阴沟肠杆菌AmpC酶的检测及耐药性分析

目的了解某医院阴沟肠杆菌产AmpC酶情况及其对10种常用抗菌药物的耐药性，以指导临床合理选择抗菌药物。方法收集该院2007年8月-2008年7月临床分离的非重复阴沟肠杆菌98株，采用头孢西丁纸片扩散法进行AmpC酶初筛，酶提取物三维试验确证阴沟肠杆菌高产AmpC酶，聚合酶链反应检测AmpC酶基因。以K B纸片扩散法进行药敏试验。结果98株阴沟肠杆菌中有36株携带AmpC酶，检出率36.73％。在36株产AmpC酶阴沟肠杆菌中，检测到仅携带DHA基因株6株(16.67%)；仅携带ACC基因株20株(55.56%)；同时携带ACC和MIR基因株8株(22.22%)；同时携带ACC、MIR和FOX基因株2株(5.56%)。产AmpC酶菌株对头孢西丁全部耐药，对第三代头孢菌素、联合抑酶剂、氨曲南、阿米卡星及环丙沙星均有不同程度耐药（44.44%~91.67%）；对头孢吡肟及亚胺培南较敏感，耐药率分别为27.78%、0.00%。结论阴沟肠杆菌AmpC酶携带率高，是导致其对第三代头孢菌素耐药的重要原因；治疗阴沟肠杆菌感染应以药敏检测结果为依据。

Detection of AmpC gene and investigation of drug resistance in Enterobacter cloacae

Objective To investigate the AmpC enzyme production in Enterobacter cloacae （E. cloacae） of a hospital, and drug resistance of E. cloacae to 10 kinds of commonly used antimicrohials, so as to guide clinical rational choice of antimicrobials. Methods Ninety-eight strains of non-repeat clinical isolated E. cloacae were collected from the hospital from August 2007 to July 2008, cefoxitin disk diffusion method was used to screen AmpC enzyme, AmpC enzyme of E. cloacae was confirmed by enzyme extract three-dimensional high-yield tests, the AmpC enzyme gene was detected with polymerase chain reaction. Resistance of drugs was detected by Kirby-Bauer agar diffusion method. Results Among 98 clinical isolated E. cloacae,36 strains produced AmpC β-lactamases, the detection rate was 36. 73%. In 36 AmpC-positive strains, 6 only carried DHA gene （16. 67%）; 20 only carried ACC gene （55. 56%）; 8 carried ACC and MIR gene together （22. 22%）; 2 carried ACC, MIR and FOX genes together （5.56%）. AmpC-positive strains were almost resistant to cefoxitin, and were sensitive to third generation cephalosporins, enzyme inhibitors, aztreonam, amikacin and ciprofloxacin with varying degrees（44. 44% -91.67%）, but sensitive to cefepime and imipenem, drug resistant rate was 27. 78% and 0. 00% respectively. Conclusion E. cloacae carries high rate of AmpC enzyme, which is the main cause of drug-resistance to the third generation cephalosporins, treatment of E. cloacae infection should be based on the results of antimicrobial susceptibility test.