目的·探寻鲍曼不动杆菌（Acinetobacter baumannii）在环境中碳青霉烯类药物美罗培南浓度改变时耐药性变化的机制。方法·通过改变鲍曼不动杆菌标准敏感株ATCC19606和临床耐药株AB.2014培养环境中的美罗培南浓度等条件，诱导对美罗培南不同耐药程度的衍生株。测量所得菌株的生长曲线，并提取各菌株的DNA和RNA，采用PCR分析菌株耐药性改变后的碳青霉烯酶基因IMI、KPC、GES-1、IMP、VIM、NDM-1、OXA23、OXA24、OXA51、OXA58的表达情况；通过实时荧光定量PCR（real-time fluorescent quantitative PCR，RT-qPCR）分析不同耐药程度的鲍曼不动杆菌耐药基因，包括OXA51，外排泵基因adeB、adeG、adeJ，孔蛋白基因carO、omp33-36、oprC，青霉素结合蛋白基因ponA的表达水平变化；通过全基因组测序及生物信息学工具分析耐药性改变后菌株的差异基因富集情况的变化。结果·获得了鲍曼不动杆菌ATCC19606与AB.2014对美罗培南不同耐药程度的11个衍生株，最低抑菌浓度（minimum inhibitory concentration，MIC）为1~128 μg/mL。ATCC19606及其衍生株的生长速度和峰值随着耐药性的增加而降低，但AB.2014及其衍生株并没有表现出这种趋势。ATCC19606及其衍生株表达3个碳青霉烯酶基因OXA51、VIM和IMP，AB.2014及其多数衍生株表达4个碳青霉烯酶基因OXA23、OXA51、VIM和IMP，仅AB.2014的一个复敏衍生株出现了OXA23丢失。RT-qPCR结果显示，仅在ATCC19606及其耐药衍生株中oprC基因的表达量随着耐药性的升高而降低，多数耐药基因的表达水平与菌株的耐药水平变化一致。生物信息学分析提示ATCC19606不同衍生株之间的差异基因主要富集于铁载体摄取跨膜转运体活性、细胞外膜、细菌分泌系统和群体感应等，而AB.2014不同衍生株之间的差异基因主要富集于细胞外膜、细胞对化学刺激的反应、阿特拉津降解和RNA聚合酶等。结论·碳青霉烯类药物环境压力会引起鲍曼不动杆菌耐药性发生变化，碳青霉烯酶、外排泵、孔蛋白、青霉素结合蛋白多种基因可能同时参与了菌株耐药性的变化；碳青霉烯酶OXA23丢失可能导致耐药鲍曼不动杆菌对碳青霉烯类药物复敏。

Objective ·To explore the mechanism of changes in resistance to meropenem (MEM), a carbapenem drug, in Acinetobacter baumannii (A. baumannii) cultured in different antibiotic concentrations. Methods ·Through changing the MEM concentration and other culture conditions of the standard sensitive strain of A. baumannii ATCC19606 and the clinical drug-resistant strain AB.2014, the derived strains with different levels of MEM-resistance were induced. The growth curves of all the stains were detected. DNA and RNA of them were extracted. PCR was used to analyze the expression of carbapenemase genes, including IMI, KPC, GES-1, IMP, VIM, NDM-1, OXA23, OXA24, OXA51, and OXA58. Real-time fluorescent quantitative PCR (RT-qPCR) was used to analyze the expression levels of the carbapenemase gene (OXA51), efflux pump genes (adeB, adeG, and adeJ), pore protein genes (carO, omp33-36, and oprC)and the penicillin-binding protein gene (ponA)in the A. baumannii strains with different resistance to MEM, of which the differential gene enrichment was also detected by whole genome sequencing and bioinformatics tools. Results ·The 11 derived strains of ATCC19606 and AB.2014 with different levels of resistance to MEM were obtained, of which the minimum inhibitory concentrations (MIC) were 1?128 μg/mL. The growth rates and peak values of ATCC19606 and its derivatives decreased with the increase of drug resistance, but AB.2014 and its derivatives did not show this trend. ATCC19606 and its derived strains expressed 3 carbapenemase genes, i.e., OXA51, VIM and IMP, while AB.2014 and most of its derived strains expressed 4 carbapenemase genes, i.e., OXA23, OXA51, VIM and IMP, with only one sensitized derivative of AB.2014 losing OXA23 gene. RT-qPCR results showed that only in ATCC19606 and its drug-resistant derivatives, the expression level of oprC gene decreased with the increase of drug resistance, and the expression levels of most drug-resistant genes were consistent with the changes of drug resistance levels of the strains. Bioinformatics analysis indicated that the differential genes among different ATCC19606 strains were mainly enriched in the siderophore uptake transmembrane transporter activity, cell outer membrane, bacterial secretion system and quorum sensing, while those among AB.2014 strains were mainly enriched in cell outer membrane, cellular response to chemical stimulus, atrazine degradation and RNA polymerase. Conclusion ·The environmental pressure from carbapenems will cause the change of drug resistance of A. baumannii with the involvement of the genes of carbapenemases, efflux pumps, pore proteins and penicillin-binding proteins. The loss of carbapenemase gene OXA23 may lead to the desensitization of drug-resistant A. baumannii strains to carbapenems.