一株弗劳地枸橼酸杆菌中检出新ampC基因

目的探讨1株耐亚胺培南弗劳地枸橼酸杆菌的耐药机制。方法采用浓度梯度法（Etest）检测对抗菌药物的最低抑菌浓度（MIC）。通过金属酶初筛试验（协同法）检测金属酶;改良Hoged试验检测碳青霉烯酶;头孢西丁三维试验检测AmpC酶;聚合酶链反应（PCR）检测耐药基因;DNA测序决定基因型;接合试验检测耐药基因的转移性。结果弗劳地枸橼酸杆菌临床分离株NC118对亚胺培南的MIC为〉16μg/ml,金属酶初筛试验阴性,Hoged表型确证试验碳青霉烯酶阳性,AmpC酶阳性,PCR扩增及测序显示含有blaKPC-2、blaAmpC基因,该菌株所产AmpC酶基因与CMY-45型AmpC酶（GenBank：ACU00152.1）比较有5个氨基酸发生了改变,该blaCMY-2-like基因为一个新型的AmpC酶基因。结论在弗劳地枸橼酸杆菌中发现一种新的ampC基因（blaCMY-49）。

A new ampC gene detected in Citrobacter freundii

Objective To investigate the imipenem resistance mechanism of a clinical isolate of Citrobacter freundii NC118.Method The minimum inhibitory centrations（MICs） were determined by Etest.Double-disk synergy test was used for metallo-β-lactamase screening. Three dimention test was applied to identify AmpCs. Polymerase chain reaction（PCR） and DNA sequencing were carried out for determining antimicrobial resistance genes. Conjugation experiment was performed to determine whether resistance to carbapenem was likely transferred by plasmid.Result C. freundii strain NC118 was resistant to most of the clinically used antimicrobial agents.The isolate was negative for metallo-β-lactamase genes,but positive for blaKPC-2.The clinical isolate also produced AmpCs. A total of eleven antimicrobial-resistant genes were simultaneously detected in C. freundii strain NC118,including blaKPC-2,and blaCMY-49.Conclusion A new ampC gene,blaCMY-49,was discovered in Citrobacter freundii.