgABC外，第二类突变体如HPG-5被发现上调了新型RND泵，称为ParXY / TtgC，可容纳头孢哌酮，氟喹诺酮和氨基糖苷。正如基因删除实验所证明的那样，TtgABC和ParXY / TtgC都处于两组分系统PpeRS的阳性控制之下。全基因组序列分析表明，突变型HPG-5具有使琥珀酰CoA合成酶（三羧酸循环酶）的基因（sucD）失活的突变。sucD的破坏在菌株KT2440中，其复制了HPG-5的抗性表型，并激活了乙醛酸分流器。最后，两个MDR临床分离株的鉴定P。恶臭假单胞菌该共同过表达TtgABC和ParXY / TTGC，其中之一是一个sucD突变体，突出显示了这些外排系统的抗生素抗性决定因素的作用。