Serra Cristiano, Bouharkat Bakhta, Tir Touil-Meddah Aicha, Guénin Stéphanie, Mullié Catherine
Laboratoire des Agents Infectieux, Resistance et Chimiothérapie - EA 4294, UFR de Pharmacie, Université de Picardie Jules Verne, Amiens, France.
Laboratoire de Bioconversion, Génie Microbiologique et Sécurité Sanitaire N°145, Faculté des Sciences de la Nature et de la Vie, Université Mustapha Stambouli, Mascara, Algeria.
Front Microbiol. 2019 Feb 26;10:366. doi: 10.3389/fmicb.2019.00366. eCollection 2019.
Modulation of the membrane permeability through a decrease in porin-mediated antibiotic entry and/or an increase in antibiotic efflux is one of the resistance mechanisms to antibiotics evolved by Gram-negative bacteria. To assess whether the outer membrane porin OprD and Resistance-Nodulation-Division (RND) efflux pumps were similarly expressed in 33 ciprofloxacin-resistant clinical strains of and in 30 non-clinical strains originating from the hospital environment (mainly waterborne ), the expression of , , , and genes was investigated. Overall, the expression of was not detected by RT-qPCR in 14 (22%) strains and underexpressed in 35 (56%) more. No significant difference in expression was detected between clinical and non-clinical strains. As for efflux pumps, 23 (70%) of the clinical strains overexpressed at least one of the tested RND genes. Overexpression of , and was detected in 27, 12, and 45% of the clinical strains, respectively. In the 30 non-clinical strains, no overexpression could be found for , , or On the contrary, a global underexpression of the tested efflux pump genes was recorded. In both clinical and environmental strains, a positive correlation was found between the expressions of and . Similarly, the expressions of and were positively correlated. This result contrasts with the inverse correlation between both MexAB-OprM/MexEF-OprN and OprD previously described in carbapenem-resistant strains. The only positive correlation between phenotypic ciprofloxacin minimum inhibitory concentrations (MICs) and the expression of efflux pump gene was witnessed with (analysis on pooled results for clinical and environmental strains). However, in clinical strains, no statistically significant link could be found between the degree of reduction in ciprofloxacin MICs witnessed with Phenylalanine-Arginine β-naphthylamide (PAβN) and the expression of any of the 3 RND genes tested.
通过减少孔蛋白介导的抗生素进入和/或增加抗生素外排来调节膜通透性是革兰氏阴性菌进化出的抗生素耐药机制之一。为了评估外膜孔蛋白OprD和耐药-固氮-细胞分裂（RND）外排泵在33株耐环丙沙星临床菌株和30株源自医院环境（主要是水源性）的非临床菌株中是否有相似表达，研究了ompD、mexA、mexB和mexE基因的表达。总体而言，14株（22%）菌株经RT-qPCR未检测到ompD表达，另有35株（56%）表达下调。临床菌株和非临床菌株之间未检测到ompD表达的显著差异。至于外排泵，23株（70%）临床菌株至少过表达一种测试的RND基因。分别在27%、12%和45%的临床菌株中检测到mexA、mexB和mexE过表达。在30株非临床菌株中，未发现mexA、mexB或mexE过表达，相反，记录到测试的外排泵基因整体表达下调。在临床菌株和环境菌株中，ompD和mexA的表达之间均发现正相关。同样，mexB和mexE的表达也呈正相关。这一结果与先前在耐碳青霉烯类铜绿假单胞菌菌株中描述的MexAB-OprM/MexEF-OprN和OprD之间的负相关形成对比。仅在mexE（临床菌株和环境菌株汇总结果分析）中观察到表型环丙沙星最低抑菌浓度（MIC）与外排泵基因表达之间存在正相关。然而，在临床菌株中，用苯丙氨酸-精氨酸β-萘酰胺（PAβN）观察到的环丙沙星MIC降低程度与测试的3种RND基因中任何一种的表达之间均未发现统计学上的显著关联。
