产头孢菌素酶肺炎克雷伯菌耐药表型与基因型分析

Antibiotic-resistant phenotype and genotype of AmpC β-lactamase of Klebsiella pneumoniae

目的分析肺炎克雷伯菌产头孢菌素酶(AmpC酶)的耐药表型与基因型,了解其耐药特征和流行趋势。方法对温州医科大学附属苍南医院和永嘉县人民医院呼吸内科2015年7~12月住院患者下呼吸道感染样本中分离的97株肺炎克雷伯菌,作产AmpC酶耐药表型与基因型分析,采用VITEK-60型全自动细菌鉴定仪鉴定细菌;采用头孢西丁纸片扩散法筛选产AmpC酶菌株;采用三维试验确证产AmpC酶菌株;采用PCR和DNA测序检测分析AmpC酶基因型别。结果 97株肺炎克雷伯菌经头孢西丁敏感试验选出疑产AmpC酶菌株21株,经三维试验确证产AmpC酶菌株有15株,21株疑产AmpC酶菌株经PCR检测有15株菌株显示阳性,经DNA测序证实均为DHA-1型AmpC酶。结论产AmpC酶的肺炎克雷伯菌表型与基因型不完全相同,二者的结果有一定的关联性但同时存在差异,应以PCR扩增结果为准。

Objective To analyze the antibiotic-resistant phenotype and genotype of AmpCβ-lactamase of Klebsiella pneumonia,and to understand the antibiotic characteristics and epidemic trend. Methods From July 2015 to December,97 strains of Klebsiella pneumoniae were isolated from inpatients with lower respiratory tract infection in Cangnan Hospital of Wenzhou Medical University and Yongjia County People′s Hospital,the AmpC enzyme resistant phenotype and genotype were analyzed.Bacterial stains were identified using VITEK-60,positive strains harboring AmpC enzyme gene were screened with cefoxitin disk diffusion method,strains producing AmpC enzyme were confirmed by a three-dimensional test,polymerase chain reaction（PCR）as well as DNA sequencing were used to identify the genotype of AmpC enzyme gene. Results 21 strains were identified as suspected AmpC enzyme producing bacteria out of 97 strains of klebsiella pneumonia by cefoxitin sensitive test,and 15 strains were confirmed by 3dtest.15 out of the 21 strains were PCR positive and they were all DHA-type 1 confirmed by DNA sequencing. Conclusions The phenotype and genotype of klebsiella pneumonia producing AmpC enzyme are not completely same,they are correlated but certain differences exist,which should be determined by PCR and DNA sequencing.