质粒介导的超广谱β-内酰胺酶(ESBLs)的特性研究

THE RESEARCH OF THE CHARACTERISTICS OF THE PLASMID-MEDIATED EXTENDED SPECTRUMβ-LACTAMASES(ESBLS)

三代头孢菌素由于抗菌作用强、抗菌谱广、毒性低，因而是临床众多抗菌药物中应用较多的一类抗生素。但自从１９８３年欧洲首次发现耐药菌后，十几年来耐药菌株日益增多。研究显示细菌对三代头孢菌素的耐药主要是因为产生了能水解抗生素的新的酶类－超广谱β－内酰胺酶（ｅｘｔｅｎｄｅｄ－ｓｐｅｃｔｒｕｍβ－ｌａｃｔａｍａｓｅｓ，ＥＳＢＬｓ）。通过对８６６株北京地区临床分离致病菌的筛选，其中７８株对三代头孢菌素（头孢哌酮、头孢他定、头孢噻肟和头孢曲松）均耐药。我们对其中４株高度产酶耐药菌进行了较系统的研究。且对２株菌所产β－内酰胺酶用ＦＰＬＣ进行了纯化。分别被纯化了１０５．９３和２４４．２２倍。研究表明，４株菌产生的β－内酰胺酶主要水解头孢噻肟、头孢曲松和头孢哌酮，而头孢他啶对其稳定。４种酶的ｐＩ＞７，提示不属于目前已知的ＴＥＭ系列。能够被棒酸所抑制，属于ＣｌａｓｓＡ酶。质粒转化实验及以ＳＨＶ－１ＤＮＡ片断作为探针的Ｓｏｕｔｈｅｒｎ杂交进一步提示上述四种酶的耐药基因由质粒介导，且与ＳＨＶ系列的酶不具有同源性，可能属于新的非ＴＥＭ和非ＳＨＶ（ｎｏｎ－ＴＥＭｏｒＳＨＶｄｅｒｉｖｅｄβ－ｌａｃｔａｍａｓｅｓ）系列的酶。

The Third generation cephalosporins is one of the widely used antibiotics in clinic. Since 1983, many resistant organisms isolated from clinic were be found that the resistance is due to new enzymes-extended spectrum β-lactamaces(ESBLs). In our present paper, 78 strains resistant to cefoperazone, cefotaxime, ceftriaxone and ceftazidime were isolated from 866 clinical pathogens in Beijing district. 4 isolates were chosen to be further studied with respect to their β-lactamases and genetic background. Two β-lactamases were purified 105.93 and 244.22 folds respectively by using FPLC. The study showed that 4 β-lactamases had a strong hydrolyzing activity against cefotaxime, ceftriaxone and cefoperazone but not to ceftazidime. The isoelectric points of these β-lactamases were >7, This suggested that they were not derived from TEM family. They could be inhibited by suicide β-lactamase inhibitor and were class A enzyme. The study of transformation and Southern hybridization showed these β-lactamases were mediated by plasmid and not belong to the SHV family. These β-lactamases may belong to the new group of non TEM or SHV derived β-lactamases..