Magallon Arnaud, Bador Julien, Garrigos Thomas, Demeule Caroline, Chapelle Anaïs, Varin Véronique, Neuwirth Catherine, Amoureux Lucie
Department of Bacteriology, University Hospital of Dijon, BP 37013, 21070 Dijon Cedex, France.
UMR AgroEcologie 1347, INRAE, University of Bourgogne, 21065 Dijon Cedex, France.
Antibiotics (Basel). 2025 May 23;14(6):536. doi: 10.3390/antibiotics14060536.
BACKGROUND/OBJECTIVES: and are emerging opportunistic pathogens. Several Resistance-Nodulation-cell Division (RND) efflux systems are involved in intrinsic or acquired antibiotic resistance (AxyABM, AxyXY-OprZ, and AxyEF-OprN). The aim of this study was to explore the resistance mechanisms in one-step mutants in which the efflux systems described to date are not involved: one mutant of AXX-A (AXX-A-Do1) and two mutants of CIP102236 (CIP102236-El9 and CIP102236-Eo4) selected on fluoroquinolones.
In vitro mutants were compared to parental isolates by WGS. RT-qPCR and gene inactivation were used to explore the role of the new efflux systems detected.
In the AXX-A mutant (AXX-A-Do1), WGS showed a substitution in the putative regulator of the new RND efflux system AinCDJ. The transporter gene was 79-fold overexpressed in AXX-A-Do1, compared to its parental strain. The inactivation of in AXX-A-Do1 led to a decrease in MICs of ciprofloxacin (8-fold), levofloxacin (8-fold), cefepime (≥8-fold), meropenem (4-fold), doripenem (4-fold), doxycycline (4-fold), minocycline (4-fold), tigecycline (4-fold) and chloramphenicol (≥8-fold). The MICs values obtained were similar to those of the parental strain AXX-A. The same approach allowed the detection of the new efflux system AxySUV in CIP102236 mutants, in which substitutions in the putative AxySUV regulator were associated with the overexpression of the transporter gene . inactivation in the mutants led to a decrease in MICs of ciprofloxacin (8- to 16-fold), levofloxacin (4- to 8-fold), doripenem (4-fold), doxycycline (4-fold), minocycline (4-fold), and chloramphenicol (≥4-fold). Interestingly, is present in only about 50% of available genomes, whereas is detected in all genomes.
This study demonstrated that AinCDJ overproduction is involved in the acquired resistance of to cefepime, meropenem, doripenem, fluoroquinolones, minocycline, doxycycline, tigecycline, and chloramphenicol and that AxySUV overproduction is involved in the acquired resistance of to meropenem, fluoroquinolones, minocycline, doxycycline, and chloramphenicol.
背景/目的：[细菌名称1]和[细菌名称2]是新出现的机会致病菌。几种耐药-结瘤-细胞分裂（RND）外排系统与内在或获得性抗生素耐药性有关（AxyABM、AxyXY-OprZ和AxyEF-OprN）。本研究的目的是探索一步突变体中的耐药机制，这些突变体不涉及迄今为止描述的外排系统：在氟喹诺酮类药物上筛选出的一株[细菌名称1]突变体（AXX-A-Do1）和两株[细菌名称2]突变体（CIP102236-El9和CIP102236-Eo4）。
通过全基因组测序（WGS）将体外突变体与其亲本菌株进行比较。采用逆转录定量聚合酶链反应（RT-qPCR）和基因失活技术来探索检测到的新外排系统的作用。
在[细菌名称1]突变体（AXX-A-Do1）中，全基因组测序显示新RND外排系统AinCDJ的假定调节因子发生了替代。与亲本菌株相比，转运蛋白基因在AXX-A-Do1中过表达79倍。在AXX-A-Do1中使[基因名称]失活导致环丙沙星（8倍）、左氧氟沙星（8倍）、头孢吡肟（≥8倍）、美罗培南（4倍）、多利培南（4倍）、多西环素（4倍）、米诺环素（4倍）、替加环素（4倍）和氯霉素（≥8倍）的最低抑菌浓度（MIC）降低。获得的MIC值与亲本菌株AXX-A相似。同样的方法在[细菌名称2]突变体中检测到了新的外排系统AxySUV，其中假定的AxySUV调节因子的替代与转运蛋白基因的过表达有关。突变体中[基因名称]失活导致环丙沙星（8至16倍）、左氧氟沙星（4至8倍）、多利培南（4倍）、多西环素（4倍）、米诺环素（4倍）和氯霉素（≥4倍）的MIC降低。有趣的是，[基因名称]仅存在于约50%的可用[细菌名称1]基因组中，而[基因名称]在所有[细菌名称2]基因组中均被检测到。
本研究表明，AinCDJ的过量产生参与了[细菌名称1]对头孢吡肟、美罗培南、多利培南、氟喹诺酮类、米诺环素、多西环素、替加环素和氯霉素的获得性耐药，并且AxySUV的过量产生参与了[细菌名称2]对美罗培南、氟喹诺酮类、米诺环素、多西环素和氯霉素的获得性耐药。
